Homocysteine harasses the imprinting expression of IGF2 and H19 by demethylation of differentially methylated region between IGF2/H19 genes.

Homocysteine (Hcy) can induce proliferation of vascular smooth muscle cells (VSMCs), which is a key event in the genesis of the lesions of atherosclerosis. Insulinlike growth factor 2 (IGF2) and H19 are two important regulating molecules of cell proliferation. The role of Hcy in the proliferation of smooth muscle cell by regulating IGF2 and H19 has not been shown or analyzed so far. This study aims to investigate the potential impact of Hcy on gene imprinting of IGF2 and H19. Cultured human umbilical VSMCs were treated with different concentrations of Hcy. The DNA methylation status of VSMCs was assayed by nested methylationspecific polymerase chain reaction (PCR). The mRNA levels of H19, IGF2, and CCCTC-binding factor (CTCF) were detected by reverse transcription PCR, and the protein expression of IGF2 by Western blotting. The results showed that the Hcy treatment resulted in hypomethylation of the sixth CTCF-binding site upstream of H19 of VSMCs. The expression of H19 was increased, whereas the IGF2 mRNA and protein were decreased, the CTCF expression increased with the increase in Hcy concentration. These data indicated that Hcy could induce hypomethylation of the sixth CTCF-binding sites upstream of H19, which is an important regulating area for the imprinting expression of IGF2 and H19. The increased CTCF expression may be a potential mechanism for the demethylation modification of DNA, which resulted from the Hcy treatment.