Vitamin B(12) promotes Cx40 and HCN4 gene expression at an early stage of cardiomyocyte differentiation.

Vitamin B(12) (VB(12)) was investigated for its ability to influence the expression of genes required for cardiac cell differentiation from mouse embryonic stem cells. When VB(12) (0.5 mM) was added to the medium on day 3 of culture, the levels of Cx40 and HCN4 expression increased over those in the control, 2 to 3 days before the start of cardiomyocyte beating. In contrast, the expression levels of alpha-MHC, MLC-2a, and MLC-2v were almost the same as those of the control throughout the culture period. Our results suggest that VB(12) is involved in the promotion of the intercellular conducting system rather than the generation of contractile proteins.