Cell Stem Cell
Previews metabolism, which was reverted by antisense oligonucleotides to target C9orf72 mRNA. Taken together, these studies reveal that iPSC-derived motoneurons from ALS patients develop common pathological features resembling early stages of the disease that could be used to test novel therapeutic strategies, and they support the occurrence of an intrinsic vulnerability to stress. They also caution that the appearance of morphological changes does not always culminate in motoneuron loss. These reports additionally suggest a substantial prevalence of gain-of-toxic and cell-autonomous mechanisms of neurodegeneration in ALS. The current studies illustrate that the use of combinatorial approaches to study iPSC-derived motoneurons offers a well-controlled cell culture model of ALS. The identification of robust and inherited morphological, biochemical, and electrophysiological phenotypes in iPSC-derived neurons supports and sometimes contrasts with the well-established animal models of the disease and will open the possibility of developing
novel drug screenings with therapeutic potential and the identification of novel biomarkers of ALS. These advances will also facilitate the future generation of personalized medicine through the testing of drugs to alleviate selective pathological events that may be unique to the specific genetic landscape of each patient, opening important avenues for the treatment of this fatal disease.
Chen, H., Qian, K., Du, Z., Cao, J., Petersen, A., Liu, H., Blackbourn, L.W.t., Huang, C.L., Errigo, A., Yin, Y., et al. (2014). Cell Stem Cell 14, this issue, 796–809. Donnelly, C.J., Zhang, P.W., Pham, J.T., Heusler, A.R., Mistry, N.A., Vidensky, S., Daley, E.L., Poth, E.M., Hoover, B., Fines, D.M., et al. (2013). Neuron 80, 415–428. Egawa, N., Kitaoka, S., Tsukita, K., Naitoh, M., Takahashi, K., Yamamoto, T., Adachi, F., Kondo, T., Okita, K., Asaka, I., et al. (2012). Sci Transl Med 4, 145ra104. Hetz, C., and Mollereau, B. (2014). Nat. Rev. Neurosci. 15, 233–249.
ACKNOWLEDGMENTS The authors are supported by P09-015-F, FONDECYT 1100176, ALS Therapy Alliance, Muscular Dystrophy Association, FONDEF D11I1007, and ACT1109 grants (C.H.), FONDECYT 11121524 (S.M.), and 3130351 (D.M.).
REFERENCES
Kiskinis, E., Sandoe, J., Williams, L.A., Boulting, G.L., Moccia, R., Wainger, B.J., Han, S., Peng, T., Thams, S., Mikkilineni, S., et al. (2014). Cell Stem Cell 14, this issue, 781–795. Sareen, D., O’Rourke, J.G., Meera, P., Muhammad, A.K., Grant, S., Simpkinson, M., Bell, S., Carmona, S., Ornelas, L., Sahabian, A., et al. (2013). Sci Transl Med 5, 208ra149.
Bilican, B., Serio, A., Barmada, S.J., Nishimura, A.L., Sullivan, G.J., Carrasco, M., Phatnani, H.P., Puddifoot, C.A., Story, D., Fletcher, J., et al. (2012). Proc. Natl. Acad. Sci. USA 109, 5803–5808.
Wainger, B.J., Kiskinis, E., Mellin, C., Wiskow, O., Han, S.S., Sandoe, J., Perez, N.P., Williams, L.A., Lee, S., Boulting, G., et al. (2014). Cell Rep. 7, 1–11.
Burkhardt, M.F., Martinez, F.J., Wright, S., Ramos, C., Volfson, D., Mason, M., Garnes, J., Dang, V., Lievers, J., Shoukat-Mumtaz, U., et al. (2013). Mol. Cell. Neurosci. 56, 355–364.
Yang, Y.M., Gupta, S.K., Kim, K.J., Powers, B.E., Cerqueira, A., Wainger, B.J., Ngo, H.D., Rosowski, K.A., Schein, P.A., Ackeifi, C.A., et al. (2013). Cell Stem Cell 12, 713–726.
Human Somatic Cell Nuclear Transfer Is Alive and Well Jose B. Cibelli1,2,* 1Departments
of Physiology and Animal Science, Michigan State University, East Lansing, MI, 48834, USA BIONAND, 29590 Campanillas, Ma´laga, Spain *Correspondence: [email protected] http://dx.doi.org/10.1016/j.stem.2014.05.013 2LARCel,
In this issue, Chung et al. (2014) generate human embryonic stem cells by fusing an adult somatic cell to a previously enucleated human oocyte, in agreement with recent reports by the Mitalipov and Egli groups. We can now safely say that human somatic cell nuclear transfer is alive and well. Last year, the group led by Shoukhrat Mitalipov published, for the first time, their success in generating hESCs using cloned human embryos (Tachibana et al., 2013). The field of SCNT, launched by Dolly in 1997, has since been developed by the successful cloning of more than twenty different mammalian species. Using hSCNT to generate hESCs, however, turned out to be more challenging (Cibelli et al., 2001; Fan et al., 2011; French et al., 2008; Noggle et al., 2011; Stojkovic
et al., 2005). Mitalipov’s group spent a significant amount of time refining SCNT, first with monkeys and then with humans. As a result, we now know how to overcome some fundamental roadblocks. The study by Chung et al. (2014), published in this issue along with a recently published paper by Yamada et al. (2014), brings to light fundamental aspects of hSCNT, reasserting this technique as a powerful research and therapeutic tool (Chung et al., 2014; Yamada et al., 2014).
Prior to the publication of this work and based on studies comparing donor nuclei from ESCs with those of somatic cells, there was a general notion that less differentiated cells would serve as better sources of donor nuclei. Chung et al.(2104) successfully dedifferentiated somatic cells from a 75-year-old donor, which is a landmark achievement that refutes the hypothesis that cells from an older individual are harder to dedifferentiate. Borrowing from half a century’s
Cell Stem Cell 14, June 5, 2014 ª2014 Elsevier Inc. 699
Cell Stem Cell
Previews
worth of data on SCNT in for humans and bovines, mammals, we can safely say 2 hr is the Goldilocks point— that the biological age of the not immediately after fusion, nuclear donor will not be a not 4 hr after—somewhere limitation when it comes around 2 hr works best (Liu to making autologous ESCs et al., 2013). If this is so, how by SCNT in humans. It recould Tachibana et al. (2013) mains to be determined if and Yamada et al. (2014) the variability on resistance generate cloned blastocysts to nuclear reprogramming worthy of hESC isolation observed in animal studies without waiting 2 hr? The between and within donor answer to this riddle seems cell types will influence the to be in the use of histone efficiency of the procedure. deacetylase inhibitors. It was A successful SCNT procerecently reported that rDNA dure, measured by the numis not properly reactivated in ber of blastocysts or ESCs the genome of the somatic Figure 1. Streamlined Process for Somatic Cell Nuclear Transfer produced, depends on multicell and that this is directly with Human Cells ple factors. Among the most linked to histone acetylation. A list of steps that enabled a higher efficiency of the SCNT process in human. Prior to 2013, these factors were individually tested in animal protocols. Idenimportant are oocyte quality, The more quickly and effitifying oocyte donors with oocytes endowed with the highest epigenetic power type of enucleation used, ciently a pattern of embryonic to reprogram a somatic cell nucleus should be the next priority. If oocytes with cell fusion, oocyte activation, acetylated histones is estabthe described conditions were readily available, multiple autologous-ESC lines could be produced by a single donor. time of oocyte activation, cullished, the greater the chanture medium, and type and ces for normal development. cell cycle stage of the donor It turns out that adding histone nucleus. The final efficiency is equal to In most species, and humans are no deacetylase inhibitors such as Trichosthe cumulative efficiency of each step. exception, the oocyte cannot divide by tatin A or scriptaid, a step that was Once Tachibana et al. (2013) established itself without fertilization. Special proce- included in all three hSCNT-ESC reports, the protocol, Chung et al. (2014) were dures are implemented during SCNT can facilitate this process (Zheng et al., able to dispel the notion that the human to trigger embryonic development. The 2012). It will be interesting to learn whether egg was somehow deficient on two cen- challenge is to establish the most suitable waiting 2 hr after fusion to activate the trosomal proteins and was inducing time point after fusion of the somatic cell egg, without using these compounds, aneuploidy in the embryos. They then at which to activate development. Trig- will yield high quality blastocysts as well. Which is the SCNT variable, off all the honed in on the time of activation after gering the activation of an MII oocyte fusion and demonstrated that waiting simultaneously with fusion is detrimental ones analyzed by these three excellent 2 hr is ideal. Their findings show that a to embryonic development. It is better to manuscripts, that matters the most? fundamental variable determining the ‘‘marinate’’ the nucleus in an oocyte’s Where should we center our research outcome of the procedure is the oocyte’s cytosol before inducing egg activation. efforts? Identifying and characterizing cytosol and that only cohorts donated by Chung et al. (2014) built upon the method the oocyte’s cytosol with the strongest some women shared such favorable reported by Mitalipov’s group (Tachibana epigenetic power to reprogram a somatic cytosol. Independently of the age of the et al., 2013), demonstrating that the ideal cell nucleus must be our next priority somatic cell donor and of the period of period is 2 hr. According to the results (Figure 1). In hindsight, the idea that time preceding activation of the recon- reported in this issue, we can expect oocytes vary in this regard is not new. It structed oocytes, the oocyte cytosol that more blastocysts of better quality — was first reported in 1991 by Latham and from three of the seven women who hatched and with a robust inner cell Solter, who performed pronuclear exchanges between fertilized oocytes using donated oocytes best supported embry- mass — will be produced. onic development and ESC derivation. In trying to explain some of the differ- different strains of mice, but this process This was suggested by Tachibana et al. ences that arise from fusing and activat- was never tested in humans (Latham and (2013)—eight oocytes donated by a ing the somatic cell at different times, Solter, 1991). Yamada et al. (2014) and Tasingle woman produced four SCNT- we must look closely at the early re- chibana et al. (2013) made some strides in ESCs—and the current publication now programming events during SCNT. As the right direction by showing correlations confirms it. Yamada et al. (2014) also soon as the somatic cell nucleus comes between the hormonal regime used and contribute more evidence that the into contact with the MII oocyte’s cytosol, oocyte donor age with the developmental oocyte cytosol is a major variable and nuclear envelope breakdown and chro- potential of the oocytes; however, they point out that we must be extremely matin condensation begin. Given enough also presented contradictory evidence careful during cell fusion not to induce time, these early nuclear remodeling about the importance of the number of premature activation in the egg, a step events work in favor of somatic cell oocytes recovered per superovulation that was considered innocuous prior to dedifferentiation, but only to a point — cycle. For Tachibana et al. (2013), fewer their work. and how much is enough? Apparently, oocytes yielded better quality embryos, 700 Cell Stem Cell 14, June 5, 2014 ª2014 Elsevier Inc.
Cell Stem Cell
Previews whereas Yamada et al. (2014) could not replicate the finding—one hSCNT-ESC line was derived from an oocyte that was picked from among 31 oocytes donated at once by a single donor. Overall, these data indicate that the oocyte cytosols of different women differ in important ways that go beyond the donors’ ages. Finding the specific reason why some women have better cytosol than others could have a huge impact in the reprograming field and, more importantly, in the evergrowing field of human-assisted reproductive technologies. To find the answers, though, we will have to rely on SCNT, a technique in which at least one variable, the genomic DNA, is fixed; only then can we really test the reprograming potential of oocyte-cytosols from different women. Human SCNT, a technique that not so long ago was considered passe´, is now
back in the toolbox; this time, at least for the task of finding the best human egg, it will not be replaced by induced pluripotent stem cells. REFERENCES
Liu, J., Wang, Y., Su, J., Wang, L., Li, R., Li, Q., Wu, Y., Hua, S., Quan, F., Guo, Z., and Zhang, Y. (2013). Cell Reprogram 15, 134–142. Noggle, S., Fung, H.L., Gore, A., Martinez, H., Satriani, K.C., Prosser, R., Oum, K., Paull, D., Druckenmiller, S., Freeby, M., et al. (2011). Nature 478, 70–75.
Chung, Y.G., Eum, J.H., Lee, J.E., Shim, S.H., Sepilian, V., Hong, S.W., Lee, Y., Treff, N.R., Choi, Y.H., Kimbrel, E.A., et al. (2014). Cell Stem Cell 14, this issue, 777–780.
Stojkovic, M., Stojkovic, P., Leary, C., Hall, V.J., Armstrong, L., Herbert, M., Nesbitt, M., Lako, M., and Murdoch, A. (2005). Reprod. Biomed. Online 11, 226–231.
Cibelli, J.B., Kiessling, A.A., Cunniff, K., Richards, C., Lanza, R.P., and West, M.D. (2001). e-biomed: the Journal of Regenerative Medicine 2, 26–31, http://dx.doi.org/10.1089/152489001753262168.
Tachibana, M., Amato, P., Sparman, M., Gutierrez, N.M., Tippner-Hedges, R., Ma, H., Kang, E., Fulati, A., Lee, H.-S., Sritanaudomchai, H., et al. (2013). Cell 153, 1228–1238.
Fan, Y.Y., Jiang, Y.Y., Chen, X.X., Ou, Z.Z., Yin, Y.Y., Huang, S.S., Kou, Z.Z., Li, Q.Q., Long, X.X., Liu, J.J., et al. (2011). Stem Cells Dev. 20, 1951–1959. French, A.J., Adams, C.A., Anderson, L.S., Kitchen, J.R., Hughes, M.R., and Wood, S.H. (2008). Stem Cells 26, 485–493. Latham, K.E., and Solter, D. (1991). Development 113, 561–568.
Yamada, M., Johannesson, B., Sagi, I., Burnett, L.C., Kort, D.H., Prosser, R.W., Paull, D., Nestor, M.W., Freeby, M., Greenberg, E., et al. (2014). Nature. Published online April 28, 2014. Zheng, Z., Jia, J.L., Bou, G., Hu, L.L., Wang, Z.D., Shen, X.H., Shan, Z.Y., Shen, J.L., Liu, Z.H., and Lei, L. (2012). J. Biol. Chem. 287, 19949–19960.
Stem Cells Go Soft: Pliant Substrate Surfaces Enhance Motor Neuron Differentiation Ning Wang1,2,* 1Department of Biomedical Engineering, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China 2Department of Mechanical Science and Engineering, College of Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA *Correspondence: [email protected] http://dx.doi.org/10.1016/j.stem.2014.05.007
Derivation of motor neurons from human pluripotent stem cells is inefficient and requires complex culture protocols. Recently in Nature Materials, Sun et al. (2014) report that differentiating human pluripotent stem cells on soft substrates increases the efficiency of mature motor neuron differentiation by altering cytoskeletal mechanotransduction through the Hippo/YAP/Smad pathway. Efficient derivation of motor neurons (MNs) from human pluripotent stem cells (hPSCs) is limited by our current understanding of the mechanisms underlying MN differentiation as well as drawbacks arising from inefficient and lengthy existing protocols. Human MNs derived from in vitro cultures can be used for cellular mechanistic studies as well as in vivo studies testing cell replacement strategies and modeling human disease in animal models, with the ultimate goal of replacing dysfunctional MNs in degenera-
tive disorders like amyotrophic lateral sclerosis. To enhance MN differentiation and surmount some of these existing difficulties, Jianping Fu and colleagues (Sun et al., 2014) developed a mechanical platform that enhances differentiation efficiency of hPSCs into MNs by >4-fold and significantly shortens the time period required for MN maturation. This platform capitalizes on advances using micromolded poly-(dimethylsiloxane) (PDMS) micropost arrays (PMAs) to culture cells (Fu et al., 2010). PDMS is
widely used to construct microscale devices for cell culture and microfluidic applications (Fu et al., 2010). PDMS surfaces are continuous and thus cannot change rigidity without altering other characteristics of the material. In contrast, PMAs have a constant surface geometry whose rigidity is varied by adjusting heights of isolated microposts to cover the stiffness range exhibited by soft tissues without altering the contact area available for cell-matrix interactions or tethering of cell-surface integrins to
Cell Stem Cell 14, June 5, 2014 ª2014 Elsevier Inc. 701
Previews metabolism, which was reverted by antisense oligonucleotides to target C9orf72 mRNA. Taken together, these studies reveal that iPSC-derived motoneurons from ALS patients develop common pathological features resembling early stages of the disease that could be used to test novel therapeutic strategies, and they support the occurrence of an intrinsic vulnerability to stress. They also caution that the appearance of morphological changes does not always culminate in motoneuron loss. These reports additionally suggest a substantial prevalence of gain-of-toxic and cell-autonomous mechanisms of neurodegeneration in ALS. The current studies illustrate that the use of combinatorial approaches to study iPSC-derived motoneurons offers a well-controlled cell culture model of ALS. The identification of robust and inherited morphological, biochemical, and electrophysiological phenotypes in iPSC-derived neurons supports and sometimes contrasts with the well-established animal models of the disease and will open the possibility of developing
novel drug screenings with therapeutic potential and the identification of novel biomarkers of ALS. These advances will also facilitate the future generation of personalized medicine through the testing of drugs to alleviate selective pathological events that may be unique to the specific genetic landscape of each patient, opening important avenues for the treatment of this fatal disease.
Chen, H., Qian, K., Du, Z., Cao, J., Petersen, A., Liu, H., Blackbourn, L.W.t., Huang, C.L., Errigo, A., Yin, Y., et al. (2014). Cell Stem Cell 14, this issue, 796–809. Donnelly, C.J., Zhang, P.W., Pham, J.T., Heusler, A.R., Mistry, N.A., Vidensky, S., Daley, E.L., Poth, E.M., Hoover, B., Fines, D.M., et al. (2013). Neuron 80, 415–428. Egawa, N., Kitaoka, S., Tsukita, K., Naitoh, M., Takahashi, K., Yamamoto, T., Adachi, F., Kondo, T., Okita, K., Asaka, I., et al. (2012). Sci Transl Med 4, 145ra104. Hetz, C., and Mollereau, B. (2014). Nat. Rev. Neurosci. 15, 233–249.
ACKNOWLEDGMENTS The authors are supported by P09-015-F, FONDECYT 1100176, ALS Therapy Alliance, Muscular Dystrophy Association, FONDEF D11I1007, and ACT1109 grants (C.H.), FONDECYT 11121524 (S.M.), and 3130351 (D.M.).
REFERENCES
Kiskinis, E., Sandoe, J., Williams, L.A., Boulting, G.L., Moccia, R., Wainger, B.J., Han, S., Peng, T., Thams, S., Mikkilineni, S., et al. (2014). Cell Stem Cell 14, this issue, 781–795. Sareen, D., O’Rourke, J.G., Meera, P., Muhammad, A.K., Grant, S., Simpkinson, M., Bell, S., Carmona, S., Ornelas, L., Sahabian, A., et al. (2013). Sci Transl Med 5, 208ra149.
Bilican, B., Serio, A., Barmada, S.J., Nishimura, A.L., Sullivan, G.J., Carrasco, M., Phatnani, H.P., Puddifoot, C.A., Story, D., Fletcher, J., et al. (2012). Proc. Natl. Acad. Sci. USA 109, 5803–5808.
Wainger, B.J., Kiskinis, E., Mellin, C., Wiskow, O., Han, S.S., Sandoe, J., Perez, N.P., Williams, L.A., Lee, S., Boulting, G., et al. (2014). Cell Rep. 7, 1–11.
Burkhardt, M.F., Martinez, F.J., Wright, S., Ramos, C., Volfson, D., Mason, M., Garnes, J., Dang, V., Lievers, J., Shoukat-Mumtaz, U., et al. (2013). Mol. Cell. Neurosci. 56, 355–364.
Yang, Y.M., Gupta, S.K., Kim, K.J., Powers, B.E., Cerqueira, A., Wainger, B.J., Ngo, H.D., Rosowski, K.A., Schein, P.A., Ackeifi, C.A., et al. (2013). Cell Stem Cell 12, 713–726.
Human Somatic Cell Nuclear Transfer Is Alive and Well Jose B. Cibelli1,2,* 1Departments
of Physiology and Animal Science, Michigan State University, East Lansing, MI, 48834, USA BIONAND, 29590 Campanillas, Ma´laga, Spain *Correspondence: [email protected] http://dx.doi.org/10.1016/j.stem.2014.05.013 2LARCel,
In this issue, Chung et al. (2014) generate human embryonic stem cells by fusing an adult somatic cell to a previously enucleated human oocyte, in agreement with recent reports by the Mitalipov and Egli groups. We can now safely say that human somatic cell nuclear transfer is alive and well. Last year, the group led by Shoukhrat Mitalipov published, for the first time, their success in generating hESCs using cloned human embryos (Tachibana et al., 2013). The field of SCNT, launched by Dolly in 1997, has since been developed by the successful cloning of more than twenty different mammalian species. Using hSCNT to generate hESCs, however, turned out to be more challenging (Cibelli et al., 2001; Fan et al., 2011; French et al., 2008; Noggle et al., 2011; Stojkovic
et al., 2005). Mitalipov’s group spent a significant amount of time refining SCNT, first with monkeys and then with humans. As a result, we now know how to overcome some fundamental roadblocks. The study by Chung et al. (2014), published in this issue along with a recently published paper by Yamada et al. (2014), brings to light fundamental aspects of hSCNT, reasserting this technique as a powerful research and therapeutic tool (Chung et al., 2014; Yamada et al., 2014).
Prior to the publication of this work and based on studies comparing donor nuclei from ESCs with those of somatic cells, there was a general notion that less differentiated cells would serve as better sources of donor nuclei. Chung et al.(2104) successfully dedifferentiated somatic cells from a 75-year-old donor, which is a landmark achievement that refutes the hypothesis that cells from an older individual are harder to dedifferentiate. Borrowing from half a century’s
Cell Stem Cell 14, June 5, 2014 ª2014 Elsevier Inc. 699
Cell Stem Cell
Previews
worth of data on SCNT in for humans and bovines, mammals, we can safely say 2 hr is the Goldilocks point— that the biological age of the not immediately after fusion, nuclear donor will not be a not 4 hr after—somewhere limitation when it comes around 2 hr works best (Liu to making autologous ESCs et al., 2013). If this is so, how by SCNT in humans. It recould Tachibana et al. (2013) mains to be determined if and Yamada et al. (2014) the variability on resistance generate cloned blastocysts to nuclear reprogramming worthy of hESC isolation observed in animal studies without waiting 2 hr? The between and within donor answer to this riddle seems cell types will influence the to be in the use of histone efficiency of the procedure. deacetylase inhibitors. It was A successful SCNT procerecently reported that rDNA dure, measured by the numis not properly reactivated in ber of blastocysts or ESCs the genome of the somatic Figure 1. Streamlined Process for Somatic Cell Nuclear Transfer produced, depends on multicell and that this is directly with Human Cells ple factors. Among the most linked to histone acetylation. A list of steps that enabled a higher efficiency of the SCNT process in human. Prior to 2013, these factors were individually tested in animal protocols. Idenimportant are oocyte quality, The more quickly and effitifying oocyte donors with oocytes endowed with the highest epigenetic power type of enucleation used, ciently a pattern of embryonic to reprogram a somatic cell nucleus should be the next priority. If oocytes with cell fusion, oocyte activation, acetylated histones is estabthe described conditions were readily available, multiple autologous-ESC lines could be produced by a single donor. time of oocyte activation, cullished, the greater the chanture medium, and type and ces for normal development. cell cycle stage of the donor It turns out that adding histone nucleus. The final efficiency is equal to In most species, and humans are no deacetylase inhibitors such as Trichosthe cumulative efficiency of each step. exception, the oocyte cannot divide by tatin A or scriptaid, a step that was Once Tachibana et al. (2013) established itself without fertilization. Special proce- included in all three hSCNT-ESC reports, the protocol, Chung et al. (2014) were dures are implemented during SCNT can facilitate this process (Zheng et al., able to dispel the notion that the human to trigger embryonic development. The 2012). It will be interesting to learn whether egg was somehow deficient on two cen- challenge is to establish the most suitable waiting 2 hr after fusion to activate the trosomal proteins and was inducing time point after fusion of the somatic cell egg, without using these compounds, aneuploidy in the embryos. They then at which to activate development. Trig- will yield high quality blastocysts as well. Which is the SCNT variable, off all the honed in on the time of activation after gering the activation of an MII oocyte fusion and demonstrated that waiting simultaneously with fusion is detrimental ones analyzed by these three excellent 2 hr is ideal. Their findings show that a to embryonic development. It is better to manuscripts, that matters the most? fundamental variable determining the ‘‘marinate’’ the nucleus in an oocyte’s Where should we center our research outcome of the procedure is the oocyte’s cytosol before inducing egg activation. efforts? Identifying and characterizing cytosol and that only cohorts donated by Chung et al. (2014) built upon the method the oocyte’s cytosol with the strongest some women shared such favorable reported by Mitalipov’s group (Tachibana epigenetic power to reprogram a somatic cytosol. Independently of the age of the et al., 2013), demonstrating that the ideal cell nucleus must be our next priority somatic cell donor and of the period of period is 2 hr. According to the results (Figure 1). In hindsight, the idea that time preceding activation of the recon- reported in this issue, we can expect oocytes vary in this regard is not new. It structed oocytes, the oocyte cytosol that more blastocysts of better quality — was first reported in 1991 by Latham and from three of the seven women who hatched and with a robust inner cell Solter, who performed pronuclear exchanges between fertilized oocytes using donated oocytes best supported embry- mass — will be produced. onic development and ESC derivation. In trying to explain some of the differ- different strains of mice, but this process This was suggested by Tachibana et al. ences that arise from fusing and activat- was never tested in humans (Latham and (2013)—eight oocytes donated by a ing the somatic cell at different times, Solter, 1991). Yamada et al. (2014) and Tasingle woman produced four SCNT- we must look closely at the early re- chibana et al. (2013) made some strides in ESCs—and the current publication now programming events during SCNT. As the right direction by showing correlations confirms it. Yamada et al. (2014) also soon as the somatic cell nucleus comes between the hormonal regime used and contribute more evidence that the into contact with the MII oocyte’s cytosol, oocyte donor age with the developmental oocyte cytosol is a major variable and nuclear envelope breakdown and chro- potential of the oocytes; however, they point out that we must be extremely matin condensation begin. Given enough also presented contradictory evidence careful during cell fusion not to induce time, these early nuclear remodeling about the importance of the number of premature activation in the egg, a step events work in favor of somatic cell oocytes recovered per superovulation that was considered innocuous prior to dedifferentiation, but only to a point — cycle. For Tachibana et al. (2013), fewer their work. and how much is enough? Apparently, oocytes yielded better quality embryos, 700 Cell Stem Cell 14, June 5, 2014 ª2014 Elsevier Inc.
Cell Stem Cell
Previews whereas Yamada et al. (2014) could not replicate the finding—one hSCNT-ESC line was derived from an oocyte that was picked from among 31 oocytes donated at once by a single donor. Overall, these data indicate that the oocyte cytosols of different women differ in important ways that go beyond the donors’ ages. Finding the specific reason why some women have better cytosol than others could have a huge impact in the reprograming field and, more importantly, in the evergrowing field of human-assisted reproductive technologies. To find the answers, though, we will have to rely on SCNT, a technique in which at least one variable, the genomic DNA, is fixed; only then can we really test the reprograming potential of oocyte-cytosols from different women. Human SCNT, a technique that not so long ago was considered passe´, is now
back in the toolbox; this time, at least for the task of finding the best human egg, it will not be replaced by induced pluripotent stem cells. REFERENCES
Liu, J., Wang, Y., Su, J., Wang, L., Li, R., Li, Q., Wu, Y., Hua, S., Quan, F., Guo, Z., and Zhang, Y. (2013). Cell Reprogram 15, 134–142. Noggle, S., Fung, H.L., Gore, A., Martinez, H., Satriani, K.C., Prosser, R., Oum, K., Paull, D., Druckenmiller, S., Freeby, M., et al. (2011). Nature 478, 70–75.
Chung, Y.G., Eum, J.H., Lee, J.E., Shim, S.H., Sepilian, V., Hong, S.W., Lee, Y., Treff, N.R., Choi, Y.H., Kimbrel, E.A., et al. (2014). Cell Stem Cell 14, this issue, 777–780.
Stojkovic, M., Stojkovic, P., Leary, C., Hall, V.J., Armstrong, L., Herbert, M., Nesbitt, M., Lako, M., and Murdoch, A. (2005). Reprod. Biomed. Online 11, 226–231.
Cibelli, J.B., Kiessling, A.A., Cunniff, K., Richards, C., Lanza, R.P., and West, M.D. (2001). e-biomed: the Journal of Regenerative Medicine 2, 26–31, http://dx.doi.org/10.1089/152489001753262168.
Tachibana, M., Amato, P., Sparman, M., Gutierrez, N.M., Tippner-Hedges, R., Ma, H., Kang, E., Fulati, A., Lee, H.-S., Sritanaudomchai, H., et al. (2013). Cell 153, 1228–1238.
Fan, Y.Y., Jiang, Y.Y., Chen, X.X., Ou, Z.Z., Yin, Y.Y., Huang, S.S., Kou, Z.Z., Li, Q.Q., Long, X.X., Liu, J.J., et al. (2011). Stem Cells Dev. 20, 1951–1959. French, A.J., Adams, C.A., Anderson, L.S., Kitchen, J.R., Hughes, M.R., and Wood, S.H. (2008). Stem Cells 26, 485–493. Latham, K.E., and Solter, D. (1991). Development 113, 561–568.
Yamada, M., Johannesson, B., Sagi, I., Burnett, L.C., Kort, D.H., Prosser, R.W., Paull, D., Nestor, M.W., Freeby, M., Greenberg, E., et al. (2014). Nature. Published online April 28, 2014. Zheng, Z., Jia, J.L., Bou, G., Hu, L.L., Wang, Z.D., Shen, X.H., Shan, Z.Y., Shen, J.L., Liu, Z.H., and Lei, L. (2012). J. Biol. Chem. 287, 19949–19960.
Stem Cells Go Soft: Pliant Substrate Surfaces Enhance Motor Neuron Differentiation Ning Wang1,2,* 1Department of Biomedical Engineering, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China 2Department of Mechanical Science and Engineering, College of Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA *Correspondence: [email protected] http://dx.doi.org/10.1016/j.stem.2014.05.007
Derivation of motor neurons from human pluripotent stem cells is inefficient and requires complex culture protocols. Recently in Nature Materials, Sun et al. (2014) report that differentiating human pluripotent stem cells on soft substrates increases the efficiency of mature motor neuron differentiation by altering cytoskeletal mechanotransduction through the Hippo/YAP/Smad pathway. Efficient derivation of motor neurons (MNs) from human pluripotent stem cells (hPSCs) is limited by our current understanding of the mechanisms underlying MN differentiation as well as drawbacks arising from inefficient and lengthy existing protocols. Human MNs derived from in vitro cultures can be used for cellular mechanistic studies as well as in vivo studies testing cell replacement strategies and modeling human disease in animal models, with the ultimate goal of replacing dysfunctional MNs in degenera-
tive disorders like amyotrophic lateral sclerosis. To enhance MN differentiation and surmount some of these existing difficulties, Jianping Fu and colleagues (Sun et al., 2014) developed a mechanical platform that enhances differentiation efficiency of hPSCs into MNs by >4-fold and significantly shortens the time period required for MN maturation. This platform capitalizes on advances using micromolded poly-(dimethylsiloxane) (PDMS) micropost arrays (PMAs) to culture cells (Fu et al., 2010). PDMS is
widely used to construct microscale devices for cell culture and microfluidic applications (Fu et al., 2010). PDMS surfaces are continuous and thus cannot change rigidity without altering other characteristics of the material. In contrast, PMAs have a constant surface geometry whose rigidity is varied by adjusting heights of isolated microposts to cover the stiffness range exhibited by soft tissues without altering the contact area available for cell-matrix interactions or tethering of cell-surface integrins to
Cell Stem Cell 14, June 5, 2014 ª2014 Elsevier Inc. 701
