A muskrat tissue atlas of small non-coding RNAs and their regulatory roles in muskrat musk secretion.

Abstract

Muskrat musk, secreted by the male muskrat scent gland during the secretion period, is a valuable natural product with promising pharmacological activities. Its synthesis is regulated not only by coding genes but also by small non-coding RNAs (sncRNAs). However, a comprehensive tissue atlas of sncRNAs in muskrats has been lacking. To address this issue, we systematically profiled the expression levels of 6 sncRNA categories (piRNA [PIWI-interacting RNA], miRNA [microRNA], snoRNA [small nucleolar RNA], snRNA [small nuclear RNA], tRNA [transfer RNA], and other RNAs) across 13 tissues of the muskrat via deep sequencing. We identified 23,957 sncRNAs (∼ 65%) exhibiting tissue-specific expression patterns throughout the body. The results show that miRNA is the main contributor to tissue specificity. Eleven tissues showed a significantly higher number of miRNA-5p arm expressions compared to the 3p arm, although the brain was an exception. Quantitative results imply that miR-477-3p/5p and miR-794-3p are potentially involved in the regulation of muskrat musk synthesis and secretion in the muskrat scent glands. Their target genes were enriched in pathways related to energy supply, lipid metabolism, and cyclic morphological changes of the scent gland. Furthermore, we constructed a set of co-expressed miRNAs based on the hormone-dominated "brain-testis-scent gland" axis and the energy metabolism-dominated "brain-liver-scent gland" axis. These results provide the most comprehensive description to date of tissue-specific and ubiquitous sncRNAs in individual muskrat tissues. We anticipate that these data will enhance the understanding of the molecular regulation underlying muskrat musk synthesis and secretion.