Understanding kidney failure in individuals with DiGeorge syndrome - ABSTRACT Heterozygous microdeletions at chromosome 22q11.2, causing DiGeorge syndrome (DGS), with prevalence of 1 in 2,000-4,000 live births, constitute the most common yet understudied microdeletion disorder in humans. Hallmark features include cardiac, palate, immune, neurologic and kidney disease. The resultant DiGeorge- associated kidney diseases (DGS-KD) are heterogenous and suggest the activity of a dosage-sensitive molecular signaling mechanism. We showed that haploinsufficiency of the adaptor protein CRKL, located within this locus, is the main genetic kidney driver (NEJM 2017, NG 2019). We recently contributed to a manuscript reporting that 22q11.2 deletion and CRKL haploinsufficiency result in neural tube defects, broadening the relevance of our work (Science 2024). Via alternative splicing, CRKL encodes two distinct transcript isoforms that serve to link tyrosine kinase signaling to downstream pathways. We hypothesize that proper isoform expression regulates Crkl engagement of receptor tyrosine kinases, guanine exchange factors and GTP-ases. These assemblies, in turn, regulate downstream cellular processes such as growth, cell division and migration. To unravel the pathobiology induced by aberrant CRKL signaling, and aid discovery of new diagnostics and therapeutics, we will combine genetics, transcriptomics and proteomics, and correlate patient cell lines with analogous mouse models. This will help identify the mechanisms underlying DGS-KD biology and define the role of alternative gene splicing that tightly controls morphogenetic events. Matched human and animal genetic models will provide translational relevance and potentially create new personalized tools for study of disease and screening of therapeutics. We will analyze a panel of genetic variants that affect Crkl expression with spatiotemporal specificity. Using high-resolution structural analyses, we will quantify the structural consequences of aberrant Crkl signaling. Using phosphoproteomic approaches, we will study CRKL interacting partners and the resulting signaling pathways. We also will create a panel of mouse- and patient-derived iPSCs to generate in vitro assays that model DGS-KD to help develop a new disease-modeling and screening platform for bench- to-bedside functional genomics. These will serve as translational tools to model kidney disease, which can be utilized to devise drug therapies and intervention strategies. Finally, we will use a multiomic approach to analyze, at the single nuclear level, comprehensive gene expression, gene regulation, cell trajectory and epigenomics in human and mouse models to define the pathobiology of CRKL-mediated kidney disease.
