Myelin oligodendrocyte glycoprotein antibodies in genetic leukodystrophies.

Accumulation of intermediate metabolites due to enzyme deficiencies and demyelination can provoke inflammation in genetic leukodystrophies. Thirty patients with genetic leukodystrophy and 48 healthy control sera were tested for anti-myelin oligodendrocyte glycoprotein (MOG) antibodies by fixed and/or live cell-based assays. MOG-IgG was detected in two late infantile metachromatic leukodystrophy (MLD) cases, both of which were also weakly positive for IgG1, and one with IgG3 as the dominant anti-MOG IgG subclass. MOG-IgG was borderline positive in a vanishing white matter (VWM) disease patient. These results suggest that inherited metabolic or degenerative processes can have an autoimmune component, possibly as an epiphenomenon.

Comprehensive clinical, biochemical, radiological and genetic analysis of 28 Turkish cases with suspected metachromatic leukodystrophy and their relatives.

Metachromatic leukodystrophy (MLD) is a glycosphingolipid storage disease caused by deficiency of the lysosomal enzyme arylsulfatase A (ASA) or its activator protein saposin B. MLD can affect all age groups in severity varying from a severe fatal form to milder adult onset forms. Diagnosis is usually made by measuring leukocyte ASA activity. However, this test can give false negative or false positive laboratory results due to pseudodeficiency of ASA and saposin B deficiency, respectively. Therefore, we aimed to evaluate patients with suspected MLD in a Turkish population by comprehensive clinical, biochemical, radiological, and genetic analyses for molecular and phenotypic characterization. We analyzed 28 suspected MLD patients and 41 relatives from 24 families. ASA activity was found to be decreased in 21 of 28 patients. Sixteen patients were diagnosed as MLD (11 late infantile, 2 juvenile and 3 adult types), 2 MSD, 2 pseudodeficiency (PD) and the remaining 8 patients were diagnosed as having other leukodystrophies. Enzyme analysis showed that the age of onset of MLD did not correlate with residual ASA activity. Sequence analysis showed 11 mutations in ARSA, of which 4 were novel (p.Trp195GlyfsTer5, p.Gly298Asp, p.Arg301Leu, and p.Gly311Asp), and 2 mutations in SUMF1 causing multiple sulfatase deficiency, and confirmed the diagnosis of MLD in 2 presymptomatic relatives. All individuals with confirmed mutations had low ASA activity and urinary sulfatide excretion. Intra- and inter-familial variability was high for the same ARSA missense genotypes, indicating the contribution of other factors to disease expression. Imaging findings were evaluated through a modified brain MRI scoring system which indicated patients with protein-truncating mutations had more severe MRI findings and late-infantile disease onset. MRI findings were not specific for the diagnosis. Anti-sulfatide IgM was similar to control subjects, and IgG, elevated in multiple sulfatase deficiency. In conclusion, the knowledge on the biochemical, clinical and genetic basis of MLD was expanded, a modified diagnostic laboratory algorithm for MLD based on integrated evaluation of ASA activity, urinary sulfatide excretion and genetic tests was devised.

A Monogenic Disease with a Variety of Phenotypes: Deficiency of Adenosine Deaminase 2.

OBJECTIVE: Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive autoinflammatory disorder associated with ADA2 mutations. We aimed to investigate the characteristics and ADA2 enzyme activities of patients with DADA2 compared to non-DADA2 patients. METHODS: This is a descriptive study of 24 patients with DADA2 who were admitted to the Adult and Pediatric Rheumatology, Pediatric Haematology, and Pediatric Immunology Departments of Hacettepe University. All ADA2 exons were screened by Sanger sequencing. Serum ADA2 enzyme activity was measured by modified spectrophotometric method. RESULTS: Twenty-four patients with DADA2 were included: 14 with polyarteritis nodosa (PAN)-like phenotype (Group 1); 9 with Diamond-Blackfan anemia (DBA)-like features, and 1 with immunodeficiency (Group 2). Fourteen PAN-like DADA2 patients did not have the typical thrombocytosis seen in classic PAN. Inflammatory attacks were evident only in Group 1 patients. Serum ADA2 activity was low in all patients with DADA2 except one, who was tested after hematopoietic stem cell transplantation. There was no significant difference in ADA2 activities between PAN-like and DBA-like patients. In DADA2 patients with one ADA2 mutation, serum ADA2 activities were as low as those of patients with homozygote DADA2. ADA2 activities were normal in non-DADA2 patients. ADA2 mutations were affecting the dimerization domain in Group 1 patients and the catalytic domain in Group 2 patients. CONCLUSION: We suggest assessing ADA2 activity along with genetic analysis because there are patients with one ADA2 mutation and absent enzyme activity. Our data suggest a possible genotype-phenotype correlation in which dimerization domain mutations are associated with PAN-like phenotype, and catalytic domain mutations are associated with hematological manifestations.

Inflammatory response and its relation to sphingolipid metabolism proteins: Chaperones as potential indirect anti-inflammatory agents.

Lysosome is the organelle responsible for breaking down macromolecules to maintain homeostasis and to fight infection. The disruption of normal lysosomal function due to mutations in the sphingolipid metabolism proteins leads to a class of lysosomal storage diseases (LSDs). Defective autophagy and activation of inflammation are observed in most LSDs. The crosstalk between these key metabolic pathways suggests that therapeutic approaches used in the treatment of LSDs may provide anti-inflammatory therapies against chronic inflammatory diseases such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease. Here, we review the role of sphingolipids in the inflammatory response and build a protein-protein interaction network for proteins related with sphingolipid metabolism and inflammation to identify key interaction partners for the crosstalk between sphingolipids and inflammation. In addition, we present an overview of LSDs in relation with sphingolipids and inflammation, and review the pharmacological chaperones identified for these diseases.

Metachromatic leukodystrophy: Biochemical characterization of two (p.307Glu→Lys, p.318Trp→Cys) arylsulfatase A mutations.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by Arylsulfatase A (ASA) deficiency. The hallmark of the disease is central and peripheral neurodegeneration. More than 200 mutations have been identified in ARSA gene so far. Some of these mutations were characterized. The aim of this study is to reinforce genotype-phenotype correlation and to understand the effect of mutations on the enzyme by biochemical characterization. Two missense mutations (c.919G→A, p.307Glu→Lys and c.954G→T, p.318Trp→Cys in exon 5) were constructed on WT-ASA cDNA and were confirmed by DNA sequence analysis. Plasmid DNA carrying mutant or normal ASA cDNA was transferred to Chinese Hamster Ovary (CHO) cells through transient transfection. ASA protein was produced by CHO cells. Hexosaminidase beta-subunit gene was cotransfected into the CHO cells as a control gene of transfection efficiency. 48 hours after transfection, cells were collected and homogenized. ASA and hexosaminidase activities were measured in supernatant. ASA enzyme activity is decreased 100% according to the control by the effect of both mutations. The mutations are located in the higly conserved region of the protein. In this study, we showed that both mutations result in null ASA activity in CHO cells making the protein nonfunctional. We confirmed that p.307Glu→Lys and p.318Trp→Cys mutations cause late infantile form of MLD disease.

Four novel mutations in the ß-galactosidase gene identified in infantile type of GM1 gangliosidosis.

OBJECTIVES: The aim of this study is to find out mutations of Turkish GM1 gangliosidosis patients and to make genotype-phenotype correlations. DESIGN AND METHODS: ß-galactosidase activities were measured by using fluorometric substrate. Mutation screening of 16 exons of ß-galactosidase gene and mutation detection were done by PCR-SSCP and DNA sequencing, respectively. RESULTS: Four new mutations, c.188_189insT in exon 2, c.569_570insA in exon 6, p.K142Q in exon 4, p.G190D in exon 6, and one known mutation p.P549L in exon 15, were identified in the ß-galactosidase gene in 5 Turkish patients. Mutations in exons 4 and 6 are in the active site and mutation in exon is in the galactose-binding domain of the ß-galactosidase gene. CONCLUSION: This is the first mutational analysis performed in Turkish GM1 gangliosidosis patients and shows the molecular heterogeneity of the disease in Turkish population. All identified mutations result in severe enzyme deficiency and infantile phenotype.

Two novel alpha-galactosidase A mutations causing Fabry disease: A missense mutation M11V in a heterozygote woman and a nonsense mutation R190X in a hemizygote man.

OBJECTIVES: To evaluate the nature of the molecular lesions in the alpha-galactosidase A gene of two patients having Fabry disease. METHODS: Enzyme analyses were done using 4-methylumbellyferyl alpha-galactoside as substrate. Single stranded conformational polymorphism analysis and DNA sequencing were performed following PCR amplification of seven exons of alpha-galactosidase A gene. RESULTS: Two new mutations, M11V and R190X, were identified. The female patient with M11V mutation had rheumatologic symptoms, microalbuminuria. The male patient with R190X mutation had a classical phenotype. M11V mutation is in the signal sequence of the peptide and may affect the targeting of the ribosomes to ER. R190X mutation causes premature termination, and probably leads to degradation of the protein. CONCLUSION: This is the first study in our country investigating the molecular aspects of Fabry disease. It provides the molecular basis for understanding the underlying mechanism of Fabry disease, allows prenatal diagnosis and provides genotype/phenotype correlations.

Why are they having infant colic? A nested case-control study.

We aimed to analyse infant (birth characteristics, feeding type, faecal enzyme activities) and environmental (maternal smoking, nutrition and psychological status, mother-child bonding, family structure, support for the mother, familial atopy) risk factors for infant colic and to follow infants with respect to physical growth, sleeping status up to 8 months of age in a nested case-control study. 660 mothers who delivered at Dr Zekai Tahir Burak Maternity Hospital, were enrolled within 3-72 h post delivery. Each infant with inconsolable persistent crying and four matched infants with no crying episodes were invited by phone to Hacettepe University Ihsan Dogramaci Children's Hospital at 30-45 days post partum. At 40-55 days, we examined the infants and gave mothers a questionnaire, including crying characteristics of the infants; 47 infants were diagnosed with colic and 142 as non-colic. When the infants were 7-8 months old, another interview was done. The colic group had higher proportions of less-educated (≤ 8 years) and smoking mothers, extended family and families with domestic violence than the non-colic group. The colic group of mothers had significantly higher rates of 'impaired bonding' in the Postpartum Bonding Questionnaire, higher scores on the Edinburgh Postnatal Depression Scale, higher scores for hostility subscales of the Brief Symptom Inventory and a more irregular sleep pattern than the non-colic group. No differences were revealed for faecal enzyme activities. At 7-8 months, the colic group was shorter than the non-colic group. Colic was associated with various perinatal factors (maternal education, smoking habits, cheese consumption, hostility scores and domestic violence) and having colic in infancy negatively affected the sleeping pattern and the height of the infant.

Recent advances in the biochemistry and genetics of sphingolipidoses.

Sphingolipidoses are a subgroup of lysosomal storage diseases. They are defined as disorders caused by a genetic defect in catabolism of sphingosine-containing lipids. Catabolism of these lipids involves enzymes and activator proteins. After the discovery of lysosomes by de Duve and the demonstration of the first defective lysosomal enzyme by Hers in 1963, the first enzyme deficiency for sphingolipidoses was characterized in 1965 and all the defective enzymes were demonstrated in the last three decades. In 1984, the first activator protein was found and it expanded the concept of sphingolipidoses. In the following years, many researches have been undertaken to understand the molecular basis of these diseases, the mechanism of pathogenesis, the mechanism of lysosomal digestion of glycosphingolipids (GSLs) and the functional domains of lysosomal enzymes. New hypotheses and theories have been put forward for the mechanism of lysosomal digestion and pathogenesis. However, although much has been done, the pathogenesis of sphingolipidoses has not been fully elucidated. Mouse models of these diseases have facilitated the elucidation of pathogenesis and the development of therapeutic strategies for these diseases, which are not treatable at present except for Fabry and type 1 Gaucher disease. The purpose of this review is to collect information on the recent researches related to sphingolipidoses. The review includes the hydrolysis of GSLs in lysosome, mechanism of hydrolysis, pathogenesis and genetics of sphingolipidoses, a brief mouse model and therapeutic strategies of these diseases.

Sphingolipidoses in Turkey.

During the last 5 years 2057 children under the age of 5 with various neurologic symptoms with the suspected diagnosis of lysosomal storage diseases were referred to our hospital from different universities and state hospitals. We were able to separate sphingolipidoses by lysosomal enzyme screening. A total of 300 patients (15%) with sphingolipidoses were diagnosed; there were deficiencies of arylsulfatase A [metachromatic leukodystrophy (MLD)] in 93 (31%), hexosaminidase [Sandhoff disease (SHD)] in 62 (20.7%), hexosaminidase A [Tay-Sachs disease (TSD)] in 15 (5%), beta-galactosidase (GM1 gangliosidosis) in 35 (11.7%), alpha-galactosidase (Fabry disease) in one (0.3%) cerebroside beta-galactosidase (Krabbe disease) in 65 (21.7%) and glucosylceramidase (Gaucher disease) in 29 (9.6%). SHD (20.7%), MLD (31%) and Krabbe disease (21.7%) were common. Prenatal enzymatic diagnosis was made in 70 at risk pregnancies, 64 for TSD and SHD, three for MLD and three for GM1 gangliosidosis by using chorionic villus biopsy in 54, cord blood samples in 12 and cultured amniotic fluid cells in four. Seventeen fetuses were found to be affected. We have calculated the relative frequency and minimum incidence of sphingolipidoses in Turkey. The combined incidence of sphingolipidoses is 4.615 per 100,000 live births. The calculated incidences are 1.43, 0.95, 1, 0.23, 0.54, 0.45, 0.015 per 100,000 live births for MLD, SHD, Krabbe, Gaucher, TSD, GM1 gangliosidosis and Fabry diseases, respectively. The real incidence, which covers all subtypes of this group of diseases, should be greater than this number. The results suggested that, as a group, sphingolipidoses are relatively common and represent an important health problem in Turkey and some rare autosomal recessive diseases of Turkey are due to 'founder effect' created by consanguineous marriages.

Characterization of two Turkish beta-hexosaminidase mutations causing Tay-Sachs disease.

Two homoallelic mutations have recently been identified in the alpha-subunit of hexosaminidase A (EC 3.2.1.52) causing the infantile form of Tay-Sachs disease in Turkish patients. Both of these mutations, a 12 bp deletion (1096-1107 or 1098-1108 or 1099-1109) in exon 10 and a point mutation (G1362 to A, Gly454 to Asp) in exon 12, are located in the catalytic domain of the hexosaminidase alpha-chain. In order to determine whether these mutations affect the function of the catalytic domain or result in an instable protein, both mutant cDNAs were overexpressed in COS-1 cells. As judged by Western blotting, transfections of wild-type cDNA produced pro-alpha-chain and mature alpha-chain in parallel with a fivefold increase in cellular hexosaminidase activity using the synthetic substrate 4-methylumbelliferyl beta-N-acetylglucosamine 6-sulfate (MUGS). However, both mutants produced only pro-alpha-chains, although no mature form or detectable hexosaminidase activity towards two different synthetic substrates was observed. These data are consistent with the biochemical phenotype of infantile Tay-Sachs disease. We conclude that the overexpressed mutant pro-alpha-chains were misfolded and could not undergo further proteolytic processing to the active form of the enzyme in the lysosome.

A new point mutation (G412 to A) at the last nucleotide of exon 3 of hexosaminidase alpha-subunit gene affects splicing.

We report the sixth mutation associated with the infantile form of Tay-Sachs disease in the Turkish population. The mutation is a single nucleotide transition (G to A) at the last nucleotide of exon 3 of hexosaminidase A (HEX A) alpha-subunit gene. The 14 exons and their flanking sequences of the HEX A gene were amplified and analyzed by polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP). Sequencing of exon 3 showed a homozygous mutation. Cultured patient's fibroblasts produced no detectable mRNA for HEX A alpha-subunit gene by Northern blot analysis. We speculate that abnormal mRNA was rapidly degraded following transcription. Our data are consistent with the idea that the severe infantile form of Tay-Sachs disease is associated with a total lack of Hex A activity in the patient. A similar mutation (G to T) had been observed at the 5'-donor splice site of exon 3. It resulted in abnormal splicing and skipping of exon 3. The other acceptor and donor splice site mutations described in the HEX A gene ablate normal mRNA splicing. Identification of multiple mutant HEX A alleles shows molecular heterogeneity of infantile Tay-Sachs disease in our population.