Transcriptomics identified crucial candidate genes and pathways regulating early testicular development of drakes in the hypothalamic-pituitary-gonadal/thyroid axes

BACKGROUND: The crosstalk between the hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-thyroid (HPT) axes plays an important role in gonadal development. However, the mechanism by which these 2 axes regulate early testicular development in drakes remains largely unknown. Therefore, the aim of the present study was to compare the morphology, histology, and transcriptomics between the precocious puberty (PP) and delayed puberty (DP) Longyan Shan-ma drakes (Anas platyrhynchos) to preliminarily reveal the mechanisms regulating early testicular development. RESULT: The histomorphological results showed that the colloid area and integrated optical density (IOD) of thyroid in PP group were significantly lower than those in DP group (P < 0.05), and the testis weight, testis index, seminiferous tubule diameter, and number of spermatogonia in PP group were significantly higher than those in DP group (P < 0.05). The transcriptomic results showed that between PP and DP groups, a total of 232, 574, 572, and 4,129 differentially expressed genes (DEGs) were identified in the hypothalamus, pituitary, thyroid, and testis, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that DEGs in hypothalamus, pituitary, thyroid, and testis were significantly enriched in 3, 14, 16, and 27 KEGG pathways (P < 0.05), respectively, with the neuroactive ligand-receptor interaction pathway being the only one commonly enriched in all 4 tissues. Further, 11 key genes (GNRH1, AGT, AGTR1, COL1A1, ITGB6, PIK3CB, PLCB4, CALML4, ADCY1, PDE1C, and BUB1) were identified through screening based on enrichment in core reproductive pathways (including neuroactive ligand-receptor interaction and progesterone-mediated oocyte maturation) and functional links to testicular development. Their expression trends were validated by qRT-PCR (R²=0.89), confirming reliability. These genes may serve as critical nodes in HPG/HPT axis crosstalk to regulate early testicular development. CONCLUSION: This study is the first systematically comparing the transcriptomes of the HPG and HPT axes between DP and PP drakes. These results will provide novel insights into the mechanisms of crosstalk regulation of the HPG and HPT axes on early testicular development in drakes.