Abstract
It is well established that miR-9 contributes to retinal neurogenesis. However, little is known about its presence and effects in the postnatal period. To expand our knowledge, miRNA-small RNA sequencing and in situ hybridization supported by RT-qPCR measurement were carried out. Mir-9 expression showed two peaks in the first three postnatal weeks in Wistar rats. The first peak was detected at postnatal Day 3 (P3) and the second at P10, then the expression gradually decreased until P21. Furthermore, we performed in silico prediction and established that miR-9 targets OneCut2 or synaptotagmin-17. Another two microRNAs (mir-135, mir-218) were found from databases which also target these proteins. They showed a similar tendency to mir-9; their lowest expression was at P7 and afterwards, they showed increase. We revealed that miR-9 is localized mainly in the inner retina. Labeling was observed in ganglion and amacrine cells. Additionally, horizontal cells were also marked. By dual miRNA-in situ hybridization/immunocytochemistry and qPCR, we revealed alterations in their temporal and spatial expression. Our results shed light on the significance of mir-9 regulation during the first three postnatal weeks in rat retina and suggest that miRNA could act on their targets in a stage-specific manner.
Highlights
MiRNAs are members of small endogenous noncoding RNA molecules with a prominent regulatory function on gene expression and show tissue-specific action in vertebrates [1]
Mir-9 and mir-218 had a smaller peak at postnatal Day 3 (P3); on the other hand, mir-135 had only one peak at postnatal Day 10 (P10), where mir-9 showed the highest expression level. qPCR measurements mostly supported the sequencing data concerning mir-9 (Figure 2; Table S1)
We observed that mir-9 peaked two times in the first three postnatal weeks: a more than twofold expression was measured at P3 and at P10 (p < 0.0001; p = 0.0087)
Summary
MiRNAs are members of small endogenous noncoding RNA molecules with a prominent regulatory function on gene expression and show tissue-specific action in vertebrates [1]. Considerable attention has been paid to the highly conserved mir-9, which was expressed in the neurogenic regions of the brain, besides being present in the peripheral nervous system [4,13,25,26,27,28]. Loscher and his colleagues made an analysis where they compared the miRNA expression patterns of the brain and the retina. Novel mir-9 expression in Müller cells of the retinal neuronal stem cells has been described [28]
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