Glycolipid Storage and Phenotypes in a New Rat Model of Fabry Disease

Abstract

Fabry disease is an X‐linked lysosomal storage disease caused by mutations in the GLA gene, which encodes for the acid hydrolase, α‐galactosidase A (α‐Gal A). When α‐Gal A activity is deficient, glycolipids with terminal α‐galactosyl residues accumulate and lead to cellular dysfunction and ultimately organ pathophysiology. Patients with Fabry disease experience severe pain starting in childhood, develop corneal and lenticular opacities, and eventually suffer from end stage renal disease. In order to study the development of these phenotypes on a molecular level, we generated an α‐Gal A deficient (Gla KO) rat using CRISPR/Cas9 technology. Gla KO rats have undetectable serum α‐Gal A activity, but have similar levels of serum α‐mannosidase activity as wild type (WT) rats. As measured by mass spectrometry in serum and tissues (kidney and heart), Gla KO rats have dramatic increases in molecules containing terminal α‐galactosyl residues, including globotriaosylceramide (>100‐fold), globotriaosylsphingosine (>30‐fold), and blood group B glycolipids (>10‐fold), which are established biomarkers for patients with Fabry disease. Non‐α‐galactosyl glycolipids, such as ganglioside GM3, exist in similar concentrations in both Gla KO and WT rat serum and tissues. Electron microscopy of Gla KO kidneys and dorsal root ganglia reveal the presence of electron dense lamellar structures, which are classically seen in patients with Fabry disease. On a macroscopic level, male Gla KO rats weigh ~10% less on average and have enlarged tongues (P < 0.001) compared to WT controls. Behavioral studies show that Gla KO rats have increased sensitivity to touch and sharp punctate force (P < 0.001), which are suggestive of a pain phenotype. Slit lamp biomicroscopy shows that male and female Gla KO rats develop corneal and lenticular opacities to a greater degree than WT controls (P < 0.01) by 13 weeks of age. Urinalysis shows that aging Gla KO rats develop increased urine calcium excretion (P < 0.001), increased urine flow (P < 0.001), and decreased urine osmolarity (P = 0.09), all of which suggest the development of distal tubule pathology. As the Gla KO rat recapitulates phenotypes seen in patients with Fabry disease, this rat model can be used to test new therapies and study the mechanistic basis of disease pathogenesis.Support or Funding InformationNIH funding: F30DK113641, K08EY024645, P30EY001931, R21NS095627, R24HL114474, T32GM080202