H3K9 di-methylation dynamics underlies mouse minor zygotic genome activation [RNA-seq of mESC]

Here we show that dynamic regulation of H3K9me2 is essential for minor ZGA. H3K9me2 levels at minor ZGA gene loci are reduced at early 2-cell and are re-established by morula.

Maternal depletion of the H3K9 demethylases KDM3A and KDM3B leads to increased H3K9me2 and impaired minor ZGA in early 2-cell, followed by developmental arrest at 2- to 4-cell. In mESCs, H3K9 at minor ZGA loci is highly di-methylated; combined loss of the H3K9 methyltransferases G9a and SETDB1 leads to synergistic de-repression of minor ZGA genes. Mechanistically, SETDB1 specifically targets Dux, while G9a broadly represses minor ZGA genes through H3K9 di-methylation linked to lamina-associated heterochromatin formation.