Functional domain mapping and selective trans-dominant effects exhibited by Cx26 disease-causing mutations

Area of Science:

• Cell biology
• Genetics
• Biochemistry

Background:

• Mutations in connexin 26 (Cx26) are a leading cause of hereditary sensorineural deafness.
• Some Cx26 mutations are linked to both hearing loss and skin disorders.

Purpose of the Study:

• To investigate the cellular localization and functional impact of two Cx26 mutants (G59A and D66H) associated with deafness and skin disease.
• To understand the dominant-negative effects of these mutants on wild-type Cx26 and other connexins (Cx32, Cx43).

Main Methods:

• Utilized green fluorescent protein (GFP)-tagged Cx26 point mutants (G59A-GFP and D66H-GFP).
• Examined subcellular localization using brefeldin A treatment.
• Assessed gap junction function via dye permeability assays.
• Investigated dominant-negative effects through co-expression studies with wild-type Cx26, Cx32, and Cx43.

Main Results:

• D66H-GFP localized to the trans-Golgi network, while G59A-GFP reached the cell surface.
• Neither mutant formed functional gap junctions permeable to dyes, indicating loss-of-function.
• Both G59A and D66H exhibited dominant-negative effects on wild-type Cx26.
• G59A showed trans-dominant negative effects on Cx32 and Cx43; D66H affected Cx43 but not Cx32.

Conclusions:

• Cx26 mutants G59A and D66H are non-functional and exert dominant-negative effects on wild-type Cx26 and other connexins.
• The severity of associated skin disease may depend on the specific mutation and its trans-dominant interactions with other connexins.
• The first extracellular loop of Cx26 is crucial for its cell surface transport and gap junction channel function.