The Effect of Knocked-Down Anti-Müllerian Hormone mRNA on Reproductive Characters of Male Nile Tilapia (Oreochromis niloticus) through Inhibition of the TGF-Beta Signaling Pathway

Anti-Müllerian hormone (amh), an important regulator of gonad development in male teleosts, regulates the development and differentiation of germ cells. We performed transcriptional knock-down of amh in Nile tilapia (Oreochromis niloticus) using antisense RNA technology, resulting in down-regulation in the expression of amh transcription and Amh protein in males. Compared with the control groups, the fish in treatment groups with down-regulated amh had increased weight and an extremely significant decrease in the gonadosomatic index. Hematoxylin–eosin staining revealed impaired testis development and significant reductions in numbers of sperm. Serum estradiol levels were significantly increased, and the levels of testosterone, luteinizing hormone, and follicle-stimulating hormone were significantly decreased. RNA-sequencing analysis of the fish in the down-regulated amh and control groups identified 12,048 differentially expressed genes, of which 1281 were up-regulated and 10,767 were down-regulated. Kyoto Encyclopedia of Genes and Genomes analysis revealed that differentially expressed genes related to growth and development were mainly enriched in the Cell cycle, Endocytosis, TGF-beta signaling pathway, Wnt signaling pathway, FoxO signaling pathway, Insulin signaling pathway, and MAPK signaling pathway. The RNA-sequencing data accuracy was verified by qRT-PCR analysis of the expression levels of selected differentially expressed genes. The abnormal TGF-beta signaling pathway may cause fish weight gain, testis dysplasia, and abnormal spermatogenesis: smad5, smad3a, tgfb2, tgfbr1b, gsdf, and amh were significantly down-regulated. These findings indicated that antisense RNA technology has strong application prospects and can specifically knock down amh in Nile tilapia, resulting in an abnormal TGF-beta signaling pathway, inhibiting testis development and inducing weight gain.