CMPK2 and obesity due to melanocortin 4 receptor deficiency: Recent studies have demonstrated the inflammatory regulatory role of the mtDNA synthesis protein CMPK2, finding that CMPK2 can combine adiposity and obesity-related proteins (FTOs) in FLS to regulate synovial inflammation via the mtDNA-mediated cGAS/STING pathway, and that inhibition of the FTO—CMPK2 axis attenuates disease progression (30).