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Iris S Kassem, James J Miller, Kazuhiro Aoki, Carly A Murphy, Jonathon Young, Michael Tiemeyer, Nancy M Dahms; Early Ocular Manifestations of Fabry Disease in α-galactosidase A-deficient Rats. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5660.
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© ARVO (1962-2015); The Authors (2016-present)
Fabry disease is an X-linked disorder caused by deficiency of lysosomal α-galactosidase A (α-Gal A) activity from mutation of the GLA gene. α-galactosyl glycolipids, notably globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3), accumulate within lysosomes, leading to cellular dysfunction. Cornea verticillata, cataracts, and vascular tortuosity are common and useful diagnostic signs. Current mouse knockout models do not report the ocular phenotype of Fabry disease. We developed rats with α-Gal A deficiency and determined if they would express any of the ocular phenotypes seen in humans.
CRISPR/Cas9 technology was used to generate α-Gal A deficient (Gla KO) rats. At 3 months of age, serum glycolipids were quantified using mass spectrometry in 3 wild type (WT) and 3 KO male rats. Mean glycolipid levels were compared between WT and KO rats using an unpaired, two-tailed t-test. Three-month-old rats were examined and photographed with slit lamp biomicroscopy for anterior segment findings of Fabry disease. Corneal and lenticular opacities were scored by a masked examiner, and mean scores were compared using a Mann-Whitney test for males (WT vs KO) and a Kruskal-Wallis test for females (WT vs heterozygous vs KO).
Gla KO rats have dramatic increases in the established biomarkers for patients with Fabry disease. Mean serum Gb3 concentration is 364 ± 59 nM in KO rats, which is elevated >100-fold above WT (P < 0.001). Mean serum lyso-Gb3 concentration is 151 ± 10 nM in KO rats, which is elevated >30-fold above WT (P < 0.001). There is no difference in serum non-α-galactosyl glycolipids, such as ganglioside GM3, in Gla KO and WT rat serum (P = 0.49). At three months, Gla KO (hemizygous males and homozygous females) rats develop significantly more anterior corneal opacities ranging from anterior deposits in a fine honeycomb pattern to a confluent plaque (P < 0.01). Lenticular opacities were also more common and ranged from multiple small punctate lenticular opacities to a denser central cataract. Histopathology revealed Oil Red O staining of the corneal epithelium and evidence of retinal vascular occlusion in KO rats.
The ocular phenotypes observed in Gla KO rats indicate that this rat model recapitulates early disease stages of Fabry disease. This genetic animal model may be used to test novel treatments and to study corneal and lenticular opacity development in Fabry disease.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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