In silico analysis of piRNAs in retina reveals potential targets in intracellular transport and retinal degeneration

Long considered to be active only in germline, PIWI/piRNA pathway is now known to play significant role in somatic cells, especially neurons. Nonetheless, so far there is no evidence for the presence of piRNAs in the neurosensory retina. In this study, we have uncovered 102 piRNAs in human retina and retinal pigment epithelium (RPE) by analysing RNA-seq data. The identified piRNAs were enriched with three motifs predicted to be involved in rRNA processing and sensory perception. Further, expression of piRNAs in donor eyes were assessed by qRT-PCR. Loss of piRNAs in HIWI2 knockdown ARPE19 cells downregulated targets implicated in intracellular transport (SNAREs and Rabs), circadian clock (TIMELESS) and retinal degeneration (LRPAP1 and RPGRIP1). Moreover, piRNAs were dysregulated under oxidative stress indicating their potential role in retinal pathology. Intriguingly, computational analysis revealed complete and partial seed sequence similarity between piR-62011 and sensory organ specific miR-183/96/182 cluster. Furthermore, the expression of retina enriched piR-62011 positively correlated with miR-182 in HIWI2 silenced Y79 cells. Thus, our data provides an evidence for the expression of piRNAs in human retina and RPE. Collectively, our work demonstrates that piRNAs dynamically regulate distinct molecular events in the maintenance of retinal homeostasis.