Supplementary Material for: Change of Epigenetic Control of Cystathionine Beta-Synthase Gene Expression through Dietary Vitamin B₁₂ Is Not Recovered by Methionine Supplementation

Background/Aims: Vitamin B₁₂ (B-12) is an essential cofactor for methionine synthase, and methionine is critical for the methylation of various biological molecules including DNA. Whether changes in B-12 levels can alter specific gene expression through DNA methylation and whether dietary methionine has any effect on general DNA methylation status still remains controversial. Methods: We raised severely B-12-deficient rats as well severely-B-12 deficient rats but supplemented with 5% methionine. mRNA levels of methionine cycle-related enzymes were analyzed. Results: Gene expression patterns changed under B-12-deficient conditions but were recovered by dietary methionine supplementation to B-12-deficient rats. However, cystathionine β-synthase mRNA levels, which had decreased under B-12-deficient conditions, did not recover with supplementary dietary methionine. The CpG island of the cystathionine β-synthase promoter was hypomethylated in B-12-deficient rats, and showed no recovery after methionine addition. Conclusions: Dietary B-12 can affect epigenetic machinery by regulating DNA methylation status and dietary methionine may have small effects on DNA methylation.