Evolutionary relationships and diversification of barhl genes within retinal cell lineages

BMC Evolutionary Biology

Research Article

Lucia Poggi¹  Shahad Albadri¹  Laura-Nadine Schuhmacher¹  Mirana Ramialison² 

[1] Centre for Organismal Studies, University of Heidelberg, 69120, Heidelberg, Germany;Centre for Organismal Studies, University of Heidelberg, 69120, Heidelberg, Germany;The Victor Chang Cardiac Research Institute, 2010, Darlinghurst, NSW, Australia;

关键词: Retina;    Zebrafish Embryo;    Amacrine Cell;    Ganglion Cell Layer;    Whole Genome Duplication;   

DOI  :  10.1186/1471-2148-11-340

 received in 2011-06-12, accepted in 2011-11-21,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundBasic helix-loop-helix and homeodomain transcription factors have been shown to specify all different neuronal cell subtypes composing the vertebrate retina. The appearance of gene paralogs of such retina-specific transcription factors in lower vertebrates, with differently evolved function and/or conserved non-coding elements, might provide an important source for the generation of neuronal diversity within the vertebrate retinal architecture. In line with this hypothesis, we investigated the evolution of the homeobox Barhl family of transcription factors, barhl1 and barhl2, in the teleost and tetrapod lineages. In tetrapod barhl2, but not barhl1, is expressed in the retina and is important for amacrine cell specification. Zebrafish has three barhl paralogs: barhl1.1, barhl1.2 and barhl2, but their precise spatio-temporal retinal expression, as well as their function is yet unknown.ResultsHere we performed a meticulous expression pattern comparison of all known barhl fish paralogs and described a novel barhl paralog in medaka. Our detailed analysis of zebrafish barhl gene expression in wild type and mutant retinas revealed that only barhl1.2 and barhl2 are present in the retina. We also showed that these two paralogs are expressed in distinct neuronal lineages and are differently regulated by Atoh7, a key retinal-specific transcription factor. Finally, we found that the two retained medaka fish barhl paralogs, barhl1 and barhl2, are both expressed in the retina, in a pattern reminiscent of zebrafish barhl1.2 and barhl2 respectively. By performing phylogenetic and synteny analysis, we provide evidence that barhl retinal expression domain is an ancestral feature, probably lost in tetrapods due to functional redundancy.ConclusionsFunctional differences among retained paralogs of key retina-specific transcription factors between teleosts and tetrapods might provide important clues for understanding their potential impact on the generation of retinal neuronal diversity. Intriguingly, within teleosts, retention of zebrafish barhl1.2 and its medaka ortholog barhl1 appears to correlate with the acquisition of distinct signalling mechanisms by the two genes within distinct retinal cell lineages. Our findings provide a starting point for the study of barhl gene evolution in relation to the generation of cell diversity in the vertebrate retina.

【 授权许可】

Unknown   
© Schuhmacher et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.