Association of ACTN4 Gene Mutation with Primary Nephrotic Syndrome in Children in Guangxi Autonomous Region, China.

Objective: To investigate the association between ACTN4 gene mutation and primary nephrotic syndrome (PNS) in children in Guangxi Autonomous Region, China. Methods: The high-throughput sequencing technology was used to sequence ACTN4 gene in 155 children with PNS in Guangxi Autonomous Region in China, with 98 healthy children serving as controls. Twenty-three exon-specific capture probes targeting ACTN4 were designed and used to hybridize with the genomic DNA library. The targeted genomic region DNA fragments were enriched and sequenced. The protein levels of ACTN4 in both case and control groups were quantified using ELISA method. Results: Bioinformatics analysis revealed five unique ACTN4 mutations exclusively in patients with PNS, including c.1516G>A (p.G506S) on one exon in 2 patients, c.1442 + 10G>A at the splice site in 1 patient, c.1649A>G (p.D550G) on exon in 1 patient, c.2191-4G>A at the cleavage site in 2 patients, and c.2315C>T (p.A772V) on one exon in 1 patient. The c.1649A>G (p.D550G) and c.2315C>T (p.A772V) were identified from the same patient. Notably, c.1649A>G (p.D550G) represents a novel mutation in ACTN4. In addition, three other ACTN4 polymorphisms occurred in both case and control groups, including c.162 + 6C>T (1 patient in case group and 2 patients in control group), c.572 + 11G>A (1 patient in case group and 2 patients in control group), and c.2191-5C>T (4 patients in the case group and 3 patients in control group). The serum ACTN4 concentration in the case group was markedly higher, averaging 544.7 ng/mL (range: 264.6-952.6 ng/mL), compared with 241.20 ng/mL (range: 110.75-542.35 ng/mL) in the control group. Conclusion: Five ACTN4 polymorphisms were identified among children with PNS in Guangxi Autonomous Region, China, including the novel mutation c.1649A>G. The lower serum levels of α-actinin-4 in the case group suggest that this protein might play a protective role in PNS.