Selection-guided discovery in South Asians implicates the MAPT locus in insulin resistance

South Asians constitute 25% of the global population yet account for 33% of individuals living with type 2 diabetes (T2D) (1). Despite this burden, they remain substantially underrepresented in genome-wide association studies (GWAS), limiting discovery of ancestry-relevant disease biology (2). This limits biological insight and hampers genomic discovery. Here we integrated genome-wide signatures of recent positive selection across 13 South Asian populations (3,4) with cross-trait genetic association data (3,4). We identified 1,797 genes residing within regions under recent positive selection and prioritised 65 shared across South Asia. Selection-prioritised loci were enriched for credible sets from the largest trans-ancestry T2D GWAS and for partitioned polygenic score clusters implicated in lipodystrophy-like fat distribution, obesity and proinsulin biology. Multi-trait fine-mapping recovered established T2D loci, including RBM6 and PEPD, and identified a signal at MAPT associated with hepatic insulin resistance, erythrocytic traits and HbA1c in two independent south Asian cohorts (5-7). These findings demonstrate that signatures of recent positive selection can be integrated with genetic association data to prioritise metabolically relevant loci and provide a complementary route to genetic discovery in underrepresented populations.