Insulin and insulin-like growth factor system components gene expression in the XXXX retina from early neurogenesis until late development and their effect on neuroepithelial cells.

@entity52664 @entity20023 @entity1573 @entity20020 @entity2090
To better understand the role of insulin-related growth factors in neural development, we have characterized by in situ hybridization in @entity1573 embryonic retina the patterns of gene expression for insulin, insulin-like growth factor I ( @entity2090 ), their respective receptors and the @entity20020 ( @entity20020 ) from early stages (E6) until late stages (E18)--an analysis not performed yet in any species. In addition, we studied the effect of insulin and @entity2090 on cultured neuroepithelial cells. @entity52664 mRNA and @entity20023 mRNA were both present and showed a similar, widespread pattern throughout retina development. Insulin mRNA could be detected only by reverse transcription coupled to polymerase chain reaction. @entity2090 mRNA was concentrated in the ciliary processes and extraocular muscles early in development (embryonic day 6; E6) and in maturing retinal ganglion cells subsequently (E9-15). @entity20020 mRNA was preferentially localized in the more differentiated central retinal zone and was maximally concentrated in the inner nuclear and ganglion cell layers at E9. These findings suggest a near constitutive expression of @entity52664 and @entity2090 receptor genes, while @entity2090 and @entity20020 showed a highly focal spatiotemporal regulation of gene expression. Insulin and @entity2090 , already at 10(-8) M, increased the proportion of PM1-positive neuroepithelial cells found in E5 retinal cultures without affecting significantly the total number of proliferating cells. Together, these data support the finding that, during early neurogenesis in @entity1573 retina, insulin and @entity2090 have a specific paracrine/autocrine action. This action, as well as possible effects elicited subsequently, may be dictated by restricted-local synthesis of the ligands and limited access to the factors contained in the vitreous humour. In the case of IGF's role, local IGFBPs expression can contribute to the fine modulation.
