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AlphaA-crystallin R49Cneo mutation influences the architecture of lens fiber cell membranes and causes posterior and nuclear cataracts in mice.

Andley UP - BMC Ophthalmol (2009)

Bottom Line: AlphaA-crystallin (CRYAA/HSPB4), a major component of all vertebrate eye lenses, is a small heat shock protein responsible for maintaining lens transparency.By 3 weeks, WT/R49Cneo mice exhibited large vacuoles in the cortical region 100 mum from the lens surface, and by 3 months posterior and nuclear cataracts had developed.It is apparent that modification of membrane and cell-cell interactions occurs in the presence of the alphaA-crystallin mutation and rapidly leads to lens cell pathology in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, Missouri, USA. andley@vision.wustl.edu

ABSTRACT

Background: AlphaA-crystallin (CRYAA/HSPB4), a major component of all vertebrate eye lenses, is a small heat shock protein responsible for maintaining lens transparency. The R49C mutation in the alphaA-crystallin protein is linked with non-syndromic, hereditary human cataracts in a four-generation Caucasian family.

Methods: This study describes a mouse cataract model generated by insertion of a neomycin-resistant (neor) gene into an intron of the gene encoding mutant R49C alphaA-crystallin. Mice carrying the neor gene and wild-type Cryaa were also generated as controls. Heterozygous knock-in mice containing one wild type gene and one mutated gene for alphaA-crystallin (WT/R49Cneo) and homozygous knock-in mice containing two mutated genes (R49Cneo/R49Cneo) were compared.

Results: By 3 weeks, WT/R49Cneo mice exhibited large vacuoles in the cortical region 100 mum from the lens surface, and by 3 months posterior and nuclear cataracts had developed. WT/R49Cneo mice demonstrated severe posterior cataracts at 9 months of age, with considerable posterior nuclear migration evident in histological sections. R49Cneo/R49Cneo mice demonstrated nearly complete lens opacities by 5 months of age. In contrast, R49C mice in which the neor gene was deleted by breeding with CreEIIa mice developed lens abnormalities at birth, suggesting that the neor gene may suppress expression of mutant R49C alphaA-crystallin protein.

Conclusion: It is apparent that modification of membrane and cell-cell interactions occurs in the presence of the alphaA-crystallin mutation and rapidly leads to lens cell pathology in vivo.

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Lens phenotypes in R49Cneo mice. (A-D) Eyes were dilated and examined by slit lamp. (A) Wild type mice (5 months old) had clear lenses (stage 0). (B) Heterozygous WT/R49Cneo αA-crystallin knock-in mice (3 months old) had opacity in the posterior and nuclear regions of the lens (stage 2). (C) Homozygous R49Cneo/R49Cneo αA-crystallin knock-in mice (3 months old) had a nearly complete cataract (stage 3–4). (D) R49Cneo/R49Cneo αA-crystallin knock-in mouse lenses showed a complete cataract at 5 months (stage 4). (E, F) Cataract in lens of a newborn R49C/R49C homozygous mouse with deletion of the neor gene by Cre-recombinase. Slit lamp image (E) shows a severe nuclear opacity at birth (stage 3). (F) Higher magnification of the lens shown in (E) shows the nuclear opacity covering ~70% of the lens.
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Figure 3: Lens phenotypes in R49Cneo mice. (A-D) Eyes were dilated and examined by slit lamp. (A) Wild type mice (5 months old) had clear lenses (stage 0). (B) Heterozygous WT/R49Cneo αA-crystallin knock-in mice (3 months old) had opacity in the posterior and nuclear regions of the lens (stage 2). (C) Homozygous R49Cneo/R49Cneo αA-crystallin knock-in mice (3 months old) had a nearly complete cataract (stage 3–4). (D) R49Cneo/R49Cneo αA-crystallin knock-in mouse lenses showed a complete cataract at 5 months (stage 4). (E, F) Cataract in lens of a newborn R49C/R49C homozygous mouse with deletion of the neor gene by Cre-recombinase. Slit lamp image (E) shows a severe nuclear opacity at birth (stage 3). (F) Higher magnification of the lens shown in (E) shows the nuclear opacity covering ~70% of the lens.

Mentions: Lens opacities were confirmed in R49Cneo mutant mice by slit lamp analysis (Figure 3). By 3 months, R49Cneo mice showed evidence of opacities in posterior and nuclear regions. Over time, the cataract progressed to a nuclear cataract and then to an all-over opacity that included the cortical fibers (Figure 3A–D). Heterozygous mice at each age showed variable lens opacities ranging from clear (stage 0) at <2 months, stage 0 to stage 2 at 2–3 months, and clear to complete opacity (stage 4) at >4 months of age. Wild type mice did not show any of these abnormalities. At least four mice were examined for each genotype at a given age (Table 1A). The neomycin cassette was deleted by breeding homozygous R49Cneo mice with Cre-EIIa transgenic mice. These neomycin-deleted R49C mutant mice had a more severe lens phenotype, with homozygous R49C/R49C knock-in neo-deleted mice exhibiting an opacity that covered three-quarters of the young lens (Figure 3E and 3F). Overall, cataract progression was more rapid in R49C/R49C mice than in R49Cneo/R49Cneo mice.


AlphaA-crystallin R49Cneo mutation influences the architecture of lens fiber cell membranes and causes posterior and nuclear cataracts in mice.

Andley UP - BMC Ophthalmol (2009)

Lens phenotypes in R49Cneo mice. (A-D) Eyes were dilated and examined by slit lamp. (A) Wild type mice (5 months old) had clear lenses (stage 0). (B) Heterozygous WT/R49Cneo αA-crystallin knock-in mice (3 months old) had opacity in the posterior and nuclear regions of the lens (stage 2). (C) Homozygous R49Cneo/R49Cneo αA-crystallin knock-in mice (3 months old) had a nearly complete cataract (stage 3–4). (D) R49Cneo/R49Cneo αA-crystallin knock-in mouse lenses showed a complete cataract at 5 months (stage 4). (E, F) Cataract in lens of a newborn R49C/R49C homozygous mouse with deletion of the neor gene by Cre-recombinase. Slit lamp image (E) shows a severe nuclear opacity at birth (stage 3). (F) Higher magnification of the lens shown in (E) shows the nuclear opacity covering ~70% of the lens.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 3: Lens phenotypes in R49Cneo mice. (A-D) Eyes were dilated and examined by slit lamp. (A) Wild type mice (5 months old) had clear lenses (stage 0). (B) Heterozygous WT/R49Cneo αA-crystallin knock-in mice (3 months old) had opacity in the posterior and nuclear regions of the lens (stage 2). (C) Homozygous R49Cneo/R49Cneo αA-crystallin knock-in mice (3 months old) had a nearly complete cataract (stage 3–4). (D) R49Cneo/R49Cneo αA-crystallin knock-in mouse lenses showed a complete cataract at 5 months (stage 4). (E, F) Cataract in lens of a newborn R49C/R49C homozygous mouse with deletion of the neor gene by Cre-recombinase. Slit lamp image (E) shows a severe nuclear opacity at birth (stage 3). (F) Higher magnification of the lens shown in (E) shows the nuclear opacity covering ~70% of the lens.
Mentions: Lens opacities were confirmed in R49Cneo mutant mice by slit lamp analysis (Figure 3). By 3 months, R49Cneo mice showed evidence of opacities in posterior and nuclear regions. Over time, the cataract progressed to a nuclear cataract and then to an all-over opacity that included the cortical fibers (Figure 3A–D). Heterozygous mice at each age showed variable lens opacities ranging from clear (stage 0) at <2 months, stage 0 to stage 2 at 2–3 months, and clear to complete opacity (stage 4) at >4 months of age. Wild type mice did not show any of these abnormalities. At least four mice were examined for each genotype at a given age (Table 1A). The neomycin cassette was deleted by breeding homozygous R49Cneo mice with Cre-EIIa transgenic mice. These neomycin-deleted R49C mutant mice had a more severe lens phenotype, with homozygous R49C/R49C knock-in neo-deleted mice exhibiting an opacity that covered three-quarters of the young lens (Figure 3E and 3F). Overall, cataract progression was more rapid in R49C/R49C mice than in R49Cneo/R49Cneo mice.

Bottom Line: AlphaA-crystallin (CRYAA/HSPB4), a major component of all vertebrate eye lenses, is a small heat shock protein responsible for maintaining lens transparency.By 3 weeks, WT/R49Cneo mice exhibited large vacuoles in the cortical region 100 mum from the lens surface, and by 3 months posterior and nuclear cataracts had developed.It is apparent that modification of membrane and cell-cell interactions occurs in the presence of the alphaA-crystallin mutation and rapidly leads to lens cell pathology in vivo.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, Missouri, USA. andley@vision.wustl.edu

ABSTRACT

Background: AlphaA-crystallin (CRYAA/HSPB4), a major component of all vertebrate eye lenses, is a small heat shock protein responsible for maintaining lens transparency. The R49C mutation in the alphaA-crystallin protein is linked with non-syndromic, hereditary human cataracts in a four-generation Caucasian family.

Methods: This study describes a mouse cataract model generated by insertion of a neomycin-resistant (neor) gene into an intron of the gene encoding mutant R49C alphaA-crystallin. Mice carrying the neor gene and wild-type Cryaa were also generated as controls. Heterozygous knock-in mice containing one wild type gene and one mutated gene for alphaA-crystallin (WT/R49Cneo) and homozygous knock-in mice containing two mutated genes (R49Cneo/R49Cneo) were compared.

Results: By 3 weeks, WT/R49Cneo mice exhibited large vacuoles in the cortical region 100 mum from the lens surface, and by 3 months posterior and nuclear cataracts had developed. WT/R49Cneo mice demonstrated severe posterior cataracts at 9 months of age, with considerable posterior nuclear migration evident in histological sections. R49Cneo/R49Cneo mice demonstrated nearly complete lens opacities by 5 months of age. In contrast, R49C mice in which the neor gene was deleted by breeding with CreEIIa mice developed lens abnormalities at birth, suggesting that the neor gene may suppress expression of mutant R49C alphaA-crystallin protein.

Conclusion: It is apparent that modification of membrane and cell-cell interactions occurs in the presence of the alphaA-crystallin mutation and rapidly leads to lens cell pathology in vivo.

Show MeSH
Related in: MedlinePlus