βA4-Crystallin Mutations Disrupt Structural Stability and Crystallin Interactions in Congenital Cataract Pathogenesis

Area of Science:

• Ophthalmology
• Molecular Biology
• Biochemistry

Background:

• Mutations in the beta A4-crystallin (CRYBA4) gene are linked to congenital cataracts.
• The precise pathogenic mechanisms underlying CRYBA4-associated cataracts are not fully understood.

Purpose of the Study:

• To investigate the structural destabilization and altered protein interactions caused by four distinct CRYBA4 mutants.
• To elucidate the pathogenic mechanisms of CRYBA4 mutations in congenital cataract formation.

Main Methods:

• Protein expression, purification, and characterization using size-exclusion chromatography, crosslinking, and circular dichroism spectroscopy.
• Assessment of protein polymerization, structural integrity, and stability.
• Yeast two-hybrid assays and antibiotic resistance screening to evaluate protein folding and interactions.

Main Results:

• Core CRYBA4 mutations (L69P, F94S) led to severe aggregation and disrupted interactions with beta B1- and beta B2-crystallin.
• An inter-motif mutation (G147V) reduced protein flexibility, while a surface mutation (Y67N) caused mild interaction disruption.
• Alpha A-crystallin preferentially stabilized aggregation-prone core mutants but had limited effects on other mutants.

Conclusions:

• CRYBA4 mutations cause congenital cataracts through distinct mechanisms dependent on their structural context.
• Alpha A-crystallin mitigates severe misfolding by stabilizing aggregation-prone conformers.
• Mutation-specific stabilization strategies, such as small-molecule chaperones or enhanced alpha A-crystallin activity, show therapeutic potential for CRYBA4-associated cataracts.