PiRNAs link epigenetic modifications to reprogramming

Abstract

Cell reprogramming is a process involved in changing epigenetic landscapes, including histone modification, DNA methylation, and expression of noncoding RNAs; and reprogramming finally leads to changes in gene expression profile and cell fate. A great challenge to this field is to overcome epigenetic suppression exerted by highly differentiated cells of those key regions that are critical for establishment and maintenance of final cell types or induced pluripotent stem cells (iPSCs). As a new class of small non-coding RNAs, piwi-interacting RNAs (piRNAs) have been shown to play important roles in transposon silencing, transcriptional/post-transcriptional regulation, and epigenetic modifications. In this review, we discuss recent advances in which piRNAs were proposed or shown to be barriers to reprogramming suppression through epigenetic silencing, and it may be necessary to overcome this piRNA-derived barrier to achieve final cellular status during reprogramming. Therefore, gaining deeper insights into the mechanism(s) by which piRNAs mediate epigenetic regulation of gene expression, genome stability and chromatin status may offer a new avenue for efficient reprogramming of somatic cells toward a pluripotent state.