title: Ash1a and Neurogenin1 function downstream of Floating head to regulate epiphysial neurogenesis.
abstract: The homeodomain transcription factor Floating head (Flh) is required for the generation of neurones in the zebrafish epiphysis. It regulates expression of two basic helix loop helix (bHLH) transcription factor encoding genes, ash1a (achaete/scute homologue 1a) and neurogenin1 (ngn1), in epiphysial neural progenitors. We show that ash1a and ngn1 function in parallel redundant pathways to regulate neurogenesis downstream of flh. Comparison of the epiphysial phenotypes of flh mutant and of ash1a/ngn1 double morphants reveals that reduced expression of ash1a and ngn1 can account for most of the neurogenesis defects in the flh-mutant epiphysis but also shows that Flh has additional activities. Furthermore, different cell populations show different requirements for ash1a and ngn1 within the epiphysis. These populations do not simply correspond to the two described epiphysial cell types: photoreceptors and projection neurones. These results suggest that the genetic pathways that involve ash1a and ngn1 are common to both neuronal types.
authors.affiliation: Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Elise
authors.initials: E
authors.lastname: Cau
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Wilson
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D019521:Body Patterning; D004268:DNA-Binding Proteins; D018507:Gene Expression Regulation, Developmental; D011495:Histone-Lysine N-Methyltransferase; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D051857:Otx Transcription Factors; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology; D010870:Pineal Gland / Q000196:embryology / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D011495:Histone-Lysine N-Methyltransferase; D018398:Homeodomain Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D051857:Otx Transcription Factors; D014157:Transcription Factors; D029961:Zebrafish Proteins; C413467:Otx5 protein, zebrafish; C064045:delta protein; C486337:neurog1 protein, zebrafish; C096660:noto protein, zebrafish; C093564:Neurogenic differentiation factor 1; C490911:ASH1L protein, human