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Abstract: Surface enhanced laser desorption/ionisation time of flight (SELDI-TOF) mass spectrometry has been used to search for new protein biomarkers in the plasma of patients with mucopolysacharidoses (MPS). Differences in the levels of some plasma proteins, particularly the apolipoprotein ApoCI, were observed between MPS patients and normal controls, using the different chromatographic surfaces (ProteinChips®). ApoCI was identified by both its mass and by immunological techniques. In plasma, it exists in two forms, ApoCI and a truncated form which lacks two N-terminal amino acids, ApoCI′. In controls, the ratio of ApoCI′:ApoCI observed using the cation-exchange surface (CM10) was approximately 1:2 whereas in most MPS patients it varied from 1:1 to 1:0.8. The ratio of ApoCI′:ApoCI in plasma is determined by the activity of dipeptidyl peptidase IV, DPP-IV (also known as the leucocyte antigen CD26), which was found to be elevated up to 3-fold in MPS patients. The DPP-IV activity decreased in MPS I patients undergoing enzyme replacement therapy, indicating that it could be a useful biomarker for monitoring the efficacy of treatment in MPS disease. As DPP-IV has an important regulatory role in metabolism, it is possible that its elevation could cause some of the secondary pathology in MPS, and inhibition of DPP-IV might have a role in MPS therapy. [Copyright &y& Elsevier] more...

The lysosomal storage disorder, mucopolysaccharidosis type I (MPS I), is caused by a deficiency of the enzyme α-L-iduronidase, which is involved in the breakdown of dermatan and heparan sulphates. There are three clinical phenotypes, ranging from the Hurler form characterised by skeletal abnormalities, hepatosplenomegaly and severe mental retardation, to the milder Scheie phenotype where there is aortic valve disease, corneal clouding, limited skeletal problems, but no mental retardation. In this study, 85 MPS I families (73 Hurler, 5 Hurler/Scheie, 7 Scheie) were screened for 9 known mutations (Q70X, A75T, 474–2a>g, L218P, A327P, W402X, P533R, R89Q, 678–7g>a). W402X was the most frequent mutation in our population (45.3%) and Q70X was the second most frequent (15.9%). In 30 families, either one or both of the mutations were not identified, which accounted for 25.9% of the total alleles. Therefore, all 14 exons of the α-L-iduronidase gene were screened in these patients and 23 different sequence changes were found, 17 of which were previously unknown. The novel sequence changes include 4 deletions (153delC, 628del5, 740delC, 747delG), 5 nonsense mutations (Q60X, Y167X, Q400X, R619X, R628X), 6 missense mutations (C205Y, G208V, H240R, A319V, P496R, S633L), a splice site mutation (IVS12+5g>a), and a rare polymorphism (A591T). The polymorphism and novel missense mutations were transiently expressed in COS-7 cells and all of them except the polymorphism showed complete loss of enzyme activity. In total, 165 of the 170 mutant alleles were identified in this study and despite the high frequency of W402X and Q70X, the identification of many novel mutations unique to individual families further highlights the genetic heterogeneity of MPS I. [ABSTRACT FROM AUTHOR] more...

Mucopolysaccharidosis IIIC (MPS IIIC, or Sanfilippo C syndrome) is a lysosomal storage disorder caused by the inherited deficiency of the lysosomal membrane enzyme acetyl-coenzyme A:α-glucosaminide N-acetyltransferase (N-acetyltransferase), which leads to impaired degradation of heparan sulfate. We report the narrowing of the candidate region to a 2.6-cM interval between D8S1051 and D8S1831 and the identification of the transmembrane protein 76 gene (TMEM76), which encodes a 73-kDa protein with predicted multiple transmembrane domains and glycosylation sites, as the gene that causes MPS IIIC when it is mutated. Four nonsense mutations, 3 frameshift mutations due to deletions or a duplication, 6 splice-site mutations, and 14 missense mutations were identified among 30 probands with MPS IIIC. Functional expression of human TMEM76 and the mouse ortholog demonstrates that it is the gene that encodes the lysosomal Nacetyltransferase and suggests that this enzyme belongs to a new structural class of proteins that transport the activated acetyl residues across the cell membrane. [ABSTRACT FROM AUTHOR] more...

In this study we have investigated a group of 29 Brazilian patients, who had been diagnosed with the lysosomal storage disorder, Mucopolysaccharidosis type I (MPS-I). MPS I is caused by a deficiency in the lysosomal hydrolase, α-l-iduronidase. Ninety percent of the MPS I patients in this study were genotyped and revealed 10 recurrent and thirteen novel IDUA gene mutations. Eight of these new mutations and three common mutations W402X, P533R, and R383H were individually expressed in CHO-K1 cells and analyzed for α-l-iduronidase protein and enzyme activity. A correlation was observed between the MPS I patient clinical phenotype and the associated mutant α-l-iduronidase protein/enzyme activity expressed in CHO-K1 cells. This was the first time that Brazilian MPS I patients had been thoroughly analyzed and highlighted the difficulties of mutation screening and clinical phenotype assessment in populations with high numbers of unique mutations. [Copyright &y& Elsevier] more...