Identification and characterization of MicroRNAs expressed in the mouse eye

PURPOSE. MicroRNAs ( miRNAs) are a class of small, endogenous RNAs that negatively regulate gene expression post-transcriptionally by binding to target sites in the 3' untranslated region (UTR) of messenger RNAs. Although they have been found to regulate developmental and physiological processes in several organs and tissues, their role in the eye transcriptome is completely unknown. This study was conducted to gain understanding of their eye-related function in mammals, by looking for miRNAs significantly expressed in the mouse eye by means of high-resolution expression analysis. METHODS. The spatiotemporal localization of miRNAs was analyzed in the murine embryonic and postnatal eye by RNA in situ hybridization ( ISH) using LNA-modified oligonucleotide probes. RESULTS. Seven miRNAs were expressed in the eye with diverse and partially overlapping patterns, which may reflect their role in controlling cell differentiation of the retina as well as of other ocular structures. Most eye-expressed miRNAs overlap with or are in the near vicinity of transcripts derived predominantly from eye cDNA libraries. We found that these transcripts share very similar cellular distribution with their corresponding miRNAs, suggesting that miRNAs may share common expression regulatory elements with their host genes. CONCLUSIONS. The data provide a detailed characterization of expression of eye-enriched miRNAs. Knowledge of the spatiotemporal distribution of miRNAs is an essential step toward the identification of their targets and eventually the elucidation of their biological role in eye development and function.