Abstract
Purpose::
Although they provide a newly recognized level of regulation of gene expression, contributions of microRNAs (miRNAs) to the development and function of mammalian retina are still largely unknown. The goal of current study is to 1) identify the microRNA expression profiles in adult mouse retina; 2) identify and characterization of retinal specific microRNAs; 3) identify candidate microRNAs possibly involved in the circadian rhythm.
Methods::
To approach these questions, we performed miRNA expression profiling in adult mouse retina, brain and heart by microarray analysis. Subtraction of the miRNAs expressed in the brain and heart, we identified candidate retina-specific niRNAs; miRNA expression profiles of the retinas at midday (Zeitgerber time 5) and midnight (ZT17) were obtained to identify candidate miRNAs with diurnal variation in their expression pattern. Quantitative RT-PCR on multiple tissue RNAs and in situ hybridization were employed to confirm the tissue specificity of the candidate miRNAs.
Results::
At least 79 miRNAs are expressed in adult mouse retina, 21 of which are potentially retina specific. Among these, we identified a polycistronic, sensory organ-specific paralogous miRNA cluster that includes miR-96, miR-182, and miR-183 on mouse chromosome 6qA3 with conservation of synteny to human chromosome 7q32.2. In situ analysis showed that the members of this cluster are expressed in both outer and inner nuclear layers of the retina. We also identified a subgroup of 12 miRNAs with diurnal variation in expression pattern, including miR-182, which may be involved in circadian rhythm through the regulation on its downstream targets, e.g. adenylyl cyclase VI.
Conclusions::
miRNAs are expressed in mouse retina, some of which are highly, specifically expressed in retina at various developmental stages, suggesting that miRNAs play important roles in the gene expression regulation in retina. Further functional study will ellucidate their roles in the normal develpment and function of the retina and their involvement in retinal diseases when defective.
Keywords: retina • gene microarray • circadian rhythms