Activation of the ΓE-crystallin pseudogene in the human hereditary Coppock-like cataract

Brakenhoff, Ruud H.; Henskens, Hans A.M.; Rossum, M.W.P.C. van; Lubsen, Nicolette H.; Schoenmakers, John G.G.

doi:10.1093/hmg/3.2.279

Cited by 75 publications

(37 citation statements)

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“…These results contradict a common view of cataract formation, according to which protein unfolding or significant destabilization of the protein structure is a prerequisite for protein aggregation and cataract formation (30)(31)(32)(33)(34). An example of this view is the hereditary Coppock-like cataract, in which a truncated form of ␥E crystallin was believed to be overexpressed in the lens (3,33). Recent studies (30) now link this cataract to a mutation in the ␥C crystallin gene.…”

Section: Resultscontrasting

confidence: 65%

Molecular basis of a progressive juvenile-onset hereditary cataract

Pande

Asherie

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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We have expressed recombinant wild-type human ␥D crystallin (HGD) and its Arg-14 to Cys mutant (R14C) in Escherichia coli and show that R14C forms disulfide-linked oligomers, which markedly raise the phase separation temperature of the protein solution. Eventually, R14C precipitates. In contrast, HGD slowly forms only disulfide-linked dimers and no oligomers. These data strongly suggest that the observed cataract is triggered by the thiolmediated aggregation of R14C. The aggregation profiles of HGD and R14C are consistent with our homology modeling studies that reveal that R14C contains two exposed cysteine residues, whereas HGD has only one. Our CD, fluorescence, and differential scanning calorimetric studies show that HGD and R14C have nearly identical secondary and tertiary structures and stabilities. Thus, contrary to current views, unfolding or destabilization of the protein is not necessary for cataractogenesis.I n the hereditary, juvenile-onset cataract described by Stefan et al. (1), the lens, which is clear at birth, develops punctate opacities progressively, such that by two years of age the cataract is readily detectable, and matures by early childhood or adolescence. The punctate opacities seen in this cataract are in the nucleus and inner cortex, regions of the lens that are enriched in the ␥-crystallins. In the human lens, only two members of the ␥-crystallin family, ␥C and ␥D, are expressed in appreciable amounts, and only ␥D crystallin continues to be expressed until late childhood (2, 3). In affected individuals, a single point mutation has been identified in the ␥D crystallin gene that corresponds to the substitution of Arg-14 by a Cys. The identification of this mutation and the parallel between the time course of the pathology and the physiological expression of human ␥D crystallin strongly implicate the Arg-14 3 Cys mutant of ␥D in the development of this cataract. However, the molecular mechanism invoked to explain the observed opacity has been speculative (1).In the past, it has not been possible to conduct detailed studies on human ␥D crystallin because of the difficulty of obtaining sufficient quantities of pure protein from young, normal human lenses (4). Therefore, to characterize the normal protein thoroughly and investigate the mechanism by which the Arg-14 3 Cys mutation in ␥D could lead to cataract, we cloned and expressed human ␥D crystallin and its Arg-14 3 Cys mutant in Escherichia coli. Both the wild-type recombinant ␥D crystallin (HGD) and its Arg-14 3 Cys mutant (R14C) folded efficiently in E. coli and accumulated as soluble proteins. We isolated and purified the HGD and R14C proteins and determined their solution properties. Our results suggest that the disulfidecrosslinked oligomerization of R14C is responsible for the observed cataract. Furthermore, such oligomerization occurs without significant change in protein structure, conformation, and stability. Materials and MethodsCloning, Expression, and Isolation of Proteins. The human ␥D crystallin coding sequence was amplif...

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Section: Resultscontrasting

confidence: 65%

Molecular basis of a progressive juvenile-onset hereditary cataract

Pande

Asherie

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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130

184

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“…A putative pathological mutation has been described in a ''gene'' encoding a paternally expressed antisense transcript of the GNAS complex locus (GNASAS; MIM] 610540) [Bastepe et al, 2005], whereas a functional polymorphism has been reported within an enhancer at the 3 0 end of the CDKN2BAS ''gene'' (MIM] 600431), which encodes an antisense RNA transcript [Jarinova et al, 2009]. A CRYGEP1 (MIM] 123660) pseudogene-reactivating mutation associated with hereditary cataract formation [Brakenhoff et al, 1994] probably also falls into this category.…”

Section: Mutations In Nonprotein-coding Genesmentioning

confidence: 99%

Genes, mutations, and human inherited disease at the dawn of the age of personalized genomics

et al. 2010

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The number of reported germline mutations in human nuclear genes, either underlying or associated with inherited disease, has now exceeded 100,000 in more than 3,700 different genes. The availability of these data has both revolutionized the study of the morbid anatomy of the human genome and facilitated “personalized genomics.” With ∼300 new “inherited disease genes” (and ∼10,000 new mutations) being identified annually, it is pertinent to ask how many “inherited disease genes” there are in the human genome, how many mutations reside within them, and where such lesions are likely to be located? To address these questions, it is necessary not only to reconsider how we define human genes but also to explore notions of gene “essentiality” and “dispensability.” Answers to these questions are now emerging from recent novel insights into genome structure and function and through complete genome sequence information derived from multiple individual human genomes. However, a change in focus toward screening functional genomic elements as opposed to genes sensu stricto will be required if we are to capitalize fully on recent technical and conceptual advances and identify new types of disease‐associated mutation within noncoding regions remote from the genes whose function they disrupt. Hum Mutat 31:631–655, 2010. © 2010 Wiley‐Liss, Inc.

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“…The same cleavage of ␥-crystallin between residues Asp 73 and Ser 74 during ␣3 (Ϫ/Ϫ) cataractogenesis is also observed in cases of human cataracts (13). Furthermore, Asp 73 to Gly mutations found in CAT2 mice result in a nuclear cataract (29), and expression of truncated forms of ␥-crystallin is associated with human hereditary Coppock-like cataracts (30). These results suggest that this region within ␥-crystallin is important for maintaining the correct folding and hence the solubility of the protein.…”

Section: 28mentioning

confidence: 99%

Defining a Link between Gap Junction Communication, Proteolysis, and Cataract Formation

Baruch¹,

Greenbaum²,

Levy³

et al. 2001

Journal of Biological Chemistry

103

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Disruption of the connexin ␣3 (Cx46) gene (␣3 (؊/؊)) in mice results in severe cataracts within the nuclear portion of the lens. These cataracts are associated with proteolytic processing of the abundant lens protein ␥-crystallin, leading to its aggregation and subsequent opacification of the lens. The general cysteine protease inhibitor, E-64, blocked cataract formation and ␥-crystallin cleavage in ␣3 (؊/؊) lenses. Using a new class of activity-based cysteine protease affinity probes, we identified the calcium-dependent proteases, m-calpain and Lp82, as the primary targets of E-64 in the lens. Profiling changes in protease activities throughout cataractogenesis indicated that Lp82 activity was dramatically increased in ␣3 (؊/؊) lenses and correlated both spatially and temporally with cataract formation. Increased Lp82 activity was due to calcium accumulation as a result of increased influx and decreased outflux of calcium ions in ␣3 (؊/؊) lenses. These data establish a role for ␣3 gap junctions in maintaining calcium homeostasis that in turn is required to control activity of the calcium-dependent cysteine protease Lp82, shown here to be a key initiator of the process of cataractogenesis.

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Activation of the ΓE-crystallin pseudogene in the human hereditary Coppock-like cataract

Cited by 75 publications

References 0 publications

Molecular basis of a progressive juvenile-onset hereditary cataract

Molecular basis of a progressive juvenile-onset hereditary cataract

Genes, mutations, and human inherited disease at the dawn of the age of personalized genomics

Defining a Link between Gap Junction Communication, Proteolysis, and Cataract Formation

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