Diagnosis and prevention of lysosomal storage diseases in Russia

Molecular diagnosis of a Chinese pedigree with α-mannosidosis and identification of a novel missense mutation

α-Mannosidosis storage disease is a rare autosomal recessive disease that is caused by a deficiency of the lysosomal enzyme α-mannosidase. In this article, a proband in China was preliminarily diagnosed as having α-mannosidosis by clinical symptoms, imaging examination, and enzyme assay. Definitive diagnosis was performed by directly sequencing the MAN2B1 gDNA and cDNA of the peripheral blood leukocyte from the patient. Finally, denaturing high-performance liquid chromatography screening, conservative analysis, and protein secondary structure prediction were used to identify the novel mutation. The results showed that the patient has compound heterozygous mutations in the MAN2B1 gene, c.856G>A (p.E286K, novel) and c.788C>T (p.P263L). Her parents are heterozygote that carry one of these two mutations respectively. Pathogenicity identification of the novel mutation showed that the p.E286K mutation is a disease-causing mutation. Our work enriches the human MAN2B1 gene mutation database. As far as we know, this research is thus far the first gene diagnosis case of a Chinese patient with α-mannosidosis.

Seven novel acid sphingomyelinase gene mutations in Niemann-Pick type A and B patients

We have analyzed acid sphingomyelinase (SMPD1; E.C. 3.1.4.12) gene mutations in four Niemann-Pick disease (NPD) type A and B patients of Turkish ancestry and in three patients of Dutch origin. Among four NPD type A patients we found two homozygotes for the g.1421C > T (H319Y) and g.3714T > C (Y537H) mutations and two compound heterozygotes, one for the g.3337T > C (F463S) and g.3373C > T (P475L) mutations and the other for the g.84delC (G29fsX74) and g.1208A > C (S248R) mutations. One of the type B patients was homozygous for the g.2629C>T (P371S) mutation. The last two type B patients were homozygotes for the common g.3927_3929delCGC (R608del) mutation. The G29fsX74, S248R, H319Y, P371S, F463S, P475L and Y537H SMPD1 mutations are all novel and were verified by PCR/RFLP and/or ARMS. All of the identified mutations are likely to be rare or private, with the exception of R608del which is prevalent among NPD type B patients from the North-African Maghreb region. Geographical and/or social isolation of the affected families are likely contributing factors for the high number of homozygotes in our group.

Molecular genetics of mucopolysaccharidosis type I: diagnostic, clinical, and biological implications

Mucopolysaccharidosis type I (MPS-I) is an autosomal recessive disease caused by mutations in the alpha-L-iduronidase (IDUA) gene. These mutations lead to a deficiency of the glycosidase alpha-L-iduronidase (IDUA), which is required for the degradation of heparan sulphate and dermatan sulphate and thus the storage of these glycosaminoglycans in the lysosome. There is a wide range of clinical phenotypes in MPS-I (eponyms: Hurler syndrome, severe; Hurler/Scheie syndrome, intermediate; Scheie syndrome, mild), which makes prediction of disease severity and genetic counselling difficult. However, since cloning of the IDUA gene, mutation analysis has provided some molecular explanations for the range of MPS-I phenotypes, in turn facilitating the selection and evaluation of patients undergoing experimental treatment protocols such as bone marrow transplantation. A total of 46 mutations now have been defined for MPS-I consisting of 8 nonsense mutations, 21 missense mutations, 3 splice site mutations, and 14 minor deletions and/or insertions. Furthermore, 30 polymorphisms or nonpathogenic sequence variants have been defined, including 7 amino acid substitutions. Among patients of European origin, there are two major MPS-I mutations and a number of less frequent mutations. It is possible to follow mutation analysis of 292 patients, which can be divided into eight main patient groups of different ethnic and/or geographic origin with significant variation in mutant allele frequencies. A complex picture of molecular heterogeneity is emerging, building a valuable database for genotype/phenotype correlation. Mutation analysis is also providing some of the first clues into the structure and function of IDUA.

High-resolution loading tests in the study of genetic heterogeneity in gangliosidosis fibroblasts

GM1- and GM2-gangliosides were isolated from brain and radiolabelled. The labelled moieties were localized by hydrolysis with lysosomal enzymes, followed by thin-layer chromatography of the products. High-resolution loading tests with labelled gangliosides were developed and found to differentiate infantile and juvenile forms of GM1- and GM2-gangliosidoses as well as the identification of B, O and AB types of GM2-gangliosidosis.