title: The homeobox gene Xbh1 cooperates with proneural genes to specify ganglion cell fate within the Xenopus neural retina.
abstract: Recent studies on vertebrate eye development have focused on the molecular mechanisms of specification of different retinal cell types during development. Only a limited number of genes involved in this process has been identified. In Drosophila, BarH genes are necessary for the correct specification of R1/R6 eye photoreceptors. Vertebrate Bar homologues have been identified and are expressed in vertebrate retinal ganglion cells during differentiation; however, their retinal function has not yet been addressed. In this study, we report on the role of the Xenopus Bar homologue Xbh1 in retinal ganglion cell development and its interaction with the proneural genes Xath5 and Xath3, whose ability to promote ganglion cell fate has been demonstrated. We show that XHB1 plays a crucial role in retinal cell determination, acting as a switch towards ganglion cell fate. Detailed expression analysis, animal cap assays and in vivo lipofection assays, indicate that Xbh1 acts as a late transcriptional repressor downstream of the atonal genes Xath3 and Xath5. However, the action of Xbh1 on ganglion cell development is different and more specific than that of the Xath genes, and accounts for only a part of their activities during retinogenesis.
authors.affiliation: Dipartimento di Fisiologia e Biochimica, Laboratorio di Biologia Cellulare e dello Sviluppo, Università di Pisa, 56010 Ghezzano, Pisa, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Poggi
authors.forename: Teresa
authors.initials: T
authors.lastname: Vottari
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Barsacchi
authors.forename: Joachim
authors.initials: J
authors.lastname: Wittbrodt
authors.forename: Robert
authors.initials: R
authors.lastname: Vignali
mesh_terms: D000818:Animals; D019521:Body Patterning; D004625:Embryo, Nonmammalian / Q000502:physiology; D005801:Genes, Homeobox / Q000235:genetics*; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D012160:Retina / Q000196:embryology*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology*; D014981:Xenopus; D029867:Xenopus Proteins / Q000235:genetics*
chemical_list: C501324:Barhl2 protein, Xenopus; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D012097:Repressor Proteins; D029867:Xenopus Proteins