RNA-Seq reveals ACTH-induced steroid hormone pathway participating in goat adrenal gland response to castration

The content of androgen from adrenal is elevated under castration, and the mechanisms of compensatory secretion of adrenal androgen remain unknown. This study was designed to compare the transcript profiles between adrenals from noncastrated, orchiectomized and immunocastrated Yiling goats. Fifteen goats were randomly divided into three groups: pVAX-asd injection (control) group, pVAX-B2L-(G₄S)₃-kisspeptin-54-asd immunization (PBK-asd) group, and surgical castration (SC) group. Subsequently, serum was collected every two weeks after the initial immunization for hormone assays. At week 14 after immunization, adrenal glands were collected for transcriptome sequencing and qPCR. Serum testosterone concentration was significantly reduced in PBK-asd and SC group, demonstrating the effectiveness of castration. Both surgical and immunized castration resulted in adrenal hyperplasia, and thickness of adrenal cortex elevated. The specific genes involving castration were enriched in many pathways, including Steroid hormone biosynthesis pathway. The adrenocorticotropic hormone (ACTH), which promotes the production of adrenal steroids, and dehydroepiandrosterone (DHEA), a steroid hormone secreted by adrenal glands, both increased after castration. Further construction of co-expression network for transcription genes and traits (including adrenal weight and cortex thickness, ACTH and DHEA concentration) showed that the trait-related genes were enriched in multiple steroid-related pathways. These results showed that adrenal compensatory hyperplasia and androgen secretion caused by castration may involve in ACTH-induced steroid hormone synthesis.