J Huazhong Univ Sci Technol [Med Sci] 35(2):316-318,2015 DOI 10.1007/s11596-015-1430-5 J Huazhong Univ Sci Technol［Med Sci］ 35(2):2015
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A Novel HSF4 Mutation in a Chinese Family with Autosomal Dominant Congenital Cataract* Ling LIU (刘 凌), Qing ZHANG (张 晴), Lu-xin ZHOU (周璐昕), Zhao-hui TANG (唐朝晖)# College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China © Huazhong University of Science and Technology and Springer-Verlag Berlin Heidelberg 2015
Summary: This study was aimed to identify the mutation of the whole coding region of shock transcription factor 4 (HSF4) gene in a Chinese family with autosomal dominant congenital cataract (ADCC). All exons of HSF4 were amplified by PCR. Sequence analysis of PCR products was performed. Restriction fragment length polymorphism (RFLP) analysis was conducted to confirm the pathogenic mutation. The results showed that a C to T substitution occurred at nucleotide 331 in patients of this family, leading to the replacement of the amino acid arginine-111 with cysteine in exon 3. RFLP analysis showed that the amino acid change was co-segregated with all affected individuals. It was concluded that the new mutation of c.331C>T in HSF4 DNA may be responsible for the autosomal dominant congenital cataract in this family. Key words: congenital cataract; mutation; heat shock protein transcription factor 4; restriction fragment length polymorphism
Heat shock transcription factor 4 (HSF4) is a member of the heat shock transcription factor family in vertebrates[1, 2]. It is a transcription factor mainly expressed in the eye, and is vital for lens development[3, 4]. In 2002, Bu et al identified HSF4 mutations as a cause of perinuclear cataract[5]. They found four missense mutations in HSF4 in patients of four autosomal dominant congenital cataract families, p.Ala20Asp, p.Ile87Val, p.Leu115Pro, and p.Arg120Cys. These four mutations are all located at the DNA binding domain of the HSF4 protein. Later, we reported in 2006 that the p.Arg74His mutation of HSF4 can also cause autosomal dominant congenital cataract. Moreover, Smaoui et al and Forshe et al discovered that mutations in splicing sites, p.Arg175Pro, c.595_599delGGGCC, and p.Arg450X, are also a cause of congenital cataract[6–9]. HSF4 has two transcripts with different splicing, a and b. Both transcripts lack the carboxyl-terminal hydrophobic repeat domain (HR-C), which can suppress the formation of the homotrimer, allowing for the binding of HSF4 protein with DNA. Studies show that HSF4a is a suppressor of heat shock transcription factor family proteins, while HSF4b activates the expression of heat shock transcription factor proteins[1, 2]. In mouse tissues, HSF4b is the main expression form[2]. The human HSF4 is located at chromosome 16q21-q22.1[1]. The DNA binding site is coded by the first three of its 13 exons, between amino acids 19–123[2]. Most HSF4 mutations known to cause hereditary cataract happen at this area. In this study, we analyzed a Chinese family with autosomal dominant hereditary cataract. By mutational analysis of all the exons of HSF4 in the proband, we discovered a novel missense mutation, c.331C>T (p.Arg111Cys), which was co-segregated with the patients in the pedi-
Ling LIU, E-mail: [email protected] # Corresponding author, E-mail: [email protected] * This work was supported by grants from the National Natural Science Foundation of China (No. 81371064 and No. J1103514).
gree and might be a cause of hereditary cataract in the family. 1 SUBJECTS AND METHODS 1.1 Subjects We studied a family with three generations of hereditary cataract from Hubei province, China. Cataract was inherited in an autosomal dominant manner. The family consisted of 15 members, including 7 males and 8 females. Seven members of the family (4 males and 3 females) were diagnosed as having cataract. Blood was drawn from 13 members of the family (including 6 patients) after written consents were obtained. The pedigree structure of this family is shown in fig. 1A. 1.2 Methods 1.2.1 Extraction of Genomic DNA Genomic DNA was extracted from peripheral blood of all participants. DNA extraction was performed using Wizard DNA Purification Kit (Promega, USA) according to instructions. All DNA were dissolved in TE buffer. DNA quantity and quality were tested using ultraviolet spectrophotometry. DNA samples were stored at –20°C. 1.2.2 DNA Sequence Analysis Primers targeting all exons of HSF4 (NM_001538.3) were designed as previously described[6]. PCR products were purified using QIAquick Gel Extraction Kit (Qiagen Inc., USA) and were sequenced at both directions. Sequences were analyzed using BigDye Terminator Cycle Sequencing v3.1 kit and AMI PRISM 3100 (Applied Biosystems)[10]. 1.2.3 Restriction Fragment Length Polymorphism (RFLP) Analysis The c.331C>T mutation in the third exon of HSF4 destroyed the NotⅠ restriction enzyme cleavage site (GCGGCCGC), making RFLP analysis of patients and normal people possible. The third exon of all members of the family and 103 normal controls was amplified using PCR. The primers used were forward: 5'GTGCGCCAACTCAACATGTGT-3' and reverse: 5'TCCCAGAGATCGCCCATAAG-3'. Resulting se-
J Huazhong Univ Sci Technol［Med Sci］ 35(2):2015
quences were processed with NotⅠ (TaKaRa, Dalian, China) at 37°C for 4 h. Results were detected using 2.5% agarose gel electrophoresis, as reflected in fig. 1B.
317 These findings lend support to the c.331C>T mutation of HSF4 as a possible molecular basis of the hereditary cataract in this family.
2 RESULTS We studied a Chinese cataract family with autosomal dominant hereditary. Six patients and 7 normal members of the family took part in the study. First, we sequenced the whole code region and all of exon-intron boundaries of HSF4 gene and discovered a c.331C>T single nucleotide variant in the DNA binding region of the HSF4. This mutation caused the 111th amino acid of the HSF4 protein to change from arginine to cysteine (fig. 2A). Comparison with available database showed this to be a novel mutation. The c.331C>T mutation of HSF4 caused a 600 bp fragment, resulting in the loss of HSF4 NotⅠ digestion site. Therefore, after NotⅠdigestion, two types of resulting fragments, CC type (199+401 bp) and CT type (600+199+401 bp), would be obtained (fig. 2B). PCRRFLP analysis of the DNA samples of members of the family showed that all of the 6 patients carried this mutation, while the 7 normal members had CC type bands, demonstrating the absence of the c.331C>T mutation. This result indicated that the c.331C>T mutation was cosegregated with the patients in this family (fig. 1). Further RFLP analysis of DNA from 103 normal controls failed to discover the presence of the c.331C>T mutation.
Fig. 1 Pedigree structure of the Chinese family with autosomal dominant congenital cataract and mutation cosegregation with the disorder in the family A: pedigree structure of the Chinese family. Filled squares or filled circles represent individuals suffering from autosomal dominant congenital cataract. The proband (II1) is indicated by an arrow. B: RFLP showing cosegregations of c.331C>T mutation with disease in the cataract family. RFLP analysis of the DNA samples of 6 patients showed 3 bands; the 7 normal members in the family had only 2 bands.
Fig. 2 Identification of a novel heterozygous mutation c.331C>T (p. R111C) of HSF4 in a Chinese cataract family A: DNA sequencing profile around the position c.331C>T. The mutation results in the substitution of cysteine for arginine at 111 residue of HSF4. B: alignment of the amino acid sequences of HSF4 from different species. The R111 residue of HSF4, which is highlighted by red color, is highly conserved during evolution.
3 DISCUSSION We studied a family of hereditary cataract from Hubei province of China. Sequence analysis of the coding region of HSF4 revealed a novel c.331C>T (p.Arg111Cys) missense mutation in the third exon. This mutation was co-segeregated with the phenotype in the family, but it was not found in normal controls. Sequence comparison showed that the Arg111 of HSF4 was highly conservative in mice, bovine, and swine. These results indicate that the p.Arg111Cys missense mutation is the cause of the cataract found in this family.
Our discovery adds one more mutation to the cause of hereditary cataract. In 1988, Eiberg et al mapped the gene responsible for Marner’s cataract to chromosome 16[11]. In 2002, Bu et al found that the T to C mutation at nucleotide 348 of HSF4 caused the mutation of leucine to proline (p.Leu115Pro) within the DNA binding domain, resulting in lamellar cataract[5]. In a Danish family, the C to T mutation of nucleotide 362 caused the mutation p.Arg120Cys and hence Marner’s cataract[5]. Bu et al also discovered the mutations p.Ala20Asp and p.Ile87Val in other cases of cataract[5]. These four mis-
318 sense mutations all happen within the DNA binding domain of HSF4. The p.Arg74His we discovered previously[6] and the p.Arg111Cys mutation described in this study are also located within this area, indicating the vital function of this domain. Heat shock proteins (HSPs) are widely found in the lens. They are involved in protein synthesis, assembly, transportation, folding, reparation and degradation as chaperones. Abnormalities in the structure and function of these proteins cause cataract[12–14]. HSF4 is found to modulate the expression of various HSPs, such as HSP25, HSP70, HSP90a and HSP27. For example, HSP25, which is a regulator in cataract formation, is reduced nearly 80 times when HSF4 is missing. This shows that HSF4 has important functions in maintaining normal lens development and function[15]. The DNA binding domain is a vital domain on the HSF4 protein. The binding of this domain to the HSE of downstream HSPs can regulate the transcription of HSPs. Mutations in this area may obstruct the binding of HSF4 to HSPs, causing HSF4 to lose its ability to activate HSP transcription, in turn affecting the function of HSPs, leading to cataract. The latest findings of our lab showed that HSF4 may be involved in DNA damage repair, and may regulate the disassembly of the nucleus in lens formation by regulating DLAD[16, 17]. The discovery of more disease-causing mutations of HSF4 not only has important applications in genetic diagnosis, but can also provide insight on the study of the normal function of HSF4.
J Huazhong Univ Sci Technol［Med Sci］ 35(2):2015
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Conflict of Interest Statement The authors declare that there is no conflict of interest with any financial organization or corporation or individual that can inappropriately influence this work. REFERENCE 1 Nakai A,Tanabe M, Kawazoe Y, et al. HSF4, a new member of the human heat shock factor family which lacks properties of a transcriptional activator. Mol Cell Biol, 1997,17(1):469-481 2 Tanabe M, Sasai N, Nagata K, et al. The mammalian HSF4 gene generates both an activator and a repressor of heat shock genes by alternative splicing. J Biol Chem, 1999,274(39):27845-27856 3 Bagchi M, Ireland M, Katar M, et al. Heat shock proteins of chicken lens. J Cell Biochem, 2001,82(3):409-414
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Bagchi M, Katar M, Maisel H. Heat shock proteins of adult and embryonic human ocular lenses. J Cell Biochem, 2002,84(2):278-284 Bu L, Jin Y, Shi Y, et al. Mutant DNA-binding domain of HSF4 is associated with autosomal dominant lamellar and Marner cataract. Nat Genet, 2002,31(3):276-278 Ke T, Wang QK, Ji B, et al. Novel HSF4 mutation causes congenital total white cataract in a Chinese family. Am J Ophthalmol, 2006,142(2):298-303 Smaoui N, Beltaief O, BenHamed S, et al. A homozygous splice mutation in the HSF4 gene is associated with an autosomal recessive congenital cataract. Invest Ophthalmol Vis Sci, 2004,45(8):2716-2721 Forshe T, Johnson CA, Khaliq S, et al. Locus heterogeneity in autosomal recessive congenital cataracts: linkage to 9q and germline HSF4 mutations. Hum Genet, 2005,117(5): 452-459 Sajjad N, Goebel I, Kakar N, et al. A novel HSF4 gene mutation (p.R405X) causing autosomal recessive congenital cataracts in a large consanguineous family from Pakistan. BMC Med Genet, 2008,9:99 Wang Q, Liu M, Xu C, et al. Novel CACNA1S mutation causes autosomal dominant hypokalemic periodic paralysis in a Chinese family. J Mol Med, 2005,83(3):203-208 Eiberg H, Marner E, Rosenberg T, et al. Marner’s cataract (CAM) assigned to chromosome 16: linkage to haptoglobin. Clin Genet, 1988,34(4):272-275 Hartl FU. Molecular chaperones in cellular protein folding. Nature, 1996,381(6583):571-579 Bukau B, Horwich AL. The Hsp70 and Hsp60 chaperone machines. Cell, 1998,92(3):351-366 Berry V, Francis P, Reddy MA, et al. Alpha-B crystallin gene (CRYAB) mutation causes dominant congenital posterior polar cataract in humans. Am J Hum Genet, 2001,69(5):1141-1145 Min JN, Zhang Y, Moskophidis D, et al. Unique contribution of heat shock transcription factor 4 in ocular lens development and fiber cell differentiation. Genesi, 2004,40(4):205-217 Cui X, Zhang J, Du R, et al. HSF4 is involved in DNA damage repair through regulation of Rad51. Biochim Biophys Acta, 2012,1822(8):1308-1315 Cui X, Wang L, Zhang J, et al. HSF4 regulates DLAD expression and promotes lens de-nucleation. Biochim Biophys Acta, 2013,1832(8):1167-1172 (Received Jun. 17, 2014; revised Oct. 24, 2014)
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A Novel HSF4 Mutation in a Chinese Family with Autosomal Dominant Congenital Cataract* Ling LIU (刘 凌), Qing ZHANG (张 晴), Lu-xin ZHOU (周璐昕), Zhao-hui TANG (唐朝晖)# College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China © Huazhong University of Science and Technology and Springer-Verlag Berlin Heidelberg 2015
Summary: This study was aimed to identify the mutation of the whole coding region of shock transcription factor 4 (HSF4) gene in a Chinese family with autosomal dominant congenital cataract (ADCC). All exons of HSF4 were amplified by PCR. Sequence analysis of PCR products was performed. Restriction fragment length polymorphism (RFLP) analysis was conducted to confirm the pathogenic mutation. The results showed that a C to T substitution occurred at nucleotide 331 in patients of this family, leading to the replacement of the amino acid arginine-111 with cysteine in exon 3. RFLP analysis showed that the amino acid change was co-segregated with all affected individuals. It was concluded that the new mutation of c.331C>T in HSF4 DNA may be responsible for the autosomal dominant congenital cataract in this family. Key words: congenital cataract; mutation; heat shock protein transcription factor 4; restriction fragment length polymorphism
Heat shock transcription factor 4 (HSF4) is a member of the heat shock transcription factor family in vertebrates[1, 2]. It is a transcription factor mainly expressed in the eye, and is vital for lens development[3, 4]. In 2002, Bu et al identified HSF4 mutations as a cause of perinuclear cataract[5]. They found four missense mutations in HSF4 in patients of four autosomal dominant congenital cataract families, p.Ala20Asp, p.Ile87Val, p.Leu115Pro, and p.Arg120Cys. These four mutations are all located at the DNA binding domain of the HSF4 protein. Later, we reported in 2006 that the p.Arg74His mutation of HSF4 can also cause autosomal dominant congenital cataract. Moreover, Smaoui et al and Forshe et al discovered that mutations in splicing sites, p.Arg175Pro, c.595_599delGGGCC, and p.Arg450X, are also a cause of congenital cataract[6–9]. HSF4 has two transcripts with different splicing, a and b. Both transcripts lack the carboxyl-terminal hydrophobic repeat domain (HR-C), which can suppress the formation of the homotrimer, allowing for the binding of HSF4 protein with DNA. Studies show that HSF4a is a suppressor of heat shock transcription factor family proteins, while HSF4b activates the expression of heat shock transcription factor proteins[1, 2]. In mouse tissues, HSF4b is the main expression form[2]. The human HSF4 is located at chromosome 16q21-q22.1[1]. The DNA binding site is coded by the first three of its 13 exons, between amino acids 19–123[2]. Most HSF4 mutations known to cause hereditary cataract happen at this area. In this study, we analyzed a Chinese family with autosomal dominant hereditary cataract. By mutational analysis of all the exons of HSF4 in the proband, we discovered a novel missense mutation, c.331C>T (p.Arg111Cys), which was co-segregated with the patients in the pedi-
Ling LIU, E-mail: [email protected] # Corresponding author, E-mail: [email protected] * This work was supported by grants from the National Natural Science Foundation of China (No. 81371064 and No. J1103514).
gree and might be a cause of hereditary cataract in the family. 1 SUBJECTS AND METHODS 1.1 Subjects We studied a family with three generations of hereditary cataract from Hubei province, China. Cataract was inherited in an autosomal dominant manner. The family consisted of 15 members, including 7 males and 8 females. Seven members of the family (4 males and 3 females) were diagnosed as having cataract. Blood was drawn from 13 members of the family (including 6 patients) after written consents were obtained. The pedigree structure of this family is shown in fig. 1A. 1.2 Methods 1.2.1 Extraction of Genomic DNA Genomic DNA was extracted from peripheral blood of all participants. DNA extraction was performed using Wizard DNA Purification Kit (Promega, USA) according to instructions. All DNA were dissolved in TE buffer. DNA quantity and quality were tested using ultraviolet spectrophotometry. DNA samples were stored at –20°C. 1.2.2 DNA Sequence Analysis Primers targeting all exons of HSF4 (NM_001538.3) were designed as previously described[6]. PCR products were purified using QIAquick Gel Extraction Kit (Qiagen Inc., USA) and were sequenced at both directions. Sequences were analyzed using BigDye Terminator Cycle Sequencing v3.1 kit and AMI PRISM 3100 (Applied Biosystems)[10]. 1.2.3 Restriction Fragment Length Polymorphism (RFLP) Analysis The c.331C>T mutation in the third exon of HSF4 destroyed the NotⅠ restriction enzyme cleavage site (GCGGCCGC), making RFLP analysis of patients and normal people possible. The third exon of all members of the family and 103 normal controls was amplified using PCR. The primers used were forward: 5'GTGCGCCAACTCAACATGTGT-3' and reverse: 5'TCCCAGAGATCGCCCATAAG-3'. Resulting se-
J Huazhong Univ Sci Technol［Med Sci］ 35(2):2015
quences were processed with NotⅠ (TaKaRa, Dalian, China) at 37°C for 4 h. Results were detected using 2.5% agarose gel electrophoresis, as reflected in fig. 1B.
317 These findings lend support to the c.331C>T mutation of HSF4 as a possible molecular basis of the hereditary cataract in this family.
2 RESULTS We studied a Chinese cataract family with autosomal dominant hereditary. Six patients and 7 normal members of the family took part in the study. First, we sequenced the whole code region and all of exon-intron boundaries of HSF4 gene and discovered a c.331C>T single nucleotide variant in the DNA binding region of the HSF4. This mutation caused the 111th amino acid of the HSF4 protein to change from arginine to cysteine (fig. 2A). Comparison with available database showed this to be a novel mutation. The c.331C>T mutation of HSF4 caused a 600 bp fragment, resulting in the loss of HSF4 NotⅠ digestion site. Therefore, after NotⅠdigestion, two types of resulting fragments, CC type (199+401 bp) and CT type (600+199+401 bp), would be obtained (fig. 2B). PCRRFLP analysis of the DNA samples of members of the family showed that all of the 6 patients carried this mutation, while the 7 normal members had CC type bands, demonstrating the absence of the c.331C>T mutation. This result indicated that the c.331C>T mutation was cosegregated with the patients in this family (fig. 1). Further RFLP analysis of DNA from 103 normal controls failed to discover the presence of the c.331C>T mutation.
Fig. 1 Pedigree structure of the Chinese family with autosomal dominant congenital cataract and mutation cosegregation with the disorder in the family A: pedigree structure of the Chinese family. Filled squares or filled circles represent individuals suffering from autosomal dominant congenital cataract. The proband (II1) is indicated by an arrow. B: RFLP showing cosegregations of c.331C>T mutation with disease in the cataract family. RFLP analysis of the DNA samples of 6 patients showed 3 bands; the 7 normal members in the family had only 2 bands.
Fig. 2 Identification of a novel heterozygous mutation c.331C>T (p. R111C) of HSF4 in a Chinese cataract family A: DNA sequencing profile around the position c.331C>T. The mutation results in the substitution of cysteine for arginine at 111 residue of HSF4. B: alignment of the amino acid sequences of HSF4 from different species. The R111 residue of HSF4, which is highlighted by red color, is highly conserved during evolution.
3 DISCUSSION We studied a family of hereditary cataract from Hubei province of China. Sequence analysis of the coding region of HSF4 revealed a novel c.331C>T (p.Arg111Cys) missense mutation in the third exon. This mutation was co-segeregated with the phenotype in the family, but it was not found in normal controls. Sequence comparison showed that the Arg111 of HSF4 was highly conservative in mice, bovine, and swine. These results indicate that the p.Arg111Cys missense mutation is the cause of the cataract found in this family.
Our discovery adds one more mutation to the cause of hereditary cataract. In 1988, Eiberg et al mapped the gene responsible for Marner’s cataract to chromosome 16[11]. In 2002, Bu et al found that the T to C mutation at nucleotide 348 of HSF4 caused the mutation of leucine to proline (p.Leu115Pro) within the DNA binding domain, resulting in lamellar cataract[5]. In a Danish family, the C to T mutation of nucleotide 362 caused the mutation p.Arg120Cys and hence Marner’s cataract[5]. Bu et al also discovered the mutations p.Ala20Asp and p.Ile87Val in other cases of cataract[5]. These four mis-
318 sense mutations all happen within the DNA binding domain of HSF4. The p.Arg74His we discovered previously[6] and the p.Arg111Cys mutation described in this study are also located within this area, indicating the vital function of this domain. Heat shock proteins (HSPs) are widely found in the lens. They are involved in protein synthesis, assembly, transportation, folding, reparation and degradation as chaperones. Abnormalities in the structure and function of these proteins cause cataract[12–14]. HSF4 is found to modulate the expression of various HSPs, such as HSP25, HSP70, HSP90a and HSP27. For example, HSP25, which is a regulator in cataract formation, is reduced nearly 80 times when HSF4 is missing. This shows that HSF4 has important functions in maintaining normal lens development and function[15]. The DNA binding domain is a vital domain on the HSF4 protein. The binding of this domain to the HSE of downstream HSPs can regulate the transcription of HSPs. Mutations in this area may obstruct the binding of HSF4 to HSPs, causing HSF4 to lose its ability to activate HSP transcription, in turn affecting the function of HSPs, leading to cataract. The latest findings of our lab showed that HSF4 may be involved in DNA damage repair, and may regulate the disassembly of the nucleus in lens formation by regulating DLAD[16, 17]. The discovery of more disease-causing mutations of HSF4 not only has important applications in genetic diagnosis, but can also provide insight on the study of the normal function of HSF4.
J Huazhong Univ Sci Technol［Med Sci］ 35(2):2015
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Conflict of Interest Statement The authors declare that there is no conflict of interest with any financial organization or corporation or individual that can inappropriately influence this work. REFERENCE 1 Nakai A,Tanabe M, Kawazoe Y, et al. HSF4, a new member of the human heat shock factor family which lacks properties of a transcriptional activator. Mol Cell Biol, 1997,17(1):469-481 2 Tanabe M, Sasai N, Nagata K, et al. The mammalian HSF4 gene generates both an activator and a repressor of heat shock genes by alternative splicing. J Biol Chem, 1999,274(39):27845-27856 3 Bagchi M, Ireland M, Katar M, et al. Heat shock proteins of chicken lens. J Cell Biochem, 2001,82(3):409-414
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Bagchi M, Katar M, Maisel H. Heat shock proteins of adult and embryonic human ocular lenses. J Cell Biochem, 2002,84(2):278-284 Bu L, Jin Y, Shi Y, et al. Mutant DNA-binding domain of HSF4 is associated with autosomal dominant lamellar and Marner cataract. Nat Genet, 2002,31(3):276-278 Ke T, Wang QK, Ji B, et al. Novel HSF4 mutation causes congenital total white cataract in a Chinese family. Am J Ophthalmol, 2006,142(2):298-303 Smaoui N, Beltaief O, BenHamed S, et al. A homozygous splice mutation in the HSF4 gene is associated with an autosomal recessive congenital cataract. Invest Ophthalmol Vis Sci, 2004,45(8):2716-2721 Forshe T, Johnson CA, Khaliq S, et al. Locus heterogeneity in autosomal recessive congenital cataracts: linkage to 9q and germline HSF4 mutations. Hum Genet, 2005,117(5): 452-459 Sajjad N, Goebel I, Kakar N, et al. A novel HSF4 gene mutation (p.R405X) causing autosomal recessive congenital cataracts in a large consanguineous family from Pakistan. BMC Med Genet, 2008,9:99 Wang Q, Liu M, Xu C, et al. Novel CACNA1S mutation causes autosomal dominant hypokalemic periodic paralysis in a Chinese family. J Mol Med, 2005,83(3):203-208 Eiberg H, Marner E, Rosenberg T, et al. Marner’s cataract (CAM) assigned to chromosome 16: linkage to haptoglobin. Clin Genet, 1988,34(4):272-275 Hartl FU. Molecular chaperones in cellular protein folding. Nature, 1996,381(6583):571-579 Bukau B, Horwich AL. The Hsp70 and Hsp60 chaperone machines. Cell, 1998,92(3):351-366 Berry V, Francis P, Reddy MA, et al. Alpha-B crystallin gene (CRYAB) mutation causes dominant congenital posterior polar cataract in humans. Am J Hum Genet, 2001,69(5):1141-1145 Min JN, Zhang Y, Moskophidis D, et al. Unique contribution of heat shock transcription factor 4 in ocular lens development and fiber cell differentiation. Genesi, 2004,40(4):205-217 Cui X, Zhang J, Du R, et al. HSF4 is involved in DNA damage repair through regulation of Rad51. Biochim Biophys Acta, 2012,1822(8):1308-1315 Cui X, Wang L, Zhang J, et al. HSF4 regulates DLAD expression and promotes lens de-nucleation. Biochim Biophys Acta, 2013,1832(8):1167-1172 (Received Jun. 17, 2014; revised Oct. 24, 2014)
