RESEARCH ARTICLE
Potocki–Shaffer Deletion Encompassing ALX4 in a Patient With Frontonasal Dysplasia Phenotype Alessandra Ferrarini,#1 Muriel Gaillard,#2 Frederic Guerry,2 Gianpaolo Ramelli,1 Fodstad Heidi,2 Caroline Verley Keddache,2 Ilse Wieland,3 Jacques S. Beckmann,2,4 Se´bastien Jaquemont,2 and Danielle Martinet2* 1
Division of Pediatrics, San Giovanni Hospital, Bellinzona, Switzerland
2
Service of Medical Genetics, CHUV, Lausanne, Switzerland Institut fu¨r Humangenetik, Otto-von-Guericke-Universita¨t, Magdeburg, Germany 4 Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland 3
Manuscript Received: 24 May 2013; Manuscript Accepted: 21 June 2013
Frontonasal dysplasia (FND) is a genetically heterogeneous malformation spectrum with marked hypertelorism, broad nasal tip and bifid nose. Only a small number of genes have been associated with FND phenotypes until now, the first gene being EFNB1, related to craniofrontonasal syndrome (CFNS) with craniosynostosis in addition, and more recently the aristalesslike homeobox genes ALX3, ALX4, and ALX1, which have been related with distinct phenotypes named FND1, FND2, and FND3 respectively. We here report on a female patient presenting with severe FND features along with partial alopecia, hypogonadism and intellectual disability. While molecular investigations did not reveal mutations in any of the known genes, ALX4, ALX3, ALX1 and EFNB1, comparative genomic hybridization (array CGH) techniques showed a large heterozygous de novo deletion at 11p11.12p12, encompassing the ALX4 gene. Deletions in this region have been described in patients with Potocki–Shaffer syndrome (PSS), characterized by biparietal foramina, multiple exostoses, and intellectual disability. Although the patient reported herein manifests some overlapping features of FND and PPS, it is likely that the observed phenotype maybe due to a second unidentified mutation in the ALX4 gene. The phenotype will be discussed in view of the deleted region encompassing the ALX4 gene. Ó 2013 Wiley Periodicals, Inc.
Key words: fronto-nasal dysplasia; ALX4; 11p11p12; Potocki– Shaffer syndrome
INTRODUCTION Frontonasal dysplasia (FND) is a heterogeneous disorder associated with hypertelorism, abnormal nasal configuration and oral, palatal, or facial clefting. In addition to isolated FND, Wu et al. [2007] have classified FND patients into different subtypes based on associated malformations: OAFNS (oculoauriculovertebral syndrome), acromelic, cardiac or neuronal migration anomalies, and Poland syndrome. Most cases of FND are sporadic and the genetic etiology
Ó 2013 Wiley Periodicals, Inc.
How to Cite this Article: Ferrarini A, Gaillard M, Guerry F, Ramelli G, Heidi F, Keddache CV, Wieland I, Beckmann JS, Jaquemont S, Martinet D. 2014. Potocki–Shaffer deletion encompassing ALX4 in a patient with frontonasal dysplasia phenotype. Am J Med Genet Part A 164A:346–352.
of FND is identified in a small number of cases. Mutations in the gene encoding ephrin-B1 (EFNB1), a ligand to ephrin receptor tyrosine kinases, have been associated with FND and craniosynostosis phenotype named as craniofrontonasal syndrome (CFNS, OMIM#304110) [Twigg et al., 2004; Wieland et al., 2004, 2007]. CFNS is an X-linked disorder characterized by a more severe phenotype in heterozygous females than in hemizygous males. While heterozygous females present the full blown phenotype for CFNS, hemizygous males show no features or are mildly affected as having hypertelorism, cleft lip and palate. Twigg et al. have reported homozygous loss-of-function mutations in the aristalesslike homeobox 3 (ALX3) gene in 11 patients from seven consanguineous families. These patients presented a distinctive facial appearance with hypertelorism, wide nasal bridge, short nasal ridge, bifid nasal tip, broad columella, widely separated slit-like nares, long philtrum and a midline notch in the upper lip and alveolus. #
Alessandra Ferrarini and Muriel Gaillard contributed equally to this work. Correspondence to: Danielle Martinet, Service of Medical Genetics, CHUV, 1011 Lausanne, Switzerland. E-mail: [email protected] Article first published online in Wiley Online Library (wileyonlinelibrary.com): 13 December 2013 DOI 10.1002/ajmg.a.36140
346
FERRARINI ET AL. They concluded that recessive mutations of ALX3 are responsible for this distinct phenotype named frontorhiny or frontonasal dysplasia 1 (FND1, OMIM 136760) [Twigg et al., 2009]. Kayserili and co-workers reported four cases in two Turkish families with a homozygous nonsense mutation in ALX4 (frontonasal dysplasia 2; FND2, OMIM 613451). Patients presented with severe FND with striking associated features including total alopecia, large skull defects, coronal craniosynostosis, bifid nasal tip, hypogonadism, callosal body agenesis, marked hypertelorism, telecanthus, blepharophimosis, microphthalmia, strabismus, nystagmus, and intellectual disability [Kayserili et al., 2009]. A milder phenotype with hypertelorism, broad nasal bridge and columella, bifid nasal tip, cleft alae nasi, preauricular tag and large bilateral parietal foramina was recently reported in a patient with the homozygous missense mutation c.673C>G in ALX4 [Kayserili et al., 2011]. Patients with frontonasal dysplasia 3 (FND3, OMIM 613456) carrying homozygous ALX1 mutations have a more severe phenotype associated with upper eyelid coloboma, lack of eyelashes and eyebrows, hypertelorism, microphtalmia, wide nasal bridge, hypoplasia of the ala nasi, bilateral cleft lip, cleft palate and palpable midline cranial cleft [Uz et al., 2010]. In view of the illustrations reported by Uz et al. [2010], there is pathognomonic nasal configuration in each FND and a clinician can predict the ALX-related gene from the phenotype. Here we report a new patient presenting with FND features and ectodermal involvement. Molecular investigation did not reveal any mutations or unknown variants (exons and neighboring intronic regions) in the FND related genes ALX4, ALX3, ALX1, or EFNB1 gene. However, a large heterozygous deletion in the 11p11.12p12 chromosomal region encompassing the ALX4 gene was identified. The deletion of this region has been described as causal for Potocki–Shaffer syndrome (PSS), which is a contiguous gene disorder due to haploinsufficiency of the 11p11.2p12 region. It has never been associated with FND and is characterized by biparietal foramina, multiple exostoses, and moderate to severe intellectual disability [Swarr et al., 2010]. Our patient presents with a PSS genotype but has clinical features of both FND and PSS. The genetic and clinical aspects will be discussed in view of the deleted region with the hypothesis of a second hit.
CLINICAL REPORT The patient was the third child of nonconsanguineous parents of Swiss origin from Ticino. Two siblings and the mother were healthy. Family history was uneventful except for the father who was diagnosed with Addison disease. The patient was born at 40 þ 2/7 weeks of gestation, after an uneventful pregnancy. Apgar score was 8/9/10; height was 50 cm (50–90th centile), weight 3,370 g (50–90th centile), head circumference was 35 cm (50–90th centile). At initial examination the child presented with marked hypertelorism, broad nasal bridge, bifid nose, unilateral cleft lip and palate. She also presented with left congenital hip dislocation and a supravalvular aortic stenosis. Cerebral ultrasonography and MRI showed hydrocephaly, agenesis of corpus callosum, vermis hypoplasia and a cyst of the septum pellucidum. She was operated for orofacial cleft and ventriculoperitoneal shunt was implemented for hydrocephaly. She had
347 severe neuromotor developmental delay: she never started walking or speaking. At 22 years of age, growth parameters were G]) and exon 3 (rs12419361, c.[879C>T]). A third single nucleotide polymorphism (SNP) rs11037929, c.[467–45T>C] was located in the intronic region, upstream of exon 2. These three SNPs were all
348
AMERICAN JOURNAL OF MEDICAL GENETICS PART A
FIG. 1. The proband at 22 years of age. a: Frontal and lateral view shows areas of alopecia, sparse hair, frontal bossing, severe hypertelorism, downslanting palpebral fissures, broad base to nose, depressed nasal tip and low-set ears. b: Cranial 3D CT images show marked hypertelorism and nasal bone aplasia. c: Cranial 3D CT images showing normal parietal and occipital bones with unilateral (right) ventriculoperitoneal shunt line.
inherited from the mother. The father was homozygous for rs3824915, c.[104G>C], but this change was not observed in the proband’s sample suggesting that a de novo deletion occurred on the paternal allele. Array CGH analyses identified a deletion of 8.45 Mb in the 11p11.12–11p12 region, between the positions 42,835,195 and 51,387,923 bp (GRCh37/hg19). This deletion includes 15 OMIM morbid genes (F2, LRP4, SLC39A13, EXT2,
ALX4, CD82, SLC35C1, MAPK81P1, PEX16, DDB2, ACP2, MYBPC3, RAPSN, NDUFS3, and PTPR) (Table I) and has been reported responsible of the PSS (OMIM#601224). Sequencing of the paralogous ALX genes, ALX1 and ALX3 did not reveal any disease-causing mutations. Second change, a duplication of 186 kb was identified in the Xq28 region, in the array-CGH analysis between positions
Full gene name Coagulation factor F2
Low density lipoprotein receptor-related protein 4
Solute carrier family 39 (zinc transporter), member 13
Exostosin 2
Aristaless-like 4
CD82 antigen
Solute carrier family 35
Mitogen-activated protein kinase 8 interacting protein 1
Gene F2
LRP4
SLC39A13
EXT2a
ALX4a
CD82
SLC35C1
MAPK8IP1
604641
605881
600623
605420
608210
608735
604270
OMIM 176930
Diabetes mellitus, noninsulindependent (125853)
AD
AR
AD —
Parietal foramina 2 (609597) Prostate cancer, susceptibility to (176807) Congenital disorder of glycosylation, type IIc (266265)
AR
Frontonasal dysplasia 2 (613451)
AD
AR/AD AR
Sclerosteosis 2 (614305) Spondylocheirodysplasia, Ehlers–Danlos syndrome-like (612350)
Exostoses, multiple, type 2 (133701)
AR
Type AR
Cenani-Lenz syndactyly syndrome (212780)
Syndrome (OMIM) Prothrombin deficiency (613679)
Highly expressed in brain. Expressed in neurons, in the pancreas, testis and prostate. Low levels in heart, ovary and small
Decidual cells, islets of Langerhans, squamous epithelia Ubiquitous expression (BioGPS.org)
Expression is likely to be restricted to bone. Found in parietal bone (UniProt.org)
Squamous epithelium, nasopharynx, renal/urinary tract, skeletal muscle, intestinal tract, Leydig cells, Purkinje cells and chondrocytes Ubiquitous expression (UniProt.org)
Tissue expression In plasma and low to medium cytoplasmic expression in a subset of different tissues Ubiquitous expression
TABLE I. OMIM Morbid Genes Included in the 11p11p12 Deleted Region
(Continued)
KO mice: severe growth retardation, high postnatal mortality lung alveoles/hypocellular lymph nodes [Hellbusch et al., 2007 JBC] KO mice: viable and fertile/ resistant to excitotoxic stress/resistant to diet-induced obesity [Whitmarsh et al., 2001]
Not established
EXT2 heterozygous mice: multiple exostosis. The KO model is lethal [Stickens et al., 2005] ALX4 mouse model: homozygous and heterozygous lossof-function mutations in Alx4 cause the phenotype of Strong’s luxoid polydactylous mutants characterized by preaxial polydactyly [Qu et al., 1998]
KO mice: growth retardation, kyphosis [Fukada et al., 2008]
Animal models KO mice: >50% embryonic lethality [Sun et al., 1998] KO mice: growth retarded/ polysyndactyly/abnormal tooth development [Johnson et al., 2005]
FERRARINI ET AL. 349
DNA damage-binding protein 2
Acid phosphatase 2, lysosomal
Myosin-binding protein C, cardiac
Receptor-associated protein of the synapse
NADH-ubiquinone oxidoreductase Fe–S protein 3 Protein-tyrosine phosphatase, receptor-type J
DDB2
ACP2
MYBPC3
RAPSN
NDUFS3
600925
603846
601592
600958
171650
600811
OMIM þ603360
TABLE I. (Continued )
Colon cancer, somatic (114500)
Myasthenic syndrome, congenital (608931) Leigh syndrome (256000)
Cardiomyopathy, dilated (115200)/hypertrophic, 4 (115197) Fetal akinesia deformation sequence (208150)
Lysosomal acid phosphatase deficiency (200950)
Xeroderma pigmentosum, group E, DDB-negative subtype (278740)
Syndrome (OMIM) Zellweger syndrome (214100)
AR, autosomal recessive; AD, autosomal dominant. a Implicated in Potocki–Shaffer syndrome phenotype. Tissue expression: Human Protein Atlas (www.proteinatlas.org) if not stated otherwise.
PTPRJ
Full gene name Peroxisome biogenesis factor 16
Gene PEX16
AR
AR
AR
AD
?
AR
Type AR
Ubiquitous expression
Ubiquitous expression
Ubiquitous expression
Cardiac specific (UniProt.org)
High expression in liver (BioGPS.org)
Tissue expression intestine Most normal tissues have weak to moderate cytoplasmic and/or nuclear positivity. Strong cytoplasmic and membranous expression in stomach Ubiquitous expression
Not established
Not established
KO mice: hypersensitive to UV-induced skin carcinogenesis [Alekseev et al., 2005] KO mice: adult mice develop alterations of bone structure and a minority develop generalized seizures [Saftig et al., 1997]. Homozygous mutation: severe growth retardation/delayed or absent appearance of body hair/ tremor and an ataxia-like phenotype [Mannan et al., 2004] KO mice: defect in diastolic relaxation [Pohlmann et al., 2007] KO mice: viable but die soon after birth due to failure of acetylcholine-receptor aggregation at neuromuscular junctions [Gautam et al., 1995]
Animal models Not established
350 AMERICAN JOURNAL OF MEDICAL GENETICS PART A
FERRARINI ET AL. 147,557,492 and 147,743,956 bp (GRCh37/hg19), implicating the OMIM morbid gene AFF2 (OMIM300806). This gene is a member of the AF4/FMR2 gene family and is associated with the folatesensitive fragile X E locus on chromosome Xq28. A repeat polymorphism in the fragile X E locus results in silencing of AFF2 causing the X-linked mental retardation syndrome Fragile X E (OMIM#309548). Deletions in this gene have been found causal for intellectual disability in male patients [Stettner et al., 2011].
DISCUSSION We present a patient with characteristic clinical features of frontonasal and ectodermal dysplasia with a heterozygous deletion of the 11p11.12p12 region encompassing ALX4. The deleted region is associated with PSS [Wakui et al., 2005; Swarr et al., 2010]. All patients with PSS described by Swarr et al. presented with developmental delay and intellectual disability and pronounced deficit in language. Fifty percent of the reported patients meet criteria for autism spectrum disorder. Cerebral MRI showed choroid plexus cysts, prominence of the CFS spaces, mega cysterna magna or posterior fossa cyst, agenesis of the corpus callosum. Craniofacial anomalies included microcephaly, prominent nasal bridge, broad depressed nasal tip, hypoplastic nares, short philtrum, downturned mouth, micrognatia, and high palate. Eighty percent of the reported patients had parietal foramina and about 60% had exostoses of tubular and long bones. EXT2 and ALX4 are, among several other genes, included in the PSS deleted region (Table I). The multiple exostoses of PSS are caused by haploinsufficiency of EXT2 [Potocki and Shaffer, 1996], whereas the biparietal foramina is likely due to deletion of ALX4 in this region [Wu et al., 2000]. The patient reported herein shows clinical features of PSS as severe developmental delay, cognitive disability and scoliosis while she does not have exostosis and parietal foramina observed in a majority of PSS cases. In particular, the fronto-nasal malformation in our patient has never been described in PSS patients with deletions covering the same region [Patient 13 and 07 in Wakui et al., 2005] or extending further into 11p13. The haploinsufficiency of ALX4, present in most cases of PSS, has not been associated with FND and even hypertelorism has never been reported in PSS cases [Wakui et al., 2005; Swarr et al., 2010]. Among the genes included in the deleted region, ALX4 is of interest in relation to the phenotype of the patient. Point mutations resulting in biallelic loss-of-function of ALX4 have previously been reported in five patients [Kayserili et al., 2009]. The patients reported by Kayserili et al. and the one reported herein share several clinical features: FND, hypogonadism, callosal body agenesis, intellectual disability and total/partial alopecia (Fig. 1). The absence of large skull defects, craniosynostosis, large parietal foramina, bifid nasal tip, cleft alae nasi, preauricular tag and blepharophimosis, microphthalmia, strabismus and nystagmus can be suggestive for a heterozygote change in ALX4, excluding biallelic mutations (Fig. 1). The murine orthologue Alx-4, is expressed in craniofacial mesenchyme during embryogenesis and is involved in skull development [Qu et al., 1998]. In mice, mutations cause a decrease in the size of the parietal bone, among other craniofacial and
351 developmental features. Human ALX4 is also expressed in parietal bones and haploinsufficiency of this gene causes parietal foramina in humans [Wu et al., 2000]. We did not detect any mutations on the second ALX4 allele and the screening of other genes involved in FND (EFNB1, ALX3, ALX1) did not reveal any deleterious variants. We are therefore unable to identify a second mutation in this patient, but it is reasonable to suggest that an additional variant is interacting with the deleted region encompassing ALX4 to produce this striking FND phenotype and partial alopecia never observed in deletions overlapping the same region [Wakui et al., 2005; Swarr et al., 2010]. There are 15 OMIM morbid genes in the 11p11p12-deleted region and only a few of them will contribute to the phenotype in the heterozygote state. Of the OMIM morbid genes included in the 11p11p12 deleted region (Table I), MYBPC3 is of interest as our patient presented with hypertrophic cardiomyopathy. MYBPC3 mutations are the most common cause of autosomal dominant hypertrophic cardiomyopathy [Pohlmann et al., 2007] and thus be the underlying etiopathogenesis of hypertrophic cardiomyopathy observed in the patient. Our patient presented with patchy alopecia and absence of body hair. A similar phenotype was reported in the ACP2-mutated “nax” (for naked and taxia) mouse model reported by Mannan et al. [2004]. Their mouse model exhibited delayed hair appearance due to abnormal hair follicles of the skin, an ataxia-like phenotype, and growth retardation. This phenotype was associated with an autosomal recessive missense mutation in ACP2 (Table I). Interestingly, the skin abnormalities in the nax-mouse model were not reported in the ACP2 gene knock-out model, which presented generalized tonicclonic seizures (in 7% of mice) and alterations of bony structures from the age of 6 months [Saftig et al., 1997]. It is noteworthy that the phenotypes described in these mouse models are observed only in homozygous state. Thus it remains open to further discussion whether the deletion of ACP2 could be causal for the hair abnormalities observed in our patient. The presence of a potential secondhit on the other ACP2 allele has not been investigated. No other OMIM morbid genes included in the deleted region seem to be responsible for the clinical features observed in our patient. In conclusion, our patient shows a deletion typical for PSS and additional remarkable features of frontonasal dysplasia and patchy alopecia which have never been reported in any PSS patient. Although we failed to identify mutations in any of the genes involved in FND, it is reasonable to assume that an additional variant interacts with the deletion and results in this unique phenotype that may be considered as a variant of PSS or FND. Mutations in the non-deleted allele leading to two hits, maybe much more frequent than previously anticipated [Girirajan et al., 2012] and sequencing of target regions may help to solve the phenotypic variability in these rarely encountered cases. Future similar cases and the nowadays available molecular approaches will allow to identify and to better understand the impact of genetic alterations detected in these patients.
REFERENCES Alekseev S, Kool H, Rebel H, Fousteri M, Moser J, Backendorf C, de Gruijl FR, Vrieling H, Mullenders LH. 2005. Enhanced DDB2 expression
352
AMERICAN JOURNAL OF MEDICAL GENETICS PART A
protects mice from carcinogenic effects of chronic UV-B irradiation. Cancer Res 65:10298–10306.
phosphatase develop lysosomal storage in the kidney and central nervous system. J Biol Chem 272:18628–18635.
Fukada T, Civic N, Furuichi T, Shimoda S, Mishima K, Higashiyama H, Idaira Y, Asada Y, Kitamura H, Yamasaki S, Hojyo S, Nakayama M, Ohara O, Koseki H, Dos Santos HG, Bonafe L, Ha-Vinh R, Zankl A, Unger S, Kraenzlin ME, Beckmann JS, Saito I, Rivolta C, Ikegawa S, Superti-Furga A, Hirano T. 2008. The zinc transporter SLC39A13/ZIP13 is required for connective tissue development; its involvement in BMP/TGF-beta signaling pathways. PLoS ONE 3:e3642.
Stettner GM, Shoukier M, Ho¨ger C, Brockmann K, Auber B. 2011. Familial intellectual disability and autistic behavior caused by a small FMR2 gene deletion. Am J Med Genet Part A 155A:2003–2007.
Gautam M, Noakes PG, Mudd J, Nichol M, Chu GC, Sanes JR, Merlie JP. 1995. Failure of postsynaptic specialization to develop at neuromuscular junctions of rapsyn-deficient mice. Nature 377:232–236. Girirajan S, Rosenfeld JA, Coe BP, Parikh S, Friedman N, Goldstein A, Filipink RA, McConnell JS, Angle B, Meschino WS, Nezarati MM, Asamoah A, Jackson KE, Gowans GC, Martin JA, Carmany EP, Stockton DW, Schnur RE, Penney LS, Martin DM, Raskin S, Leppig K, Thiese H, Smith R, Aberg E, Niyazov DM, Escobar LF, El-Khechen D, Johnson KD, Lebel RR, Siefkas K, Ball S, Shur N, McGuire M, Brasington CK, Spence JE, Martin LS, Clericuzio C, Ballif BC, Shaffer LG, Eichler EE. 2012. Phenotypic heterogeneity of genomic disorders and rare copy-number variants. N Engl J Med 367:1321–1331. Hellbusch CC, Sperandio M, Frommhold D, Yakubenia S, Wild MK, Popovici D, Vestweber D, Gro¨ne HJ, von Figura K, Lu¨bke T, Ko¨rner C. 2007. Golgi GDP-fucose transporter-deficient mice mimic congenital disorder of glycosylation IIc/leukocyte adhesion deficiency II. J Biol Chem 282:10762–10772. Johnson EB, Hammer RE, Herz J. 2005. Abnormal development of the apical ectodermal ridge and polysyndactyly in Megf7-deficient mice. Hum Mol Genet 14:3523–3538. Kayserili H, Uz E, Niessen C, Vargel I, Alanay Y, Tuncbilek G, Yigit G, Uyguner O, Candan S, Okur H, Kaygin S, Balci S, Mavili E, Alikasifoglu M, Haase I, Wollnik B, Akarsu NA. 2009. ALX4 dysfunction disrupts craniofacial and epidermal development. Hum Mol Genet 18:4357–4366. Kayserili H, Altunoglu U, Ozgur H, Basaran S, Uyguner ZO. 2011. Mild nasal malformations and parietal foramina caused by homozygous ALX4 mutations. Am J Med Genet Part A 158A:236–244. Mannan AU, Roussa E, Kraus C, Rickmann M, Maenner J, Nayernia K, Krieglstein K, Reis A, Engel W. 2004. Mutation in the gene encoding lysosomal acid phosphatase (Acp2) causes cerebellum and skin malformation in mouse. Neurogenetics 5:229–238. Martinet D, Filges I, Besuchet Schmutz N, Morris MA, Gaide AC, Dahoun S, Bottani A, Addor MC, Antonarakis SE, Beckmann JS, Be´na F. 2008. Subtelomeric 6p deletion: Clinical and array-CGH characterization in two patients. Am J Med Genet Part A 146A:2094–2102. Pohlmann L, Kro¨ger I, Vignier N, Schlossarek S, Kra¨mer E, Coirault C, Sultan KR, El-Armouche A, Winegrad S, Eschenhagen T, Carrier L. 2007. Cardiac myosin-binding protein C is required for complete relaxation in intact myocytes. Circ Res 101:928–938. Potocki L, Shaffer LG. 1996. Interstitial deletion of 11(p11.2p12): A newly described contiguous gene deletion syndrome involving the gene for hereditary multiple exostoses (EXT2). Am J Med Genet 62:319–325. Qu S, Tucker SC, Ehrlich JS, Levorse JM, Flaherty LA, Wisdom R, Vogt TF. 1998. Mutations in mouse Aristaless-like4 cause Strong’s luxoid polydactyly. Development 125:2711–2721. Saftig P, Hartmann D, Lu¨llmann-Rauch R, Wolff J, Evers M, Ko¨ster A, Hetman M, von Figura K, Peters C. 1997. Mice deficient in lysosomal acid
Stickens D, Zak BM, Rougier N, Esko JD, Werb Z. 2005. Mice deficient in Ext2 lack heparan sulfate and develop exostoses. Development 132:5055– 5068. Sun WY, Witte DP, Degen JL, Colbert MC, Burkart MC, Holmba¨ck K, Xiao Q, Bugge TH, Degen SJ. 1998. Prothrombin deficiency results in embryonic and neonatal lethality in mice. Proc Natl Acad Sci 95:7597– 7602. Swarr DT, Bloom D, Lewis RA, Elenberg E, Friedman EM, Glotzbach C, Wissman SD, Shaffer LG, Potocki L. 2010. Potocki–Shaffer syndrome: Comprehensive clinical assessment, review of the literature, and proposals for medical management. Am J Med Genet Part A 152A: 565–572. Twigg SR, Kan R, Babbs C, Bochukova EG, Robertson SP, Wall SA, Morriss-Kay GM, Wilkie AO. 2004. Mutations of ephrin-B1 (EFNB1), a marker of tissue boundary formation, cause craniofrontonasal syndrome. Proc Natl Acad Sci USA 101:8652–8657. Twigg SR, Versnel SL, Nu¨rnberg G, Lees MM, Bhat M, Hammond P, Hennekam RC, Hoogeboom AJ, Hurst JA, Johnson D, Robinson AA, Scambler PJ, Gerrelli D, Nu¨rnberg P, Mathijssen IM, Wilkie AO. 2009. Frontorhiny, a distinctive presentation of frontonasal dysplasia caused by recessive mutations in the ALX3 homeobox gene. Am J Hum Genet 84:698–705. Uz E, Alanay Y, Aktas D, Vargel I, Gucer S, Tuncbilek G, von Eggeling F, Yilmaz E, Deren O, Posorski N, Ozdag H, Liehr T, Balci S, Alikasifoglu M, Wollnik B, Akarsu NA. 2010. Disruption of ALX1 causes extreme microphthalmia and severe facial clefting: Expanding the spectrum of autosomal-recessive ALX-related frontonasal dysplasia. Am J Hum Genet 86:789–796. Wakui K, Gregato G, Ballif BC, Glotzbach CD, Bailey KA, Kuo PL, Sue WC, Sheffield LJ, Irons M, Gomez EG, Hecht JT, Potocki L, Shaffer L. 2005. Construction of a natural panel of 11p11.2 deletions and further delineation of the critical region involved in Potocki-Shaffer syndrome. Eur J Hum Genet 13:528–540. Whitmarsh AJ, Kuan CY, Kennedy NJ, Kelkar N, Haydar TF, Mordes JP, Appel M, Rossini AA, Jones SN, Flavell RA, Rakic P, Davis RJ. 2001. Requirement of the JIP1 scaffold protein for stress-induced JNK activation. Genes Dev 15:2421–2432. Wieland I, Jakubiczka S, Muschke P, Cohen M, Thiele H, Gerlach KL, Adams RH, Wieacker P. 2004. Mutations of the ephrin-B1 gene cause craniofrontonasal syndrome. Am J Hum Genet 74:1209–1215. Wieland I, Weidner C, Ciccone R, Lapi E, McDonald-McGinn D, Kress W, Jakubiczka S, Collmann H, Zuffardi O, Zackai E, Wieacker P. 2007. Contiguous gene deletions involving EFNB1, OPHN1, PJA1 and EDA in patients with craniofrontonasal syndrome. Clin Genet 72:506–516. Wu YQ, Badano JL, McCaskill C, Vogel H, Potocki L, Shaffer LG. 2000. Haploinsufficiency of ALX4 as a potential cause of parietal foramina in the 11p11.2 contiguous gene-deletion syndrome. Am J Hum Genet 67:1327–1332. Wu E, Vargevik K, Slavotinek AM. 2007. Subtypes of frontonasal dysplasia are useful in determining clinical prognosis. Am J Med Genet Part A 143A:3069–3078.
Potocki–Shaffer Deletion Encompassing ALX4 in a Patient With Frontonasal Dysplasia Phenotype Alessandra Ferrarini,#1 Muriel Gaillard,#2 Frederic Guerry,2 Gianpaolo Ramelli,1 Fodstad Heidi,2 Caroline Verley Keddache,2 Ilse Wieland,3 Jacques S. Beckmann,2,4 Se´bastien Jaquemont,2 and Danielle Martinet2* 1
Division of Pediatrics, San Giovanni Hospital, Bellinzona, Switzerland
2
Service of Medical Genetics, CHUV, Lausanne, Switzerland Institut fu¨r Humangenetik, Otto-von-Guericke-Universita¨t, Magdeburg, Germany 4 Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland 3
Manuscript Received: 24 May 2013; Manuscript Accepted: 21 June 2013
Frontonasal dysplasia (FND) is a genetically heterogeneous malformation spectrum with marked hypertelorism, broad nasal tip and bifid nose. Only a small number of genes have been associated with FND phenotypes until now, the first gene being EFNB1, related to craniofrontonasal syndrome (CFNS) with craniosynostosis in addition, and more recently the aristalesslike homeobox genes ALX3, ALX4, and ALX1, which have been related with distinct phenotypes named FND1, FND2, and FND3 respectively. We here report on a female patient presenting with severe FND features along with partial alopecia, hypogonadism and intellectual disability. While molecular investigations did not reveal mutations in any of the known genes, ALX4, ALX3, ALX1 and EFNB1, comparative genomic hybridization (array CGH) techniques showed a large heterozygous de novo deletion at 11p11.12p12, encompassing the ALX4 gene. Deletions in this region have been described in patients with Potocki–Shaffer syndrome (PSS), characterized by biparietal foramina, multiple exostoses, and intellectual disability. Although the patient reported herein manifests some overlapping features of FND and PPS, it is likely that the observed phenotype maybe due to a second unidentified mutation in the ALX4 gene. The phenotype will be discussed in view of the deleted region encompassing the ALX4 gene. Ó 2013 Wiley Periodicals, Inc.
Key words: fronto-nasal dysplasia; ALX4; 11p11p12; Potocki– Shaffer syndrome
INTRODUCTION Frontonasal dysplasia (FND) is a heterogeneous disorder associated with hypertelorism, abnormal nasal configuration and oral, palatal, or facial clefting. In addition to isolated FND, Wu et al. [2007] have classified FND patients into different subtypes based on associated malformations: OAFNS (oculoauriculovertebral syndrome), acromelic, cardiac or neuronal migration anomalies, and Poland syndrome. Most cases of FND are sporadic and the genetic etiology
Ó 2013 Wiley Periodicals, Inc.
How to Cite this Article: Ferrarini A, Gaillard M, Guerry F, Ramelli G, Heidi F, Keddache CV, Wieland I, Beckmann JS, Jaquemont S, Martinet D. 2014. Potocki–Shaffer deletion encompassing ALX4 in a patient with frontonasal dysplasia phenotype. Am J Med Genet Part A 164A:346–352.
of FND is identified in a small number of cases. Mutations in the gene encoding ephrin-B1 (EFNB1), a ligand to ephrin receptor tyrosine kinases, have been associated with FND and craniosynostosis phenotype named as craniofrontonasal syndrome (CFNS, OMIM#304110) [Twigg et al., 2004; Wieland et al., 2004, 2007]. CFNS is an X-linked disorder characterized by a more severe phenotype in heterozygous females than in hemizygous males. While heterozygous females present the full blown phenotype for CFNS, hemizygous males show no features or are mildly affected as having hypertelorism, cleft lip and palate. Twigg et al. have reported homozygous loss-of-function mutations in the aristalesslike homeobox 3 (ALX3) gene in 11 patients from seven consanguineous families. These patients presented a distinctive facial appearance with hypertelorism, wide nasal bridge, short nasal ridge, bifid nasal tip, broad columella, widely separated slit-like nares, long philtrum and a midline notch in the upper lip and alveolus. #
Alessandra Ferrarini and Muriel Gaillard contributed equally to this work. Correspondence to: Danielle Martinet, Service of Medical Genetics, CHUV, 1011 Lausanne, Switzerland. E-mail: [email protected] Article first published online in Wiley Online Library (wileyonlinelibrary.com): 13 December 2013 DOI 10.1002/ajmg.a.36140
346
FERRARINI ET AL. They concluded that recessive mutations of ALX3 are responsible for this distinct phenotype named frontorhiny or frontonasal dysplasia 1 (FND1, OMIM 136760) [Twigg et al., 2009]. Kayserili and co-workers reported four cases in two Turkish families with a homozygous nonsense mutation in ALX4 (frontonasal dysplasia 2; FND2, OMIM 613451). Patients presented with severe FND with striking associated features including total alopecia, large skull defects, coronal craniosynostosis, bifid nasal tip, hypogonadism, callosal body agenesis, marked hypertelorism, telecanthus, blepharophimosis, microphthalmia, strabismus, nystagmus, and intellectual disability [Kayserili et al., 2009]. A milder phenotype with hypertelorism, broad nasal bridge and columella, bifid nasal tip, cleft alae nasi, preauricular tag and large bilateral parietal foramina was recently reported in a patient with the homozygous missense mutation c.673C>G in ALX4 [Kayserili et al., 2011]. Patients with frontonasal dysplasia 3 (FND3, OMIM 613456) carrying homozygous ALX1 mutations have a more severe phenotype associated with upper eyelid coloboma, lack of eyelashes and eyebrows, hypertelorism, microphtalmia, wide nasal bridge, hypoplasia of the ala nasi, bilateral cleft lip, cleft palate and palpable midline cranial cleft [Uz et al., 2010]. In view of the illustrations reported by Uz et al. [2010], there is pathognomonic nasal configuration in each FND and a clinician can predict the ALX-related gene from the phenotype. Here we report a new patient presenting with FND features and ectodermal involvement. Molecular investigation did not reveal any mutations or unknown variants (exons and neighboring intronic regions) in the FND related genes ALX4, ALX3, ALX1, or EFNB1 gene. However, a large heterozygous deletion in the 11p11.12p12 chromosomal region encompassing the ALX4 gene was identified. The deletion of this region has been described as causal for Potocki–Shaffer syndrome (PSS), which is a contiguous gene disorder due to haploinsufficiency of the 11p11.2p12 region. It has never been associated with FND and is characterized by biparietal foramina, multiple exostoses, and moderate to severe intellectual disability [Swarr et al., 2010]. Our patient presents with a PSS genotype but has clinical features of both FND and PSS. The genetic and clinical aspects will be discussed in view of the deleted region with the hypothesis of a second hit.
CLINICAL REPORT The patient was the third child of nonconsanguineous parents of Swiss origin from Ticino. Two siblings and the mother were healthy. Family history was uneventful except for the father who was diagnosed with Addison disease. The patient was born at 40 þ 2/7 weeks of gestation, after an uneventful pregnancy. Apgar score was 8/9/10; height was 50 cm (50–90th centile), weight 3,370 g (50–90th centile), head circumference was 35 cm (50–90th centile). At initial examination the child presented with marked hypertelorism, broad nasal bridge, bifid nose, unilateral cleft lip and palate. She also presented with left congenital hip dislocation and a supravalvular aortic stenosis. Cerebral ultrasonography and MRI showed hydrocephaly, agenesis of corpus callosum, vermis hypoplasia and a cyst of the septum pellucidum. She was operated for orofacial cleft and ventriculoperitoneal shunt was implemented for hydrocephaly. She had
347 severe neuromotor developmental delay: she never started walking or speaking. At 22 years of age, growth parameters were G]) and exon 3 (rs12419361, c.[879C>T]). A third single nucleotide polymorphism (SNP) rs11037929, c.[467–45T>C] was located in the intronic region, upstream of exon 2. These three SNPs were all
348
AMERICAN JOURNAL OF MEDICAL GENETICS PART A
FIG. 1. The proband at 22 years of age. a: Frontal and lateral view shows areas of alopecia, sparse hair, frontal bossing, severe hypertelorism, downslanting palpebral fissures, broad base to nose, depressed nasal tip and low-set ears. b: Cranial 3D CT images show marked hypertelorism and nasal bone aplasia. c: Cranial 3D CT images showing normal parietal and occipital bones with unilateral (right) ventriculoperitoneal shunt line.
inherited from the mother. The father was homozygous for rs3824915, c.[104G>C], but this change was not observed in the proband’s sample suggesting that a de novo deletion occurred on the paternal allele. Array CGH analyses identified a deletion of 8.45 Mb in the 11p11.12–11p12 region, between the positions 42,835,195 and 51,387,923 bp (GRCh37/hg19). This deletion includes 15 OMIM morbid genes (F2, LRP4, SLC39A13, EXT2,
ALX4, CD82, SLC35C1, MAPK81P1, PEX16, DDB2, ACP2, MYBPC3, RAPSN, NDUFS3, and PTPR) (Table I) and has been reported responsible of the PSS (OMIM#601224). Sequencing of the paralogous ALX genes, ALX1 and ALX3 did not reveal any disease-causing mutations. Second change, a duplication of 186 kb was identified in the Xq28 region, in the array-CGH analysis between positions
Full gene name Coagulation factor F2
Low density lipoprotein receptor-related protein 4
Solute carrier family 39 (zinc transporter), member 13
Exostosin 2
Aristaless-like 4
CD82 antigen
Solute carrier family 35
Mitogen-activated protein kinase 8 interacting protein 1
Gene F2
LRP4
SLC39A13
EXT2a
ALX4a
CD82
SLC35C1
MAPK8IP1
604641
605881
600623
605420
608210
608735
604270
OMIM 176930
Diabetes mellitus, noninsulindependent (125853)
AD
AR
AD —
Parietal foramina 2 (609597) Prostate cancer, susceptibility to (176807) Congenital disorder of glycosylation, type IIc (266265)
AR
Frontonasal dysplasia 2 (613451)
AD
AR/AD AR
Sclerosteosis 2 (614305) Spondylocheirodysplasia, Ehlers–Danlos syndrome-like (612350)
Exostoses, multiple, type 2 (133701)
AR
Type AR
Cenani-Lenz syndactyly syndrome (212780)
Syndrome (OMIM) Prothrombin deficiency (613679)
Highly expressed in brain. Expressed in neurons, in the pancreas, testis and prostate. Low levels in heart, ovary and small
Decidual cells, islets of Langerhans, squamous epithelia Ubiquitous expression (BioGPS.org)
Expression is likely to be restricted to bone. Found in parietal bone (UniProt.org)
Squamous epithelium, nasopharynx, renal/urinary tract, skeletal muscle, intestinal tract, Leydig cells, Purkinje cells and chondrocytes Ubiquitous expression (UniProt.org)
Tissue expression In plasma and low to medium cytoplasmic expression in a subset of different tissues Ubiquitous expression
TABLE I. OMIM Morbid Genes Included in the 11p11p12 Deleted Region
(Continued)
KO mice: severe growth retardation, high postnatal mortality lung alveoles/hypocellular lymph nodes [Hellbusch et al., 2007 JBC] KO mice: viable and fertile/ resistant to excitotoxic stress/resistant to diet-induced obesity [Whitmarsh et al., 2001]
Not established
EXT2 heterozygous mice: multiple exostosis. The KO model is lethal [Stickens et al., 2005] ALX4 mouse model: homozygous and heterozygous lossof-function mutations in Alx4 cause the phenotype of Strong’s luxoid polydactylous mutants characterized by preaxial polydactyly [Qu et al., 1998]
KO mice: growth retardation, kyphosis [Fukada et al., 2008]
Animal models KO mice: >50% embryonic lethality [Sun et al., 1998] KO mice: growth retarded/ polysyndactyly/abnormal tooth development [Johnson et al., 2005]
FERRARINI ET AL. 349
DNA damage-binding protein 2
Acid phosphatase 2, lysosomal
Myosin-binding protein C, cardiac
Receptor-associated protein of the synapse
NADH-ubiquinone oxidoreductase Fe–S protein 3 Protein-tyrosine phosphatase, receptor-type J
DDB2
ACP2
MYBPC3
RAPSN
NDUFS3
600925
603846
601592
600958
171650
600811
OMIM þ603360
TABLE I. (Continued )
Colon cancer, somatic (114500)
Myasthenic syndrome, congenital (608931) Leigh syndrome (256000)
Cardiomyopathy, dilated (115200)/hypertrophic, 4 (115197) Fetal akinesia deformation sequence (208150)
Lysosomal acid phosphatase deficiency (200950)
Xeroderma pigmentosum, group E, DDB-negative subtype (278740)
Syndrome (OMIM) Zellweger syndrome (214100)
AR, autosomal recessive; AD, autosomal dominant. a Implicated in Potocki–Shaffer syndrome phenotype. Tissue expression: Human Protein Atlas (www.proteinatlas.org) if not stated otherwise.
PTPRJ
Full gene name Peroxisome biogenesis factor 16
Gene PEX16
AR
AR
AR
AD
?
AR
Type AR
Ubiquitous expression
Ubiquitous expression
Ubiquitous expression
Cardiac specific (UniProt.org)
High expression in liver (BioGPS.org)
Tissue expression intestine Most normal tissues have weak to moderate cytoplasmic and/or nuclear positivity. Strong cytoplasmic and membranous expression in stomach Ubiquitous expression
Not established
Not established
KO mice: hypersensitive to UV-induced skin carcinogenesis [Alekseev et al., 2005] KO mice: adult mice develop alterations of bone structure and a minority develop generalized seizures [Saftig et al., 1997]. Homozygous mutation: severe growth retardation/delayed or absent appearance of body hair/ tremor and an ataxia-like phenotype [Mannan et al., 2004] KO mice: defect in diastolic relaxation [Pohlmann et al., 2007] KO mice: viable but die soon after birth due to failure of acetylcholine-receptor aggregation at neuromuscular junctions [Gautam et al., 1995]
Animal models Not established
350 AMERICAN JOURNAL OF MEDICAL GENETICS PART A
FERRARINI ET AL. 147,557,492 and 147,743,956 bp (GRCh37/hg19), implicating the OMIM morbid gene AFF2 (OMIM300806). This gene is a member of the AF4/FMR2 gene family and is associated with the folatesensitive fragile X E locus on chromosome Xq28. A repeat polymorphism in the fragile X E locus results in silencing of AFF2 causing the X-linked mental retardation syndrome Fragile X E (OMIM#309548). Deletions in this gene have been found causal for intellectual disability in male patients [Stettner et al., 2011].
DISCUSSION We present a patient with characteristic clinical features of frontonasal and ectodermal dysplasia with a heterozygous deletion of the 11p11.12p12 region encompassing ALX4. The deleted region is associated with PSS [Wakui et al., 2005; Swarr et al., 2010]. All patients with PSS described by Swarr et al. presented with developmental delay and intellectual disability and pronounced deficit in language. Fifty percent of the reported patients meet criteria for autism spectrum disorder. Cerebral MRI showed choroid plexus cysts, prominence of the CFS spaces, mega cysterna magna or posterior fossa cyst, agenesis of the corpus callosum. Craniofacial anomalies included microcephaly, prominent nasal bridge, broad depressed nasal tip, hypoplastic nares, short philtrum, downturned mouth, micrognatia, and high palate. Eighty percent of the reported patients had parietal foramina and about 60% had exostoses of tubular and long bones. EXT2 and ALX4 are, among several other genes, included in the PSS deleted region (Table I). The multiple exostoses of PSS are caused by haploinsufficiency of EXT2 [Potocki and Shaffer, 1996], whereas the biparietal foramina is likely due to deletion of ALX4 in this region [Wu et al., 2000]. The patient reported herein shows clinical features of PSS as severe developmental delay, cognitive disability and scoliosis while she does not have exostosis and parietal foramina observed in a majority of PSS cases. In particular, the fronto-nasal malformation in our patient has never been described in PSS patients with deletions covering the same region [Patient 13 and 07 in Wakui et al., 2005] or extending further into 11p13. The haploinsufficiency of ALX4, present in most cases of PSS, has not been associated with FND and even hypertelorism has never been reported in PSS cases [Wakui et al., 2005; Swarr et al., 2010]. Among the genes included in the deleted region, ALX4 is of interest in relation to the phenotype of the patient. Point mutations resulting in biallelic loss-of-function of ALX4 have previously been reported in five patients [Kayserili et al., 2009]. The patients reported by Kayserili et al. and the one reported herein share several clinical features: FND, hypogonadism, callosal body agenesis, intellectual disability and total/partial alopecia (Fig. 1). The absence of large skull defects, craniosynostosis, large parietal foramina, bifid nasal tip, cleft alae nasi, preauricular tag and blepharophimosis, microphthalmia, strabismus and nystagmus can be suggestive for a heterozygote change in ALX4, excluding biallelic mutations (Fig. 1). The murine orthologue Alx-4, is expressed in craniofacial mesenchyme during embryogenesis and is involved in skull development [Qu et al., 1998]. In mice, mutations cause a decrease in the size of the parietal bone, among other craniofacial and
351 developmental features. Human ALX4 is also expressed in parietal bones and haploinsufficiency of this gene causes parietal foramina in humans [Wu et al., 2000]. We did not detect any mutations on the second ALX4 allele and the screening of other genes involved in FND (EFNB1, ALX3, ALX1) did not reveal any deleterious variants. We are therefore unable to identify a second mutation in this patient, but it is reasonable to suggest that an additional variant is interacting with the deleted region encompassing ALX4 to produce this striking FND phenotype and partial alopecia never observed in deletions overlapping the same region [Wakui et al., 2005; Swarr et al., 2010]. There are 15 OMIM morbid genes in the 11p11p12-deleted region and only a few of them will contribute to the phenotype in the heterozygote state. Of the OMIM morbid genes included in the 11p11p12 deleted region (Table I), MYBPC3 is of interest as our patient presented with hypertrophic cardiomyopathy. MYBPC3 mutations are the most common cause of autosomal dominant hypertrophic cardiomyopathy [Pohlmann et al., 2007] and thus be the underlying etiopathogenesis of hypertrophic cardiomyopathy observed in the patient. Our patient presented with patchy alopecia and absence of body hair. A similar phenotype was reported in the ACP2-mutated “nax” (for naked and taxia) mouse model reported by Mannan et al. [2004]. Their mouse model exhibited delayed hair appearance due to abnormal hair follicles of the skin, an ataxia-like phenotype, and growth retardation. This phenotype was associated with an autosomal recessive missense mutation in ACP2 (Table I). Interestingly, the skin abnormalities in the nax-mouse model were not reported in the ACP2 gene knock-out model, which presented generalized tonicclonic seizures (in 7% of mice) and alterations of bony structures from the age of 6 months [Saftig et al., 1997]. It is noteworthy that the phenotypes described in these mouse models are observed only in homozygous state. Thus it remains open to further discussion whether the deletion of ACP2 could be causal for the hair abnormalities observed in our patient. The presence of a potential secondhit on the other ACP2 allele has not been investigated. No other OMIM morbid genes included in the deleted region seem to be responsible for the clinical features observed in our patient. In conclusion, our patient shows a deletion typical for PSS and additional remarkable features of frontonasal dysplasia and patchy alopecia which have never been reported in any PSS patient. Although we failed to identify mutations in any of the genes involved in FND, it is reasonable to assume that an additional variant interacts with the deletion and results in this unique phenotype that may be considered as a variant of PSS or FND. Mutations in the non-deleted allele leading to two hits, maybe much more frequent than previously anticipated [Girirajan et al., 2012] and sequencing of target regions may help to solve the phenotypic variability in these rarely encountered cases. Future similar cases and the nowadays available molecular approaches will allow to identify and to better understand the impact of genetic alterations detected in these patients.
REFERENCES Alekseev S, Kool H, Rebel H, Fousteri M, Moser J, Backendorf C, de Gruijl FR, Vrieling H, Mullenders LH. 2005. Enhanced DDB2 expression
352
AMERICAN JOURNAL OF MEDICAL GENETICS PART A
protects mice from carcinogenic effects of chronic UV-B irradiation. Cancer Res 65:10298–10306.
phosphatase develop lysosomal storage in the kidney and central nervous system. J Biol Chem 272:18628–18635.
Fukada T, Civic N, Furuichi T, Shimoda S, Mishima K, Higashiyama H, Idaira Y, Asada Y, Kitamura H, Yamasaki S, Hojyo S, Nakayama M, Ohara O, Koseki H, Dos Santos HG, Bonafe L, Ha-Vinh R, Zankl A, Unger S, Kraenzlin ME, Beckmann JS, Saito I, Rivolta C, Ikegawa S, Superti-Furga A, Hirano T. 2008. The zinc transporter SLC39A13/ZIP13 is required for connective tissue development; its involvement in BMP/TGF-beta signaling pathways. PLoS ONE 3:e3642.
Stettner GM, Shoukier M, Ho¨ger C, Brockmann K, Auber B. 2011. Familial intellectual disability and autistic behavior caused by a small FMR2 gene deletion. Am J Med Genet Part A 155A:2003–2007.
Gautam M, Noakes PG, Mudd J, Nichol M, Chu GC, Sanes JR, Merlie JP. 1995. Failure of postsynaptic specialization to develop at neuromuscular junctions of rapsyn-deficient mice. Nature 377:232–236. Girirajan S, Rosenfeld JA, Coe BP, Parikh S, Friedman N, Goldstein A, Filipink RA, McConnell JS, Angle B, Meschino WS, Nezarati MM, Asamoah A, Jackson KE, Gowans GC, Martin JA, Carmany EP, Stockton DW, Schnur RE, Penney LS, Martin DM, Raskin S, Leppig K, Thiese H, Smith R, Aberg E, Niyazov DM, Escobar LF, El-Khechen D, Johnson KD, Lebel RR, Siefkas K, Ball S, Shur N, McGuire M, Brasington CK, Spence JE, Martin LS, Clericuzio C, Ballif BC, Shaffer LG, Eichler EE. 2012. Phenotypic heterogeneity of genomic disorders and rare copy-number variants. N Engl J Med 367:1321–1331. Hellbusch CC, Sperandio M, Frommhold D, Yakubenia S, Wild MK, Popovici D, Vestweber D, Gro¨ne HJ, von Figura K, Lu¨bke T, Ko¨rner C. 2007. Golgi GDP-fucose transporter-deficient mice mimic congenital disorder of glycosylation IIc/leukocyte adhesion deficiency II. J Biol Chem 282:10762–10772. Johnson EB, Hammer RE, Herz J. 2005. Abnormal development of the apical ectodermal ridge and polysyndactyly in Megf7-deficient mice. Hum Mol Genet 14:3523–3538. Kayserili H, Uz E, Niessen C, Vargel I, Alanay Y, Tuncbilek G, Yigit G, Uyguner O, Candan S, Okur H, Kaygin S, Balci S, Mavili E, Alikasifoglu M, Haase I, Wollnik B, Akarsu NA. 2009. ALX4 dysfunction disrupts craniofacial and epidermal development. Hum Mol Genet 18:4357–4366. Kayserili H, Altunoglu U, Ozgur H, Basaran S, Uyguner ZO. 2011. Mild nasal malformations and parietal foramina caused by homozygous ALX4 mutations. Am J Med Genet Part A 158A:236–244. Mannan AU, Roussa E, Kraus C, Rickmann M, Maenner J, Nayernia K, Krieglstein K, Reis A, Engel W. 2004. Mutation in the gene encoding lysosomal acid phosphatase (Acp2) causes cerebellum and skin malformation in mouse. Neurogenetics 5:229–238. Martinet D, Filges I, Besuchet Schmutz N, Morris MA, Gaide AC, Dahoun S, Bottani A, Addor MC, Antonarakis SE, Beckmann JS, Be´na F. 2008. Subtelomeric 6p deletion: Clinical and array-CGH characterization in two patients. Am J Med Genet Part A 146A:2094–2102. Pohlmann L, Kro¨ger I, Vignier N, Schlossarek S, Kra¨mer E, Coirault C, Sultan KR, El-Armouche A, Winegrad S, Eschenhagen T, Carrier L. 2007. Cardiac myosin-binding protein C is required for complete relaxation in intact myocytes. Circ Res 101:928–938. Potocki L, Shaffer LG. 1996. Interstitial deletion of 11(p11.2p12): A newly described contiguous gene deletion syndrome involving the gene for hereditary multiple exostoses (EXT2). Am J Med Genet 62:319–325. Qu S, Tucker SC, Ehrlich JS, Levorse JM, Flaherty LA, Wisdom R, Vogt TF. 1998. Mutations in mouse Aristaless-like4 cause Strong’s luxoid polydactyly. Development 125:2711–2721. Saftig P, Hartmann D, Lu¨llmann-Rauch R, Wolff J, Evers M, Ko¨ster A, Hetman M, von Figura K, Peters C. 1997. Mice deficient in lysosomal acid
Stickens D, Zak BM, Rougier N, Esko JD, Werb Z. 2005. Mice deficient in Ext2 lack heparan sulfate and develop exostoses. Development 132:5055– 5068. Sun WY, Witte DP, Degen JL, Colbert MC, Burkart MC, Holmba¨ck K, Xiao Q, Bugge TH, Degen SJ. 1998. Prothrombin deficiency results in embryonic and neonatal lethality in mice. Proc Natl Acad Sci 95:7597– 7602. Swarr DT, Bloom D, Lewis RA, Elenberg E, Friedman EM, Glotzbach C, Wissman SD, Shaffer LG, Potocki L. 2010. Potocki–Shaffer syndrome: Comprehensive clinical assessment, review of the literature, and proposals for medical management. Am J Med Genet Part A 152A: 565–572. Twigg SR, Kan R, Babbs C, Bochukova EG, Robertson SP, Wall SA, Morriss-Kay GM, Wilkie AO. 2004. Mutations of ephrin-B1 (EFNB1), a marker of tissue boundary formation, cause craniofrontonasal syndrome. Proc Natl Acad Sci USA 101:8652–8657. Twigg SR, Versnel SL, Nu¨rnberg G, Lees MM, Bhat M, Hammond P, Hennekam RC, Hoogeboom AJ, Hurst JA, Johnson D, Robinson AA, Scambler PJ, Gerrelli D, Nu¨rnberg P, Mathijssen IM, Wilkie AO. 2009. Frontorhiny, a distinctive presentation of frontonasal dysplasia caused by recessive mutations in the ALX3 homeobox gene. Am J Hum Genet 84:698–705. Uz E, Alanay Y, Aktas D, Vargel I, Gucer S, Tuncbilek G, von Eggeling F, Yilmaz E, Deren O, Posorski N, Ozdag H, Liehr T, Balci S, Alikasifoglu M, Wollnik B, Akarsu NA. 2010. Disruption of ALX1 causes extreme microphthalmia and severe facial clefting: Expanding the spectrum of autosomal-recessive ALX-related frontonasal dysplasia. Am J Hum Genet 86:789–796. Wakui K, Gregato G, Ballif BC, Glotzbach CD, Bailey KA, Kuo PL, Sue WC, Sheffield LJ, Irons M, Gomez EG, Hecht JT, Potocki L, Shaffer L. 2005. Construction of a natural panel of 11p11.2 deletions and further delineation of the critical region involved in Potocki-Shaffer syndrome. Eur J Hum Genet 13:528–540. Whitmarsh AJ, Kuan CY, Kennedy NJ, Kelkar N, Haydar TF, Mordes JP, Appel M, Rossini AA, Jones SN, Flavell RA, Rakic P, Davis RJ. 2001. Requirement of the JIP1 scaffold protein for stress-induced JNK activation. Genes Dev 15:2421–2432. Wieland I, Jakubiczka S, Muschke P, Cohen M, Thiele H, Gerlach KL, Adams RH, Wieacker P. 2004. Mutations of the ephrin-B1 gene cause craniofrontonasal syndrome. Am J Hum Genet 74:1209–1215. Wieland I, Weidner C, Ciccone R, Lapi E, McDonald-McGinn D, Kress W, Jakubiczka S, Collmann H, Zuffardi O, Zackai E, Wieacker P. 2007. Contiguous gene deletions involving EFNB1, OPHN1, PJA1 and EDA in patients with craniofrontonasal syndrome. Clin Genet 72:506–516. Wu YQ, Badano JL, McCaskill C, Vogel H, Potocki L, Shaffer LG. 2000. Haploinsufficiency of ALX4 as a potential cause of parietal foramina in the 11p11.2 contiguous gene-deletion syndrome. Am J Hum Genet 67:1327–1332. Wu E, Vargevik K, Slavotinek AM. 2007. Subtypes of frontonasal dysplasia are useful in determining clinical prognosis. Am J Med Genet Part A 143A:3069–3078.
