Adjacent to the IrxB cluster, within the significant LWL1 QTL, we located the fat mass and obesity‐associated (FTO) gene and Retinitis pigmentosa GTPase regulator interacting protein 1‐like (Rpgrip1l) gene, together identified as a topologically associated domain (TAD) structure in which any transcriptional perturbation during development may potentially affect bodyweight index.59 The Rpgrip1l gene (MGI: 1920563) is highly involved in growth/early development and suggested to be a tumor suppressor of hepatocellular carcinoma.60 The gene discussed is RPGRIP1L; the disease is obesity due to melanocortin 4 receptor deficiency.