That the tyrosine kinase regulation of FSGS mutation binding to actin filaments can occur in cells was shown by phosphorylation on Y4 and Y31 of the K225E after extended exposure of cells to EGF, with a decrease in ACTN4 aggregates in fibroblasts.
Synonymous mutations or protein expression losses in ACTN4 are associated with kidney diseases, including focal segmental glomerulosclerosis, characterized by proteinuria and podocyte injury.
FSGS lesions resembling human FSGS developed spontaneously by 7 months of age, and could be induced earlier by accelerating kidney hypertrophy by nephrectomy.
Mutations in the ACTN4 gene, encoding the actin-binding protein α-actinin-4, are a rare cause of autosomal dominant familial focal segmental glomerulosclerosis (FSGS).
Her clinical presentation is different from previous descriptions of ACTN4 mediated FSGS, which is characterized by sub-nephrotic proteinuria and slow progression to end stage kidney disease.
The prevalence of pathogenic mutations in five genes (NPHS2, TRPC6, ACTN4, INF2 and PLCE1) and of APOL1 risk alleles (G1 and G2) was ascertained in children and adults diagnosed between 1984 and 2011 with FSGS by renal biopsy.
We crossed Col1α1-eGFP-L10a mice with the Actn4(-/-) and Actn4(+/K256E) models of FSGS and analyzed podocyte transcriptional profiles at 2, 6, and 44 weeks of age.
To quantify the contribution of various genes contributing to FSGS, we sequenced INF2 where all mutations have previously been described (exons 2 to 5) in a total of 215 probands and 281 sporadic individuals with FSGS, along with other known genes accounting for autosomal dominant FSGS (ACTN4, TRPC6, and CD2AP) in 213 probands.
We used genomic DNA of 48 patients with focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) to screen for ACTN4 mutations by high-resolution melting analysis (HRM).
The autosomal dominant form of FSGS is a heterogenic disease caused by mutations within three known genes: α-actinin 4 (ACTN4), canonical transient receptor potential 6 (TRPC6), and the inverted formin 2 (INF2) gene.
Genomic DNA was extracted from peripheral blood cells, and Sanger sequencing was performed for all exons and exon-intron boundaries of TRPC6 and ACTN4 in the probands of all FSGS pedigrees enrolled in this study.
Our data provide the first link between FSGS-linked ACTN4 mutants and transcriptional activation by nuclear receptor such as RARα and peroxisome proliferator-activated receptor γ.
Mutations in alpha-actinin-4 have been linked to familial focal segmental glomerulosclerosis (FSGS), a common renal disorder in humans, and produce an apparent increase in the actin-binding affinity of alpha-actinin-4 in vitro.
Familial and genetic forms of focal segmental glomerulosclerosis (FSGS) are associated with six different mutations in genes affecting the podocyte (NPHS2, ACTN4, CD2AP, WT1, TRPC6, and PLCE1).