Effects of a novel ANLN E841K mutation associated with SRNS on podocytes and its mechanism

Background: Steroid-resistant nephrotic syndrome (SRNS) is characterized by unrelieved proteinuria after an initial 4-8 weeks of glucocorticoid therapy. Genes in podocytes play an important role in causing SRNS.

Objective: This study aimed to report a pathogenic mutation in SRNS patients and investigate its effects on podocytes, as well as the pathogenic mechanism.

Methods: We screened out a novel mutation by using whole-exon Sequencing in the SRNS cohort and verified it via Sanger Sequencing. Conservative analysis and bioinformatic analysis were used to predict the pathogenicity of the mutation. In vitro, stable podocyte cell lines were constructed to detect the effect of the mutation on the function of the podocyte. Moreover, an in vivo mouse model of podocyte ANLN gene knockout (ANLN^podKO) was used to confirm clinical manifestations. Transcriptome analysis was performed to identify differential gene expression and related signaling pathways.

Results: ANLN E841K was screened from three unrelated families. ANLN E841K occurred in the functional domain and was predicted to be harmful. The pathological type of A-II-1 renal biopsy was minimal change disease, and the expression of ANLN was decreased. Cells in the mutation group showed disordered Cytoskeleton, faster cell migration, decreased adhesion, increased endocytosis, slower proliferation, increased Apoptosis, and weakened interaction with CD2 association protein. ANLN^podKO mice exhibited more obvious proteinuria, more severe mesangial proliferation, glomerular atrophy, foot process fusion, and increased tissue Apoptosis levels than ANLN^flox/flox mice after tail vein injection of adriamycin. Upregulated differentially expressed genes in cells of the mutation group were mainly enriched in the PI3K-AKT pathway.

Conclusion: The novel mutation known as ANLN E841K affected the function of the ANLN protein by activating the PI3K/Akt/mTOR/Apoptosis pathway, thus resulting in structural and functional changes in podocytes. Our study indicated that ANLN played a vital role in maintaining the normal function of podocytes. Video Abstract.

ANLN mutation; Podocyte; Podocyte-specific knockout mouse; SRNS.