CCT2 Mutations Evoke Leber Congenital Amaurosis due to Chaperone Complex Instability

Area of Science:

• Genetics
• Ophthalmology
• Molecular Biology

Background:

• Leber congenital amaurosis (LCA) is a severe inherited retinal dystrophy.
• The CCT2 gene encodes the CCTβ molecular chaperone, crucial for cellular function.
• The role of CCTβ mutations in human LCA was previously unknown.

Purpose of the Study:

• To identify novel genetic causes of LCA.
• To investigate the functional impact of CCTβ mutations on cellular processes.
• To explore the role of CCTβ in retinal cell biology.

Main Methods:

• Genetic analysis to identify mutations in LCA patients.
• Biochemical assays to assess protein stability and subunit interactions.
• Cell culture studies using patient-derived induced pluripotent stem cells (iPSCs) and 661W cells.
• Analysis of CCTβ and CCTγ expression in mouse retina.

Main Results:

• Novel compound heterozygous mutations (T400P and R516H) in CCT2 were identified as causative for LCA.
• Mutant CCTβ proteins showed biochemical instability and altered affinity for CCTγ.
• Patient-derived iPSCs with CCTβ mutations exhibited reduced proliferation.
• CCT2 knockdown in 661W cells decreased Gβ1 levels, a key client protein.

Conclusions:

• CCT2 mutations represent a novel genetic cause of Leber congenital amaurosis.
• Mutant CCTβ proteins exhibit impaired chaperone function, affecting cellular proliferation and protein homeostasis.
• These findings highlight the critical role of CCTβ in retinal development and function.