MCTP2 and type 1 diabetes mellitus: Recent studies in type 1 diabetes (T1D) cohorts have highlighted robust loci such as protective variants in COL4A3 (e.g., rs55703767), as well as signals in AFF3, FRMD3, and the RGMA–MCTP2 region, which are consistently associated with albuminuria, eGFR decline, and ESKD (24, 25).