Mutation of CRYAB encoding a conserved mitochondrial chaperone and antiapoptotic protein causes hereditary optic atrophy
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
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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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 6

Assessment of apoptosis and OXPHOS activities.

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Assessment of apoptosis and OXPHOS activities. (A) Fluorescence analysis...
(A) Fluorescence analysis of cleaved caspase-3 protein level in mouse retina at 8 weeks of age. Cleaved caspase-3 was shown in red fluorescence, and DAPI-labeled nucleus was shown in blue fluorescence. (B) Western blot analysis. Proteins (20 μg) from mouse retinas were electrophoresed, electroblotted, and hybridized with several apoptosis-associated protein antibodies: cytochrome c, uncleaved/cleaved caspase-3, Bax and Bcl-xl, with GAPDH as a loading control. (C) The steady-state levels of 5 OXPHOS complexes by BN-PAGE. Mitochondrial proteins (30 μg) from MT and WT mice brains were electrophoresed through a BN gel, electroblotted, and hybridized with antibodies for Ndufs1, Sdhb, Uqcrc2, Cox5a, and Atp5a (subunits of complex I, II, III, IV, and V, respectively). (D) Quantification of relative levels of complexes assembly. (E) In-gel activities of complexes I, II, IV, and V. Mitochondrial proteins from MT and WT mice were used for BN gel, and the activities of complexes were measured in the presence of specific substrates, as described previously (42). (F) Average relative levels of complexes I, IV, and V content per cell were normalized to the average levels per cell of complex II in the MT and WT mice brains. Data are shown as mean ± SEM of triplicates. *P < 0.05; **P < 0.01, by 1-way ANOVA followed by Bonferroni’s post hoc test.