This gene encodes a transcriptional coactivator that induces and coordinates gene expression regulating mitochondrial biogenesis, respiration, hepatic gluconeogenesis, thermogenic program in brown fat and muscle fiber-type switching. Mice lacking the encoded protein exhibit reduced thermogenic capacity, hyperactivity and resistance to diet-induced obesity. Mice lacking the encoded protein specifically in the heart exhibit peripartum cardiomyopathy. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Sep 2015]