The role of DNA methylation in regulation of the murine Lhx3 gene.

LHX3 is a LIM-homeodomain transcription factor with critical roles in pituitary and nervous system development. Mutations in the LHX3 gene are associated with pediatric diseases featuring severe hormone deficiencies, hearing loss, developmental delay, and other symptoms. The mechanisms that govern LHX3/Lhx3 transcription are poorly understood. In this study, we examined the role of DNA methylation in the expression status of the mouse Lhx3 gene. Pituitary cells that do not normally express Lhx3 (Pit-1/0 cells) were treated with 5-aza-2'-deoxycytidine, a demethylating reagent. This treatment leads to activation of Lhx3 gene expression suggesting that methylation contributes to Lhx3 regulation. Treatment of Pit-1/0 pituitary cells with a combination of a demethylating reagent and a histone deacetylase inhibitor led to rapid activation of Lhx3 expression, suggesting possible crosstalk between DNA methylation and histone modification processes. To assess DNA methylation levels, treated and untreated Pit-1/0 genomic DNAs were subjected to bisulfite conversion and sequencing. Treated Pit-1/0 cells had decreased methylation at specific sites in the Lhx3 locus compared to untreated cells. Chromatin immunoprecipitation assays demonstrated interactions between the MeCp2 methyl binding protein and Lhx3 promoter regions in the Pit-1/0 cell line. Overall, this study demonstrates that DNA methylation patterns of the Lhx3 gene are associated with its expression status.