Abstract
Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis, but it is absent in some mammals, including pigs. During development, BAT progenitors are derived from paired box 7 (Pax7)-expressing somitic mesodermal stem cells, which also give rise to skeletal muscle. However, the intrinsic mechanisms underlying the fate decisions between brown fat and muscle progenitors remain elusive across species. In this study, we analyzed the dynamics of chromatin landscape during the segregation and specification of brown fat and muscle lineages from Pax7+ multipotent mesodermal stem cells, aiming to uncover epigenetic factors that drive de novo BAT formation. Notably, myogenic progenitors were specified at embryonic day (E) 12.5, exhibiting high levels of H3K4me3 and low H3K27me3 at muscle-related genes. In contrast, the specification of the BAT lineage occurred much later, with coordinated step-wise depositions of histone modifications at BAT-associated genes from E10.5 to E14.5. We identified the transcription factor early B-cell factor 2 (EBF2) as a key driver of the progressive specification of brown fat lineage and the simultaneous deviation away from the muscle lineage. Mechanistically, EBF2 interacts with transcriptional co-activators CREB binding protein/ E1A-binding protein p300 (CBP/P300) to induce H3K27ac deposition and chromatin activation at BAT-associated genes to promote brown adipogenesis. Both mouse and pig EBF2 could potently stimulate adipogenesis in unspecified multipotent mesodermal stem cells. However, in pigs, EBF2 expression was depleted during the critical lineage specification time window, thus preventing the embryonic formation and development of porcine BAT. Hence, the elevation of EBF2 in mice, but not in pigs, promote chromatin activation to drive the progressive specification of brown fat lineage.