Early Postnatal Treatment with Valproate Induces Promoter Remodeling in the Brain and Reduces Apnea Episodes in -Null Mice

The deletion of , the gene encoding methyl-CpG-binding protein 2, causes severe breathing defects and developmental anomalies in mammals. In -null mice, impaired GABAergic neurotransmission is demonstrated at the early stage of life. GABAergic dysfunction in neurons in the rostral ventrolateral medulla (RVLM) is considered as a primary cause of breathing abnormality in -null mice, but its molecular mechanism is unclear. Here, we report that mRNA expression levels of , which encodes glutamate decarboxylase 67 (GAD67), in the RVLM of -null (, B6.129P2(C)-/J) mice is closely related to the methylation status of its promoter, and valproate (VPA) can upregulate transcription from through epigenetic mechanisms. The administration of VPA (300 mg/kg/day) together with L-carnitine (30 mg/kg/day) from day 8 to day 14 after birth increased mRNA expression in the RVLM and reduced apnea counts in mice on postnatal day 15. Cytosine methylation levels in the promoter were higher in the RVLM of mice compared to wild-type mice born to C57BL/6J females, while VPA treatment decreased the methylation levels in mice. Chromatin immunoprecipitation assay revealed that the VPA treatment reduced the binding of methyl-CpG binding domain protein 1 (MBD1) to the promoter in mice. These results suggest that VPA improves breathing of mice by reducing the promoter methylation, which potentially leads to the enhancement of GABAergic neurotransmission in the RVLM.