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Brain : a Journal of Neurology Dec 2017Mutations in the glucocerebrosidase gene (GBA), which cause Gaucher disease, are also potent risk factors for Parkinson's disease. We examined whether a genetic burden...
Mutations in the glucocerebrosidase gene (GBA), which cause Gaucher disease, are also potent risk factors for Parkinson's disease. We examined whether a genetic burden of variants in other lysosomal storage disorder genes is more broadly associated with Parkinson's disease susceptibility. The sequence kernel association test was used to interrogate variant burden among 54 lysosomal storage disorder genes, leveraging whole exome sequencing data from 1156 Parkinson's disease cases and 1679 control subjects. We discovered a significant burden of rare, likely damaging lysosomal storage disorder gene variants in association with Parkinson's disease risk. The association signal was robust to the exclusion of GBA, and consistent results were obtained in two independent replication cohorts, including 436 cases and 169 controls with whole exome sequencing and an additional 6713 cases and 5964 controls with exome-wide genotyping. In secondary analyses designed to highlight the specific genes driving the aggregate signal, we confirmed associations at the GBA and SMPD1 loci and newly implicate CTSD, SLC17A5, and ASAH1 as candidate Parkinson's disease susceptibility genes. In our discovery cohort, the majority of Parkinson's disease cases (56%) have at least one putative damaging variant in a lysosomal storage disorder gene, and 21% carry multiple alleles. Our results highlight several promising new susceptibility loci and reinforce the importance of lysosomal mechanisms in Parkinson's disease pathogenesis. We suggest that multiple genetic hits may act in combination to degrade lysosomal function, enhancing Parkinson's disease susceptibility.
Topics: Acid Ceramidase; Adult; Aged; Aged, 80 and over; Case-Control Studies; Cathepsin D; Cohort Studies; Exome; Female; Genetic Predisposition to Disease; Genotype; Glucosylceramidase; Humans; Lysosomal Storage Diseases; Male; Middle Aged; Mutation; Organic Anion Transporters; Parkinson Disease; Sphingomyelin Phosphodiesterase; Symporters
PubMed: 29140481
DOI: 10.1093/brain/awx285 -
Experimental Neurology Jan 2018Tay-Sachs disease is a severe lysosomal storage disorder caused by mutations in Hexa, the gene that encodes for the α subunit of lysosomal β-hexosaminidase A (HEXA),...
Tay-Sachs disease is a severe lysosomal storage disorder caused by mutations in Hexa, the gene that encodes for the α subunit of lysosomal β-hexosaminidase A (HEXA), which converts GM2 to GM3 ganglioside. Unexpectedly, Hexa mice have a normal lifespan and show no obvious neurological impairment until at least one year of age. These mice catabolize stored GM2 ganglioside using sialidase(s) to remove sialic acid and form the glycolipid GA2, which is further processed by β-hexosaminidase B. Therefore, the presence of the sialidase (s) allows the consequences of the Hexa defect to be bypassed. To determine if the sialidase NEU3 contributes to GM2 ganglioside degradation, we generated a mouse model with combined deficiencies of HEXA and NEU3. The HexaNeu3 mice were healthy at birth, but died at 1.5 to 4.5months of age. Thin-layer chromatography and mass spectrometric analysis of the brains of HexaNeu3 mice revealed the abnormal accumulation of GM2 ganglioside. Histological and immunohistochemical analysis demonstrated cytoplasmic vacuolation in the neurons. Electron microscopic examination of the brain, kidneys and testes revealed pleomorphic inclusions of many small vesicles and complex lamellar structures. The HexaNeu3 mice exhibited progressive neurodegeneration with neuronal loss, Purkinje cell depletion, and astrogliosis. Slow movement, ataxia, and tremors were the prominent neurological abnormalities observed in these mice. Furthermore, radiographs revealed abnormalities in the skeletal bones of the HexaNeu3 mice. Thus, the HexaNeu3 mice mimic the neuropathological and clinical abnormalities of the classical early-onset Tay-Sachs patients, and provide a suitable model for the future pre-clinical testing of potential treatments for this condition.
Topics: Animals; Brain Chemistry; Cytoplasmic Vesicles; Gangliosidoses, GM2; Gliosis; Glycosphingolipids; Hexosaminidase B; Lameness, Animal; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuraminidase; Neurons; Purkinje Cells; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tay-Sachs Disease
PubMed: 28974375
DOI: 10.1016/j.expneurol.2017.09.012 -
Pediatric Neurology Sep 2017Likely pathogenic variants in SLC17A5 results in allelic disorders of free sialic acid metabolism including (1) infantile free sialic acid storage disease with severe... (Review)
Review
BACKGROUND
Likely pathogenic variants in SLC17A5 results in allelic disorders of free sialic acid metabolism including (1) infantile free sialic acid storage disease with severe global developmental delay, coarse facial features, hepatosplenomegaly, and cardiomegaly; (2) intermediate severe Salla disease with moderate to severe global developmental delay, hypotonia, and hypomyelination with or without coarse facial features, and (3) Salla disease with normal appearance, mild cognitive dysfunction, and spasticity.
PATIENT DESCRIPTION
This five-year-old girl presented with infantile-onset severe global developmental delay, truncal hypotonia, and generalized dystonia following normal development during her first six months of life. Brain magnetic resonance imaging showed marked hypomyelination and a thin corpus callosum at age 19 months, both unchanged on follow-up at age 28 months. Urine free sialic acid was moderately elevated. Cerebrospinal fluid free sialic acid was marginally elevated. Sequencing of SLC17A5 revealed compound heterozygous likely pathogenic variants, namely, a known missense (c.291G>A) variant and a novel truncating (c.819+1G>A) variant, confirming the diagnosis of Salla disease at age 3.5 years.
CONCLUSION
We report a new patient with intermediate severe Salla disease. Normal or marginally elevated urine or cerebrospinal fluid free sialic acid levels cannot exclude Salla disease. In patients with progressive global developmental delay and hypomyelination on brain magnetic resonance imaging, Salla disease should be included into the differential diagnosis.
Topics: Child, Preschool; Corpus Callosum; Databases, Bibliographic; Female; Humans; Magnetic Resonance Imaging; Mutation; Olivopontocerebellar Atrophies; Organic Anion Transporters; Sialic Acid Storage Disease; Symporters
PubMed: 28662915
DOI: 10.1016/j.pediatrneurol.2017.05.022 -
FASEB Journal : Official Publication of... Aug 2017Gangliosides (sialylated glycolipids) play an essential role in the CNS by regulating recognition and signaling in neurons. Metabolic blocks in processing and catabolism...
Gangliosides (sialylated glycolipids) play an essential role in the CNS by regulating recognition and signaling in neurons. Metabolic blocks in processing and catabolism of gangliosides result in the development of severe neurologic disorders, including gangliosidoses manifesting with neurodegeneration and neuroinflammation. We demonstrate that 2 mammalian enzymes, neuraminidases 3 and 4, play important roles in catabolic processing of brain gangliosides by cleaving terminal sialic acid residues in their glycan chains. In neuraminidase 3 and 4 double-knockout mice, G ganglioside is stored in microglia, vascular pericytes, and neurons, causing micro- and astrogliosis, neuroinflammation, accumulation of lipofuscin bodies, and memory loss, whereas their cortical and hippocampal neurons have lower rate of neuritogenesis Double-knockout mice also have reduced levels of G ganglioside and myelin in neuronal axons. Furthermore, neuraminidase 3 deficiency drastically increased storage of G in the brain tissues of an asymptomatic mouse model of Tay-Sachs disease, a severe human gangliosidosis, indicating that this enzyme is responsible for the metabolic bypass of β-hexosaminidase A deficiency. Together, our results provide the first evidence that neuraminidases 3 and 4 have important roles in CNS function by catabolizing gangliosides and preventing their storage in lipofuscin bodies.-Pan, X., De Britto Pará De Aragão, C., Velasco-Martin, J. P., Priestman, D. A., Wu, H. Y., Takahashi, K., Yamaguchi, K., Sturiale, L., Garozzo, D., Platt, F. M., Lamarche-Vane, N., Morales, C. R., Miyagi, T., Pshezhetsky, A. V. Neuraminidases 3 and 4 regulate neuronal function by catabolizing brain gangliosides.
Topics: Animals; Brain; Cells, Cultured; Embryo, Mammalian; Gangliosides; Gene Expression Regulation, Enzymologic; Mice; Mice, Knockout; Motor Activity; Mucolipidoses; Neuraminidase; Neurons
PubMed: 28442549
DOI: 10.1096/fj.201601299R -
Experimental Neurology May 2017Slc17a5 mice represent an animal model for the infantile form of sialic acid storage disease (SASD). We analyzed genetic and histological time-course expression of...
Slc17a5 mice represent an animal model for the infantile form of sialic acid storage disease (SASD). We analyzed genetic and histological time-course expression of myelin and oligodendrocyte (OL) lineage markers in different parts of the CNS, and related this to postnatal neurobehavioral development in these mice. Sialin-deficient mice display a distinct spatiotemporal pattern of sialic acid storage, CNS hypomyelination and leukoencephalopathy. Whereas few genes are differentially expressed in the perinatal stage (p0), microarray analysis revealed increased differential gene expression in later postnatal stages (p10-p18). This included progressive upregulation of neuroinflammatory genes, as well as continuous down-regulation of genes that encode myelin constituents and typical OL lineage markers. Age-related histopathological analysis indicates that initial myelination occurs normally in hindbrain regions, but progression to more frontal areas is affected in Slc17a5 mice. This course of progressive leukoencephalopathy and CNS hypomyelination delays neurobehavioral development in sialin-deficient mice. Slc17a5 mice successfully achieve early neurobehavioral milestones, but exhibit progressive delay of later-stage sensory and motor milestones. The present findings may contribute to further understanding of the processes of CNS myelination as well as help to develop therapeutic strategies for SASD and other myelination disorders.
Topics: Age Factors; Animals; Animals, Newborn; Brain; Developmental Disabilities; Disease Models, Animal; Gene Expression Regulation, Developmental; Glial Fibrillary Acidic Protein; Intermediate Filaments; Leukoencephalopathies; Lysosomal-Associated Membrane Protein 1; Mental Disorders; Mice; Mice, Inbred C57BL; Mice, Transgenic; Organic Anion Transporters; Sialic Acid Storage Disease; Symporters
PubMed: 28189729
DOI: 10.1016/j.expneurol.2017.02.009 -
Orphanet Journal of Rare Diseases Feb 2017Sialic acid storage diseases are neurodegenerative disorders characterized by accumulation of sialic acid in the lysosome. These disorders are caused by mutations in...
BACKGROUND
Sialic acid storage diseases are neurodegenerative disorders characterized by accumulation of sialic acid in the lysosome. These disorders are caused by mutations in SLC17A5, the gene encoding sialin, a sialic acid transporter located in the lysosomal membrane. The most common form of sialic acid storage disease is the slowly progressive Salla disease, presenting with hypotonia, ataxia, epilepsy, nystagmus and findings of cerebral and cerebellar atrophy. Hypomyelination and corpus callosum hypoplasia are typical as well. We report a 16 year-old boy with an atypically mild clinical phenotype of sialic acid storage disease characterized by psychomotor retardation and a mixture of spasticity and rigidity but no ataxia, and only weak features of hypomyelination and thinning of corpus callosum on MRI of the brain.
RESULTS
The thiobarbituric acid method showed elevated levels of free sialic acid in urine and fibroblasts, indicating sialic acid storage disease. Initial Sanger sequencing of SLC17A5 coding regions did not show any pathogenic variants, although exon 9 could not be sequenced. Whole exome sequencing followed by RNA and genomic DNA analysis identified a homozygous 6040 bp insertion in intron 9 of SLC17A5 corresponding to a long interspersed element-1 retrotransposon (KF425758.1). This insertion adds two splice sites, both resulting in a frameshift which in turn creates a premature stop codon 4 bp into intron 9.
CONCLUSIONS
This study describes a novel pathogenic variant in SLC17A5, namely an intronic transposal insertion, in a patient with mild biochemical and clinical phenotypes. The presence of a small fraction of normal transcript may explain the mild phenotype. This case illustrates the importance of including lysosomal sialic acid storage disease in the differential diagnosis of developmental delay with postnatal onset and hypomyelination, as well as intronic regions in the genetic investigation of inborn errors of metabolism.
Topics: DNA Transposable Elements; Exons; Fibroblasts; Humans; Introns; Male; N-Acetylneuraminic Acid; Organic Anion Transporters; Polymerase Chain Reaction; Sialic Acid Storage Disease; Skin; Symporters; Exome Sequencing
PubMed: 28187749
DOI: 10.1186/s13023-017-0584-6 -
Chembiochem : a European Journal of... Jul 2017Sialuria is a rare autosomal dominant disorder of mammalian metabolism, caused by defective feedback inhibition of the UDP-N-acetylglucosamine-2-epimerase...
Sialuria is a rare autosomal dominant disorder of mammalian metabolism, caused by defective feedback inhibition of the UDP-N-acetylglucosamine-2-epimerase N-acetylmannosamine kinase (GNE), the key enzyme of sialic acid biosynthesis. Sialuria is characterized by overproduction of free sialic acid in the cell cytoplasm. Patients exhibit vastly increased urinary excretion of sialic acid and show differently pronounced developmental delays. The physiopathology of sialuria is not well understood. Here we established a transgenic mouse line that expresses GNE containing the sialuria mutation R263L, in order to investigate the influence of an altered sialic acid concentration on the organism. The transgenic mice that expressed the mutated RNA excreted up to 400 times more N-acetylneuraminic acid than wild-type mice. Additionally, we found higher sialic acid concentration in the brain cytoplasm. Analyzing the (poly)sialylation of neural cell adhesion molecule (NCAM) revealed increased polysialylation in brains of transgenic mice compared to wild-type. However, we found only minor changes in membrane-bound sialylation in various organs but, surprisingly, a significant increase in surface sialylation on leukocytes. Our results suggest that the intracellular sialic acid concentration regulates polysialylation on NCAM in vivo; this could play a role in the manifestation of the developmental delays in sialuria patients.
Topics: Age Factors; Animals; Brain; Disease Models, Animal; Feedback, Physiological; Humans; Leukocytes; Liver; Mice; Mice, Transgenic; Multienzyme Complexes; Mutation; N-Acetylneuraminic Acid; Neural Cell Adhesion Molecules; Organ Specificity; Protein Processing, Post-Translational; Sialic Acid Storage Disease
PubMed: 27966821
DOI: 10.1002/cbic.201600580 -
Molecular Genetics and Metabolism... Mar 2017Lysosomal storage diseases (LSD) often manifest with cherry red macular spots. Diagnosis is based on clinical features and specific biochemical and enzymatic patterns....
Multigene panel next generation sequencing in a patient with cherry red macular spot: Identification of two novel mutations in gene causing sialidosis type I associated with mild to unspecific biochemical and enzymatic findings.
BACKGROUND
Lysosomal storage diseases (LSD) often manifest with cherry red macular spots. Diagnosis is based on clinical features and specific biochemical and enzymatic patterns. In uncertain cases, genetic testing with next generation sequencing can establish a diagnosis, especially in milder or atypical phenotypes. We report on the diagnostic work-up in a boy with sialidosis type I, presenting initially with marked cherry red macular spots but non-specific urinary oligosaccharide patterns and unusually mild excretion of bound sialic acid.
METHODS
Biochemical, enzymatic and genetic tests were performed in the patient. The clinical and electrophysiological data was reviewed and a genotype-phenotype analysis was performed. In addition a systematic literature review was carried out.
CASE REPORT AND RESULTS
Cherry red macular spots were first noted at 6 years of age after routine screening myopia. Physical examination, psychometric testing, laboratory investigations as well as cerebral MRI were unremarkable at 9 years of age. So far no clinical myoclonic seizures occurred, but EEG displays generalized epileptic discharges and visual evoked potentials are prolonged bilaterally. Urine thin layer chromatography showed an oligosaccharide pattern compatible with different LSD including sialidosis, galactosialidosis, GM1 gangliosidosis or mucopolysaccharidosis type IV B. Urinary bound sialic acid excretion was mildly elevated in spontaneous and 24 h urine samples. In cultured fibroblasts, α-sialidase activity was markedly decreased to < 1%; however, bound and free sialic acid were within normal range. Diagnosis was eventually established by multigene panel next generation sequencing of genes associated to LSD, identifying two novel, compound heterozygous variants in gene (c.699C > A, p.S233R in exon 4 and c.803A > G; p.Y268C in Exon 5 in transcript NM_000434.3), leading to amino acid changes predicted to impair protein function.
DISCUSSION
Sialidosis should be suspected in patients with cherry red macular spots, even with non-significant urinary sialic acid excretion. Multigene panel next generation sequencing can establish a definite diagnosis, allowing for counseling of the patient and family.
PubMed: 27942463
DOI: 10.1016/j.ymgmr.2016.11.004 -
Molecular Genetics and Metabolism Jun 2016Sialuria, a rare inborn error of metabolism, was diagnosed in a healthy 12-year-old boy through whole exome sequencing. The patient had experienced mild delays of speech...
UNLABELLED
Sialuria, a rare inborn error of metabolism, was diagnosed in a healthy 12-year-old boy through whole exome sequencing. The patient had experienced mild delays of speech and motor development, as well as persistent hepatomegaly. Identification of the 8th individual with this disorder, prompted follow-up of the mother-son pair of patients diagnosed over 15years ago. Hepatomegaly was confirmed in the now 19-year-old son, but in the 46-year-old mother a clinically silent liver tumor was detected by ultrasound and MRI. The tumor was characterized as an intrahepatic cholangiocarcinoma (IHCC) and DNA analysis of both tumor and normal liver tissue confirmed the original GNE mutation. As the maternal grandmother in the latter family died at age 49years of a liver tumor, a retrospective study of the remaining pathology slides was conducted and confirmed it to have been an IHCC as well. The overall observation generated the hypothesis that sialuria may predispose to development of this form of liver cancer. As proof of sialuria in the grandmother could not be obtained, an alternate cause of IHCC cannot be ruled out. In a series of 102 patients with IHCC, not a single instance was found with the allosteric site mutation in the GNE gene. This confirms that sialuria is rare even in a selected group of patients, but does not invalidate the concern that sialuria may be a risk factor for IHCC.
SYNOPSIS
Sialuria is a rare inborn error of metabolism characterized by excessive synthesis and urinary excretion of free sialic acid with only minimal clinical morbidity in early childhood, but may be a risk factor for intrahepatic cholangiocarcinoma in adulthood.
Topics: Bile Duct Neoplasms; Child; Cholangiocarcinoma; Female; Hepatomegaly; Heterozygote; Humans; Liver; Liver Neoplasms; Male; Middle Aged; N-Acetylneuraminic Acid; Rare Diseases; Retrospective Studies; Risk Factors; Sialic Acid Storage Disease; Exome Sequencing; Young Adult
PubMed: 27142465
DOI: 10.1016/j.ymgme.2016.04.004 -
Scientific Reports Mar 2016The bifunctional enzyme UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE) plays a key role in sialic acid production. It is different from the non-hydrolyzing enzymes for...
The bifunctional enzyme UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE) plays a key role in sialic acid production. It is different from the non-hydrolyzing enzymes for bacterial cell wall biosynthesis, and it is feed-back inhibited by the downstream product CMP-Neu5Ac. Here the complex crystal structure of the N-terminal epimerase part of human GNE shows a tetramer in which UDP binds to the active site and CMP-Neu5Ac binds to the dimer-dimer interface. The enzyme is locked in a tightly closed conformation. By comparing the UDP-binding modes of the non-hydrolyzing and hydrolyzing UDP-GlcNAc epimerases, we propose a possible explanation for the mechanistic difference. While the epimerization reactions of both enzymes are similar, Arg113 and Ser302 of GNE are likely involved in product hydrolysis. On the other hand, the CMP-Neu5Ac binding mode clearly elucidates why mutations in Arg263 and Arg266 can cause sialuria. Moreover, full-length modelling suggests a channel for ManNAc trafficking within the bifunctional enzyme.
Topics: Allosteric Regulation; Amino Acid Sequence; Carbohydrate Epimerases; Catalytic Domain; Conserved Sequence; Crystallography, X-Ray; Cytidine Monophosphate; Enzyme Inhibitors; Humans; Hydrogen Bonding; Hydrolysis; Kinetics; Models, Molecular; N-Acetylneuraminic Acid; Protein Binding; Protein Structure, Quaternary; Sialic Acids; Uridine Diphosphate
PubMed: 26980148
DOI: 10.1038/srep23274