Characteristics of steroidogenesis-related factors in the musk gland of Chinese forest musk deer (Moschus berezovskii)

Musk secreted by Chinese forest musk deer (FMD; Moschus berezovskii) is a highly valuable ingredient in the fields of perfumery and medicine, and the main factor affecting the production of musk is the androgen level of male FMD. To clarify whether the musk gland of FMD can synthesize androgen, we compared and analyzed the expression patterns of steroid hormone biosynthesis-related genes in the musk gland and testis of FMD by RNA-seq and RT-qPCR. We obtained 33,308 and 38,602 unigenes from the musk gland and testis, respectively, and 26,780 co-expressed unigenes. Analysis of co-expressed genes revealed that 12,647 genes were annotated to 11,484 Gene Ontology terms and 10,941 genes were annotated to 6120 pathways, including several pathways important in metabolic and synthetic activity. Next, 21 steroid hormone synthesis-related genes were screened from the transcriptome of the musk gland of 4-month-old FMD. The expression levels of three key genes of steroid hormone biosynthesis (CYP11A1, CYP17A1, and HSD3B) in the musk gland differed from their expression levels in the testis based on RT-qPCR. Furthermore, immunohistochemistry indicated that CYP11A1, CYP17A1, and HSD3B were localized in the glandular tubular columnar cells of the musk gland. These results suggested that the musk gland of male FMD has the potential to locally synthesize steroid hormone and thus plays a critically important role in musk secretion.