Further Microarray Analysis of Gene Expression in the Early Developing Ocular Retardation Eye

Abstract

Abstract: : Purpose: Our goal is to understand the role of the Chx10 transcription factor in retinal development. The purpose of the present study is to determine the genes in the early developing eye that are regulated by Chx10. Chx10 encodes a homeodomain protein that is initially expressed in dividing retinal neuroepithelial cells. It is down-regulated as differentiation proceeds, but later it is strongly and selectively expressed in bipolar cells. We showed previously that ocular retardation (or^J) mutant mice carry a null allele of Chx10 (Burmeister et al., 1996) and an eye-specific phenotype. Three fundamental aspects of retinal development are affected: (1) proliferation of retinal neuroepithelial cells is reduced, leading to microphthalmia; (2) intraretinal retinal ganglion cell (RGC) axon guidance is profoundly disrupted, leading to optic nerve aplasia; and (3) a failure of bipolar cell differentiation. In order to understand the molecular changes in or^J eye morphogenesis resulting in these defects, we are using mouse I-gene arrays to develop an expression profile of the early developing or^J eye. Our findings are being confirmed using real-time RT-PCR, in situ hybridization, and immunohistochemistry. Methods: I-gene arrays, containing >6500 eye genes/ESTs printed in duplicate onto glass slides, were hybridized to Cy3- or Cy5-labeled target RNA from embryonic day 15.5 wild-type (+/+) and or^J/or^J eyes. Data was analyzed using DigitalGenome (MolecularWare) and Spotfire (Spotfire). Results: Preliminary analysis of the data has revealed a set of genes that are differentially expressed in the or^J/or^J eye. Almost half are upregulated and the other down-regulated. We have identified a number of novel genes, some of these are represented as RIKEN clones derived from mouse embryo libraries. We are currently validating the microarray data by real-time RT-PCR. Conclusions: Efforts to discover the molecular pathways regulated by Chx10 are defining molecular candidates that will be investigated to determine whether they are expressed in retinal progenitors or specific differentiated retinal cell types, as well as whether they are expressed in developmental pathways involved in cell differentiation or axon outgrowth.

Keywords: gene microarray • retinal development • transcription factors