nephrin and Nephritis--Hereditary

Alport syndrome (AS) is a hereditary disease caused by mutations in COL4A3-5 genes. Recently, comprehensive genetic analysis has become the first-line diagnostic tool for AS. However, no reports comparing mutation identification rates between conventional sequencing and comprehensive screening have been published.. In this study, 441 patients clinically suspected of having AS were divided into two groups and compared. The initial mutational analysis method involved targeted exome sequencing using next-generation sequencing (NGS) (n = 147, NGS group) or Sanger sequencing for COL4A3/COL4A4/COL4A5 (n = 294, Sanger group).. In the NGS group, 126 patients (86%) were diagnosed with AS by NGS, while two had pathogenic mutations in other genes, NPHS1 and EYA1. Further, 239 patients (81%) were diagnosed with AS by initial analysis in the Sanger group. Thirteen patients who were negative for mutation detection in the Sanger group were analyzed by NGS; three were diagnosed with AS. Two had mutations in CLCN5 or LAMB2. The final variant detection rate was 90%.. Our results reveal that Sanger sequencing and targeted exome sequencing have high diagnostic ability. NGS also has the advantage of detecting other inherited kidney diseases and pathogenic mutations missed by Sanger sequencing.

Topics: Adult; Chloride Channels; Collagen; Female; Humans; Intracellular Signaling Peptides and Proteins; Laminin; Male; Membrane Proteins; Nephritis, Hereditary; Nuclear Proteins; Protein Tyrosine Phosphatases; Sequence Analysis, DNA

Kidney injury due to focal segmental glomerulosclerosis (FSGS) is the most common primary glomerular disorder causing end-stage renal disease. Homozygous mutations in either glomerular basement membrane or slit diaphragm genes cause early renal failure. Heterozygous carriers develop renal symptoms late, if at all. In contrast to mutations in slit diaphragm genes, hetero- or hemizygous mutations in the X-chromosomal

Topics: Acute Kidney Injury; Adult; Child; Child, Preschool; Collagen Type IV; Female; Genetic Predisposition to Disease; Glomerulosclerosis, Focal Segmental; Hemizygote; Heterozygote; Humans; Infant; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Mutation; Nephritis, Hereditary; Pedigree; Polymorphism, Single Nucleotide

The pathogenesis of proteinuria in Alport syndrome (AS) remains unclear. Vascular endothelial growth factor A (VEGFA) is a key regulator of the glomerular filtration barrier (GFB). This study explored the expression of VEGFA in the glomeruli and its accumulation in the glomerular basement membrane (GBM) and their relationship with podocyte injury and proteinuria in Alport syndrome (AS). Clinical data and renal tissues of control patients (11 cases) and AS patients (25 cases) were included. AS patients were further divided into 2 groups according to the quantities of their urinary protein: mild to moderate proteinuria group (proteinuria <50 mg/kg/d, 15 cases) and heavy proteinuria group (proteinuria ≥50 mg/kg/d, 10 cases). The expression and distribution of VEGFA and VEGF receptor 2 (VEGFR2) in the GFB, the phosphorylation of VEGFR2 (p-VEGFR2) and nephrin (p-nephrin), and the expression of synaptopodin and nephrin in the glomeruli were detected by immune electron microscopy and/or immunofluorescence, and their relationships to proteinuria in AS patients were analyzed. The accumulation of VEGFA in the GBM was increased in AS patients. The expression of VEGFA and the levels of p-VEGFR2 and p-nephrin in glomeruli were increased and were positively correlated with the degree of proteinuria in AS patients. The expression of synaptopodin and nephrin were decreased and were negatively correlated with the degree of proteinuria in AS patients. The over expressed VEGFA in the glomeruli and its accumulation in the GBM may activate the VEGFA-VEGFR2 and nephrin signaling pathways and lead to podocyte injury and occurrence of proteinuria in AS.

Topics: Adolescent; Biomarkers; Case-Control Studies; Child; Child, Preschool; Female; Glomerular Basement Membrane; Humans; Male; Membrane Proteins; Microfilament Proteins; Nephritis, Hereditary; Phosphorylation; Podocytes; Proteinuria; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

A girl aged 6 presented with haematuria and her sister (aged 5) presented with haematuria and proteinuria. Family history showed multiple individuals suffering from end stage renal failure from the paternal side of the pedigree. Following kidney biopsy in the father and paternal grandmother, the pathological diagnosis was of focal segmental glomerulosclerosis (FSGS). Exome sequencing was undertaken in the proband's sister and grandmother. Genetic variants shared by both affected individuals were interrogated to identify the genetic cause of disease. Candidate variants were then sequenced in all the family members to determine segregation with the disease. A mutation of COL4A5 known to cause Alport syndrome segregated with disease from the paternal side of the pedigree and a variant in NPHS1 was present in both paediatric cases and inherited from their mother. This study highlights the advantages of exome sequencing over single gene testing; disease presentation can be heterogeneous with several genes representing plausible candidates; candidate gene(s) may be unavailable as a diagnostic test; consecutive, single gene testing typically concludes once a single causal mutation is identified. In this family, we were able to confirm a diagnosis of Alport syndrome, which will facilitate testing in other family members.

Topics: Adult; Biopsy; Child; Child, Preschool; Collagen Type IV; Diagnosis, Differential; Exome; Female; Glomerulosclerosis, Focal Segmental; Humans; Kidney; Male; Membrane Proteins; Middle Aged; Mutation; Nephritis, Hereditary; Pedigree; Sequence Analysis, DNA