Upper panels show the whole glomerulus (403), and lower sections in A, C, and Deb show higher original magnification (1007)

Upper panels show the whole glomerulus (403), and lower sections in A, C, and Deb show higher original magnification (1007). been shown to interact with nephrin and regulate podocyte cytoskeleton and slit diaphragm dynamics, MAGI2mutations have not been described in human SRNS. We detected two exclusive frameshift mutations and 1 duplication in three patients (two families); two siblings shared the same homozygous frameshift mutation, whereas one individual with 42-(2-Tetrazolyl)rapamycin sporadic SRNS exhibited substance heterozygosity. Two mutations were predicted to introduce premature stop codons, and 1 was predicted to result in read through from the normal translational termination codon. Immunohistochemistry in kidney areas from these patients revealed that mutations resulted in lack of or diminished podocyte MAGI2 expression. Our data support the finding that mutations in theMAGI2gene are causal for congenital SRNS. Keywords: podocyte, genetic renal disease, nephrin, familial nephropathy, proteinuria, nephrotic syndrome Steroidresistant nephrotic syndrome (SRNS), a disorder of glomerular filtration, results in severe proteinuria, hypoalbuminaemia, and edema. Currently, 53 genes are implicated (Supplemental Table 1), but these take into account only 20%30% of patients 42-(2-Tetrazolyl)rapamycin with hereditary cases and only 10%20% of patients with sporadic cases, supporting significant genetic heterogeneity. 18To date, all known SRNSassociated genes encode proteins expressed in podocytes (or associated basement membrane), polarized cells connected by highly specialized junctions called slit diaphragms. Correct podocyte morphology is essential intended for maintaining glomerular filtration barrier (GFB) honesty, and the podocyte actin cytoskeleton is tightly regulated by cell surface receptors, including the multiprotein complex at the slit diaphragm. Known SRNS gene mutations disrupt key cellular functions, resulting in podocyte injury and disruption of glomerular permselectivity. Typically, patients with a mutation in an SRNSassociated gene are less prone to respond to immunosuppressive treatment but have a reduced risk of disease recurrence after kidney transplant. 9SRNS may present at birth (congenital nephrotic 42-(2-Tetrazolyl)rapamycin syndrome [CNS]), usually with an early and severe phenotype, with about 80%10of patients with cases ascribed to only six causal genes: NPHS1, NPHS2, LAMB2, WT1, PLCE1, andLMX1B, 11all important players in podocyte biology; the genetic cause of the remainder is unfamiliar. The majority of patients with SRNS in ATN1 child years have an autosomal recessive mode of inheritance. == Results == == Screening the Known Nephrotic Genes == We expanded the study originally described in the work by McCarthyet al. 1and performed whole-exome sequencing on a deeply phenotyped cohort of 187 patients with childhood SRNS (onset <18 years old; 11. 8% familial and 7% consanguineous; 48. 7% girls and 51. 3% boys; 69. 5% white and 30. 5% South Asian, mixed race, African, and East Asian) collectedviaa United Kingdomwide registry. The cohort was first screened intended for the presence of disease-causing mutations in the 53 released 42-(2-Tetrazolyl)rapamycin genes known associate with SRNS (Supplemental Table 1, mapping statistics are presented inSupplemental Table 2). Our findings correlated with previous released studies, 2, 12in that mutations in known SRNS genes were only detected in approximately 25% of patients. Assuming that mutations in the exome were present in a proportion from the remaining 75% of patients, variants detected in the whole exome were filtered to identify potential mutations in genes not previously directly associated with SRNS. == MembraneAssociated Guanylate Kinase, WW, and PDZ DomainContaining 2Mutations Recognized by Whole-Exome Sequencing == After filtering and additional 42-(2-Tetrazolyl)rapamycin analysis of potentially pathogenic mutations in genes not previously directly associated with SRNS, we recognized three book, likely diseasecausing frameshift mutations (Figure 1) inmembraneassociated guanylate kinase, WW, and PDZ domaincontaining 2(MAGI2; MIM: 606382) in one patient with a sporadic case (180) (Supplemental Physique 1) and two patients with familial cases (175 and 175S) (Supplemental Physique 2) showing with nonsyndromic congenital SRNS. Because the parents of patients 175 and 175S were consanguineous, autosomal recessive inheritance was considered the most likely mechanism of inheritance (Supplemental Physique 3). == Figure 1 . == MAGI2mutations causing CNS. (A) The exon structure ofMAGI2cDNA (NM_012301. 3); 22 coding exons with start and stop codons are indicated. (B) Domain name structure from the MAGI2 protein. Six PDZ domains (PDZ0PDZ5) are shown in blue, one guanylate kinase (GK) domain is shown in yellow, and two WW domains are shown in green. (C) Frameshift variants found in three patients with CNS. Individual 180 is a compound heterozygote: the variant in exon 1 was inherited from the father (180F), and the variant in exon 20 was inherited from the mother (180M). Individual 175 and her sister, 175S, are homozygous for a single-nucleotide deletion in exon 22. The mother of the siblings is heterozygous for the variant. Whole-exome sequencing was performed on patients 175 and 180. Subsequent segregation analysis.