Integrated Circular RNAs Analysis Across the Hypothalamic-Pituitary-Ovarian Axis Identifies Regulatory Modules Shaping Reproductive Traits in Geese.

Circular RNAs (circRNAs) are increasingly recognized as key post-transcriptional regulators. However, their functions within the avian hypothalamic-pituitary-ovarian (HPO) axis remain poorly understood. To investigate potential associations of circRNAs with breed differentiation and reproductive traits, we constructed cross-tissue circRNA profiles through whole-transcriptome sequencing of the HPO axis in Zi and Xianghai flying geese. A total of 90, 80, and 90 DE-circRNAs were identified in the hypothalamus, ovary, and pituitary, respectively, corresponding to 248 non-redundant DE-circRNA IDs across the three tissues. Functional enrichment analysis revealed that their host genes were significantly enriched in reproduction-related signaling pathways, including cAMP, PI3K-Akt, FoxO, JAK-STAT, GnRH, and VEGF signaling pathways. GO terms related to reproduction, reproductive process, and growth were significantly enriched, with protein interaction analysis identifying CYP19A1, FSHR, BMP15, and ESR1 as central network hubs. Furthermore, through systematic integration of cross-tissue circRNA, miRNA, and mRNA expression profiles and a series of analytical steps including correlation-based filtering and hypergeometric testing, we thereby constructed a cross-tissue ceRNA network. Several functional modules were identified, including novel_circ_000988-miR-1451-y/miR-216-x/miR-735-x-IL20RA, novel_circ_019479-miR-1338-y/miR-1388-y-GLRA2, and novel_circ_010669-miR-143-z-Med27. Our results indicate that circRNAs may be associated with a cross-tissue neuroendocrine-ovarian regulatory network through putative ceRNA-associated interactions, providing candidate molecular insights into reproductive trait variation in geese.