Developmental remodelling of non-CG methylation at satellite DNA repeats

The latest from our lab is out in Nucleic Acids Research. This exciting project was led by the very talented Sam Ross who uncovered a novel non-CG DNA (mCH) methylation signature that is highly abundant at zebrafish MOsaic SATellite repeats (MOSAT). MOSAT mCH is high in gonads, decreases during cleavage stages, and reaches its lowest point at ZGA. Unlike mammalian mCH – that is mostly present in oocytes and in the nervous system – MOSAT mCH increases during gastrulation and is deposited in tissues originating from all embryonic layers. Also, in contrast to mammals, this mCH type positively correlates with heterochromatin (H3K9me3). We uncovered the actinopterygian-specific Dnmt3ba as the principal MOSAT mCH DNA methyltransferase and fully resolved its phylogenetic origin. This work thus provides proof for yet another “love story” between repetitive elements and DNMTs in the animal kingdom.