Simulation-predicted and -explained inheritance model of pathogenicity confirmed by transgenic mice models

Area of Science:

• Genetics
• Biophysics
• Molecular Biology

Background:

• Hereditary hearing impairment is frequently caused by variants in the gap junction beta-2 (GJB2) gene.
• The precise mechanisms by which GJB2 variants induce structural and functional changes in connexin 26 (Cx26) ion channels, leading to hearing loss, are not fully understood.

Purpose of the Study:

• To investigate the impact of GJB2 variants on Cx26 hexameric ion channel structure and function using molecular dynamics simulations.
• To elucidate the physicochemical and structural alterations caused by specific GJB2 variants.
• To validate a computational platform for assessing the pathogenicity of GJB2 variants.

Main Methods:

• Molecular dynamics (MD) simulations of wild-type (WT) and variant Cx26 hexamers.
• Analysis of channel ion flow, conformational energetics, and N-terminal "plug" behavior.
• Creation and simulation of an artificial V37M mutant to predict its effect on hearing loss.
• Phenotypic analysis of homozygous V37M transgenic mice.

Main Results:

• The prevalent human V37I GJB2 variant causes detached N-terminal "plugs" that reduce ion flow.
• Simulations of the V37M mutant revealed abnormal N-terminal affinity in homo-hexamers, blocking the channel, while stable hetero-hexamers remained unaffected.
• Homozygous V37M mice exhibited hearing loss, consistent with a recessive inheritance pattern and reduced channel conductivity in specific cochlear cells.
• The computational platform accurately predicted the pathogenic effects of the V37M variant.

Conclusions:

• Specific GJB2 variants, like V37I and V37M, disrupt Cx26 channel function through distinct structural mechanisms, primarily affecting N-terminal plug interactions and ion flow.
• The study proposes a model where unaffected carriers may result from dominant WT Cx26 influence or stable hetero-hexamer formation, while homozygous variants lead to dysfunctional channels.
• The developed computational platform shows promise as a tool for predicting the pathogenicity and inheritance patterns of GJB2-related hearing impairments and other connexin channelopathies.