Frequent SLC12A3 mutations in Chinese Gitelman syndrome patients: structure and function disorder

Area of Science:

• Genetics and Molecular Biology
• Renal Physiology

Background:

• Gitelman syndrome (GS) is a genetic disorder affecting renal salt reabsorption.
• Mutations in the SLC12A3 gene, encoding the human sodium-chloride cotransporter (hNCC), are the primary cause of GS.

Purpose of the Study:

• To identify frequent SLC12A3 gene mutations in Chinese Gitelman syndrome patients.
• To predict the structural impact of these mutations on the hNCC.
• To functionally assess the identified and novel mutations in vitro and in vivo.

Main Methods:

• Systematic review of reported Chinese GS patients' SLC12A3 mutations.
• In silico prediction of wild-type and mutant hNCC structures using I-TASSER.
• In vitro functional analysis via 22Na+ uptake assays in Xenopus laevis oocytes.
• In vivo thiazide testing in GS patients and healthy controls.

Main Results:

• Identified frequent mutations (T60M, D486N, R928C) and novel mutations (L215F, N534K, Q617R) in Chinese GS families.
• Predicted alterations in the three-dimensional structure of hNCC for all tested mutations.
• Demonstrated significantly reduced thiazide-sensitive 22Na+ uptake for all six mutations compared to wild-type hNCC.
• Thiazide test results showed impaired chloride excretion in GS patients, correlating with specific mutations.

Conclusions:

• Frequent and novel SLC12A3 mutations identified in Chinese GS patients lead to hNCC structural changes.
• These mutations impair hNCC function, evidenced by reduced sodium uptake in vitro.
• The functional deficits are consistent with clinical observations in Gitelman syndrome patients.