Integrative multi-omics Mendelian randomization and functional validation identifies RNASET2 as a novel therapeutic target for autoimmune thyroiditis.

Objective: Autoimmune thyroiditis (AIT), a prevalent autoimmune disorder that frequently leads to hypothyroidism. A critical unmet need exists for disease-modifying therapies that target its underlying pathogenesis. This study aimed to identify and validate novel therapeutic targets for AIT. Methods: We employed an integrative genomics approach, combining genome-wide association studies (GWAS) with molecular quantitative trait loci (QTL) analyses, including expression (eQTL), protein (pQTL), and DNA methylation QTL (mQTL), across two independent AIT cohorts for discovery and replication. We performed two-sample bidirectional Mendelian randomization (MR) with sensitivity analyses, followed by summary-data-based MR (SMR) and heterogeneity in dependent instruments (HEIDI) tests. Top candidates were further evaluated via phenome-wide association study (PheWAS) and computational drug screening. Guided by these findings, we quantified plasma levels of the top-priority candidate, Ribonuclease T2 (RNASET2), via ELISA in AIT patients and non-AIT controls. To functionally validate its therapeutic potential, we developed a novel three-dimension (3D) inflammatory thyrocyte spheroid model and evaluated potential therapeutic effects of recombinant RNASET2. Loss-of-function (small interfering RNA-mediated knockdown) and gain-of-function (recombinant protein RNASET2 rescue) experiments further supported RNASET2 as a therapeutic target. Results: Multi-omics integration consistently nominated RNASET2 as a causal protective factor against AIT. Signals of pQTL and eQTL for RNASET2 were associated with decreased AIT risk, while three mQTLs were correlated with increased risk. PheWAS indicated minimal pleiotropic effects, supporting its therapeutic suitability. Computational drug screening nominated genistein, a soy isoflavone known to upregulate RNASET2 expression, as a repurposing candidate. Empirically, plasma RNASET2 levels were moderately elevated in AIT patients, potentially reflecting a compensatory anti-inflammatory response. Crucially, recombinant RNASET2 effectively mitigated inflammation and apoptosis in the thyrocyte spheroid model, confirming its functional protective role. Consistently, RNASET2 knockdown heightened susceptibility to inflammatory cell death and cytokine expression, a phenotype reversed by recombinant RNASET2 supplementation. Conclusions: By integrating large-scale genomic analyses with functional validation, our study establishes RNASET2 as a promising therapeutic target for AIT. RNASET2 augmentation represents a potential disease-modifying strategy, providing a translational bridge from genetic discovery to clinical application.