Mutation of CRYAB encoding a conserved mitochondrial chaperone and antiapoptotic protein causes hereditary optic atrophy
Chenghui Wang, … , Yanchun Ji, Min-Xin Guan
Chenghui Wang, … , Yanchun Ji, Min-Xin Guan
Published November 19, 2024
Citation Information: JCI Insight. 2025;10(1):e182209. https://doi.org/10.1172/jci.insight.182209.
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Research Article Genetics Ophthalmology

Mutation of CRYAB encoding a conserved mitochondrial chaperone and antiapoptotic protein causes hereditary optic atrophy

Abstract

The degeneration of retinal ganglion cells (RGC) due to mitochondrial dysfunctions manifests optic neuropathy. However, the molecular components of RGC linked to optic neuropathy manifestations remain largely unknown. Here, we identified a potentially novel optic atrophy-causative CRYAB gene encoding a highly conserved major lens protein acting as mitochondrial chaperone and possessing antiapoptotic activities. The heterozygous CRYAB mutation (c.313G>A, p. Glu105Lys) was cosegregated with autosomal dominant inheritance of optic atrophy in 3 Chinese families. The p.E105K mutation altered the structure and function of CRYAB, including decreased stability, reduced formation of oligomers, and decreased chaperone activity. Coimmunoprecipitation indicated that the p.E105K mutation reduced the interaction of CRYAB with apoptosis-associated cytochrome c and voltage-dependent anion channel protein. The cell lines carrying the p.E105K mutation displayed promotion of apoptosis and defective assembly, stability, and activities of oxidative phosphorylation system as well as imbalance of mitochondrial dynamics. Involvement of CRYAB in optic atrophy was confirmed by phenotypic evaluations of Cryabp.E105K-knockin mice. These mutant mice exhibited ocular lesions that included alteration of intraretinal layers, degeneration of RGCs, photoreceptor deficits, and abnormal retinal vasculature. Furthermore, Cryab-deficient mice displayed elevated apoptosis and mitochondrial dysfunctions. Our findings provide insight of pathophysiology of optic atrophy arising from RGC degeneration caused by CRYAB deficiency–induced elevated apoptosis and mitochondrial dysfunctions.

Authors

Chenghui Wang, Liyao Zhang, Zhipeng Nie, Min Liang, Hanqing Liu, Qiuzi Yi, Chunyan Wang, Cheng Ai, Juanjuan Zhang, Yinglong Gao, Yanchun Ji, Min-Xin Guan

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Figure 2

In vitro analysis of structure and function of WT and MT CRYAB.

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In vitro analysis of structure and function of WT and MT CRYAB. (A) Sche...
(A) Schematic model for the α-crystallin domain (ACD) of CRYAB homodimer (PDB ID: 2klr) for WT (tawny) and MT (blue) contains chain A and chain B after MD simulations of 500 ns. The MT site was indicated. (B) Time evolution of the root mean square deviation (RMSD) values of all α-carbon (α-Cα) atoms for the WT (black line) and MT (red line) proteins. (C) Analysis for the oligomer formation of CRYAB. Both WT and MT proteins, labeled by Flag/His Tag, were expressed and purified from HeLa and BL21, electrophoresed through a blue native gel, and electroblotted and hybridized with antibodies specific for Flag-Tag, His-Tag, CRYAB, and GAPDH. (D) The chaperone activities of MT and WT CRYAB with DTT-induced denatured insulin. Insulin (0.4 mg/mL in 50 mM phosphate buffer [pH 7.4]) was reduced with 20 mM DTT, and the aggregation of the insulin CRYAB was monitored by measuring the apparent absorption at 360 nm. The aggregation rates were calculated. (E and F) Reduced interactions of CRYAB with cytochrome c (E) or VDAC (F). HEK293T cells, transiently expressing with WT, MT CRYAB-HA, or CRYAB-FLAG and empty vector, were solubilized with a lysis buffer. Lysate proteins and immunoprecipitates were immunoprecipitated with immunocapture buffer (IgG) (left), cytochrome c or VDAC antibody (right). Immunoprecipitates were then analyzed by SDS-PAGE and hybridized with anti-CRYAB and anti–cytochrome c or with anti-VDAC antibodies. Representative of 3 independent experiments.