Vitamin D Deficiency Activates Gdnf-Ret-pErk1/2 Signal and Induces Kidney Malformations in Mice

Congenital anomalies of the kidney and urinary tract (CAKUT) constitute the most common underlying cause of chronic kidney disease in pediatric populations. Maternal hypovitaminosis D links to mesoderm-related birth defects, leading to our hypothesis that maternal vitamin D deficiency (VDD) impairs renal development (a mesoderm-derived process) and induces offspring CAKUT. To investigate whether a low-vitamin D level can cause CAKUT, we used vitamin D-free diets to induce a maternal vitamin D deficiency mice model. The maternal vitamin D deficiency (VDD) mice models and normal vitamin D status (CON) were successfully established by administering a vitamin D-free or vitamin D-sufficient diet for 4 weeks prior to pregnancy. The overall incidence of CAKUT was significantly increased in VDD neonatal mice (19.4% vs. 2.44%; p = 0.0006), with a higher incidence of early duplicated budding in E11.5. E11.5 ureteric bud tissue revealed significantly increased activity of Gdnf-Ret-p-Erk1/2 signaling in the VDD group. In vivo intervention with the p-Erk1/2 antagonist U0126 in the pregnant VDD mice model at E10.5 improved CAKUT occurrence in offspring with p-Erk1/2 expression decreasing toward normal levels. Early metanephric ureteric bud H3K4me3 CUT&TAG analysis at E12.5 revealed chromatin activation patterns, which revealed that the downregulation of Hnf1β promoter region peaks was accompanied by reduced Hnf1β expression, and Robo2 promoter region peak was upregulated with increased Robo2 expression in the VDD group. Maternal vitamin D deficiency in mice significantly increased offspring CAKUT incidence. This phenotype was mediated by enhanced Gdnf-Ret-p-Erk1/2 signaling and reversed by p-Erk1/2 inhibition, with VDD inducing epigenetic remodeling of Hnf1β and Robo2 promoters.