Abstract 14239: Extracellular Matrix Disorganization Caused by ADAMTS16 Deficiency Leads to Bicuspid Aortic Valve

Background: Extracellular matrix (ECM) is involved in aortic valve development and aortic valve anomaly. ADAMTS gene mediated ECM dysfunction was reported to be related to aortic valve diseases. Hypothesis: The ADAMTS gene family members can contribute to aortic valve diseases. Methods: Morpholino based adamts gene-targeted phenotype-screening of outflow tract anomaly in zebrafish and the 19 ADAMTS family gene-targeted exon sequencing on a cohort BAV patients (304 BAV and 301 normal controls) were performed. Accordingly, both specific genetic tracing and different gene modified mouse models were generated to evaluate the role of specific genes in the aortic valve formation process. Movat’s pentachrome staining was used to describe the altered ECM maturation process. Bulk RNA-seq was performed on both mouse heart tissue and human iPSC-induced ECs to explore the potential molecular pathways, which was further confirmed in ex vivo embryonic outflow tract tissue culture studies. Results: We identified some novel adamts genes that resulted in cardiac outflow valve defects in zebrafish, while exon sequencing identified ADAMTS16 p.H357Q variant in an inherited BAV family. The generated Adamts16-Cre;Rosa26-tdTomato mice showed Adamts16-expressing cells were primarily restricted to valvular endothelial cells (VECs) at E12.5 and then expressed in valvular mesenchymal cells (VICs) at E13.5. Both Adamts16+/- and Adamts16+/H355Q mice exhibited an R-NC-type BAV phenotype, with progressive aortic valve thickening. Conditional Adamts16 mutant mouse models demonstrated that endothelial lineage cell deficiency in Adamts16 recapitulated the BAV phenotype, which was associated with worse ECM deposition without ECM trilaminar structure. Bulk RNA sequencing unveiled enhanced FAK signaling, which was accompanied by elevated fibronectin levels. Both in vitro iPSC-ECs culture and ex vivo embryonic tissue explant studies validated the altered FAK signaling resulted in exaggerated cell proliferation. Conclusions: Our present study identified a novel BAV-causing ADAMTS16 p. H357Q variant. ADAMTS16 deficiency led to BAV formation.