GDF9, NPHS1, and RET Mark Gastric Neuroendocrine Cells and Their Disruption in a PKA-Driven Gastric Preneoplasia Model

The gastric endocrine population comprises functionally distinct cell types that exhibit both neuronal and endocrine characteristics; however, their molecular markers remain incompletely defined. Here, we identify growth differentiation factor 9 (GDF9), nephrin (NPHS1), and rearranged during transfection (RET) as novel markers of gastric endocrine cells. A co-immunofluorescence (IF) analysis demonstrated that GDF9, NPHS1, and RET are co-expressed with chromogranin A (CHGA), a well-known marker of gastrointestinal endocrine cells. Further Co-IF analysis revealed that GDF9-expressing cells were negative for ghrelin and somatostatin, whereas NPHS1 was co-expressed with both hormones. A subpopulation of RET-positive cells co-expressed ghrelin but not somatostatin. Notably, GDF9- and RET-positive cells co-expressed dopamine decarboxylase (DDC), consistent with enrichment in enterochromaffin-like (ECL) cells. Revisitation of our previous mRNA-sequencing data revealed reduced transcript levels of Gdf9, Nphs1, and Ret in CA-PKA mice, which express constitutively active protein kinase A (PKA) and develop gastric preneoplastic lesions. Co-IF and cellular quantification showed a localized reduction in the density of GDF9 and CHGA-positive endocrine cells, together with altered abundance of NPHS1- and RET-expressing cells in CA-PKA stomachs. These changes occurred in the context of extensive hyperplasia of the surrounding epithelium, indicating that the observed alterations reflect localized reduction and non-cell-autonomous effects of epithelial expansion. Notably, we observed RET misexpression outside the endocrine compartment in CA-PKA mice, suggesting that aberrant RET signaling may contribute to lesions by promoting abnormal glandular branching. Together, these findings identify GDF9, NPHS1, and RET as novel markers of gastric endocrine cells and their potential role in gastric homeostasis.