O6-methylguanine DNA methyltransferase (MGMT),
a DNA repair
enzyme, has been reported in some congenital malformations, but it is less frequently reported in
neural tube defects. This study investigated MGMT
mRNA expression and methylation levels in the early embryo and in different embryonic stages, as well as the relationship between MGMT and
neural tube defects.
Spina bifida aperta was induced in rats by a single intragastric administration of
all-trans retinoic acid on embryonic day (
E) 10, whereas normal control rats received the same amount of
olive oil on the same embryonic day. DNA damage was assessed by detecting γ-H2A.X in
spina bifida aperta rats. Real time-polymerase chain reaction was used to examine
mRNA expression of MGMT in normal control and
spina bifida aperta rats. In normal controls, the MGMT
mRNA expression decreased with increasing embryonic days, and was remarkably reduced from E11 to E14, reaching a minimum at E18. In the
spina bifida aperta model, γ-H2A.X
protein expression was increased, and
mRNA expression of MGMT was markedly decreased on E14, E16, and E18.
Bisulfite sequencing polymerase chain reaction for MGMT promoter methylation demonstrated that almost all CpG sites in the MGMT promoter remained unmethylated in both
spina bifida aperta rats and normal controls, and there was no significant difference in methylation level between the two groups on either E14 or E18. Our results show that DNA damage occurs in
spina bifida aperta rats. The
mRNA expression of MGMT is downregulated, and this downregulation is independent of promoter DNA methylation.