Molecular Neurobiology

, Volume 32, Issue 2, pp 157–171 | Cite as

bHLH genes and retinal cell fate specification



The various cell types in the vertebrate retina arise from a pool of common progenitors. The way that the cell types are specified has been a long-standing issue. Decades of research have yielded a large body of information regarding the involvement of extrinsic factors, and only recently has the function of intrinsic factors begun to emerge. This article reviews recent studies addressing the role of basic helix-loop-helix (bHLH) factors in specifying retinal cell types, with an emphasis on bHLH hierarchies leading to photoreceptor production. Photoreceptor genesis appears to employ two transcriptional pathways: ngn2→neuroD→raxL and ath5→neuroD→raxL. ngn2 and ath5 function in progenitors, which can potentially develop into different cell types. neuroD represents one of the central steps in photoreceptor specification. Ath5 is also essential for ganglion cell development. It remains to be demonstrated whether a bHLH gene functions as a key player in specifying the other types of retinal cells. Genetic knockout studies have indicated intricate cross-regulation among bHLH genes. Future studies are expected to unveil the mechanism by which bHLH factors network with intrinsic factors and communicate with extrinsic factors to ensure a balanced production of the various types of retinal cells.

Index Entries

bHLH genes neuroD photoreceptor cells RPE transdifferentiation INL cell generation 


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  1. 1.
    Curcio C. A. (2001) Photoreceptor topography in ageing and age-related maculopathy. Eye 15, 376–383.PubMedGoogle Scholar
  2. 2.
    Turner D. L. and Cepko C. L. (1987) A common progenitor for neurons and glial persists in rat retina late in development. Nature 328, 131–136.PubMedCrossRefGoogle Scholar
  3. 3.
    Raymond P. A. (1991) Cell determination and positional cues in the teleost retina: development of photoreceptors and horizontal cells. In: Development of the Visual System, Lam D. -K. and Shatz C. J., eds., Cambridge, MA: The MIT Press, pp. 59–78.Google Scholar
  4. 4.
    Reh T. A. (1991) Determination of cell fate during retinal histogenesis: Intrinsic and extrinsic mechanisms. In: Development of the Visual System, Lam D.-K. and Shatz C. J., eds. Cambridge, MA: The MIT Press, pp. 79–94.Google Scholar
  5. 5.
    Adler R. and Hatlee M. (1989) Plasticity and differentiation of embryonic retinal cells after terminal mitosis. Science 243, 391–393.PubMedCrossRefGoogle Scholar
  6. 6.
    Adler R. (2000) A model of retinal cell differentiation in the chick embryo. Prog. Retina Eye Res. 19, 529–557.CrossRefGoogle Scholar
  7. 7.
    Lillien L. (1995) Changes in retinal cell fate induced by overexpression of EGF receptor. Nature 377, 158–162.PubMedCrossRefGoogle Scholar
  8. 8.
    McFarlane S., Zuber M. E., and Holt C. E. (1998) A role for the fibroblast growth factor receptor in cell fate decisions in the developing vertebrate retina. Development 125, 3967–3975.PubMedGoogle Scholar
  9. 9.
    Levine E. M., Roelink H., Turner J., and Reh T. A. (1997) Sonic hedgehog promotes rod photoreceptor differentiation in mammalian retinal cells in vitro. J. Neurosci. 17, 6277–6288.PubMedGoogle Scholar
  10. 10.
    Stenkamp D. L., Frey R. A., Prabhudesai S. N., and Raymond P. A. (2000) Function for Hedgehog genes in zebrafish retinal development. Dev. Biol. 220, 238–252.PubMedCrossRefGoogle Scholar
  11. 11.
    Levine E. M., Fuhrmann. S., and Reh T. A. (2000) Soluble factors and the development of rod photoreceptors. Cell Mol. Life Sci. 57, 224–234.PubMedCrossRefGoogle Scholar
  12. 12.
    Huang S. and Moody S. A. (1997) Three types of serotonin-containing amacrine cells in tadpole retina have distinct clonal origins. J. Comp. Neurol. 387, 42–52.PubMedCrossRefGoogle Scholar
  13. 13.
    Alexiades M. R. and Cepko C. L. (1997) Subsets of retinal progenitors display temporally regulated and distinct biases in the fates of their progeny. Development 124, 1119–1131.PubMedGoogle Scholar
  14. 14.
    Braisted J. E., Essman T. F., and Raymond P. A. (1994) Selective regeneration of photoreceptors in goldfish retina. Development 120, 2409–2419.PubMedGoogle Scholar
  15. 15.
    Cepko C. L., Austin C. P., Yang X., Alexiades M., and Ezzeddine D. (1996) Cell fate determination in the vertebrate retina. Proc. Natl. Acad. Sci. USA 93, 589–595.PubMedCrossRefGoogle Scholar
  16. 16.
    Belliveau M. J., Young T. L., and Cepko C. L. (2000) Late retinal progenitor cells show intrinsic limitations in the production of cell types and the kinetics of opsin synthesis. J. Neurosci. 20, 2247–2254.PubMedGoogle Scholar
  17. 17.
    Cayouette M., Barres B. A., and Raff M. (2003) Importance of intrinsic mechanisms in cell fate decisions in the developing rat retina. Neuron 40, 897–904.PubMedCrossRefGoogle Scholar
  18. 18.
    Tomita K., Nakanishi S., Guillemot F., and Kageyama R. (1996) Mash1 promotes neuronal differentiation in the retina. Genes Cells 1, 765–774.PubMedCrossRefGoogle Scholar
  19. 19.
    Jasoni C. L., Walker M. B., Morris M. D., and Reh T. A. (1994) A chicken achaete-scute homolog (CASH-1) is expressed in a temporally and spatially discrete manner in the developing nervous system. Development 120, 769–783.PubMedGoogle Scholar
  20. 20.
    Turner D. L. and Weintraub H. (1994) Expression of achaete-scute homolog 3 in Xenopus embryos converts ectodermal cells to a neural fate. Genes Dev. 8, 1434–1447.PubMedCrossRefGoogle Scholar
  21. 21.
    Kanekar S., Perron M., Dorsky R., et al. (1997) Xath5 participates in a network of bHLH genes in the developing Xenopus retina. Neuron 19, 981–994.PubMedCrossRefGoogle Scholar
  22. 22.
    Perron M., Opdecamp K., Butler K., Harris W. A., and Bellefroid E. J. (1999) X-ngnr-1 and Xath3 promote ectopic expression of sensory neuron markers in the neurula ectoderm and have distinct inducing properties in the retina. Proc. Natl. Acad. Sci. USA 96, 14,996–15,001.CrossRefGoogle Scholar
  23. 23.
    Hatakeyama J., Tomita K., Inoue T., and Kageyama R. (2001) Roles of homeobox and bHLH genes in specification of a retinal cell type. Development 128, 1313–1322.PubMedGoogle Scholar
  24. 24.
    Brown N. L., Kanekar S., Vetter M. L., Tucker P. K., Gemza D. L., and Glaser T. (1998) Math5 encodes a murine basic helix-loop-helix transcription factor expressed during early stages of retinal neurogenesis. Development 125, 4821–4833.PubMedGoogle Scholar
  25. 25.
    Masai I., Stemple D. L., Okamoto H., and Wilson S. W. (2000) Midline signals regulate retinal neurogenesis in zebrafish. Neuron 27, 251–263.PubMedCrossRefGoogle Scholar
  26. 26.
    Wang S. W., Kim B. S., Ding K., et al. (2001) Requirement for math5 in the development of RGCs. Genes Dev. 15, 24–29.PubMedCrossRefGoogle Scholar
  27. 27.
    Brown N. L., Patel S., Brzezinski J., and Glaser T. (2001) Math5 is required for retinal ganglion cell and optic nerve formation. Development 128, 2497–2508.PubMedGoogle Scholar
  28. 28.
    Liu W., Mo Z., and Xiang M. (2001) The Ath5 proneural genes function upstream of Brn3 POU domain transcription factor genes to promote retinal ganglion cell development. Proc. Natl. Acad. Sci. USA 98, 1649–1654.PubMedCrossRefGoogle Scholar
  29. 29.
    Kay J. N., Finger-Baier K. C., Roeser T., Staub W., and Baier H. (2001) Retinal ganglion cell genesis requires lakritz, a Zebrafish atonal Homolog. Neuron 30, 725–736.PubMedCrossRefGoogle Scholar
  30. 30.
    Stenkamp D. L. and Frey R. A. (2003) Extraretinal and retinal hedgehog signaling sequentially regulate retinal differentiation in zebrafish. Dev Biol. 258, 349–363.PubMedCrossRefGoogle Scholar
  31. 31.
    Ma W., Yan R. -T., Xie W., and Wang S. -Z. (2004). A role of ath5 in inducing neuroD and the photoreceptor pathway. J. Neurosci. 24, 7150–7158.PubMedCrossRefGoogle Scholar
  32. 32.
    Xie W., Yan R. -T., Ma W., and Wang S. -Z. (2004) Enhanced retinal ganglion cell differentiation by ath5 and NSCL1 coexpression. Invest. Ophthalmol. Vis. Sci. 45, 2922–2928.PubMedCrossRefGoogle Scholar
  33. 33.
    Yan R. -T. and Wang S. -Z. (1998) neuroD induces photoreceptor cell overproduction in vivo and de novo generation in vitro. J. Neurobiol. 36, 485–496.PubMedCrossRefGoogle Scholar
  34. 34.
    Morrow E. M., Furukawa T., Lee J. E., and Cepko C. L. (1999) NeuroD regulates multiple functions in the developing neural retina in rodent. Development 126, 23–36.PubMedGoogle Scholar
  35. 35.
    Yan R. -T. and Wang S. -Z. (2004) Requirement of neuroD for photoreceptor formation in the chick retina. Invest. Ophthalmol. Vis. Sci. 45, 48–58.PubMedCrossRefGoogle Scholar
  36. 36.
    Pennesi M. E., Cho J. H., Yang Z., et al. (2003) BETA2/NeuroD1 null mice: a new model for transcription factor-dependent photoreceptor degeneration. J. Neurosci. 23, 453–461.PubMedGoogle Scholar
  37. 37.
    Hitchcock P. and Kakuk-Atkins L. (2004) The basic helix-loop-helix transcription factor neuroD is expressed in the rod lineage of the teleost retina. J. Comp. Neurol. 477, 108–117.PubMedCrossRefGoogle Scholar
  38. 38.
    Yan R. -T., Ma W. -X. and Wang S. -Z. (2001). neurogenin2 elicits the genesis of retinal neurons from cultures of non-neural cells. Proc. Natl. Acad. Sci. USA 98, 15,014–15,019.Google Scholar
  39. 39.
    Marquardt T., Ashery-Padan R., Andrejewski N., Scardigli R., Guillemot F., and Gruss P. (2001) Pax6 is required for the multipotent state of retinal progenitor cells. Cell 105, 43–55.PubMedCrossRefGoogle Scholar
  40. 40.
    Li C. -M., Yan R. -T., and Wang S. -Z. (1999) Misexpression of cNSCL1 disrupts retinal development. Mol. Cell. Neurosci. 14, 17–27.PubMedCrossRefGoogle Scholar
  41. 41.
    Li C. -M., Yan R. -T., and Wang S. -Z. (2001) Misexpression of chick NSCL2 causes atrophy of Müller glia and photoreceptor cells. Invest. Ophthalmol. Vis. Sci. 42, 3103–3109.PubMedGoogle Scholar
  42. 42.
    Bramblett D. E., Pennesi M. E., Wu S. M., and Tsai M. J. (2004) The transcription factor Bhlhb4 is required for rod bipolar cell maturation. Neuron 43, 779–793.PubMedCrossRefGoogle Scholar
  43. 43.
    Chae J. H., Stein G. H., and Lee J. E. (2004) NeuroD: The predicted and the surprising. Mol. Cells 18, 271–288.PubMedGoogle Scholar
  44. 44.
    Inoue T., Hojo M., Bessho Y., Tano Y., and Lee J. E. (2002) Kageyama R. Math3 and NeuroD regulate amacrine cell fate specification in the retina. Development 129, 831–842.PubMedGoogle Scholar
  45. 45.
    Foster R. G. and Bellingham J. (2004) Inner retinal photoreceptors (IRPs) in mammals and teleost fish. Photochem. Photobiol. Sci. 3, 617–627.PubMedCrossRefGoogle Scholar
  46. 46.
    Soni B. G., Philp A. R., Knox B. E., and Foster R. G. (1998) Novel retinal photoreceptors. Nature 394, 27–28.PubMedCrossRefGoogle Scholar
  47. 47.
    Berson D. M., Dunn F. A., and Takao M. (2002) Phototransduction by retinal ganglion cells that set the circadian clock. Science 295, 1070–1073.PubMedCrossRefGoogle Scholar
  48. 48.
    Hoover F., Seleiro E. A., Kielland A., Brickell P. M., and Glover J. C. (1998) Retinoid X receptor gamma gene transcripts are expressed by a subset of early generated retinal cells and eventually restricted to photoreceptors. J. Comp. Neurol. 391, 204–213.PubMedCrossRefGoogle Scholar
  49. 49.
    Liu M., Pleasure S. J., Collins A. E., et al. (2000) Loss of BETA2/NeuroD leads to malformation of the dentate gyrus and epilepsy. Proc. Natl. Acad. Sci. USA 97, 865–870.PubMedCrossRefGoogle Scholar
  50. 50.
    Young R. W. (1985) Cell differentiation in the retina of the mouse. Anat Rec. 212, 199–205.PubMedCrossRefGoogle Scholar
  51. 51.
    Akagi T., Inoue T., Miyoshi G., et al. (2004) Requirement of multiple basic helix-loop-helix genes for retinal neuronal subtype specification. J. Biol. Chem. 279, 28,492–28,498.CrossRefGoogle Scholar
  52. 52.
    Yan R.-T. and Wang S.-Z. (2000) Expression of an array of photoreceptor genes in chick embryonic RPE cell cultures under the induction of neuroD. Neurosci. Lett. 280, 83–86.PubMedCrossRefGoogle Scholar
  53. 53.
    Yan R.-T. and Wang S.-Z. (2000) Differential induction of gene expression by basic fibroblast growth factor and neuroD in cultured retinal pigment epithelial cells. Vis. Neurosci. 17, 157–164.PubMedCrossRefGoogle Scholar
  54. 54.
    Chen C. M. and Cepko C. L. (2002) The chicken RaxL gene plays a role in the initiation of photoreceptor differentiation. Development 129, 5363–5375.PubMedCrossRefGoogle Scholar
  55. 55.
    Bruhn S. L. and Cepko C. L. (1996) Development of the pattern of photoreceptors in the chick retina. J. Neurosci. 16, 1430–1439.PubMedGoogle Scholar
  56. 56.
    Ng L., Hurley J. B., Dierks B., et al. (2001) A thyroid hormone receptor that is required for the development of green cone photoreceptors. Nat. Genet. 27, 94–98.PubMedGoogle Scholar
  57. 57.
    Mears A. J., Kondo M., Swain P. K., et al. (2001) Nrl is required for rod photoreceptor development. Nat. Genet. 29, 447–452.PubMedCrossRefGoogle Scholar
  58. 58.
    Chen J., Rattner A, and Nathans J. (2005) The rod photoreceptor-specific nuclear receptor Nr2e3 represses transcription of multiple conespecific genes. J Neurosci. 25, 118–129.PubMedCrossRefGoogle Scholar
  59. 59.
    Zirlinger M., Lo L., McMahon J., McMahon A. P., and Anderson D. J. (2002) Transient expression of the bHLH factor neurogenin-2 marks a subpopulation of neural crest cells biased for a sensory but not a neuronal fate. Proc. Natl. Acad. Sci. USA 99, 8084–8089.PubMedCrossRefGoogle Scholar
  60. 60.
    Yang Z., Ding K., Pan L., Deng M., and Gan L. (2003) Math5 determines the competence state of retinal ganglion cell progenitors. Dev Biol. 264, 240–254.PubMedCrossRefGoogle Scholar
  61. 61.
    Hutcheson D. A. and Vetter M. L. (2001) The bHLH factors Xath5 and XNeuroD can upregulate the expression of XBrn3d, a POU-homeodomain transcription factor. Dev. Biol. 232, 327–338.PubMedCrossRefGoogle Scholar
  62. 62.
    Ma W., Yan R.-T., Xie W., and Wang S.-Z. (2004) bHLH genes cath5 and cNSCL1 promote bFGF-stimulated RPE cells to transdifferentiate towards RGCs. Dev. Biol. 265, 320–328.PubMedCrossRefGoogle Scholar
  63. 63.
    Guillemot F. and Cepko C. L. (1992) Retinal fate and ganglion cell differentiation are potentiated by acidic FGF in an in vitro assay of early retinal development. Development 114, 743–754.PubMedGoogle Scholar
  64. 64.
    Fischer A. J., Dierks B. D., and Reh T. A. (2002) Exogenous growth factors induce the production of ganglion cells at the retinal margin. Development 129, 2283–2291.PubMedGoogle Scholar
  65. 65.
    Neumann C. J. and Nuesslein-Volhard C. (2000) Patterning of the zebrafish retina by a wave of sonic hedgehog activity. Science 289, 2137–2139.PubMedCrossRefGoogle Scholar
  66. 66.
    Zhang X. M. and Yang X. J. (2001) Regulation of retinal ganglion cell production by Sonic hedgehog. Development 128, 943–957.PubMedGoogle Scholar
  67. 67.
    Spence J. R., Madhavan M., Ewing J. D., Jones D. K., Lehman B. M., Del Rio-Tsonis K. (2004) The hedgehog pathway is a modulator of retina regeneration. Development 131, 4607–4621.PubMedCrossRefGoogle Scholar
  68. 68.
    Mu X. and Klein W. H. (2004) A gene regulatory hierarchy for retinal ganglion cell specification and differentiation. Semin. Cell Dev. Biol. 15, 115–123.PubMedCrossRefGoogle Scholar
  69. 69.
    Tomita K., Moriyoshi K., Nakanishi S., Guillemot F., and Kageyama R. (2000) Mammalian achaete-scute and atonal homologs regulate neuronal versus glial fate determination in the central nervous system. EMBO J. 19, 5460–5472.PubMedCrossRefGoogle Scholar
  70. 70.
    Liu I. S., Chen J. D., Ploder L., et al. (1994) Developmental expression of a novel murine homeobox gene (Chx10): evidence for roles in determination of the neuroretina and inner nuclear layer. Neuron 13, 377–393.PubMedCrossRefGoogle Scholar
  71. 71.
    Burmeister M., Novak J., Liang M. Y., et al. (1996) Ocular retardation mouse caused by Chx10 homeobox null allele: impaired retinal progenitor proliferation and bipolar cell differentiation. Nat. Genet. 12, 376–384.PubMedCrossRefGoogle Scholar
  72. 72.
    Dyer M. A., Livesey F. J., Cepko C. L., and Oliver G. (2003) Prox1 function controls progenitor cell proliferation and horizontal cell genesis in the mammalian retina. Nat. Genet. 34, 53–58.PubMedCrossRefGoogle Scholar
  73. 73.
    Li S., Mo Z., Yang X., Price S. M., Shen M. M., and Xiang M. (2004) Foxn4 controls the genesis of amacrine and horizontal cells by retinal progenitors. Neuron 43, 795–807.PubMedCrossRefGoogle Scholar
  74. 74.
    Moody S. A. (2000) Cell lineage analysis in Xenopus embryos. Methods Mol Biol. 135, 331–347.PubMedGoogle Scholar
  75. 75.
    Huang S. and Moody S. A. (1995) Asymmetrical blastomere origin and spatial domains of dopamine and neuropeptide Y amacrine subtypes in Xenopus tadpole retina. J. Comp. Neurol. 360, 442–453.PubMedCrossRefGoogle Scholar
  76. 76.
    Moody S. A., Chow I., and Huang S. (2000) Intrinsic bias and lineage restriction in the phenotype determination of dopamine and neuropeptide Y amacrine cells. J. Neurosci. 20, 3244–3253.PubMedGoogle Scholar
  77. 77.
    Yan R.-T. and Wang S.-Z. (2001) Embryonic abnormalities from misexpression of cNSCL1. Biochem. Biophys. Res. Cummun. 287, 949–955.CrossRefGoogle Scholar
  78. 78.
    Trousse F., Esteve P., and Bovolenta P. (2001) Bmp4 mediates apoptotic cell death in the developing chick eye. J. Neurosci. 21, 1292–1301.PubMedGoogle Scholar
  79. 79.
    Yu J., He S., Friedman J. S., et al. (2004) Altered expression of genes of the Bmp/Smad and Wnt/calcium signaling pathways in the coneonly Nrl-/- mouse retina, revealed by gene profiling using custom cDNA microarrays. J. Biol. Chem. 279, 42,211–42,220.Google Scholar
  80. 80.
    Fischer A. J., Schmidt M., Omar G., and Reh T. A. (2004) BMP4 and CNTF are neuroprotective and suppress damage-induced proliferation of Muller glia in the retina. Mol. Cell. Neurosci. 27, 531–542.PubMedCrossRefGoogle Scholar

Copyright information

© The Humana Press Inc 2005

Authors and Affiliations

  • Run-Tao Yan
    • 1
  • Wenxin Ma
    • 1
  • Lina Liang
    • 1
  • Shu-Zhen Wang
    • 1
  1. 1.Department of OphthalmologyUniversity of Alabama at BirminghamBirmingham

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