Abstract

Increase in the size of human neocortex, acquired in evolution, accounts for the unique cognitive capacity of humans. This expansion appears to reflect the evolutionarily-enhanced proliferative ability of basal progenitors (BPs) in mammalian cortex, which may have been acquired through epigenetic alterations in BPs. However, whether or how the epigenome in BPs differs across species is not known. Here, we report that histone H3 acetylation is a key epigenetic regulation in BP amplification and cortical expansion. Through epigenetic profiling of sorted BPs, we show that H3K9 acetylation is low in murine BPs and high in human BPs. Elevated H3K9ac preferentially increases BP proliferation, increasing the size and folding of the normally smooth mouse neocortex. Mechanistically, H3K9ac drives BP amplification by increasing expression of the evolutionarily regulated gene, TRNP1, in the developing cortex. Our findings demonstrate a previously unknown mechanism that controls cortical architecture. One Sentence SummaryH3K9ac promotes basal progenitor amplification, neocortex expansion and gyrification by activating TRNP1 expression in evolution.