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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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Related in: MedlinePlus

Morphological alterations in cortical fiber cell membranes of R49Cneo lenses. Lens sections were stained with haematoxylin/eosin. (A) Normal appearance of fiber cells in the lens equatorial region in 3-week-old wild type lenses. (B) Swollen fiber cells and separations between fiber cells in 3-week-old WT/R49Cneo heterozygous lenses. (C) Gaps between fiber cells in 3-week-old R49Cneo/R49Cneo homozygous lenses.
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Figure 7: Morphological alterations in cortical fiber cell membranes of R49Cneo lenses. Lens sections were stained with haematoxylin/eosin. (A) Normal appearance of fiber cells in the lens equatorial region in 3-week-old wild type lenses. (B) Swollen fiber cells and separations between fiber cells in 3-week-old WT/R49Cneo heterozygous lenses. (C) Gaps between fiber cells in 3-week-old R49Cneo/R49Cneo homozygous lenses.

Mentions: At 3 weeks, histological examination of lenses revealed the presence of both small and large swollen cells or vacuoles in the lens cortical fibers of WT/R49Cneo mice, which were even more evident in R49Cneo homozygous mouse lenses (Figure 7). Early fiber formation appeared to occur normally. Swollen fiber cells begin to appear at 3 weeks postnatal in WT/R49Cneo heterozygous mice. Swollen fiber cells were confined to a distinct band of cortical fibers ~100 μm from the lens surface in both young and old mice. Fiber cells on either side of the swollen fibers appear to be unaffected. These swollen cells appeared to be formed by membrane rupture and fusion of cytoplasmic contents from multiple cells. Extensive undulations and interdigitations of these membranes as well as large separations between fiber cells occurred in homozygous mouse lenses. These gaps are evident in fiber cells that have detached from the capsule (Figure 6C). The proportion of swollen cells and posterior changes in WT/R49Cneo and R49Cneo/R49Cneo mice examined by histology is shown in Table 1B.


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)

Morphological alterations in cortical fiber cell membranes of R49Cneo lenses. Lens sections were stained with haematoxylin/eosin. (A) Normal appearance of fiber cells in the lens equatorial region in 3-week-old wild type lenses. (B) Swollen fiber cells and separations between fiber cells in 3-week-old WT/R49Cneo heterozygous lenses. (C) Gaps between fiber cells in 3-week-old R49Cneo/R49Cneo homozygous lenses.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2724435&req=5

Figure 7: Morphological alterations in cortical fiber cell membranes of R49Cneo lenses. Lens sections were stained with haematoxylin/eosin. (A) Normal appearance of fiber cells in the lens equatorial region in 3-week-old wild type lenses. (B) Swollen fiber cells and separations between fiber cells in 3-week-old WT/R49Cneo heterozygous lenses. (C) Gaps between fiber cells in 3-week-old R49Cneo/R49Cneo homozygous lenses.
Mentions: At 3 weeks, histological examination of lenses revealed the presence of both small and large swollen cells or vacuoles in the lens cortical fibers of WT/R49Cneo mice, which were even more evident in R49Cneo homozygous mouse lenses (Figure 7). Early fiber formation appeared to occur normally. Swollen fiber cells begin to appear at 3 weeks postnatal in WT/R49Cneo heterozygous mice. Swollen fiber cells were confined to a distinct band of cortical fibers ~100 μm from the lens surface in both young and old mice. Fiber cells on either side of the swollen fibers appear to be unaffected. These swollen cells appeared to be formed by membrane rupture and fusion of cytoplasmic contents from multiple cells. Extensive undulations and interdigitations of these membranes as well as large separations between fiber cells occurred in homozygous mouse lenses. These gaps are evident in fiber cells that have detached from the capsule (Figure 6C). The proportion of swollen cells and posterior changes in WT/R49Cneo and R49Cneo/R49Cneo mice examined by histology is shown in Table 1B.

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