Combined clinical, structural and cellular studies discriminate pathogenic and benign TRPV4 variants

Area of Science:

• Genetics
• Molecular Biology
• Biophysics

Background:

• Dominant mutations in the calcium-permeable ion channel TRPV4 (transient receptor potential vanilloid 4) cause diverse channelopathies.
• Pathogenic TRPV4 mutations lead to gain of ion channel function and toxicity, with potential therapeutic targets in TRPV4 antagonists.
• The pathogenicity of numerous detected TRPV4 variants remains unclear, necessitating further investigation.

Purpose of the Study:

• To evaluate the pathogenicity of 30 TRPV4 variants using clinical data and experimental structure-function analyses.
• To characterize the functional impact of these variants on ion channel function, localization, expression, and cytotoxicity.
• To establish a framework for assessing TRPV4 variant pathogenicity and informing clinical trial patient selection.

Main Methods:

• Clinical information review for seven patients with TRPV4 variants of unknown significance.
• Extensive functional characterization of 24 TRPV4 variants, including structural position, ion channel activity, subcellular localization, expression levels, cytotoxicity, and protein-protein interactions.
• Analysis of variants within the ankyrin repeat domain, intrinsically disordered region, and transmembrane domain.

Main Results:

• Gain-of-function mutations in the TRPV4 ankyrin repeat domain affect RhoA interaction sites, while other residues show normal or reduced activity.
• A cluster of gain-of-function variants in the intrinsically disordered region may cause toxicity through altered membrane lipid interactions.
• Variants in the transmembrane domain and other intrinsically disordered regions were found to be likely benign, lacking gain-of-function activity.

Conclusions:

• Gain-of-function TRPV4 mutations are associated with congenital onset, vocal cord weakness, and motor-predominant disease.
• Likely benign TRPV4 variants are often linked to late-onset and sensory-predominant disease.
• This study provides a framework for assessing TRPV4 variant pathogenicity, crucial for guiding patient selection in future clinical trials for TRPV4 channelopathies.