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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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Analysis of retinal and optic nerve head pathology.A The relative expression levels of genes previously associated with retinal neuron pathology measured by real-time PCR on cDNA made from RNA isolated from the eyes of 1-month TL and bugeye fish. The cell populations that predominantly express the marker genes are listed below the bar graph. n = 4 independent samples of 6 pooled eyes each from TL wild-type and bugeye mutant fish. Error bars show standard error of the mean; *p<0.05. B Histological cross sections through the optic nerve head in TL wild-type (left) and bugeye (right) samples a 6 months of age. C Representative electron micrographs showing each type of axon pathology observed in cross-sections of TL wild-type (top) and bugeye (bottom) optic nerves. Arrowheads (left), degenerating axon; arrows (middle), unraveling myelin sheath; asterisks (right), lost axon. Scale bar  = 2 µm. D Quantification of the optic nerve ultrastructure analysis reported as number of axon pathologies per mm2. n = 6 and 7 nerves for 7- and 12-month TL wild-type, respectively; n = 8 nerves each for 7- and 12-month bugeye.
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pgen-1001310-g007: Analysis of retinal and optic nerve head pathology.A The relative expression levels of genes previously associated with retinal neuron pathology measured by real-time PCR on cDNA made from RNA isolated from the eyes of 1-month TL and bugeye fish. The cell populations that predominantly express the marker genes are listed below the bar graph. n = 4 independent samples of 6 pooled eyes each from TL wild-type and bugeye mutant fish. Error bars show standard error of the mean; *p<0.05. B Histological cross sections through the optic nerve head in TL wild-type (left) and bugeye (right) samples a 6 months of age. C Representative electron micrographs showing each type of axon pathology observed in cross-sections of TL wild-type (top) and bugeye (bottom) optic nerves. Arrowheads (left), degenerating axon; arrows (middle), unraveling myelin sheath; asterisks (right), lost axon. Scale bar  = 2 µm. D Quantification of the optic nerve ultrastructure analysis reported as number of axon pathologies per mm2. n = 6 and 7 nerves for 7- and 12-month TL wild-type, respectively; n = 8 nerves each for 7- and 12-month bugeye.

Mentions: In the following studies we evaluated the onset of retinal ganglion cell stress and pathology. Relative expression levels of twelve genes known to be up-regulated in animal models of retinal ganglion cell injury was surveyed by quantitative RT-PCR. This panel of markers included three transcripts expressed in microglia (aif1l, [22], [23]; apoeb, [24], [25]; arg1, [26], [27]), one expressed in Müller glia and astrocytes (gfap, [28], [29]), and eight expressed in retinal ganglion cells (atf3, [30], [31]; c1q, [32]–[34]; c-jun, [31], [35], [36]; gap43, [37], [38]; klf6a, [31], [39]; socs3a and socs3b, [31], [40], [41]; thy1, [42], [43]). Analysis was conducted on cDNA isolated from pooled 1-month-old retinas, a time just prior to when mutant eyes were measurably enlarged. We chose this early time-point to avoid measuring changes that might simply reflect significant alterations in cell proportions and density. With this assay, we found induction primarily of transcripts associated with retinal ganglion cells, but not for the glia-associated genes (Figure 7A).


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)

Analysis of retinal and optic nerve head pathology.A The relative expression levels of genes previously associated with retinal neuron pathology measured by real-time PCR on cDNA made from RNA isolated from the eyes of 1-month TL and bugeye fish. The cell populations that predominantly express the marker genes are listed below the bar graph. n = 4 independent samples of 6 pooled eyes each from TL wild-type and bugeye mutant fish. Error bars show standard error of the mean; *p<0.05. B Histological cross sections through the optic nerve head in TL wild-type (left) and bugeye (right) samples a 6 months of age. C Representative electron micrographs showing each type of axon pathology observed in cross-sections of TL wild-type (top) and bugeye (bottom) optic nerves. Arrowheads (left), degenerating axon; arrows (middle), unraveling myelin sheath; asterisks (right), lost axon. Scale bar  = 2 µm. D Quantification of the optic nerve ultrastructure analysis reported as number of axon pathologies per mm2. n = 6 and 7 nerves for 7- and 12-month TL wild-type, respectively; n = 8 nerves each for 7- and 12-month bugeye.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040661&req=5

pgen-1001310-g007: Analysis of retinal and optic nerve head pathology.A The relative expression levels of genes previously associated with retinal neuron pathology measured by real-time PCR on cDNA made from RNA isolated from the eyes of 1-month TL and bugeye fish. The cell populations that predominantly express the marker genes are listed below the bar graph. n = 4 independent samples of 6 pooled eyes each from TL wild-type and bugeye mutant fish. Error bars show standard error of the mean; *p<0.05. B Histological cross sections through the optic nerve head in TL wild-type (left) and bugeye (right) samples a 6 months of age. C Representative electron micrographs showing each type of axon pathology observed in cross-sections of TL wild-type (top) and bugeye (bottom) optic nerves. Arrowheads (left), degenerating axon; arrows (middle), unraveling myelin sheath; asterisks (right), lost axon. Scale bar  = 2 µm. D Quantification of the optic nerve ultrastructure analysis reported as number of axon pathologies per mm2. n = 6 and 7 nerves for 7- and 12-month TL wild-type, respectively; n = 8 nerves each for 7- and 12-month bugeye.
Mentions: In the following studies we evaluated the onset of retinal ganglion cell stress and pathology. Relative expression levels of twelve genes known to be up-regulated in animal models of retinal ganglion cell injury was surveyed by quantitative RT-PCR. This panel of markers included three transcripts expressed in microglia (aif1l, [22], [23]; apoeb, [24], [25]; arg1, [26], [27]), one expressed in Müller glia and astrocytes (gfap, [28], [29]), and eight expressed in retinal ganglion cells (atf3, [30], [31]; c1q, [32]–[34]; c-jun, [31], [35], [36]; gap43, [37], [38]; klf6a, [31], [39]; socs3a and socs3b, [31], [40], [41]; thy1, [42], [43]). Analysis was conducted on cDNA isolated from pooled 1-month-old retinas, a time just prior to when mutant eyes were measurably enlarged. We chose this early time-point to avoid measuring changes that might simply reflect significant alterations in cell proportions and density. With this assay, we found induction primarily of transcripts associated with retinal ganglion cells, but not for the glia-associated genes (Figure 7A).

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