Regulatory non-coding transcripts in spermatogenesis: shedding light on 'dark matter'.

Global rise in male infertility over the past decades as a result of falling sperm count and quality has been pointed out by different investigations. Therefore, it is important to understand the molecular mechanism of spermatogenesis and its regulation. Mammalian spermatogenesis, a streamlined process through which male germline cells divide and differentiate into mature spermatozoa, is strictly regulated by phase-specific gene expression which, in turn, is controlled by myriads of regulatory non-coding RNAs (ncRNAs). Rapid advancement in genome mining technologies has identified role of ncRNAs including microRNAs, PIWI-interacting RNAs, endogenous small-interfering RNAs and long non-coding RNAs as controller of gene expression at transcriptional as well as post-transcriptional level in different biological context and disease processes. Here, we discuss the recent progress in our understanding about the involvement of these molecules in spermatogenesis. In addition, we describe here the possible roles of long non-coding RNAs in controlling this process which is not delved so far.