First identification of PODXL nonsense mutations in autosomal dominant focal segmental glomerulosclerosis

In this study, we report the identification of a heterozygous nonsense PODXL mutations (Arg326X) in a Chinese pedigree featured by proteinuria and renal insufficiency with AD inheritance by whole exome sequencing (WES). Total mRNA and PODXL protein abundance were decreased in available peripheral blood cell samples of two affected patients undergoing hemodialysis, compared to those in healthy controls and hemodialysis controls without PODXL mutation. We identified another novel PODXL heterozygous nonsense mutation (c.C1133G; p.Ser378X) in a British-Indian pedigree of AD-FSGS by WES. In vitro study showed that, human embryonic kidney (HEK) 293T cells transfected with the pEGFP-PODXL-Arg326X or pEGFP-PODXL-Ser378X plasmid expressed significantly lower mRNA and PODXL protein compared to cells transfected with the wild-type plasmid. Blocking nonsense-mediated mRNA decay (NMD) significantly restored the amount of mutant mRNA and PODXL proteins, which indicated that the pathogenic effect of PODXL nonsense mutations is likely due to NMD, resulting in podocalyxin deficiency. Functional consequences caused by the PODXL nonsense mutations were inferred by siRNA knockdown in cultured podocytes and podocalyxin downregulation by siRNA resulted in decreased RhoA and ezrin activities, cell migration and stress fiber formation. Our results provided new data implicating heterozygous PODXL nonsense mutations in the development of FSGS.
Source: Clinical Science - Category: Biomedical Science Authors: Tags: PublishAheadOfPrint Source Type: research