Adipose-specific knockout of Dicer or Dgcr8, two essential proteins for microRNA biogenesis, results in depletion of most microRNAs, leading to a WAT-like phenotype in brown adipose tissue (BAT) and a defect in WAT development25, 26; even heterozygous knockout of Dicer in BAT can decrease the expression of Ucp1 and aggravate obesity-evoked deterioration of glucose metabolism27. Here, UCP1 is linked to obesity due to melanocortin 4 receptor deficiency.