Widespread expression of piRNA-like molecules in somatic tissues

Abstract

Piwi-interacting RNA (piRNA) are small RNA abundant in the germline across animal species. In fruit flies and mice, piRNA have been implicated in maintenance of genomic integrity by transposable elements silencing. Outside of the germline, piRNA have only been found in fruit fly ovarian follicle cells. Previous studies have further reported presence of multiple piRNA-like small RNA (pilRNA) in fly heads and a small number of pilRNA have been reported in mouse tissues and in human NK cells. Here, we analyze high-throughput small RNA sequencing data in more than 130 fruit fly, mouse and rhesus macaque samples. The results show widespread presence of pilRNA, displaying all known characteristics of piRNA in multiple somatic tissues of these three species. In mouse pancreas and macaque epididymis, pilRNA abundance was compatible with piRNA abundance in the germline. Using in situ hybridizations, we further demonstrate pilRNA co-localization with mRNA expression of Piwi-family genes in all macaque tissues. Further, using western blot, we have shown the expression of Miwi protein in mouse pancreas. These findings indicate that piRNA-like molecules might play important roles outside of the germline.

Piwi-Interacting RNAs (piRNAs) Are Dysregulated in Renal Cell Carcinoma and Associated with Tumor Metastasis and Cancer-Specific Survival

“…In addition to the characteristic function of the silencing of mobile elements by target slicing, piRNA function of mRNA regulation, and mechanisms of transcriptional gene silencing and mRNA deadenylation, are also described (7). Recently, studies have demonstrated that piRNAs are widely present and play important roles in somatic cells (8). However, piRNAs have not been thoroughly studied in cancers D 2 1 : 3 8 1 -3 8 8 , 2 17).…”

“…Owing to their limited expression in gonads as well as sequence diversity, piRNAs are the most mysterious subclass of sncRNAs. Although piRNAs have recently been shown to be present in somatic tissues and some human cancer cells, their functional significance is still not clear (8)(9)(10)(11). Recent studies have shown differential expression of piRNAs in gastric, liver and breast cancers (12,13).…”

piRNA pathway is not required for antiviral defense in Drosophila melanogaster

“…Nevertheless, endogenous piRNAs also have been identified in various somatic tissues from fly, mouse, and macaque, as well as in mosquito head and thorax (22,23).…”

A Novel Class of Somatic Small RNAs Similar to Germ Cell Pachytene PIWI-interacting Small RNAs

“…We and others have reported the existence of piRNA-like RNAs (pilRNAs) in both gonadal and somatic tissues (13)(14)(15)(16). However, a detailed characterization of this novel class of small RNAs expressed in somatic cells/tissues has been lacking.…”