De novo assembly of Chinese forest musk deer ( Moschus berezovskii ) transcriptome from Next-Generation mRNA Sequencing

Musk secretion in male musk deer is regarded as a propitious mode of sexual election to attract a greater number of females. However, the genetic mechanisms of musk secretion are still poorly understood and unresolved making it necessary to elucidate the possible genetic mechanisms of musk formation. In the present study, we used heart and musk gland tissues from a male musk deer for next-generation mRNA sequencing, integrated with de novo assembly, unigenes annotation and differentially expressed genes analysis. A total of 239,383 transcripts and 208,730 unigenes were obtained from 2 pooled RNA samples. Annotated analysis indicated steroid compound metabolism (steroid biosynthesis, steroid hormone biosynthesis, aldosterone-regulated sodium reabsorption, terpenoid backbone biosynthesis) related to musk formation were annotated to many pathways; relevant genes were identified as well. In addition, 8,986 differentially expressed genes (6,068 up- and 2,198 down-regulated) between heart and musk gland were identified, among them, steroid component metabolism were abundant. Further exploration of functional enrichment analysis showed that pathways involved in musk secretion were up-regulated in musk gland compared with heart, especially steroid biosynthesis and terpenoid backbone biosynthesis whose metabolic productions were key components of musk. We identified several candidate genes such as DHCR7 , DHCR24 , NSDHL , CYP3A5 , FDFT1 , FDPS and HMGCL which were closely involved in metabolism of steroid, terpenoid and ketone bodies. Our data are expected to represent the most comprehensive sequence resource available for the forest musk deer so far, and provide a basis for further research on molecular genetics and functional genomics of musk secretion.