Abstract
Abstract: :
Purpose: Loss of math5 leads to the absence of retinal ganglion cells (RGCs) and concurrently, the increase in cone and displaced amacrine cells, suggesting Math5's dual roles in promoting RGC and inhibiting non–RGC differentiation pathways. It remains unclear what factors mediate the suppressing effects of Math5 on non–RGC differentiation. Interestingly, Bhlhb5 expression is up–regulated in math5–null retina. The purpose of this study is to determine the expression profile and function of Bhlhb5 in retinal development. Methods: The expression of Bhlhb5 were analyzed by in situ hybridization and immunolabeling experiments. Retrovirus–mediated gene transfer of Bhlhb5 in mouse embryonic retinas and knockout of Bhlhb5 in mice were employed to study its gain– and loss–of–function effects in retinal development. Results: Bhlhb5 was expressed in amacrine cells and loss of math5 lead to the increase of Bhlhb5 expression in developing mouse retina and an increase in Bhlhb5–positive amacrine cells in the ganglion cell layer. Ectopic expression of Bhlhb5 resulted in the increase of amacrine cell differentiation in mice. Conclusions: These results demonstrate that Bhlhb5 plays a positive role in the amacrine cell development and that the suppression of amacrine cell differentiation by Math5 is likely mediated by Bhlhb5.
Keywords: retinal development • amacrine cells • transcription factors