Mucolipidosis type IV: the origin of the disease in the Ashkenazi Jewish population.
Mucolipidosis type IV (MLIV) is a neurodegenerative lysosomal storage disease in which most of the patients diagnosed hitherto are Ashkenazi Jews. The basic metabolic defect causing this disease is still unknown and the relevant gene has not yet been mapped or cloned. Seventeen Israel Ashkenazi families with MLIV patients had been interviewed to study their family origin. Although the families immigrated to Israel from various European countries they all could trace their roots three to four generations back to northern Poland or the immediate neighbouring country, Lithuania. Furthermore, there are only one or two ultraorthodox families among the 70-80 Ashkenazi families with MLIV patients worldwide, a marked under-representation of this group which constitutes at least 10% of the Ashkenazi population. This data indicate that MLIV mutation occurred only around the 18th and 19th centuries, after the major expansion of this population, in a founder in this defined European region belonging to a more modern, secular family. (+info)
Mucolipidosis IV consists of one complementation group.
Mucolipidosis IV (MLIV) is an autosomal recessive disorder of unknown etiology characterized by severe visual impairment and psychomotor retardation. Recently, there has been considerable interest in positional cloning of the MLIV gene. It is unknown whether MLIV is a genetically homogenous disorder. In this paper, we present experiments that determined whether the MLIV phenotype in fibroblasts could be corrected by fusing normal cells to MLIV cells and fusing fibroblasts from pairs of patients. All of our MLIV patients fulfilled several diagnostic criteria that we developed. In addition, we found high sensitivity to chloroquine in cultured fibroblasts from MLIV patients. We found that normal cells corrected the MLIV phenotype. Fusion products of normal and MLIV fibroblasts, but not MLIV fibroblasts themselves, were relatively protected against chloroquine selection. In addition, 74% of the normal-to-patient fusion products had reduced levels or total loss of MLIV characteristic autofluorescence. However, there was no complementation of the phenotype in fibroblast cultures from any of our MLIV patients, including those of non-Jewish ancestry. In fusion products of MLIV cultures from 24 patients, 90-100% of the cells remained autofluorescent. These results indicate that all of our known MLIV patients, regardless of ancestry or severity of the developmental defect, have a single mutated gene. (+info)
Mapping of the mucolipidosis type IV gene to chromosome 19p and definition of founder haplotypes.
Mucolipidosis type IV (MLIV) is a lysosomal storage disorder characterized by severe neurologic and ophthalmologic abnormalities. It is a rare autosomal recessive disease, and the majority of patients diagnosed, to date, are of Ashkenazi Jewish descent. We have mapped the MLIV gene to chromosome 19p13.2-13.3 by linkage analysis with 15 markers in 13 families. A maximum LOD score of 5.51 with no recombinants was observed with marker D19S873. Several markers in the linked interval also displayed significant linkage disequilibrium with the disorder. We constructed haplotypes in 26 Ashkenazi Jewish families and demonstrate the existence of two founder chromosomes in this population. The localization of MLIV to chromosome 19 will permit genetic prenatal diagnosis in affected families and will aid in the isolation of the disease gene. (+info)
Orthopaedic management in four cases of mucolipidosis type III.
Four patients with mucolipidosis type III, three of them brothers, were seen initially in the first two decades of life. Their main symptoms were carpal tunnel syndrome, trigger fingers and generalized joint stiffness. Radiographs showed spinal deformities and hip dysplasia, but these were not causing pain. Carpal tunnel syndrome was treated surgically but joint stiffness and hip and knee contractures were managed by physiotherapy. Up to the age of 24 none of these patients has had pelvic osteotomy for hip dysplasia; this operation, not yet reported in mucolipidosis type III, may eventually be necessary. (+info)
Molecular basis of GM1 gangliosidosis and Morquio disease, type B. Structure-function studies of lysosomal beta-galactosidase and the non-lysosomal beta-galactosidase-like protein.
GM1 gangliosidosis and Morquio B disease are distinct disorders both clinically and biochemically yet they arise from the same beta-galactosidase enzyme deficiency. On the other hand, galactosialidosis and sialidosis share common clinical and biochemical features, yet they arise from two separate enzyme deficiencies, namely, protective protein/cathepsin A and neuraminidase, respectively. However distinct, in practice these disorders overlap both clinically and biochemically so that easy discrimination between them is sometimes difficult. The principle reason for this may be found in the fact that these three enzymes form a unique complex in lysosomes that is required for their stability and posttranslational processing. In this review, I focus mainly on the primary and secondary beta-galactosidase deficiency states and offer some hypotheses to account for differences between GM1 gangliosidosis and Morquio B disease. (+info)
Molecular basis of variant pseudo-hurler polydystrophy (mucolipidosis IIIC)
Mucolipidosis IIIC, or variant pseudo-Hurler polydystrophy, is an autosomal recessive disease of lysosomal hydrolase trafficking. Unlike the related diseases, mucolipidosis II and IIIA, the enzyme affected in mucolipidosis IIIC (N-Acetylglucosamine-1-phosphotransferase [GlcNAc-phosphotransferase]) retains full transferase activity on synthetic substrates but lacks activity on lysosomal hydrolases. Bovine GlcNAc-phosphotransferase has recently been isolated as a multisubunit enzyme with the subunit structure alpha(2)beta(2)gamma(2). We cloned the cDNA for the human gamma-subunit and localized its gene to chromosome 16p. We also showed, in a large multiplex Druze family that exhibits this disorder, that MLIIIC also maps to this chromosomal region. Sequence analysis of the gamma-subunit cDNA in patients from 3 families identified a frameshift mutation, in codon 167 of the gamma subunit, that segregated with the disease, indicating MLIIIC results from mutations in the phosphotransferase gamma-subunit gene. This is to our knowledge the first description of the molecular basis for a human mucolipidosis and suggests that the gamma subunit functions in lysosomal hydrolase recognition. (+info)
Characterization of the sialidase molecular defects in sialidosis patients suggests the structural organization of the lysosomal multienzyme complex.
Sialidosis is an autosomal recessive disease caused by the genetic deficiency of lysosomal sialidase, which catalyzes the hydrolysis of sialoglycoconjugates. The disease is associated with progressive impaired vision, macular cherry-red spots and myoclonus (sialidosis type I) or with skeletal dysplasia, Hurler-like phenotype, dysostosis multiplex, mental retardation and hepatosplenomegaly (sialidosis type II). We have analyzed the genomic DNA from nine sialidosis patients of multiple ethnic origin in order to find mutations responsible for the enzyme deficiency. The activity of the identified variants was studied by transgenic expression. One patient had a frameshift mutation (G623delG deletion), which introduced a stop codon, truncating 113 amino acids. All others had missense mutations: G679G-->A (Gly227Arg), C893C-->T (Ala298Val), G203G-->T (Gly68Val), A544A-->G (Ser182Gly) C808C-->T (Leu270Phe) and G982G-->A (Gly328Ser). We have modeled the three-dimensional structure of sialidase based on the atomic coordinates of the homologous bacterial sialidases, located the positions of mutations and estimated their potential effect. This analysis showed that five mutations are clustered in one region on the surface of the sialidase molecule. These mutations dramatically reduce the enzyme activity and cause a rapid intralysosomal degradation of the expressed protein. We hypothesize that this region may be involved in the interface of sialidase binding with lysosomal cathepsin A and/or beta-galactosidase in their high-molecular-weight complex required for the expression of sialidase activity in the lysosome. (+info)
Cloning of the gene encoding a novel integral membrane protein, mucolipidin-and identification of the two major founder mutations causing mucolipidosis type IV.
Mucolipidosis type IV (MLIV) is an autosomal recessive lysosomal storage disorder characterized by severe psychomotor retardation and ophthalmologic abnormalities, including corneal opacity, retinal degeneration, and strabismus. Unlike the situation in other lysosomal disorders, the accumulation of heterogeneous storage material observed in MLIV does not result from a block in the catabolic pathways but is due to an ill-defined transport defect in the late steps of endocytosis. With the aim of cloning the MLIV gene, we searched in the 19p13.2-13.3 region, where the locus previously had been assigned by linkage mapping. In this region, we have identified a novel gene that is mutated in all patients with MLIV who were enrolled in our study. One patient was homozygous for the splice-acceptor mutation, and another was homozygous for a deletion removing the first six exons of the gene. In addition, four compound heterozygotes for these two mutations were identified. Haplotype analysis indicates that we have identified the two major founder mutations, which account for >95% of MLIV chromosomes in Ashkenazi Jewish patients. The gene, ML4, encodes a protein named "mucolipidin, " which localizes on the plasma membrane and, in the carboxy-terminal region, shows homologies to polycystin-2, the product of the polycystic kidney disease 2 gene (PKD2) and to the family of transient receptor potential Ca(2+) channels. Mucolipidin is likely to play an important role in endocytosis. (+info)