Transcriptomic and hormonal analysis of 17α-methyltestosterone induced gonadal remodeling in all-female Qi River crucian carp (Carassius gibelio)

Sex differentiation of fish is governed by environmental and endocrine factors, among which sex hormones play a pivotal role. The Qi River crucian carp ( Carassius gibelio ) is a ideal model for research on reproductive plasticity due to its natural female-biased sex ratio. In this study, 17α-methyltestosterone (MT) was used to induce masculinization in all-female Qi River crucian carp. MT treatment promoted the appearance of spermatogonia and led to reductions in body length, body weight and gonadosomatic index. Subsequently, changes in gene expression and hormone levels were analyzed by qRT-PCR and ELISA. The significant upregulation of the male maker genes Dmrt1 and Amh . The BPG axis showed a decrease in the levels of GnRH, FSH and LH in the serum. The levels of T, E2 and 11-KT increased. The expression of the steroidogenic enzymes Cyp19a1a and Hsd11β2 was significantly up-regulated in gonadal tissue. Transcriptomic analysis revealed enrichment of several sexual differentiation pathways, including PPAR, TGF-beta, FoxO and Fanconi anemia, as well as activation of the p53-mediated apoptosis pathway. These regulatory pathway changes promote gonadal remodeling. In general, this work provides molecular insights into MT induced gonadal masculinization and establishes a foundation for reproductive manipulation in gynogenetic species. • 17α-Methyltestosterone (200 mg/kg) induced spermatogonia formation in all-female Qi River crucian carp. • Transcriptomics revealed that MT treatment triggers p53-mediated apoptosis and disrupts ovarian developmental pathways, ultimately leading to the reversal of gonadal structure. • This study elucidates for the first time the regulatory role of the brain-pituitary-gonad (BPG) axis in MT-induced masculinization of Qi River crucian carp.