A distal enhancer with ETV4 binding is critical for UCP1 expression and thermogenesis in brown fat.

Brown adipose tissue (BAT) dissipates energy as heat in maintaining body temperature, and BAT mass inversely correlates with adiposity. During thermogenesis, BAT generates heat by uncoupling respiration through UCP1, and the -2.5 kb enhancer of UCP1 gene is known to activate UCP1 expression upon cold or β-adrenergic stimulation. Here, we identify a critical UCP1 enhancer located at 12 kb upstream of the UCP1 gene locus that functions through chromatin looping and uncover its essential role in UCP1 activation and thermogenesis by CRISPR activation and CRISPR interference in mice. Importantly, we identify ETV4 as a key regulator of UCP1 expression by binding the -12 kb enhancer to promote chromatin accessibility and histone acetylation. Using gain- and loss-of-function approaches, we reveal that ETV4 enhances uncoupled respiration and thermogenesis, thereby protecting mice from diet-induced obesity and insulin resistance. The -12 kb enhancer and ETV4 can be potential therapeutic targets for combating obesity and improving metabolic health.