Vitamin C inactivates c-Jun N-terminal kinase to stabilize heart and neural crest derivatives expressed 1 in regulating placentation and pregnant maintenance

Abstract

Vitamin C (VC) is an essential nutrient for anti-oxidation, metabolic reaction, and stem cell differentiation. However, the precise role of VC in placentation and pregnant maintenance remains unknown. Here, we demonstrate that physiological concentration of VC stabilizes the Hand1, a bHLH transcription factor crucial for the development of trophoblast giant cell (TGC) lineage, to promote the differentiation of trophoblast stem cells into TGCs. The role of VC depends on the inactivation of JNK kinase, which directly phosphorylates Hand1 at Ser48 and thereby induces Hand1 proteasomal degradation, whereas loss-of-function mutation of Ser48 on Hand1 robustly decreases not only the basal but also VC-induced Hand1 stabilization. As a result, VC deficiency, lentiviral knockdown of JNK or overexpression of Hand1 mutants in trophectoderm significantly affects the differentiation of primary and secondary TGCs in E8.5 mouse placentas. VC deficiency causes a severe defect in the differentiation of diverse TGCs and the formation of vascular network of labyrinth in mature mouse placentas and thereby fails to maintain the pregnancy. Thus, these results uncover JNK inactivation and subsequent Hand1 stabilization as a hitherto uncharacterized mechanism controlling VC-mediated placentation and perhaps pregnant maintenance.