Abstract
BackgroundDeciphering the functions of Y chromosome in mammals has been slow owing to the presence of repeats. Some of these repeats transcribe coding RNAs, the roles of which have been studied. Functions of the noncoding transcripts from Y chromosomal repeats however, remain unclear. While a majority of the genes expressed during spermatogenesis are autosomal, mice with different deletions of the long arm of the Y chromosome (Yq) were previously also shown to be characterized by subfertility, sterility and sperm abnormalities, suggesting the presence of effectors of spermatogenesis at this location. Here we report a set of novel noncoding RNAs from mouse Yq and explore their connection to some of the autosomal genes expressed in testis.ResultsWe describe a set of novel mouse male-specific Y long arm (MSYq)-derived long noncoding (lnc) transcripts, named Pirmy and Pirmy-like RNAs. Pirmy shows a large number of splice variants in testis. We also identified Pirmy-like RNAs present in multiple copies at different loci on mouse Y chromosome. Further, we identified eight differentially expressed autosome-encoded sperm proteins in a mutant mouse strain, XYRIIIqdel (2/3 Yq-deleted). Pirmy and Pirmy-like RNAs have homology to 5′/3′UTRs of these deregulated autosomal genes. Several lines of experiments show that these short homologous stretches correspond to piRNAs. Thus, Pirmy and Pirmy-like RNAs act as templates for several piRNAs. In vitro functional assays reveal putative roles for these piRNAs in regulating autosomal genes.ConclusionsOur study elucidates a set of autosomal genes that are potentially regulated by MSYq-derived piRNAs in mouse testis. Sperm phenotypes from the Yq-deleted mice seem to be similar to that reported in inter-specific male-sterile hybrids. Taken together, this study provides novel insights into possible role of MSYq-derived ncRNAs in male sterility and speciation.
Highlights
Deciphering the functions of Y chromosome in mammals has been slow owing to the presence of repeats
M34 is transcribed in mouse testis To address the precise function of M34, we confirmed the localization of the sex- and species-specific repeat (M34) on mouse Long arm of Y chromosome (Yq) again by fluorescence in situ hybridization (FISH) (Fig. 1A)
Our results suggest for the first time, the mechanism of P-element-induced wimpy testis (PIWI) interacting Long noncoding RNA (RNA) (piRNA)-mediated regulation of autosomal genes involved in spermiogenesis and male fertility
Summary
Deciphering the functions of Y chromosome in mammals has been slow owing to the presence of repeats. Published data have described two different strains of mice with partial deletions of the long arm of Y chromosome (Yq) [2, 13] Mice from both the genetic backgrounds exhibit male-sterile phenotypes such as subfertility, sex ratio skewed towards females, reduced number of motile sperms, aberrant sperm motility and sperm head morphological abnormalities [2, 14]. Mice with partial deletions of Yq show sperm abnormalities with less severe phenotype whereas mice with total deletion of the Yq have extensive sperm morphological aberrations and are sterile [15] This suggested the presence of multicopy spermiogenesis gene(s) on mouse Yq [2, 10, 16]. We postulated the possibility of yet undiscovered genes in the region involved in male fertility
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