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Ning Zhang, Osamu Sawada, Debarshi Mustafi, Tadao Maeda, Krzysztof Palczewski; A mouse model of Retinitis Pigmentosa with an E150K mutation in the rod opsin gene. Invest. Ophthalmol. Vis. Sci. 2012;53(14):746.
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© ARVO (1962-2015); The Authors (2016-present)
Although autosomal dominant retinitis pigmentosa (adRP) is well studied because of its prevalence among retinal degenerative diseases, far less is known about autosomal recessive retinitis pigmentosa (arRP). To better understand the pathogenesis and design possible treatments for arRP, we generated an E150K rod opsin knock-in mouse line carrying single nucleotide change in exon 2 of the rod opsin gene which results in a Glu to Lys change.
The E150K mouse line was confirmed by whole knock-in locus and rod opsin cDNA sequencing. Phenotypes of E150K mice were examined by histology, spectral-domain optical coherence tomography (SD-OCT), electron microscopy (EM), electroretinograms (ERG), scanning laser ophthalmoscopy (SLO) and immunohistochemistry. Rhodopsin interaction with chromophore or transducin was investigated by cross breeding E150K with Lrat-/- or Gnat1-/- mice.
E150K homozygous (E150K+/+) exhibited early onset retinal degeneration whereas E150K heterozygous (E150K+/-) mice manifested late onset retinal degeneration. E150K+/+ mice never properly formed rod outer segments while E150K+/- mice evidence a slower and less severe ROS phenotype. Both a-waves and b-waves of scotopic ERGs were decreased in E150K+/+ mice by the age of 1 month but this impairment was detected only after 4 months of age in E150K+/- mice. Although autofluorescent spots were barely detectible in the subretinal region of 2-month-old wild-type (E150K-/-) mice, large amounts of autofluorescent spots were seen throughout subretinal region of age matched E150K+/+ mice and a few autofluorescent spots were visible in E150K+/- mice. While rhodopsin localized to the ROS in normal retina, mutant rhodopsin was detected not only in the ROS, but also in the inner segments and perinuclear region of the 1-month-old E150K+/+ retina. Mislocalization of rhodopsin was very mild in E150K+/- mice. We then cross bred E150K mice with either Lrat-/- or Gnat1-/- mice to get genetically engineered E150K mice lacking either chromophore or rod transducin. Ablation of chromophore decelerated retinal degeneration whereas depletion of transducin slightly accelerated such degeneration in E150K+/+ mice.
These results demonstrate the successful generation of a mouse model which mimics arRP in humans and suggest a novel pathogenic mechanism for arRP.
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