-254C>G SNP in the TRPC6 Gene Promoter Influences Its Expression via Interaction with the NF-κB Subunit RELA in Steroid-Resistant Nephrotic Syndrome Children.

Xinyu Kuang,Zhuying Li,Qian Zhou,Yulin Kang,Wenyan Huang,Yujie Hu

doi:10.1155/2019/2197837

Abstract

This study is aimed at exploring the mechanism by which the −254C>G single nucleotide polymorphism (SNP) on the transient receptor potential cation channel 6 (TRPC6) gene promoter could increase its activation in steroid-resistant nephrotic syndrome children of China. Plasmids containing the TRPC6 promoter region (with the −254C or G allele) were constructed and then transfected into human embryonic kidney (HEK) 293T cells and human podocytes. Luciferase assays were used to test the promoter activity in both cell lines with or without tumor necrosis factor-α (TNF-α) treatment, and chromatin immunoprecipitation-polymerase chain reaction (ChIP-PCR) analysis was used to verify the transcription factor that could bind to this mutant sequence. Luciferase results indicate that the activity of the mutant promoter was greater than that of the normal promoter of the TRPC6 gene in both cell lines. We further predicted and verified that this variation was mediated by the nuclear factor kappa B (NF-κB) subunit RELA, and TNF-α significantly enhanced the transcription activity of TRPC6 with the −254G allele. In conclusion, the −254C>G SNP is a gain-of-function variation of the TRPC6 gene, and it is also an early and effective factor for predicting steroid-resistant nephrotic syndrome (SRNS) in Chinese children.

Highlights

Podocytes are the key components of the glomerular filtration barrier in the kidneys; their foot processes act as the final protection against protein loss into the urine [1, 2]
Advances in podocytology and genetic techniques have expanded our understanding of the pathogenesis of proteinuria, and more than 50 genes encoding glomerular podocyte proteins have been described as potential sites of mutation responsible for various renal pathologies, especially focal segmental glomerulosclerosis (FSGS) or steroid-resistant nephrotic syndrome (SRNS) [1, 4]
transient receptor potential cation channel 6 (TRPC6) is mainly positioned at the podocyte membrane and renal tubules, where it is integrated into a signaling complex that interacts with nephrin, podocin, α-actinin-4, and some other proteins critical for podocyte function [5,6,7]

Summary

Introduction

Podocytes are the key components of the glomerular filtration barrier in the kidneys; their foot processes act as the final protection against protein loss into the urine [1, 2]. Advances in podocytology and genetic techniques have expanded our understanding of the pathogenesis of proteinuria, and more than 50 genes encoding glomerular podocyte proteins have been described as potential sites of mutation responsible for various renal pathologies, especially focal segmental glomerulosclerosis (FSGS) or steroid-resistant nephrotic syndrome (SRNS) [1, 4]. Gain-offunction mutations in TRPC6 were first reported to cause familial FSGS that resulted in calcium-triggered podocyte cell death [4, 6, 8]. An increasing number of genetic studies have shown that mutations of the TRPC6 gene were detected in children with SRNS [9,10,11]

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