PROCR and obesity due to melanocortin 4 receptor deficiency: For instance, due to a significant “deficiency” of protein products of genes (CPNE1, EDEM2, PROCR, UQCC1), their expression can be extremely reduced in individuals carrying reduced fat mass and a low-productive G allele rs143384 (KOA risk factor in individuals without obesity), which may, as an important pathogenetic factor, significantly contribute to the development of KOA.