LAUSR

Haploinsufficiency of TGF-Beta Activated Kinase 1 (MAP3K7) Binding Protein 2 (TAB2) has been associated with congenital heart disease and more recently multiorgan structural abnormalities. Missense variant represents a major proportion of non-synonymous TAB2 variants reported in gnomAD (295/576) and Clinvar (16/73), most of which are Variants of uncertain significance (VUSs). However, interpretation of TAB2 missense variants remains challenging due to lack of functional assay. To address this issue, we established a cell-based luciferase assay that enables high-throughput screening of TAB2 variants to assess the functional consequence for predicting variant pathogenicity. Using this platform, we screened 47 TAB2 variants including 5 pathogenic controls and 1 benign control, and the results showed that the transcriptional activity of AP-1 but not NF-κB predicts the TAB2 variant pathogenicity. This assay provides accurate functional readout for both loss-of-function (LOF) and gain-of-function (GOF) variants, which are associated with distinct phenotypes. 22 out of 32 tested VUSs were reclassified. Genotype-phenotype association showed that most patients with partial LOF variants do not exhibit congenital heart disease but high frequency of developmental delay, hypotonia, and dysmorphic features, which suggests genetic testing for TAB2 is needed for a broader spectrum of patients with more diverse phenotypes. Molecular modeling with Npl4 zinc finger (NZF) domain variants revealed that the stability of the NZF domain in TAB2 protein is crucial for AP-1 activation. In conclusion, we developed a highly effective functional assay for TAB2 variant prediction and interpretation.