GLA Deficiency Research Articles

Restoration of peripheral neuropathy in Fabry mice via intrathecal administration of an adeno-associated virus vector encoding mGLA cDNA

Anderson-Fabry disease (FD) is an X-linked lysosomal storage disorder caused by a pathological variant of the α-galactosidase A (GLA) gene that results in deficient GLA activity. GLA deficiency leads to the accumulation of globotriaosylceramide (Gb3) and lyso-Gb3 in many tissues. A certain number of FD patients have burning pain or acroparesthesia in the feet and hands since childhood. Enzyme replacement therapy (ERT) is available for FD patients. However, ERT does not dramatically improve these FD-related peripheral neuropathic pain. We generated an adeno-associated virus serotype PHP.eB (AAV-PHP.eB) vector encoding mouse GLA cDNA, which was administered to FD mice intrathecally (it) or intravenously (iv). In the it-administered AAV (it-AAV) FD mice, the GLA enzyme activity in the lumbar dorsal root ganglion (DRG) was significantly greater than that in the untreated (NT) FD mice, and the level of activity was similar to that in wild-type (WT) B6 mice. However, in iv-administered AAV (iv-AAV) FD mice, GLA activity in the DRG did not increase compared to that in NT FD mice. Gb3 storage in the DRG of it-AAV FD mice was reduced compared to that in the DRG of NT FD mice. However, compared with NT FD mice, iv-AAV FD mice did not exhibit a significant reduction in the expression of the Gb3 substrate. Compared with WT mice, FD mice were thermally hyposensitive at 52 °C according to the hot plate test. The it-AAV FD mice showed significant recovery from thermal hyposensitivity. However, the iv-AAV FD mice did not exhibit significant improvement in thermal hyposensitivity. These results suggest that the intrathecal delivery of AAV-PHP.eB-mGLA may be a valuable tool for the treatment of FD-related peripheral neuropathic pain.

Precision medicine in Fabry disease.

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A (GLA) gene, leading to a deficiency in α-galactosidase A. The lysosomal accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3) and its deacylated form, globotriaosylsphingosine (lyso-Gb3), results in progressive renal failure, cardiomyopathy associated with cardiac arrhythmia and recurrent cerebrovascular events, significantly limiting life expectancy in affected patients. In male patients, a definitive diagnosis of FD involves demonstrating a GLA deficiency in leucocytes. In females, because of the potential high residual enzymatic activity, the diagnostic gold standard requires molecular genetic analyses. The current treatment options for FD include recombinant enzyme replacement therapies (ERTs) with intravenous agalsidase-α (0.2 mg/kg body weight) or agalsidase-β (1 mg/kg body weight) every 2 weeks as well as an oral pharmacological chaperone (migalastat 123 mg every other day) that selectively and reversibly binds to the active sites of amenable mutant forms of the GLA enzyme. These therapies facilitate cellular Gb3 clearance and an overall improvement of disease burden. However, ERT can lead to infusion-associated reactions, as well as the formation of neutralizing anti-drug antibodies in ∼40% of all ERT-treated males, leading to an attenuation of therapy efficacy. This article reviews the clinical presentation, diagnosis and interdisciplinary clinical management of FD and discusses the therapeutic options, with a special focus on precision medicine, accounting for individual variability in genetic mutations, Gb3 and lyso-Gb3 levels, allowing physicians to predict more accurately which prevention and treatment strategy is best for which patient.

Galabiosylceramide is present in human cerebrospinal fluid

Cerebrospinal fluid (CSF) contains glycosphingolipids, including lactosylceramide (LacCer, Galβ(1,4)Glcβ-ceramide). LacCer and its structural isomer, galabiosylceramide (Gb2, Galα(1,4)Galβ-ceramide), are classified as ceramide dihexosides (CDH). Gb2 is degraded by α-galactosidase A (GLA) in lysosomes, and genetic GLA deficiency causes Fabry disease, an X-linked lysosomal storage disorder. In patients with Fabry disease, Gb2 accumulates in organs throughout the body. While Gb2 has been reported to be in the liver, kidney, and urine of healthy individuals, its presence in CSF has not been reported, either in patients with Fabry disease or healthy controls. Here, we isolated CDH fractions from CSF of patients with idiopathic normal pressure hydrocephalus. Purified CDH fractions showed positive reaction with Shiga toxin, which specifically binds to the Galα(1,4)Galβ structure. The isolated CDH fractions were analyzed by hydrophilic interaction chromatography (HILIC)-electrospray ionization tandem mass spectrometry (ESI-MS/MS). HILIC-ESI-MS/MS separated LacCer and Gb2 and revealed the presence of Gb2 and LacCer in the fractions. We also found Gb2 in CSF from neurologically normal control subjects. This is the first report to show Gb2 exists in human CSF.

Enhanced thrombospondin-1 causes dysfunction of vascular endothelial cells derived from Fabry disease-induced pluripotent stem cells.

BackgroundFabry disease (FD) is a recessive X-linked lysosomal storage disorder caused by α-galactosidase A (GLA) deficiency. Although the mechanism is unclear, GLA deficiency causes an accumulation of globotriaosylceramide (Gb3), leading to vasculopathy.MethodsTo explore the relationship between the accumulation of Gb3 and vasculopathy, induced pluripotent stem cells generated from four Fabry patients (FD-iPSCs) were differentiated into vascular endothelial cells (VECs). Genome editing using CRISPR-Cas9 system was carried out to correct the GLA mutation or to delete Thrombospondin-1 (TSP-1). Global transcriptomes were compared between wild-type (WT)- and FD-VECs by RNA-sequencing analysis.FindingsHere, we report that overexpression of TSP-1 contributes to the dysfunction of VECs in FD. VECs originating from FD-iPSCs (FD-VECs) showed aberrant angiogenic functionality even upon treatment with recombinant α-galactosidase. Intriguingly, FD-VECs produced more p-SMAD2 and TSP-1 than WT-VECs. We also found elevated TSP-1 in the peritubular capillaries of renal tissues biopsied from FD patients. Inhibition of SMAD2 signaling or knock out of TSP-1 (TSP-1−/−) rescues normal vascular functionality in FD-VECs, like in gene-corrected FD-VECs. In addition, the enhanced oxygen consumption rate is reduced in TSP-1−/− FD-VECs.InterpretationThe overexpression of TSP-1 secondary to Gb3 accumulation is primarily responsible for the observed FD-VEC dysfunction. Our findings implicate dysfunctional VEC angiogenesis in the peritubular capillaries in some of the complications of Fabry disease.FundingThis study was supported by grant 2018M3A9H1078330 from the National Research Foundation of the Republic of Korea.

α-galactosidase A deficiency promotes von Willebrand factor secretion in models of Fabry disease

Fabry disease results from loss of activity of the lysosomal enzyme α-galactosidase A (GLA), leading to the accumulation of globoseries glycosphingolipids in vascular endothelial cells. Thrombosis and stroke are life-threatening complications of Fabry disease; however, the mechanism of the vasculopathy remains unclear. We explored the relationship between GLA deficiency and endothelial cell von Willebrand factor (VWF) secretion in invivo and invitro models of Fabry disease. Plasma VWF was significantly higher at two months and increased with age in Gla-null compared to wild-type mice. Disruption of GLA in a human endothelial cell line by siRNA and CRISPR/Cas9 resulted in a 3-fold and 5-fold increase in VWF secretion, respectively. The increase in VWF levels was associated with decreased endothelial nitric oxide synthase (eNOS) activity in both invitro models. Pharmacological approaches that increase nitric oxide bioavailability or decrease reactive oxygen species completely normalized the elevated VWF secretion in GLA deficient cells. In contrast, the abnormality was not readily reversed by recombinant human GLA or by inhibition of glycosphingolipid synthesis with eliglustat. These results suggest that GLA deficiency promotes VWF secretion through eNOS dysregulation, which may contribute to the vasculopathy of Fabry disease.

Dissociation of globotriaosylceramide and impaired endothelial function in α-galactosidase-A deficient EA.hy926 cells

Fabry disease, a rare, X-linked lysosomal storage disease, arises from deficiency of the lysosomal hydrolase, α-galactosidase A (GLA) which disrupts the catabolism of globo- series glycosphingolipids (GSLs). One potential link between GLA deficiency and vascular dysfunction may be changes in endothelial nitric oxide synthase (eNOS) function. GLA-deficient EA.hy926 cells were obtained by siRNA knockdown of GLA expression and by mutation of GLA with CRISPR/Cas9 gene editing to investigate the effects of GLA deficiency on eNOS. As previously observed with siRNA knockdown of GLA, globotriaosylceramide (Gb3) accumulated in EA.hy926 cells. In contrast, Gb3 did not accumulate in CRISPR/Cas9 gene edited GLA-deficient cells, but instead, globotetraosylceramide (Gb4). However, in both the siRNA and CRISPR/Cas9 models globotriaosylsphingosine (lyso-Gb3) was elevated. As was previously observed with siRNA knockdown of GLA expression, CRISPR/Cas9 GLA-deficient cells had lower eNOS activity. Restoring GLA activity in GLA-deficient cells with exogenous GLA treatment improved eNOS activity. In contrast, treating cells with the glucosylceramide synthase inhibitor, eliglustat, decreased NOS activity. These results suggest that eNOS uncoupling is due to GLA deficiency, and not necessarily due to elevated Gb3 per se. It was observed that lyso-Gb3 inhibits eNOS activity.

Impaired mitophagy causes brown adipose tissue activation and cachexia in Sanfilippo syndrome type A mice

Fabry disease, a rare, X-linked lysosomal storage disease, arises from deficiency of the lysosomal hydrolase, α-galactosidase A (GLA) which disrupts the catabolism of globo- series glycosphingolipids (GSLs). One potential link between GLA deficiency and vascular dysfunction may be changes in endothelial nitric oxide synthase (eNOS) function. GLA-deficient EA.hy926 cells were obtained by siRNA knockdown of GLA expression and by mutation of GLA with CRISPR/Cas9 gene editing to investigate the effects of GLA deficiency on eNOS. As previously observed with siRNA knockdown of GLA, globotriaosylceramide (Gb3) accumulated in EA.hy926 cells. In contrast, Gb3 did not accumulate in CRISPR/Cas9 gene edited GLA-deficient cells, but instead, globotetraosylceramide (Gb4). However, in both the siRNA and CRISPR/Cas9 models globotriaosylsphingosine (lyso-Gb3) was elevated. As was previously observed with siRNA knockdown of GLA expression, CRISPR/Cas9 GLA-deficient cells had lower eNOS activity. Restoring GLA activity in GLA-deficient cells with exogenous GLA treatment improved eNOS activity. In contrast, treating cells with the glucosylceramide synthase inhibitor, eliglustat, decreased NOS activity. These results suggest that eNOS uncoupling is due to GLA deficiency, and not necessarily due to elevated Gb3 per se. It was observed that lyso-Gb3 inhibits eNOS activity.

Disease severity scoring system for acid sphingomyelinase deficiency: Severity score domains and components

Fabry disease, a rare, X-linked lysosomal storage disease, arises from deficiency of the lysosomal hydrolase, α-galactosidase A (GLA) which disrupts the catabolism of globo- series glycosphingolipids (GSLs). One potential link between GLA deficiency and vascular dysfunction may be changes in endothelial nitric oxide synthase (eNOS) function. GLA-deficient EA.hy926 cells were obtained by siRNA knockdown of GLA expression and by mutation of GLA with CRISPR/Cas9 gene editing to investigate the effects of GLA deficiency on eNOS. As previously observed with siRNA knockdown of GLA, globotriaosylceramide (Gb3) accumulated in EA.hy926 cells. In contrast, Gb3 did not accumulate in CRISPR/Cas9 gene edited GLA-deficient cells, but instead, globotetraosylceramide (Gb4). However, in both the siRNA and CRISPR/Cas9 models globotriaosylsphingosine (lyso-Gb3) was elevated. As was previously observed with siRNA knockdown of GLA expression, CRISPR/Cas9 GLA-deficient cells had lower eNOS activity. Restoring GLA activity in GLA-deficient cells with exogenous GLA treatment improved eNOS activity. In contrast, treating cells with the glucosylceramide synthase inhibitor, eliglustat, decreased NOS activity. These results suggest that eNOS uncoupling is due to GLA deficiency, and not necessarily due to elevated Gb3 per se. It was observed that lyso-Gb3 inhibits eNOS activity.

Abstract 530: Decreased NSF S-Nitrosylation in the Aorta and an Age-Dependent Endothelial Activation in Mice with Fabry Disease

Fabry disease is an X-linked lysosomal storage disorder caused by loss of activity of the enzyme, α-galactosidase A (GLA). The loss of GLA function leads to an age-dependent accumulation of globotriaosylceramide (Gb3) in endothelial cells. Endothelial Gb3 accumulation is associated with endothelial nitric oxide synthase (eNOS) uncoupling and decreased nitric oxide (NO) bioavailability. We hypothesized that GLA deficiency promotes endothelial inflammation. von Willebrand factor (VWF) is the main component of Weibel Palade bodies (WPB) and is secreted upon endothelial inflammation. We observed significantly elevated plasma VWF in GLA null mice (FA) compared to age-matched Wild-Type mice (WT) (p=0.046 at 2 months and p<0.001 at 5 and 17 months), indicating increased endothelial inflammation in FA. Out of the many proteins that regulate WPB exocytosis, N-ethylmaleimide sensitive factor (NSF) is a critical mediator of the exocytic machinery and a major target of NO. NO can reversibly modify NSF cysteine residues via a process called S-nitrosylation (SNO), leading to decreased WPB exocytosis. To evaluate whether GLA deficiency promotes a decrease in SNO-NSF, nitrosylated cysteines of aortic homogenates from male WT and FA were first labeled with biotin through a biotin switch assay. Next, biotinylated proteins were isolated with streptavidin-agarose beads. We observed an approximately 60% decrease in the level of SNO-NSF in the aorta of FA compared to that of WT by Western blot (WT vs. Fabry: 1.0±0.03 vs. 0.4±0.11, p=0.002, n=4-5/group) whereas total protein expression of NSF and GAPDH were not different between groups. The level of thioredoxin-1 (TRX-1) was significantly elevated in FA compared to WT (WT vs. Fabry: 1.0±0.05 vs. 1.4±0.14, p=0.01, n=6-9/group), suggesting high levels of reactive oxygen species and protein denitrosylase activity in Fabry disease. In conclusion, these results provide evidence of endothelial activation in Fabry disease. GLA deficiency resulted in decreased SNO-NSF and increased TRX-1 in parallel with the robust elevation of VWF. Future study is required for further understanding of the mechanistic links between these observations, and to determine whether this is a reversible phenomenon in the setting of Fabry disease.

Abstract 395: Elevated Von Willebran Factor in an in vitro Model of Fabry Disease

Fabry disease is an X-linked disorder caused by a defect in the gene encoding the lysosomal hydrolase, alpha-galactosidase A (GLA). The loss in GLA function causes an age-dependent accumulation of globotriaosylceramide in the endothelial cells, which results in decreased nitric oxide bioavailability and premature mortality in the affected patients. Based on this, we hypothesized that GLA deficiency promotes endothelial inflammation. We observed a significant age-dependent increase in the plasma von Willebrand Factor (vWF) in Fabry mice compared to age-matched wild type mice (p=0.046 at 2 months and p=0.0004 at 17 months). To evaluate the molecular mechanisms of increased vWF in Fabry disease, small interfering RNA (siRNA) technique was used to knock-down GLA in EA.hy926 cells. Our initial studies with this cell line demonstrated that thrombin (2U/mL) induced a time-dependent vWF secretion into the cell culture medium with an 80-fold increase in the level of vWF after 90 min stimulation (p=0.001 compared to basal level; n=3 replicates per group), measured by a human antibody against vWF and AlphaLISA. Next, the siRNA studies revealed a greater than 95% knockdown of GLA protein (via western blotting) in the GLA-siRNA group compared to the control group with no effect in the scrambled (SCR) sequence-siRNA group (CON vs. GLA vs. SCR arbitrary units: 1.0±0.03 vs. 0.01±0.01 vs. 1.1±0.08, p<0.001; GLA vs. SCR). Importantly, no difference in GAPDH protein was observed between groups. To determine the direct effect of GLA deficiency on vWF, the confluent cells in each group were incubated in serum-free medium overnight. Consistent with the hypothesis, we observed approximately 60% increase in vWF in the cell culture medium in the GLA siRNA group compared with the untreated and scrambled-sequence control groups. (CON vs. GLA vs. SCR arbitrary units: 38.5±4.7 vs. 61.3±1.1 vs. 31.4±3.8, p=0.02; GLA vs. SCR; n=3 replicates per group). In conclusion, the data provide evidence of endothelial activation in the setting of GLA deficiency, demonstrated by the robust elevation of vWF mediated by GLA gene disruption. Future study is required to further understand the mechanism of the elevated vWF and decreased nitric oxide bioavailability in Fabry disease.

Globotriaosylsphingosine Accumulation and Not Alpha-Galactosidase-A Deficiency Causes Endothelial Dysfunction in Fabry Disease

BackgroundFabry disease (FD) is caused by a deficiency of the lysosomal enzyme alpha-galactosidase A (GLA) resulting in the accumulation of globotriaosylsphingosine (Gb3) in a variety of tissues. While GLA deficiency was always considered as the fulcrum of the disease, recent attention shifted towards studying the mechanisms through which Gb3 accumulation in vascular cells leads to endothelial dysfunction and eventually multiorgan failure. In addition to the well-described macrovascular disease, FD is also characterized by abnormalities of microvascular function, which have been demonstrated by measurements of myocardial blood flow and coronary flow reserve. To date, the relative importance of Gb3 accumulation versus GLA deficiency in causing endothelial dysfunction is not fully understood; furthermore, its differential effects on cardiac micro- and macrovascular endothelial cells are not known.Methods and ResultsIn order to assess the effects of Gb3 accumulation versus GLA deficiency, human macro- and microvascular cardiac endothelial cells (ECs) were incubated with Gb3 or silenced by siRNA to GLA. Gb3 loading caused deregulation of several key endothelial pathways such as eNOS, iNOS, COX-1 and COX-2, while GLA silencing showed no effects. Cardiac microvascular ECs showed a greater susceptibility to Gb3 loading as compared to macrovascular ECs.ConclusionsDeregulation of key endothelial pathways as observed in FD vasculopathy is likely caused by intracellular Gb3 accumulation rather than deficiency of GLA. Human microvascular ECs, as opposed to macrovascular ECs, seem to be affected earlier and more severely by Gb3 accumulation and this notion may prove fundamental for future progresses in early diagnosis and management of FD patients.

A Case of Fabry's Disease with Congenital Agammaglobulinemia

Fabry's disease is an X-linked lysosomal storage disorder caused by abnormalities in the α-galactosidase A (GLA) gene, which leads to a GLA deficiency and to the intracellular deposition of globotriaosylceramide (Gb3) within vascular endothelium and other tissues. It manifests as progressive multiple organ dysfunctions caused by the deposition of Gb3. On the other hand, congenital agammaglobulinemia is usually caused by mutations in Bruton's tyrosine kinase (Btk) gene with X-linked dominence, suppresses B cell maturation, and causes recurrent pyogenic infections. In former reports, the distance between the loci in the Xq22 region of the human X chromosome was found to be about 69 kilobases. A 23-yr-old man diagnosed with congenital agammaglobulinemia at age 5, showed typical clinical and laboratory and histopathological findings of Fabry's disease. The genetic basis of this combination of the two syndromes was studied in this patient. Here, we report a case of Fabry's disease with congenital agammaglobulinemia.

Adipocytes participate in storage in α‐galactosidase deficiency (Fabry disease)

Ultrastructural and histochemical studies of bioptic and postmortem tissue samples from ten Fabry hemizygotes showed lysosomal storage in adipocytes as a constant feature of the classic phenotype of α-galactosidase (GLA) deficiency. The storage was represented by a crescent-shaped line of storage lysosomes of varying thicknesses restricted to the perinuclear subplasmalemmal area. The ultrastructure of the storage lysosomes was dominated by concentric lipid membranes modified by simultaneous deposition of autofluorescent ceroid. Storage was widely expressed in adipose tissue. The number of storage lysosomes was increased, and the lysosomes were more clustered in adipocytes with less voluminous lipid content. The findings should attract interest to studies of adipose tissue biology in Fabry disease, a topic that has not been studied so far. In terms of cell biology, the observations represent indirect evidence of significant lysosomal turnover of α-galactose lipid conjugates in adipocytes demasked by GLA deficiency. The results extend the thus far limited information on the adipocyte lysosomal system and its participation in lysosomal storage disorders.

Synergistic effect of deficiency in thrombosis-related genes

To investigate the interaction of deficiency in thrombosis-related gene in a mouse model. To generate mice carrying mutations in alpha-galactosidase A (Gla) and factor V Leiden (Fvl) and analyze the phenotypes, namely, tissue fibrin deposition and thrombus formation in organs. Fibrin deposition in organs of mice carrying both mutations in Gla and Fvl was significantly increased compared with that in mice with single mutaton: [Gla(-/0) Fv(Q/Q)+Gla(-/-)Fv(Q/Q)] vs.[Gla(-/0)Fv(+/+)]=(0.28+/-0.03)% vs.(0.07+/-0.007)%, P<0.01; [Gla(-/0)Fv(Q/Q)+Gla(-/-)Fv(Q/Q)] vs.[Gla(+/0)Fv(Q/Q)+Gla(+/+)Fv(Q/Q)]=(0.28+/-0.03)% vs.(0.11+/-0.02)%, P< 0.01. Meanwhile, the number of thrombi on organ sections of mice carrying both mutations in Gla and Fvl was significantly increased compared with the single mutation carrier: [Gla(-/0)Fv(Q/Q)+Gla(-/-)Fv(Q/Q)] vs.[Gla(-/0)Fv(+/+)]=1.9+/-0.7 vs. 0.0+/-0.0, P<0.05; [Gla(-/0)Fv(Q/Q)+Gla(-/-)Fv(Q/Q)] vs. [Gla(+/0)Fv(Q/Q)+Gla(+/+)Fv(Q/Q)]=1.9+/-0.7 vs. 0.3+/-0.1, P<0.05. These observations demonstrated that there was synergistic effect in Gla and Fvl deficiency in mice. It suggested that there could be a combination of GLA deficiency and FVL or other thrombosis-related gene defect in patients with genetic severe early-onset thrombosis.

A case of minimal change disease in a Fabry patient

Fabry disease is an X-linked lysosomal storage disorder caused by mutations of the GLA gene and deficiency in alpha-galactosidase A activity. Glycosphingolipids accumulation causes renal injury that manifests early during childhood as tubular dysfunction and later in adulthood as proteinuria and renal insufficiency. Nephrotic syndrome as the first evidence of Fabry-related kidney damage is rare. We report the case of a teenager with known Fabry disease and normal renal function who developed acute nephrotic syndrome. He was found to have typical glycosphingolipids accumulation with no other findings suggestive of alternative causes of nephrotic syndrome on kidney biopsy. After treatment with enzyme replacement therapy and oral steroids, he went into complete remission from nephrotic syndrome, a response that is atypical for Fabry disease patients who develop heavy proteinuria as a result of longstanding disease and chronic renal injury. The nephrotic syndrome in this patient appears to have developed secondary to minimal change disease. We recommend considering immunotherapy in addition to enzyme replacement therapy in those patients with confirmed Fabry disease and acute nephrotic syndrome with clinical and microscopic findings suggestive of minimal change disease.