Comparative analysis of SCGN expression patterns in the anterior pituitary gland of mouse, pig, and human by single-cell transcriptomics.

Secretagogin (SCGN) is a calcium-binding protein implicated in neuroendocrine secretion. However, its expression profile in the anterior pituitary gland and potential species-specific differences remain poorly characterized. We analyzed scRNA-seq data from the pituitary glands of mice, rats, pigs, and humans, then combined it with validation by immunostaining to systematically elucidate the expression and distribution patterns of SCGN in the anterior pituitary gland. SCGN exhibited distinct species-specific expression patterns. In mice, SCGN transcripts were predominantly enriched in PIT1-lineage lactotropes and SF1-lineage gonadotropes, with immunofluorescence confirming high colocalization with LH, FSH, and PRL. In pigs, SCGN was primarily expressed in TPIT-lineage corticotropes, and immunofluorescence colocalization analysis confirmed the highest colocalization rate with ACTH. In humans, SCGN expression was confirmed in the anterior pituitary gland by immunohistochemistry, while scRNA-seq revealed predominant enrichment of its transcripts in PIT1-lineage lactotropes and somatotropes. Notably, comparative interspecies analysis indicated a high degree of similarity in SCGN enrichment within PIT1-lineage cells (particularly lactotropes) between mice and humans. In contrast, SCGN expression was undetectable in the rat anterior pituitary gland at both transcriptional and protein levels. Together, our findings suggest that SCGN may not be an essential or universal regulator of anterior pituitary hormone secretion. Instead, this study provides an informative negative example that highlights the interspecies divergence of the pituitary secretory machinery among mammals.