Discover and functionally characterize full-penetrance causes of nephrosis/FSGS. Chronic kidney diseases (CKD) take one of the highest tolls on human health, and their prevalence continuously rises. Steroid-resistant nephrotic syndrome (SRNS) is the 2nd most frequent cause of CKD before 25 yrs. By focal segmental glomerulosclerosis (FSGS) it inevitably leads to CKD with a 33% recurrence risk in a renal transplant. The pathogenesis of SRNS is unknown and no curative treatment is available. For SRNS, the primary causes (etiology) and disease mechanisms (pathogenesis) have been a conundrum for decades. However, identification of full-penetrance single-gene causes of NS (e.g. podocin) has implicated the renal glomerular podocyte at the center of the pathogenesis. Within the 2 previous R01 funding periods we: 1) Identified by whole exome sequencing 34 of the 50 currently known single-gene causes of NS and functionally characterized the related disease mechanisms; 2) Discovered that the encoded proteins cluster in protein complexes thereby defining novel disease pathways for SRNS (e.g., RhoA/Rac1/Cdc42 signaling); 3) Delineated genotype-phenotype correlations with actionable implications for personalized disease management; 4) Modeled the related disease mechanisms in the `podocyte migration assay', zebrafish & mouse models; 5) Revealed `personalized treatment' options for specific patients (e.g. CoQ10 in COQ6 or ADCK4 mutations); 6) Demonstrated in a world-wide cohort that ~30% of SRNS (<25 yrs) is caused by single-gene mutations, thereby permitting genetic mechanistic studies and personalized medicine for patients with SRNS ; 7) Discovered the first genetic causes of steroid-dependent NS (6 genes), converging on RhoA regulation. These genetic discoveries made the study of SRNS accessible to genetic approaches of `precision medicine', enabling genetic diagnostics, the study of `personalized' disease mechanisms, and treatment approaches. We, therefore will pursue the following Specific Aims: SA1. Discover the missing single-gene causes of SRNS by WES in ~1,000 SRNS families. SA2. Functionally characterize newly identified single-gene causes of SRNS/SSNS to delineate the pathogenesis and study `personalized' genotype-phenotype and genotype-treatment correlations. SA3. Perform small molecule screens in CRISPR k.o. models of novel SRNS genes identified, using established `podocyte migration assay' and zebrafish models, to discover the first drugs for SRNS. SA4. Study the 6 novel single-gene causes that we discovered in steroid-dependent NS to converge on RhoA regulation delineate mechanisms of steroid and other direct drug effects on podocytes.
Chronic kidney diseases take one of the highest tolls on human health. Steroid-resistant nephrotic syndrome (SRNS) is a rare disease that constitutes the second most frequent cause of ESKD in children and young adults. No curative treatment is available. We recently demonstrated that a single-gene cause of SRNS can be detected in ~30% of all cases with far reaching consequences for diagnostics, prognosis, and the development of treatment. Of the 50 known single-gene causes of SRNS, 34 have been discovered by whole exome sequencing (WES) and studied in the PI's laboratory. The finding that the encoded proteins cluster in well- defined protein interaction complexes has provided fundamental insights into disease mechanisms of SRNS in children and young adults. We have ascertained DNA samples and clinical data from over 4,000 families with SRNS world-wide and have clarified the molecular cause of SRNS in ~25% of cases. We here propose to: SA1. Discover the missing single-gene causes of SRNS by WES in ~1,000 SRNS families. SA2. Functionally characterize newly identified single-gene causes of SRNS/SSNS to delineate the pathogenesis and study `personalized' genotype-phenotype and genotype-treatment correlations. SA3. Perform small molecule screens in CRISPR k.o. models of novel SRNS genes identified, using estab- lished `podocyte migration assay' and zebrafish models, to discover the first drugs for SRNS. SA4. Study the 6 novel single-gene causes that we discovered in steroid-dependent NS to converge on RhoA regulation delineate mechanisms of steroid and other direct drug effects on podocytes.
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