<i>Dnmt3a</i> knockout in excitatory neurons impairs postnatal synapse maturation and increases the repressive histone modification H3K27me3.

Li, Junhao; Pinto-Duarte, Antonio; Zander, Mark; Cuoco, Michael S; Lai, Chi-Yu; Osteen, Julia; Fang, Linjing; Luo, Chongyuan et al. · Elife · 2022

basic_science · Level V

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Abstract

Two epigenetic pathways of transcriptional repression, DNA methylation and polycomb repressive complex 2 (PRC2), are known to regulate neuronal development and function. However, their respective contributions to brain maturation are unknown. We found that conditional loss of the de novo DNA methyltransferase <i>Dnmt3a</i> in mouse excitatory neurons altered expression of synapse-related genes, stunted synapse maturation, and impaired working memory and social interest. At the genomic level, loss of <i>Dnmt3a</i> abolished postnatal accumulation of CG and non-CG DNA methylation, leaving adult neurons with an unmethylated, fetal-like epigenomic pattern at ~222,000 genomic regions. The PRC2-associated histone modification, H3K27me3, increased at many of these sites. Our data support a dynamic interaction between two fundamental modes of epigenetic repression during postnatal maturation of excitatory neurons, which together confer robustness on neuronal regulation.

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