Neurogenin1 and neurogenin2 control two distinct waves of neurogenesis in developing dorsal root ganglia.
Different classes of sensory neurons in dorsal root ganglia (DRG) are generated in two waves: large-diameter trkC+ and trkB+ neurons are born first, followed by small-diameter trkA+ neurons. All such neurons require either neurogenin (ngn) 1 or 2, two neuronal determination genes encoding basic helix-loop-helix (bHLH) transcription factors. ngn2 is required primarily if not exclusively for the generation of trkC+ and trkB+ neurons, whereas the generation of most or all trkA+ neurons requires ngn1. Comparison with previous lineage tracing data in the chick suggests that this dichotomy reflects a requirement for the two ngns in distinct sensory precursor populations. The neurogenesis defect in ngn2(-/-) embryos is transient and later compensated by ngn1-dependent precursors, suggesting that feedback or competitive interactions between these precursors may control the proportion of different neuronal subtypes they normally produce. These data reveal remarkable parallels in the roles of bHLH factors during neurogenesis in the DRG, and myogenesis in the neighboring myotome.
Howard Hughes Medical Institute, Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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D000818:Animals; D017209:Apoptosis; D051792:Basic Helix-Loop-Helix Proteins; D005314:Embryonic and Fetal Development / Q000235:genetics; D005727:Ganglia, Spinal / Q000196:embryology*; D005807:Genes, Overlapping; D005838:Genotype; D005865:Gestational Age; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D051379:Mice; D018345:Mice, Knockout; D008818:Mice, Neurologic Mutants; D009024:Morphogenesis / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D009475:Neurons, Afferent / Q000166:cytology*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics; D020801:Receptor, Ciliary Neurotrophic Factor; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000096:biosynthesis* / Q000235:genetics; D014157:Transcription Factors; D029867:Xenopus Proteins
D051792:Basic Helix-Loop-Helix Proteins; D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases; D020801:Receptor, Ciliary Neurotrophic Factor; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor; D014157:Transcription Factors; D029867:Xenopus Proteins; C491183:NEUROG2 protein, human; C102938:Neurog2 protein, mouse; C101907:neurogenin, Xenopus; C486336:Neurog1 protein, mouse