Pharmacological chaperone corrects lysosomal storage in Fabry disease caused by trafficking-incompetent variants.

Fabry disease is a lysosomal storage disorder caused by deficiency of alpha-galactosidase A (alpha-Gal A) resulting in lysosomal accumulation of glycosphingolipid globotriosylceramide Gb3. Misfolded alpha-Gal A variants can have residual enzyme activity but are unstable. Their lysosomal trafficking is impaired because they are retained in the endoplasmic reticulum (ER) by quality control. Subinhibitory doses of the competitive inhibitor of alpha-Gal A, 1-deoxygalactonojirimycin (DGJ), stabilize mutant alpha-Gal A in vitro and correct the trafficking defect. We showed by immunolabeling that the chaperone-like action of DGJ significantly reduces the lysosomal Gb3 storage in human Fabry fibroblasts harboring the novel mutations T194I and V390fsX8. The specificity of the DGJ effect was proven by RNA interference. Electron microscopic morphometry demonstrated a reduction of large-size, disease-associated lysosomes and loss of characteristic multilamellar lysosomal inclusions on DGJ treatment. In addition, the pre-Golgi intermediates were decreased. However, the rough ER was not different between DGJ-treated and untreated cells. Pulse-chase experiments revealed that DGJ treatment resulted in maturation and stabilization of mutant alpha-Gal A. Genes involved in cell stress signaling, heat shock response, unfolded protein response, and ER-associated degradation show no apparent difference in expression between untreated and DGJ-treated fibroblasts. The DGJ treatment has no apparent cytotoxic effects. Thus our data show the usefulness of a pharmacological chaperone for correction of the lysosomal storage in Fabry fibroblasts harboring different mutations with residual enzyme activity. Pharmacological chaperones acting on misfolded, unstable mutant proteins that exhibit residual biological activity offer a convenient and cost-efficient therapeutic strategy.

Mutations c.459+1G>A and p.P426L in the ARSA gene: prevalence in metachromatic leukodystrophy patients from European countries.

In this multicentre study, we examined the prevalence of two mutations in the arylsulfatase A (ARSA) gene, i.e., c.459+1G>A and p.P426L, in 384 unrelated European patients presenting with different types of metachromatic leukodystrophy (MLD). In total, c.459+1G>A was found 194 times among the 768 investigated ARSA alleles (25%), whereas p.P426L was identified 143 times (18.6%). Thus, these two mutations accounted for 43.8% of investigated MLD alleles. Mutation c.459+1G>A was most frequent in late-infantile MLD patients (40%), while p.P426L was most frequent in adults (42.5%), which is consistent with earlier observations, although p.P426L was also found in a few late-infantile patients (0.9%), and c.459+1G>A was present in some adults (9%). Mutation c.459+1G>A is more frequent in countries situated at the western edges of Europe, i.e., in Great Britain and Portugal, and also in Belgium, Switzerland, and Italy, which is visible as a strand ranging from North to South, and additionally in Czech and Slovak Republics. Mutation p.P426L is most prevalent in countries assembled in a cluster containing the Netherlands, Germany, and Austria. In other Central European countries, the frequency of both c.459+1G>A and p.P426L ranges from 8 to 37.5%. Our study has confirmed that c.459+1G>A and p.P426L are the most frequently found MLD-causing mutations in Europe. The data about their prevalence reflect the population variability in Europe.

Familial X-linked cardiomyopathy (Danon disease): diagnostic confirmation by mutation analysis of the LAMP2gene.

UNLABELLED: A boy presented at age 2.5 years with mild left ventricular hypertrophy and mild myopathy. Hypertrophic cardiomyopathy progressed relentlessly, leading to death at age 16 years shortly before planned heart transplantation. During the course of the disease, his mother developed severe dilated cardiomyopathy and died of its complications at 46 years of age. The combination of myopathy and cardiomyopathy, the biochemical and electron microscopy findings in a muscle biopsy, and the pedigree suggested Danon disease (MIM 300257), an X-linked lysosomal storage disorder caused by deficiency of lysosome-associated membrane protein-2 (LAMP2). The diagnosis was confirmed by the identification of a novel mutation, G138A, in the LAMP2gene, leading to the premature stop codon W46X. CONCLUSION: Early diagnosis of Danon disease is important for genetic counselling and timely cardiac transplantation, the only effective therapeutic option.

A splicing mutation in the alpha/beta GlcNAc-1-phosphotransferase gene results in an adult onset form of mucolipidosis III associated with sensory neuropathy and cardiomyopathy.

A 47-year-old female who presented with a dilated cardiomyopathy and mild neuropathy was found to have pseudoHurler polydystrophy (mucolipidosis III). The serum lysosomal enzymes were strikingly elevated and GlcNAc-1-phosphotransferase activity in the patient's fibroblasts was 3% of normal. Sequence analysis of the patient's genomic DNA revealed a homozygous mutation of the last nucleotide of the 135-bp exon 7 of the phosphotransferase gene encoding the alpha/beta subunits, resulting in aberrant splicing and skipping of this exon. Remarkably, none of the skeletal and connective tissue anomalies characteristic of the disease were present. This case is the first example of mucolipidosis III presenting in an adult patient and further broadens the clinical spectrum of the disease.

Twenty-two novel mutations in the lysosomal alpha-glucosidase gene (GAA) underscore the genotype-phenotype correlation in glycogen storage disease type II.

Patients with glycogen storage disease type II (GSDII, Pompe disease) suffer from progressive muscle weakness due to acid alpha-glucosidase deficiency. The disease is inherited as an autosomal recessive trait with a spectrum of clinical phenotypes. We have investigated 29 cases of GSDII and thereby identified 55 pathogenic mutations of the acid alpha-glucosidase gene (GAA) encoding acid maltase. There were 34 different mutations identified, 22 of which were novel. All of the missense mutations and two other mutations with an unpredictable effect on acid alpha-glucosidase synthesis and function were transiently expressed in COS cells. The effect of a novel splice-site mutation was investigated by real-time PCR analysis. The outcome of our analysis underscores the notion that the clinical phenotype of GSDII is largely dictated by the nature of the mutations in the GAA alleles. This genotype-phenotype correlation makes DNA analysis a valuable tool to help predict the clinical course of the disease.

Leigh syndrome due to compound heterozygosity of dihydrolipoamide dehydrogenase gene mutations. Description of the first E3 splice site mutation.

UNLABELLED: A boy with recurrent episodes of hypoglycaemia and ataxia, microcephaly, mental retardation, permanent lactic acidaemia, intermittent 2-oxoglutaric aciduria as well as elevation of serum branched chain amino acids was diagnosed with dihydrolipoamide dehydrogenase (E3) deficiency. Analysis of genomic DNA revealed compound heterozygosity for two novel mutations: I393T in exon 11, located at the interface domain of the protein and possibly interfering with its dimerisation, and IVS9+1G>A located at a consensus splice site. A heterozygous polymorphism was also detected. In the patient's cDNA the I393T mutation and the polymorphism appeared to be homozygous, indicating that the mRNA coming from the IVS9+1G>A mutant allele is not stable. CONCLUSION: as opposed to the non-neurological phenotype of patients with a homozygous G229C mutation, this patient developed Leigh syndrome. Dihydrolipoamide dehydrogenase and pyruvate dehydrogenase complex activities in muscle were 29% and 14% of the lowest control values, respectively. Pyruvate dehydrogenase complex activity in fibroblasts was normal, however, indicating that the biochemical examination of defects in energy metabolism should be performed in a more energy demanding tissue.

Severe lymphatic microangiopathy in Fabry disease.

BACKGROUND: Lymphedema has been described in a few cases of Fabry disease. The etiology of lymphedema in Fabry disease is unknown. The aim of the study was to evaluate morphology and function of lymphatic microvessels in this disease. METHODS AND RESULTS: In five male patients with Fabry disease, the initial lymphatic microvessels of the skin were studied in vivo, using a nearly atraumatic technique of fluorescence microlymphography and measurement of lymph capillary pressure. In addition, five female patients heterozygous for Fabry disease and 12 healthy controls were studied. The maximum spread of the fluorescent macromolecular dye into the network of superficial skin lymphatics was increased in the three male patients presenting with lymphedema (25, 26, and 45 mm, respectively). In the two male patients without swollen legs, the maximum spread of the dye was 3 and 7 mm, respectively, and in the female patients 8.8 mm (range, 4-17 mm), whereas in the healthy controls it reached only 4.3 mm (range, 1-7 mm). Fragmentation of the microlymphatic network was found in all patients, but not in controls. In controls, the diameter of the microvessels varied in a very narrow range (45-75 microm); in patients, the range was 15-150 microm. In patients with lymphedema, microlymphatic hypertension was present. CONCLUSION: In patients with Fabry disease severe structural and functional changes of the initial lymphatics of the skin are present.

Mass spectrometric analysis of human transferrin in different body fluids.

In this study, we present a versatile new procedure for the analysis of transferrin and its isoforms isolated from human body fluids such as serum, plasma, and cerebrospinal fluid. This method is based on a three-step procedure: (i) isolation of transferrins using anion-exchange chromatography with UV detection; (ii) concentration of the transferrin fraction; (iii) detection of the transferrins with liquid chromatography-electrospray mass spectrometry. Pre-analytical sample procedures can be omitted and no immunoaffinity columns or transferrin-specific immunoassays were used. Anticoagulants such as heparin, EDTA, citrate, and oxalate do not interfere with our analysis. According to their respective molecular masses, up to ten different isoforms of transferrin could be identified in a serum sample from a patient with a congenital disorder of glycosylation type Ia (CDG-Ia). The method was successfully applied to different pathological samples from patients with CDG-Ia, CDG-Ib, CDG-Ic, CDG-Ie, CDG-If, and CDG-IIa. Additionally, samples from alcohol consumers that were found with turbidimetric immunoassay to contain increased levels of carbohydrate-deficient transferrin were analyzed.