Mapping the Regulatory Landscape of Sheep Pituitary Gland Associated With Puberty at Single-Cell Resolution.

The pituitary gland plays a pivotal role in regulating puberty and reproductive physiology; however, the precise cellular and molecular mechanisms driving the pubertal transition in large animal, such as ewes, remain poorly understood. Here, we generated a comprehensive single-cell transcriptomic atlas of the ovine anterior pituitary, specifically comparing the pre-pubertal (3 month) and post-pubertal (6 month) stages. We identified 30 335 cells classified into ten distinct clusters. Comparative analysis revealed a global transcriptional reprogramming during puberty, characterized by a marked upregulation of genes associated with ribosome biogenesis, unfolded protein response, and hormone secretion across endocrine cells, reflecting an expanded biosynthetic capacity. Specifically, we identified SCG2 as a critical regulator of gonadotroph maturation. Functional validation demonstrated that SCG2 facilitates the biogenesis of secretory granules, thereby promoting FSH synthesis and secretion. Furthermore, intercellular communication analysis uncovered a distinct shift in the pituitary microenvironment: the 6 month pituitary exhibited enhanced regulatory networks, including IGF signaling mediated by non-endocrine cells and NT signaling (e.g., BDNF-NTRK2) driven by multiple cell types. These findings suggest that the onset of puberty relies on a coordinated "endocrine-to-endocrine" and "non-endocrine-to-endocrine" crosstalk. This study provides a high-resolution molecular blueprint of the pubertal transition, highlighting the key roles of biosynthetic machinery upgrades and microenvironmental remodeling in establishing the high reproductive performance of Hu sheep.