Identification of Novel T1D Risk Loci and Their Association With Age and Islet Function at Diagnosis in Autoantibody-Positive T1D Individuals: Based on a Two-Stage Genome-Wide Association Study

Type 1 diabetes (T1D) is a highly heritable disease with much lower incidence but more adult-onset cases in the Chinese population. Although genome-wide association studies (GWAS) have identified >60 T1D loci in Caucasians, less is known in Asians. We performed the first two-stage GWAS of T1D using 2,596 autoantibody-positive T1D case subjects and 5,082 control subjects in a Chinese Han population and evaluated the associations between the identified T1D risk loci and age and fasting C-peptide levels at T1D diagnosis. We observed a high genetic correlation between children/adolescents and adult T1D case subjects ( = 0.87), as well as subgroups of autoantibody status ( ≥ 0.90). We identified four T1D risk loci reaching genome-wide significance in the Chinese Han population, including two novel loci, rs4320356 near (odds ratio [OR] 1.26, = 2.70 × 10 ) and rs3802604 in (OR 1.24, = 2.06 × 10 ), and two previously reported loci, rs1770 in MHC (OR 4.28, = 2.25 × 10 ) and rs705699 in (OR 1.46, = 7.48 × 10 ). Further fine mapping in the MHC region revealed five independent variants, including another novel locus, HLA-C position 275 (omnibus = 9.78 × 10 ), specific to the Chinese population. Based on the identified eight variants, we achieved an area under the curve value of 0.86 (95% CI 0.85-0.88). By building a genetic risk score (GRS) with these variants, we observed that the higher GRS were associated with an earlier age of T1D diagnosis ( = 9.08 × 10 ) and lower fasting C-peptide levels ( = 7.19 × 10 ) in individuals newly diagnosed with T1D. Our results extend current knowledge on genetic contributions to T1D risk. Further investigations in different populations are needed for genetic heterogeneity and subsequent precision medicine.