Mutations in the NPHS2 gene, which encodes the podocyte slit diaphragm protein podocin, cause autosomal recessive steroid-resistant nephrotic syndrome (Online Mendelian Inheritance in Man [OMIM] #600995).
Podocin related mutations are not too much associated with SRNS in adults, but we should consider the possibility of TRPC6 gene mutation in this population.
Podocin is a key component of the slit diaphragm in the glomerular filtration barrier, and mutations in the podocin-encoding gene <i>NPHS2</i> are a common cause of hereditary steroid-resistant nephrotic syndrome.
Mutation analysis was carried out by direct sequencing of the entire NPHS2 gene (eight exons) using specific primers in 200 INS (100 SRNS and 100 steroid sensitive) children and 100 healthy controls.
The most common mutated genes were ADCK4 (6.67%), NPHS1 (5.83%), WT1 (5.83%), and NPHS2 (3.33%), and the difference in the frequencies of ADCK4 and NPHS2 mutations between this study and a study on monogenic causes of SRNS in the largest international cohort of 1,783 different families was significant.
Novel NPHS2 variant in patients with familial steroid-resistant nephrotic syndrome with early onset, slow progression and dominant inheritance pattern.
The overall mutation detection rate was high at 57% (97% in CNS and 41% in SRNS); 85% of all mutations were identified by the analysis of three single genes only (NPHS1, NPHS2, and WT1), accounting for 92% of all mutations in patients with CNS and 79% of all mutations in patients with SRNS.
Mutations in NPHS2, which encodes for podocin, an integral membrane protein of the glomerular epithelial cells (podocytes), represent a frequent cause of steroid-resistant nephrotic syndrome worldwide.
Recent studies have demonstrated that mutations in 4 podocyte genes, NPHS1, NPHS2, CD2AP, and WT1, are associated with the pathogenesis of steroid-resistant nephrotic syndrome (SRNS).
Results indicate possible clustering of causative NPHS2 mutations in FSGS-proven SRNS with onset before age one year old, and provide additional evidence that patients with childhood steroid-resistant nephrotic syndrome due to focal segmental glomerulosclerosis should first undergo analysis of NPHS2 coding sequence and WT1 exons 8 and 9 and surrounding exon/intron boundary sequences, followed by gender genotyping.
Thus, screening of the entire coding sequence of NPHS2 and exons 8-9 of WT1 appears to be the most rational and cost-effective screening approach in sporadic juvenile steroid-resistant nephrotic syndrome.
Podocin is a key protein involved in the pathogenesis of steroid-resistant nephrotic syndrome and/or focal segmental glomerulosclerosis (FSGS) and is characterized by a high rate of early recurrence after renal transplantation (RTx) in children and adults.