Chromatin Remodeling Dynamics During Brown Adipogenesis

Brown adipose tissue (BAT) is specialized to expend energy through the action of the mitochondrial uncoupling protein UCP1. Increasing brown fat mass or activity through genetic or chemical manipulation in mice suppresses obesity and its comorbidities; as such, there is great interest in developing approaches to increase the amount and/or function of brown fat to combat metabolic disorders. My thesis work aimed to dissect the molecular mechanisms by which the helix- loop-helix transcription factor Early B-Cell Factor 2 (EBF2) regulates brown adipocyte commitment and terminal differentiation. Through analysis of tissue-specific knockout mouse models, we found that EBF2 is required for the development and maintenance of brown fat and mitochondrial programming in vivo. We further integrated genome-wide chromatin immunoprecipitation (ChIP) and RNA-seq data to discover that EBF2 globally orchestrates the brown fat transcriptional program by directly binding to lineage-specific enhancer regions. Mechanistically, we find that EBF2 physically interacts with BRG1 and the BAF chromatin remodeling complex, which incorporates a specific histone reader Double PHD Fingers 3 (DPF3). DPF3 is required downstream of EBF2 to activate thermogenic genes and promote mitochondrial function in brown adipocytes. Detailed analysis of the Dpf3 genomic locus using CRISPR-mediated enhancer editing revealed that Dpf3 itself is a direct transcriptional target of EBF2 during brown adipogenesis. Together, these results establish a feed-forward mechanism through which EBF2 drives Dpf3 expression and also directs DPF3-anchored BAF complexes to chromatin. Thus, EBF2 itself is able to activate components of the brown fat transcriptional machinery and further functions as a sequence-specific factor to direct these transcriptional regulatory components to the DNA. Taken together, my thesis work has revealed a novel model by which EBF2 cooperates with tissue-specific chromatin remodeling complexes to activate the thermogenic program in adipocytes