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Mutations in zebrafish lrp2 result in adult-onset ocular pathogenesis that models myopia and other risk factors for glaucoma.

Veth KN, Willer JR, Collery RF, Gray MP, Willer GB, Wagner DS, Mullins MC, Udvadia AJ, Smith RS, John SW, Gregg RG, Link BA - PLoS Genet. (2011)

Bottom Line: Detailed phenotype analyses indicated that as lrp2 mutant fish age, many individuals--but not all--develop high IOP and severe myopia with obviously enlarged eye globes.This results in retinal stretch and prolonged stress to retinal ganglion cells, which ultimately show signs of pathogenesis.Our studies implicate altered Lrp2-mediated homeostasis as important for myopia and other risk factors for glaucoma in humans and establish a new genetic model for further study of phenotypes associated with this disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America.

ABSTRACT
The glaucomas comprise a genetically complex group of retinal neuropathies that typically occur late in life and are characterized by progressive pathology of the optic nerve head and degeneration of retinal ganglion cells. In addition to age and family history, other significant risk factors for glaucoma include elevated intraocular pressure (IOP) and myopia. The complexity of glaucoma has made it difficult to model in animals, but also challenging to identify responsible genes. We have used zebrafish to identify a genetically complex, recessive mutant that shows risk factors for glaucoma including adult onset severe myopia, elevated IOP, and progressive retinal ganglion cell pathology. Positional cloning and analysis of a non-complementing allele indicated that non-sense mutations in low density lipoprotein receptor-related protein 2 (lrp2) underlie the mutant phenotype. Lrp2, previously named Megalin, functions as an endocytic receptor for a wide-variety of bioactive molecules including Sonic hedgehog, bone morphogenic protein 4, retinol-binding protein, vitamin D-binding protein, and apolipoprotein E, among others. Detailed phenotype analyses indicated that as lrp2 mutant fish age, many individuals--but not all--develop high IOP and severe myopia with obviously enlarged eye globes. This results in retinal stretch and prolonged stress to retinal ganglion cells, which ultimately show signs of pathogenesis. Our studies implicate altered Lrp2-mediated homeostasis as important for myopia and other risk factors for glaucoma in humans and establish a new genetic model for further study of phenotypes associated with this disease.

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Eye growth and relative refractive errors in bugeye/lrp2 mutants.A bugeye mutants have a greater eye area to body length ratio (E:B) than age-matched wild-types beginning at 2 months (p<0.05, t-test), which becomes more pronounced with age. Each dot represents the E:B for an individual eye. B Histological transverse sections through the whole eye show an increased depth of the vitreous chamber (from the lens to retina) in bugeye (right) as compared to wild-type fish (left). C Diagram showing the calculation of relative refractive error (RRE): lens radius (l) and retina radius (r), using a focal length of the lens (f) as 2.32 x lens radius. D The RRE measurements revealed mild but significant myopia in 1-month bugeye fish (p = 0.0002, t-test), that becomes more dramatic at 2 months of age (p<0.0001, t-test). n = 6 eyes each for 1 month TL and bugeye; n = 16 and 22 eyes for 2 month TL wild-type and bugeye, respectively.
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pgen-1001310-g003: Eye growth and relative refractive errors in bugeye/lrp2 mutants.A bugeye mutants have a greater eye area to body length ratio (E:B) than age-matched wild-types beginning at 2 months (p<0.05, t-test), which becomes more pronounced with age. Each dot represents the E:B for an individual eye. B Histological transverse sections through the whole eye show an increased depth of the vitreous chamber (from the lens to retina) in bugeye (right) as compared to wild-type fish (left). C Diagram showing the calculation of relative refractive error (RRE): lens radius (l) and retina radius (r), using a focal length of the lens (f) as 2.32 x lens radius. D The RRE measurements revealed mild but significant myopia in 1-month bugeye fish (p = 0.0002, t-test), that becomes more dramatic at 2 months of age (p<0.0001, t-test). n = 6 eyes each for 1 month TL and bugeye; n = 16 and 22 eyes for 2 month TL wild-type and bugeye, respectively.

Mentions: Having established the causative gene for bugeye, we next investigated the onset of the ocular phenotype and quantified the pathology. To characterize the development of enlarged eyes in bugeye/lrp2 mutants we performed longitudinal studies tracking wild-type and mutant fish from 1-12 months. The zebrafish eye reaches its final adult anatomy by approximately 1 month of age [16]. Because overall growth rates can vary between equally aged fish — even within the same tank — we used the ratio of eye size to body length (E:B) to determine the relative size of the eye. This ratio remained constant in wild-type fish, allowing comparison of relative eye size between individuals regardless of the overall growth of the fish. Although this ratio remained flat as wild-type fish grew, the E:B ratio increased over time for most lrp2 mutants (Figure 3A). Despite individual variability, the average body length growth rates between wild-type and lrp2 mutant fish were indistinguishable (Figure S3). For the E:B ratio, no wild-type fish had a value greater than 0.05 (most fell between 0.02 and 0.04), and mutants with visibly enlarged eyes had an E:B ratio ≥0.07. The onset of large eyes was variable both within shared tanks of siblings and between generations, but a statistically significant difference between mutant and wild-type fish was consistently found at 2 months (Figure 3A and data not shown). In general, lrp2 mutant eyes become visibly enlarged in adults between 2–6 months and eye growth often plateaus between 8–12 months.


Mutations in zebrafish lrp2 result in adult-onset ocular pathogenesis that models myopia and other risk factors for glaucoma.

Veth KN, Willer JR, Collery RF, Gray MP, Willer GB, Wagner DS, Mullins MC, Udvadia AJ, Smith RS, John SW, Gregg RG, Link BA - PLoS Genet. (2011)

Eye growth and relative refractive errors in bugeye/lrp2 mutants.A bugeye mutants have a greater eye area to body length ratio (E:B) than age-matched wild-types beginning at 2 months (p<0.05, t-test), which becomes more pronounced with age. Each dot represents the E:B for an individual eye. B Histological transverse sections through the whole eye show an increased depth of the vitreous chamber (from the lens to retina) in bugeye (right) as compared to wild-type fish (left). C Diagram showing the calculation of relative refractive error (RRE): lens radius (l) and retina radius (r), using a focal length of the lens (f) as 2.32 x lens radius. D The RRE measurements revealed mild but significant myopia in 1-month bugeye fish (p = 0.0002, t-test), that becomes more dramatic at 2 months of age (p<0.0001, t-test). n = 6 eyes each for 1 month TL and bugeye; n = 16 and 22 eyes for 2 month TL wild-type and bugeye, respectively.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040661&req=5

pgen-1001310-g003: Eye growth and relative refractive errors in bugeye/lrp2 mutants.A bugeye mutants have a greater eye area to body length ratio (E:B) than age-matched wild-types beginning at 2 months (p<0.05, t-test), which becomes more pronounced with age. Each dot represents the E:B for an individual eye. B Histological transverse sections through the whole eye show an increased depth of the vitreous chamber (from the lens to retina) in bugeye (right) as compared to wild-type fish (left). C Diagram showing the calculation of relative refractive error (RRE): lens radius (l) and retina radius (r), using a focal length of the lens (f) as 2.32 x lens radius. D The RRE measurements revealed mild but significant myopia in 1-month bugeye fish (p = 0.0002, t-test), that becomes more dramatic at 2 months of age (p<0.0001, t-test). n = 6 eyes each for 1 month TL and bugeye; n = 16 and 22 eyes for 2 month TL wild-type and bugeye, respectively.
Mentions: Having established the causative gene for bugeye, we next investigated the onset of the ocular phenotype and quantified the pathology. To characterize the development of enlarged eyes in bugeye/lrp2 mutants we performed longitudinal studies tracking wild-type and mutant fish from 1-12 months. The zebrafish eye reaches its final adult anatomy by approximately 1 month of age [16]. Because overall growth rates can vary between equally aged fish — even within the same tank — we used the ratio of eye size to body length (E:B) to determine the relative size of the eye. This ratio remained constant in wild-type fish, allowing comparison of relative eye size between individuals regardless of the overall growth of the fish. Although this ratio remained flat as wild-type fish grew, the E:B ratio increased over time for most lrp2 mutants (Figure 3A). Despite individual variability, the average body length growth rates between wild-type and lrp2 mutant fish were indistinguishable (Figure S3). For the E:B ratio, no wild-type fish had a value greater than 0.05 (most fell between 0.02 and 0.04), and mutants with visibly enlarged eyes had an E:B ratio ≥0.07. The onset of large eyes was variable both within shared tanks of siblings and between generations, but a statistically significant difference between mutant and wild-type fish was consistently found at 2 months (Figure 3A and data not shown). In general, lrp2 mutant eyes become visibly enlarged in adults between 2–6 months and eye growth often plateaus between 8–12 months.

Bottom Line: Detailed phenotype analyses indicated that as lrp2 mutant fish age, many individuals--but not all--develop high IOP and severe myopia with obviously enlarged eye globes.This results in retinal stretch and prolonged stress to retinal ganglion cells, which ultimately show signs of pathogenesis.Our studies implicate altered Lrp2-mediated homeostasis as important for myopia and other risk factors for glaucoma in humans and establish a new genetic model for further study of phenotypes associated with this disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America.

ABSTRACT
The glaucomas comprise a genetically complex group of retinal neuropathies that typically occur late in life and are characterized by progressive pathology of the optic nerve head and degeneration of retinal ganglion cells. In addition to age and family history, other significant risk factors for glaucoma include elevated intraocular pressure (IOP) and myopia. The complexity of glaucoma has made it difficult to model in animals, but also challenging to identify responsible genes. We have used zebrafish to identify a genetically complex, recessive mutant that shows risk factors for glaucoma including adult onset severe myopia, elevated IOP, and progressive retinal ganglion cell pathology. Positional cloning and analysis of a non-complementing allele indicated that non-sense mutations in low density lipoprotein receptor-related protein 2 (lrp2) underlie the mutant phenotype. Lrp2, previously named Megalin, functions as an endocytic receptor for a wide-variety of bioactive molecules including Sonic hedgehog, bone morphogenic protein 4, retinol-binding protein, vitamin D-binding protein, and apolipoprotein E, among others. Detailed phenotype analyses indicated that as lrp2 mutant fish age, many individuals--but not all--develop high IOP and severe myopia with obviously enlarged eye globes. This results in retinal stretch and prolonged stress to retinal ganglion cells, which ultimately show signs of pathogenesis. Our studies implicate altered Lrp2-mediated homeostasis as important for myopia and other risk factors for glaucoma in humans and establish a new genetic model for further study of phenotypes associated with this disease.

Show MeSH
Related in: MedlinePlus