MeCP2 is capable of binding to methylated DNA. There is a possibility that the reduction in MeCP2 occupancy at the GFAP promoter was triggered by DNA demethylation of the same region; we therefore examined the DNA methylation status of the GFAP gene in NTera-2 cells and differentiated astrocyte-like cells. However, the bisulfite sequencing analysis showed that upon differentiation toward an astrocyte-like lineage, the CpG dinucleotide around the STAT3-binding site at the promoter (primer sets P1 and P2 in Fig. 4C ) and exon 1 (primer sets E1 and E2) was not demethylated (Fig. 4C) . To further confirm these findings, we performed a quantitative methylation analysis using MALDI-TOF/MS to examine the mass signal shift of methylated DNA compared to unmethylated DNA extracted from undifferentiated NTera-2 cells, differentiated cells, and control human monocytes. This study confirmed that CpG sites scattered in the approximately 4500-bp region upstream of the GFAP transcription start site were stably methylated before and after differentiation (Fig. 4D) . We concluded that the DNA methylation status of the GFAP promoter and exon 1 remained unchanged during cellular differentiation. Our results showed that reduced expression of Sin3A is accompanied by decreased occupancy of Sin3A and MeCP2 around the STAT3-binding site of the GFAP promoter, which was not necessarily accompanied by DNA demethylation in the same region for the induction of GFAP expression. These results suggest a critical role for Sin3A in regulating GFAP expression during astrocytic differentiation.