Abstract
Purpose:
miRNAs are evolutionarily conserved small RNA molecules, which negatively regulate gene expression by binding to 3' un-translated region of transcripts. Conditional knockout of miRNA biogenesis genes such as Dicer has revealed important regulatory function of miRNAs during retinal development. However, the role of specific miRNAs in the regulation of retinal progenitors remains poorly understood. Here, we have examined the global miRNA expression profile during maintenance and differentiation of the late retinal progenitors to facilitate such understanding.
Methods:
The global miRNA expression profile was determined in an in vitro model of late retinal histogenesis. Briefly, embryonic day 18 (E18) rat retinal progenitors were enriched and maintained using neurosphere assay. The enriched E18 progenitors were cultured in the presence of E18 conditioned medium, supplemented with BMP4, RA, DAPT, and taurine to facilitate rod photoreceptor differentiation. Expression profiling was done in three different stages using the locked nucleic acid (LNA) microarrays, followed by Q-PCR and perturbation of expression analyses for validation of results.
Results:
Microarray analyses revealed 154 miRNAs differentially expressed during maintenance and differentiation of the late retinal progenitors. Cluster analysis separated these miRNAs into 9 groups on the basis of the trend of expression. Expression patterns of the representative members of these groups were independently confirmed. Two specific miRNAs, miR-17 and miR-29, whose expression decreased and increased during differentiation of the late retinal progenitors, respectively, were further examined for functional involvement in progenitor regulation. Loss of function analysis revealed that miR-17 repressed differentiation presumably by promoting self-renewal of progenitors and miR-29 promoted differentiation, presumably by regulating neurogliogenesis.
Conclusions:
miRNAs play important role in the regulation of retinal progenitors.