Direct sequencing of polymerase chain reaction products from low melting temperature agarose.
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Base Sequence↗
Biomedical subjects
J S O'Brien
Publications and source records attributed to J S O'Brien.
Fucosidosis: four new mutations and a new polymorphism.
Fucosidosis is a rare lysosomal storage disease due to a nearly complete deficiency of alpha-L-fucosidase (EC 3.2.1.51). In this study, all 8 exons of the alpha-L-fucosidase structural gene (FUCA-1) were amplified by PCR methods, and the amplified products were subcloned and sequenced. Five patient groups with fucosidosis were selected according to their ethnic backgrounds and haplotypes for RFLPs in FUCA-1. Four presumptive disease causing mutations were detected: 1) A major deletion of DNA containing the last two exons of FUCA-1 in two Algerian siblings. 2) A G to T mutation in exon 6 resulting in an in-frame termination codon (E375X) in eight Hispanic patients from Colorado and New Mexico. 3) A G to A mutation (G60D) in exon 1 in four Italian patients and in three related French-American (Cajun) patients. This G60D mutation creates a unique site for AflIII. 4) A frameshift mutation resulted from a two-base deletion in exon 2 (K151fs) in an Italian patient. This deletion obliterates a unique BstXI site and creates a new BpmI site, and was found in only this patient and in only one allele. The rationale for proposing these defects as disease causing mutations includes pedigree analysis and the predicted consequences of each defect upon the activity and the concentration of the enzyme. An A to G transition (Q281R) in exon 5 was found to be present in homozygous form in affected patients and also in normal subjects; it appears to be a newly identified polymorphism. It causes a charge change and may be responsible for the electrophoretic variant phenotype of fucosidosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Amino Acid Sequence↗
Six additional mutations in fucosidosis: three nonsense mutations and three frameshift mutations.
The rare lysosomal storage disease, fucosidosis results from an almost complete deficiency of alpha-L-fucosidase (EC 3.2.1.51). We have identified six new potential disease causing mutations detected by PCR amplification and sequencing of all 8 exons of the alpha-L-fucosidase gene FUCA1. (1) A C to T mutation (Q77X) in exon 1 of two Jewish-Italian siblings. This mutation was present in one allele and was found also in the mother who was of Italian origin. (2) A C to A mutation (W382X) in exon 6 in an Italian patient. This mutation was found in one allele and obliterates a unique Hphl site. (3) A C to A mutation (Y211X) in exon 3 in a Belgian patient. This mutation obliterates a unique Rsal site and was present in both alleles. (4) A homozygous single base (C) deletion in exon 2 in an Italian patient. This deletion results in a frameshift mutation (P141fs) and obliterates a unique Eael site. (5) A homozygous single base (C) deletion in exon 5 in a Portuguese patient, which also results in a frameshift mutation (S265fs). (6) A single base (A) deletion in exon 3 in a Canadian-Indian patient, which also results in a frameshift mutation (S216fs). The S216fs mutation was found in only one allele; the mutation in the other allele is not yet known.
Amino Acid Sequence↗
Binding and transport of gangliosides by prosaposin.
Prosaposin, the precursor of saposins A, B, C, and D, which activate lysosomal hydrolysis of sphingolipids, exists in various tissues and body fluids and is especially abundant in the nervous system. Prosaposin and saposins A,B, C, and D formed stable complexes with 13 different gangliosides as measured by an assay using column chromatography. Gangliosides of the gangliotetraose type (a series) were bound with high affinity, whereas b series gangliosides, O-acetylated gangliosides, and gangliosides with shorter carbohydrate chains, were bound with lower affinity. Prosaposin and saposins transferred gangliosides from donor liposomes to erythrocyte ghost membranes. Prosaposin also stimulated ganglioside GM1 beta-galactosidase more than mature saposins. Prosaposin exists as a secretory protein and as an integral membrane protein, and we propose that prosaposin is active as a ganglioside binding and transport protein in vivo.
Biological Transport↗
Distribution of saposins (sphingolipid activator proteins) in tissues of lysosomal storage disease patients.
Saposins are a group of small glycoproteins derived from a single precursor protein, prosaposin. Each of the four saposins are involved in lysosomal hydrolysis of various sphingolipids. Our recent investigations have shown that saposins accumulate in tissues of several lysosomal storage diseases patients, including those with Tay-Sachs disease and Gaucher disease. To obtain insight into the mechanism of accumulation and its pathological role, the subcellular distribution of saposins in brain from Tay-Sachs disease and in spleen of Gaucher disease were compared with that of GM2 ganglioside and glucocerebroside, respectively. In both Tay-Sachs brain and Gaucher spleen, saposins were found predominantly in light-density fractions while most of the GM2 ganglioside and glucocerebroside, respectively, were found in heavy-density fractions. These studies indicate that saposins that accumulate in these pathological tissues are not tightly associated with GM2 ganglioside or glucocerebroside.
Brain↗
Structure and sequence of the human alpha-L-fucosidase gene and pseudogene.
Fucosidosis is a rare lysosomal storage disease resulting from a nearly complete deficiency of alpha-L-fucosidase enzyme activity. Previously, cDNA encoding human fucosidase was cloned and sequenced. Here we report the determination of the human fucosidase gene structure and sequence as well as the sequence of the fucosidase pseudogene. The gene encoding fucosidase is composed of eight exons spanning 23 kb of DNA. Analysis of the sequence 5' of the open reading frame indicates the presence of multiple transcription factor binding sites but no TATA box. Northern blot analysis has confirmed an mRNA size of 2.3 kb in human lymphoblasts, testis, and epithelial cells. We have also sequenced the processed pseudogene of fucosidase. The sequence of the pseudogene is 80% identical to that of fucosidase cDNA but does not contain an open reading frame.
Base Sequence↗
Production and characterization of a monoclonal antibody to human saposin C.
A murine IgG1 monoclonal antibody, termed 68-12, was produced against purified human saposin C. Immunoprecipitation and binding analysis indicated that the antibody reacted only with saposin C. Dot blotting and Western analysis demonstrated that antibody 68-12 also reacted with prosaposin and a higher molecular weight protein(s) in murine spleen and cerebral grey matter. Solid phase competitive radioimmunoassay against 125I labeled saposin C (0.25 micrograms/ml) showed no cross reactivity for saposin A, B and D up to 15 micrograms/ml. At a concentration of 50 micrograms/ml saposin A, B and D cross reacted 21, 1.5, and 49% respectively. Monoclonal antibody 68-12 appears to have potential utility in the purification, detection and quantitation of human saposin C and its precursor.
Animals↗
Saposins: structure, function, distribution, and molecular genetics.
Saposins A, B, C, and D are small heat-stable glycoproteins derived from a common precursor protein, prosaposin. These mature saposins, as well as prosaposin, activate several lysosomal hydrolases involved in the metabolism of various sphingolipids. All four saposins are structurally similar to one another including placement of six cysteines, a glycosylation site, and conserved prolines in identical positions. In spite of the structural similarities, the specificity and mode of activation of sphingolipid hydrolases differs among individual saposins. Saposins appear to be lysosomal proteins, exerting their action upon lysosomal hydrolases. Prosaposin is a 70 kDa glycoprotein containing four domains, one for each saposin, placed in tandem. Prosaposin is proteolytically processed to saposins A, B, C and D, apparently within lysosomes. However, prosaposin also exists as an integral membrane protein not destined for lysosomal entry and exists uncleaved in many biological fluids such as seminal plasma, human milk, and cerebrospinal fluid, where it appears to have a different function. The physiological significance of saposins is underlined by their accumulation in tissues of lysosomal storage disease patients and the occurrence of sphingolipidosis due to mutations in the prosaposin gene. This review presents an overview of the occurrence, structure and function of these saposin proteins.
Animals↗
Human placental sialidase complex: characterization of the 60 kDa protein that cross-reacts with anti-saposin antibodies.
Sialidase isolated from human placenta is associated with several proteins including acid beta-galactosidase, carboxypeptidase, N-acetyl-alpha-galactosaminidase, and others. These proteins are thought to form an aggregated complex during isolation of sialidase. One of the proteins of 60 kDa was recently identified by Potier et al. (Biochem. Biophys. Res. Comm. 173, 449-456, 1990) as a sialidase protein: this protein also cross-reacted with anti-prosaposin antibodies. We have isolated this protein and from the following evidence identified it as a heavy chain component of immunoglobulin G and not sialidase or a derivative of prosaposin. On gel filtration HPLC, sialidase activity and the 60 kDa protein were clearly separated from one another. The 60 kDa protein cross-reacted not only with antibodies raised against human saposins A, C, and D, but also with second antibody (goat anti-rabbit immunoglobulin G antibody) alone. This 60 kDa protein strongly cross-reacted with anti-human immunoglobulin G antibodies. The sequence of the initial 15 amino acids from the N-terminus of the 60 kDa protein was identical to the sequence of an immunoglobulin G heavy chain protein Tie (gamma 1).
Amino Acid Sequence↗
Saposin proteins: structure, function, and role in human lysosomal storage disorders.
Saposins are sphingolipid activator proteins, four of which are derived from a single precursor, prosaposin, by proteolytic processing. These small heat-stable glycoproteins (12-14 kDa) are required for the lysosomal hydrolysis of a variety of sphingolipids. Characterization of these four activator proteins, two of which were recently discovered, and their importance in human health and disease are reviewed in this article.
Amino Acid Sequence↗
Fucosidosis revisited: a review of 77 patients.
Fucosidosis is a rare, autosomal recessive, lysosomal storage disorder caused by a severe deficiency of alpha-L-fucosidase in all tissues. We have conducted a review of fucosidosis, compiling data from published reports and an international questionnaire survey. Seventy-seven patients affected with fucosidosis of which 19 had not been reported before have been identified. A major aim of the present study was to define the natural history of fucosidosis. The clinical picture of fucosidosis consists of progressive mental (95%) and motor (87%) deterioration, coarse facies (79%), growth retardation (78%), recurrent infections (78%), dysostosis multiplex (58%), angiokeratoma corporis diffusum (52%), visceromegaly (44%), and seizures (38%). Whereas the original fucosidosis patients described by Durand et al. (J. Pediatr 75:665-674, 1969) were decerebrate and died before age 5 years, most fucosidosis patients have a slower course of degeneration. Mortality before age 5 years was observed in only 7 patients (9%), whereas 36 patients (64%) reached the second decade. We did not find evidence for the existence of clinical heterogeneity with a rapidly progressive type I and a slowly progressive type II fucosidosis as suggested in the literature. Instead, there seems to exist a wide continuous clinical spectrum. At the biochemical level no heterogeneity in residual fucosidase enzyme activity or cross-reacting immunoreactive fucosidase protein was observed. At the DNA level at least 4 different mutations must be responsible for fucosidosis. These genotypic differences however do not explain the observed phenotypic differences.
Carbohydrate Conformation↗
Determination of saposin proteins (sphingolipid activator proteins) in human tissues.
Saposins are small glycoproteins which are required for sphingolipid hydrolysis by lysosomal hydrolases. Each saposin (A, B, C, and D) stimulates a different enzymatic activity. A new simple HPLC method to determine the levels of saposins A, C, and D in tissue was developed. Tissues were homogenized in 20 vol of water, boiled, and centrifuged. The supernatant was lyophilized and redissolved in 5 ml of water. A 1.5-ml sample of the solution was applied to a reverse-phase HPLC column (C4 column) and eluted with an acetonitrile gradient. Most contaminants eluted from the column prior to the saposins, which were eluted later as a cluster of peaks. This cluster was collected and then analyzed by another HPLC system equipped with an AX-300 anion-exchange column using a NaCl gradient. Saposins D, A, and C eluted from the AX-300 column separately and in that order. Quantitation of the saposins was made by measuring the sizes of each peak. Standard curves made from pure saposins showed that quantification was linear over a range from 1 to 5 micrograms. Saposin B was measured by its stimulation activity on pure human liver GM1 ganglioside beta-galactosidase. Stimulation was linear up to 80 micrograms of saposin B. Application of this method to analysis of human tissues for their saposin content is presented.
Chromatography, High Pressure Liquid↗
BclI RFLP in fucosidase pseudogene (FUCA1P).
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Chromosomes, Human, Pair 2↗
Interaction of saposins, acidic lipids, and glucosylceramidase.
Activity of lysosomal glucosylceramidase is stimulated by two small glycoproteins, saposin A and C, which are, together with two other similar glycoproteins, derived from a single precursor protein. This enzyme is also stimulated by naturally occurring acidic lipids, such as phosphatidylserine and gangliosides. Using highly purified glucosylceramidase, saposins, and acidic lipids, the mechanism of enzyme stimulation was studied by investigating complex formation between the three components and by examining effects on activity caused by changing amounts of saposins and acidic lipids, individually or in combination. The results indicated that acidic lipids form a water-soluble complex with glucosylceramidase but not with saposins and that saposins and acidic lipids each bind to the enzyme at two different sites for the activation. Based on these observations, the previously proposed three-binding sites model of glucosylceramidase, activator, and substrate was modified to one composed of four binding sites: one for carbohydrate of the substrate, one for aglycon, one for acidic lipids, and one for saposins.
Female↗
Characterization of a mutation in a family with saposin B deficiency: a glycosylation site defect.
Saposins are small, heat-stable glycoproteins required for the hydrolysis of sphingolipids by specific lysosomal hydrolases. Saposins A, B, C, and D are derived by proteolytic processing from a single precursor protein named prosaposin. Saposin B, previously known as SAP-1 and sulfatide activator, stimulates the hydrolysis of a wide variety of substrates including cerebroside sulfate, GM1 ganglioside, and globotriaosylceramide by arylsulfatase A, acid beta-galactosidase, and alpha-galactosidase, respectively. Human saposin B deficiency, transmitted as an autosomal recessive trait, results in tissue accumulation of cerebroside sulfate and a clinical picture resembling metachromatic leukodystrophy (activator-deficient metachromatic leukodystrophy). We have examined transformed lymphoblasts from the initially reported saposin B-deficient patient and found normal amounts of saposins A, C, and D. After preparing first-strand cDNA from lymphoblast total RNA, we used the polymerase chain reaction to amplify the prosaposin cDNA. The patient's mRNA differed from the normal sequence by only one C----T transition in the 23rd codon of saposin B, resulting in a threonine to isoleucine amino acid substitution. An affected male sibling has the same mutation as the proband and their heterozygous mother carries both the normal and mutant sequences, providing additional evidence that this base change is the disease-causing mutation. This base change results in the replacement of a polar amino acid (threonine) with a nonpolar amino acid (isoleucine) and, more importantly, eliminates the glycosylation signal in this activator protein. One explanation for the deficiency of saposin B in this disease is that the mutation may increase the degradation of saposin B by exposing a potential proteolytic cleavage site (arginine) two amino acids to the amino-terminal side of the glycosylation site when the carbohydrate side chain is absent.
Amino Acid Sequence↗
Distribution of saposin proteins (sphingolipid activator proteins) in lysosomal storage and other diseases.
Saposins (A, B, C, and D) are small glycoproteins required for the hydrolysis of sphingolipids by specific lysosomal hydrolases. Concentrations of these saposins in brain, liver, and spleen from normal humans as well as patients with lysosomal storage disease were determined. A quantitative HPLC method was used for saposin A, C, and D and a stimulation assay was used for saposin B. In normal tissues, saposin D was the most abundant of the four saposins. Massive accumulations of saposins, especially saposin A (about 80-fold increase over normal), were found in brain of patients with Tay-Sachs disease or infantile Sandhoff disease. In spleen of adult patients with Gaucher disease, saposin A and D accumulations (60- and 17-fold, respectively, over normal) were higher than that of saposin C (about 16-fold over normal). Similar massive accumulations of saposins A and D were found in liver of patients with fucosidosis (about 70- and 20-fold, respectively, over normal). Saposin D was the primary saposin stored in the liver of a patient with Niemann-Pick disease (about 30-fold over normal). Moderate increases of saposins B and D were found in a patient with GM1 gangliosidosis. Normal or near normal levels of all saposins were found in patients with Krabbe disease, metachromatic leukodystrophy, Fabry disease, adrenoleukodystrophy, I-cell disease, mucopolysaccharidosis types 2 and 3B, or Jansky-Bielschowsky disease. The implications of the storage of saposins in these diseases are discussed.
Adult↗
Isolation, characterization, and mapping of a human acid beta-galactosidase cDNA.
A lambda gt11 human testicular cDNA library was screened with degenerate oligonucleotide probe mixtures based on amino acid sequence data generated from cyanogen bromide fragments and tryptic fragments of purified human beta-galactosidase. Six positive clones were identified after screening 2 x 10(6) plaques. The sequences of these six clones were determined and found to be derived from two different cDNAs. The sequence of the longest of these cDNAs is nearly identical to that recently determined by Oshima et al. (1988). It codes for a 76-kD protein and all 11 peptides that were generated from the purified enzyme. The second clone is shorter by 393 bp in the central portion of the coding region. Analysis by Northern blotting revealed the presence of a single mRNA species of 2.45 kb in lymphoblasts and testicular tissue. It is deduced from the amino acid sequence data that proteolytic processing of the precursor form of beta-galactosidase must occur by cleavage in the carboxy-terminal portion of the polypeptide perhaps around amino acid 530 at a uniquely hydrophilic sequence. Using a probe generated from the 3' region of the cDNA, we have mapped the locus coding for human beta-galactosidase to chromosome 3p21-3pter.
Amino Acid Sequence↗
Bone marrow transplantation in canine GM1 gangliosidosis.
Allogeneic bone marrow transplantation was carried out in an 81-day-old Portuguese water dog with GM1 gangliosidosis using a DLA identical sibling as donor. Engraftment was complete and beta-galactosidase activity in leukocytes of the transplanted dog were similar to those in the donor. Over the next 2.5 months neurological deterioration in the transplanted dog was similar to that in untreated dogs with GM1 gangliosidosis. Cerebral ganglioside GM1 concentrations were not diminished by bone marrow transplantation and cerebral beta-galactosidase activity was negligible. We conclude that allogeneic bone marrow transplantation early in life is ineffective in canine GM1 gangliosidosis.
Animals↗