Vitamin D Deficiency Activates Gdnf-Ret-pErk1/2 Signal and induces Kidney Malformations in mice

Abstract: Background: Congenital anomalies of the kidney and urinary tract (CAKUT) constitute the most common underlying cause of chronic kidney disease in pediatric populations. Some researchers suggest that adverse maternal factors during pregnancy could may contribute significantly to the pathogenesis of CAKUT. In human populations, maternal hypovitaminosis D is associated with mesoderm-related birth defects such as lower urinary tract malformations and circulatory system abnormalities. Thus, we hypothesized kidney as mesoderm-related organ might be disrupted by maternal vitamin D deficiency, resulting in CAKUT in offspring. Methods: To investigate whether a low-vitamin D level can cause CAKUT, we used vitamin D-free diets to induce maternal vitamin D deficiency mice model. Results: Maternal vitamin D deficiency (VDD) mice models and normal vitamin D status (CON) were successfully established by administering 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 VDD group. In vivo intervention with the p-Erk1/2 antagonist U0126 in pregnant VDD mice model at E10.5 improved CAKUT occurrence in offspring with p-Erk1/2 expression decreased toward normal levels. Early metanephric ureteric bud H3K4me3 CUT&TAG analysis at E12.5 revealed chromatin activation patterns revealed downregulation of Hnf1β promoter region peaks was accompanied by reduced Hnf1β expression, and Robo2 promoter region peak was upregulated with increased Robo2 expression in VDD group. Conclusions: 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.