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H S Scott

Publications and source records attributed to H S Scott.

At least 55 records · Page 3Linked to original sources
PubMed1998

Loss of LKB1 kinase activity in Peutz-Jeghers syndrome, and evidence for allelic and locus heterogeneity.

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disease characterized by mucocutaneous pigmentation and hamartomatous polyps. There is an increased risk of benign and malignant tumors in the gastrointestinal tract and in extraintestinal tissues. One PJS locus has been mapped to chromosome 19p13.3; a second locus is suspected on chromosome 19q13.4 in a minority of families. The PJS gene on 19p13.3 has recently been cloned, and it encodes the serine/threonine kinase LKB1. The gene, which is ubiquitously expressed, is composed of 10 exons spanning 23 kb. Several LKB1 mutations have been reported in heterozygosity in PJS patients. In this study, we screened for LKB1 mutations in nine PJS families of American, Spanish, Portuguese, French, Turkish, and Indian origin and detected seven novel mutations. These included two frameshift mutations, one four-amino-acid deletion, two amino-acid substitutions, and two splicing errors. Expression of mutant LKB1 proteins (K78I, D176N, W308C, and L67P) and assessment of their autophosphorylation activity revealed a loss of the kinase activity in all of these mutants. These results provide direct evidence that the elimination of the kinase activity of LKB1 is probably responsible for the development of the PJS phenotypes. In two Indian families, we failed to detect any LKB1 mutation; in one of these families, we previously had detected linkage to markers on 19q13.3-4, which suggests locus heterogeneity of PJS. The elucidation of the molecular etiology of PJS and the positional cloning of the second potential PJS gene will further elucidate the involvement of kinases/phosphatases in the development of cancer-predisposing syndromes.

AMP-Activated Protein Kinase Kinases↗
PubMed1998

Genomic structure, sequence, and refined mapping of the human intersectin gene (ITSN), which encompasses 250 kb on chromosome 21q22.1-->q22.2.

The ubiquitously expressed and brain-specific human intersectin (ITSN) isoforms are scaffold proteins probably involved in general endocytosis and synaptic vesicle recycling, respectively. Here, analysis of 21q22.1-->q22.2 genomic sequence revealed that ITSN consists of 41 exons spanning approximately 250 kb and maps between GART and D21S325. The probable function of the ITSN isoforms and mapping position of ITSN suggest that disproportionate expression of this gene may be implicated in the phenotypic characteristics of Down syndrome.

Adaptor Proteins, Vesicular Transport↗
PubMed1998

Common mutations in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy patients of different origins.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED; OMIM *240300, also called APS 1,) is a rare autosomal recessive disorder that is more frequent in certain isolated populations. It is generally characterized by two of the three major clinical symptoms that may be present, Addison's disease and/or hypoparathyroidism and/or chronic mucocutaneous candidiasis. Patients may also have a number of other clinical symptoms including chronic gastritis, gonadal failure, and rarely, autoimmune thyroid disease and insulin-dependent diabetes mellitus. We and others have recently identified the gene for APECED, which we termed AIRE (for autoimmune regulator). AIRE is expressed in thymus, lymph nodes, and fetal liver and encodes a protein containing motifs suggestive of a transcriptional regulator, including two zinc finger motifs (PHD finger), a proline-rich region, and three LXXLL motifs. Six mutations, in cluding R257X, the predominant Finnish APECED allele, have been defined. R257X was also observed in non-Finnish APECED patients occurring on different chromosomal haplotypes suggesting different mutational origins. Here we present mutation analyses in an extended series of patients, mainly of Northern Italian origin. We have detected 12 polymorphisms, including one amino acid substitution, and two additional mutations, R203X and X546C, in addition to the previously described mutations, R257X, 1096-1097insCCTG, and a 13-bp deletion (1094-1106del). R257X was also the common mutation in the Northern Italian patients (10 of 18 alleles), and 1094-1106del accounted for 5 of 18 Northern Italian alleles. Both R257X and 1094-1106del were both observed in patients of four different geo-ethnic origins, and both were associated with multiple different haplotypes using closely flanking polymorphic markers showing likely multiple mutation events (six and four, respectively). The identification of common AIRE mutations in different APECED patient groups will facilitate its genetic diagnosis. In addition, the polymorphisms presented provide the tools for investigation of the involvement of AIRE in other autoimmune diseases, particularly those affecting the endocrine system.

Female↗
PubMed1997

Dodecamer repeat expansion in cystatin B gene in progressive myoclonus epilepsy.

Progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1; MIM 254800) is an autosomal recessive disorder with onset between 6 and 13 years followed by variable progression to mental deterioration and cerebellar ataxia. It is a rare disorder but more common in Finland (1 in 20,000) and the western Mediterranean. Two point mutations in the cysteine proteinase inhibitor gene cystatin B (CSTB), proved that this gene is responsible for EPM1 (ref. 3). An extensive search in the CSTB gene revealed mutations accounting only for 14% of the 58 unrelated EPM1 alleles studied. Here we report that the majority of EPM1 alleles contain expansions of a dodecamer (12-mer) repeat located about 70 nucleotides upstream of the transcription start site nearest to the 5' end of the CSTB gene. Normal alleles contain 2 or 3 copies of this repeat whereas mutant alleles contain more than 60 such repeats and have reduced levels of CSTB messenger RNA in blood but not in cell lines. 'Premutation' CSTB alleles with 12-17 repeats show marked instability when transmitted to offspring.

Alleles↗
PubMed1997

Cloning of a human RNA editing deaminase (ADARB1) of glutamate receptors that maps to chromosome 21q22.3.

RED1 is a double-stranded RNA-specific editase characterized in the rat and is implicated in the editing of glutamate receptor subunit pre-mRNAs, particularly in the brain. Starting from human ESTs homologous to the rat RED1 sequence, we have characterized two forms of human RED1 cDNAs, one form coding for a putative peptide of 701 amino acids (similar to the shorter of two rat mRNAs) and a long form coding for a putative protein of 741 amino acids, the extra 120 bp of which are homologous to an AluJ sequence. Both forms were observed at approximately equal levels in cDNA clones and in seven different human tissues tested by RT-PCR. The human and rat short isoforms have 95 and 85% sequence identity at the amino acid and nucleotide levels, respectively. The human sequence (designated ADARB1 by the HGMW Nomenclature Committee) contains two double-stranded RNA-binding domains and a deaminase domain implicated in its editing action. Northern blot analysis detected two transcripts of 8.8 and 4.2 kb strongly expressed in brain and in many human adult and fetal tissues. ADARB1 maps to human chromosome 21q22.3, a region to which several genetic disorders map, including one form of bipolar affective disorder. Recently it was shown that heterozygous mice harboring an editing-incompetent glutamate receptor B allele have early onset fatal epilepsy. Since glutamate receptor channels are essential elements in synaptic function and plasticity and mediate pathology in many neurological disorders, and since RED1 is central in glutamate receptor channel control, ADARB1 is a candidate gene for diseases with neurological symptoms, such as bipolar affective disorder and epilepsy.

Adenosine Deaminase↗
PubMed1997

Isolation of a human gene (HES1) with homology to an Escherichia coli and a zebrafish protein that maps to chromosome 21q22.3.

Exon trapping was performed with chromosome 21 cosmids to identify those that may be involved in the pathogenesis of Down syndrome, or several of the genetic diseases that map to chromosome 21. BLASTX analysis revealed two exons with significant homology to a zebrafish protein (ES1) and an Escherichia coli protein (sigma cross-reacting protein 27A), both of unknown function. The exons also showed identity with several expressed sequence tags (ESTs). Sequences from all ESTs derived from this gene and reverse transcription-polymerase chain reaction (RT-PCR) analysis were used to determine the full cDNA sequence, which corresponded to an mRNA of 1.7 kb with an open reading frame of 268 amino acids. The mRNA from this gene, termed HES1, is ubiquitously expressed, but strongly so in heart and skeletal muscle. Potential mitochondrial targeting signals were found in both the human and zebrafish proteins, consistent with the high expression levels in muscle tissues. The strong homology between the E. coli, zebrafish and HES1 proteins suggests an important biological role. Hybridization of RT-PCR products to a cosmid contig in chromosome 21q22.3, mapped HES1 just proximal to D21S25, a critical mapping region for several genetic diseases. Given the mapping position, this gene is a candidate for involvement in these disorders, including autoimmune polyglandular disease type I and the autosomal nonsyndromic deafness loci, DFNB8 and DFNB10. In addition, the initial method of EST identification for gene isolation presented here is valid for many genes and can be used to obtain initial sequence contigs without cloning or library screening.

Amino Acid Sequence↗
PubMed1997

Localization of a novel human RNA-editing deaminase (hRED2 or ADARB2) to chromosome 10p15.

RNA-editing deaminase 2 (RED2; ADARB2) is a newly identified potential double-stranded RNA adenosine deaminase. It is the third member of this family, which includes DRADA and RED1. Genes of this family are candidates for involvement in neurological diseases such as epilepsy, because of their expression patterns and described functions. All three described genes are well expressed in brain, and DRADA and RED1 have been shown to play a role in the editing of mRNAs coding for glutamate receptor subunits in vitro, thereby changing the properties of these channels, which are the main excitatory neurotransmitter receptors in brain. Here we report the mapping of the human RED2 (hRED2; ADARB2) gene. Using the sequence of rat RED2, we identified a homologous human expressed sequence tag, and subsequently designed primers in the 3' untranslated region of the hRED2 transcript to perform polymerase chain reaction amplification on two somatic cell hybrid mapping panels. This allowed us to localize hRED2 on chromosome 10p15; until now, no genetic diseases have been mapped in this region or in the syntenic mouse chromosomal region that may involve RED2.

Adenosine Deaminase↗
PubMed1997

Mutations among Italian mucopolysaccharidosis type I patients.

A group of 27 Italian patients was screened for alpha-L-iduronidase mucopolysaccharidosis type I mutations. Mutations were found in 18 patients, with 28 alleles identified. The two most common mutations in northern Europeans (W402X and Q70X) accounted for 11% and 13% of the alleles, respectively. The R89Q mutation, uncommon in Europeans, was found only in one patient, accounting for 1 of 54 alleles (1.9%). The other mutations, P533R, A327P and G51D, accounted for 11%, 5.6% and 9.3% of the total alleles, respectively. Interestingly, the high frequency of the P533R mutation seems to be confined to Sicily and is higher than the 3% reported in a British/Australian study.

Adolescent↗
PubMed1997

Positional cloning of the APECED gene.

Autoimmune polyglandular syndrome type I (APS 1, also called APECED) is an autosomal-recessive disorder that maps to human chromosome 21q22.3 between markers D21S49 and D21S171 by linkage studies. We have isolated a novel gene from this region, AIRE (autoimmune regulator), which encodes a protein containing motifs suggestive of a transcription factor including two zinc-finger (PHD-finger) motifs, a proline-rich region and three LXXLL motifs. Two mutations, a C-->T substitution that changes the Arg 257 (CGA) to a stop codon (TGA) and an A-->G substitution that changes the Lys 83 (AAG) to a Glu codon (GAG), were found in this novel gene in Swiss and Finnish APECED patients. The Arg257stop (R257X) is the predominant mutation in Finnish APECED patients, accounting for 10/12 alleles studied. These results indicate that this gene is responsible for the pathogenesis of APECED. The identification of the gene defective in APECED should facilitate the genetic diagnosis and potential treatment of the disease and further enhance our general understanding of the mechanisms underlying autoimmune diseases.

Amino Acid Sequence↗
PubMed1997

Molecular defects in Sanfilippo syndrome type A.

Sanfilippo A syndrome (mucopolysaccharidosis type IIIA, MPS-IIIA) is an autosomal recessive neurodegenerative disorder due to an enzymatic defect of the lysosomal enzyme sulphamidase (EC 3.10.1.1) required for the degradation of heparan sulphate. In this study, molecular defects in the sulphamidase gene of MPS-IIIA patients were investigated in a group of 10 patients of Australian and American origin. The entire coding region of the sulphamidase gene was RT-PCR amplified and one polymorphism (R456H), four novel mutations (S66W, R245H, E447K, 1307 del 9) and one previously described mutation (1284 del 11) were identified by direct PCR sequencing. R245H was present in six patients including one severely affected homozygote. In three of the other patients with R245H, second mutant alleles were identified as S66W, 1284 del 11 and E447K, respectively. S66W was also detected in another patient where the other mutant allele remains undefined. In addition, 1307 del 9 was also detected in a patient with the other mutant allele remaining undefined. Allele specific oligonucleotide hybridisation was used to determine the incidence of these in a population of 26 MPS-IIIA patients (Australian and American) and 60 normal controls (Australian). R245H represented 27% (14/52 alleles) in this total patient population, while the other three changes ranged from 1.9 to 9.6% (1-5 of 52 alleles). The sequence variant, R456H, was shown to be polymorphic as it was present in 55% of normal and 38% of patient alleles. The total combined incidence of these five is 46% of alleles. This is the first study of the molecular defects in MPS-IIIA patients and will greatly assist the development of molecular analysis for MPS-IIIA patients and studies concerned with genotype to phenotype relationships.

Age of Onset↗
PubMed1997

Cloning of two human homologs of the Drosophila single-minded gene SIM1 on chromosome 6q and SIM2 on 21q within the Down syndrome chromosomal region.

As part of our effort to clone genes of human chromosome 21 that may contribute to Down syndrome, we have previously isolated four exons with homology to Drosophila single-minded (sim) gene, which encodes a transcription factor that is a master regulator of fruit fly neurogenesis. These exons were used to clone and characterize two human homologs of the Drosophila sim gene, SIM1 and SIM2, which map to chromosomes 6q16.3-q21 and 21q22.2, respectively; SIM2 maps within the so-called Down syndrome chromosomal region. Recently, two mouse homologs, Sim1 and Sim2, also have been identified. There is a high level of homology among human, mouse, and Drosophila sim genes in their amino-terminal half where the conserved bHLH, PAS1, PAS2, and HST domains are present. In contrast, the carboxy-terminal parts are only homologous between SIM1 and Sim1 and SIM2 and Sim2. Two isoforms (SIM2 and SIM2s) of human SIM2 have been detected that differ in their 3' ends. Northern blot analysis revealed one mRNA SIM1 species of approximately 9.5 kb and four different mRNA SIM2 species of 2.7, 3, 4.4, and 6 kb in human fetal kidney. The function of both human SIM1 and SIM2 is unknown. However, three copies of SIM2 may contribute to some specific Down syndrome phenotypes because of (1) mapping position, (2) potential function as transcriptional repressor, (3) likely dimerization with other transcription factors, (4) the temporal and spatial expression pattern of mouse Sim2, and (5) the potentially analogous role of human SIM2 to that of Drosophila sim during neurogenesis.

Amino Acid Sequence↗
PubMed1996

Structure and sequence of the human sulphamidase gene.

Sanfilippo A syndrome (MPS-IIIA) is a mucopolysaccharide lysosomal storage disorder caused by a deficiency in the lysosomal enzyme, sulphamidase (EC 3.10.1.1), which is required for the degradation of heparan sulphate. A genomic clone containing the entire sulphamidase gene was isolated from a chromosome 17-specific gridded cosmid library. The structure of the gene and the sequence of the exon/intron boundaries and the 5' promoter region were determined. The sulphamidase gene is split into 8 exons spanning approximately 11 kb.

Base Sequence↗
PubMed1996

Cloning and expression of the gene involved in Sanfilippo B syndrome (mucopolysaccharidosis III B).

Sanfilippo B syndrome is caused by a deficiency of alpha-N-acetylglucosaminidase, a lysosomal enzyme involved in the degradation of heparan sulphate. Accumulation of the substrate in lysosomes results in degeneration of the central nervous system with progressive dementia often combined with hyperactivity and aggressive behaviour. In order to clone the deficient gene, we purified the enzyme from human placenta and obtained amino acid sequence information. Alignment of one of the CNBr generated internal peptides to sequence from the database revealed the chromosomal location of the gene in the 5' upstream flanking region of the gene for 17-beta-hydroxysteroid-dehydrogenase at 17q21.1. The available DNA sequence was used to clone the cDNA coding for alpha-N-acetylglucosaminidase and analyse its gene structure. The gene is fully contained in the 5' upstream flanking region of the gene for 17-beta-hydroxysteroid-dehydrogenase and interrupted by five introns. The cDNA clone has a length of 2575 bp and encodes a protein of 743 amino acids. Chinese hamster ovary cells transfected with the cDNA construct show alpha-N-acetylglucosaminidase activity about 17-fold over background. This will allow correction studies with NAG deficient Sanfilippo B cell lines and facilitate the development of enzyme replacement therapy for these patients.

Acetylglucosaminidase↗
PubMed1995

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.

Codon, Nonsense↗
PubMed1995

Cloning of the sulphamidase gene and identification of mutations in Sanfilippo A syndrome.

Sanfilippo A syndrome is one of four recognised Sanfilippo sub-types (A, B, C and D) that result from deficiencies of different enzymes involved in the lysosomal degradation of heparan sulphate; patients suffer from severe neurological disorders. The Sanfilippo syndrome sub-types are also known as mucopolysaccharidosis (MPS) type III (MPS-IIIA, B, C and D), and are part of the large group of lysosomal storage disorders. Each of the MPS-III types is inherited as an autosomal recessive disorder with considerable variation in severity of clinical phenotype. The incidence of Sanfilippo syndrome has been estimated at 1:24,000 in The Netherlands with MPS IIIA (MIM #252900) the most common. MPS-IIIA is the predominant MPS-III in the United Kingdom, and has a similar high incidence to that found in The Netherlands (E. Wraith, personal communication). There is a particularly high incidence of a clinically severe form of MPS-IIIA in the Cayman Islands with a carrier frequency of 0.1 (ref. 4). Due to the mild somatic disease compared to other MPS disorders there is difficulty in diagnosing mild cases of MPS-III, hence Sanfilippo syndrome may be underdiagnosed, especially in patients with mild mental retardation. Here, we report the isolation, sequence and expression of cDNA clones encoding the enzyme sulphamidase (EC 3.10.1.1). In addition, we report the chromosomal localisation of the sulphamidase gene as being 17q25.3. An 11-bp deletion, present in sulphamidase cDNA from two unrelated Sanfilippo A patients, is described.

Amino Acid Sequence↗
PubMed1994

Mutation analysis of 19 North American mucopolysaccharidosis type I patients: identification of two additional frequent mutations.

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive genetic disorder caused by deficiency of the lysosomal glycosidase alpha-L-iduronidase. Patients with this disorder present with varied clinical phenotypes ranging from early severe onset of disease and death in early childhood to mild manifestations compatible with adult life. An understanding of the molecular basis of iduronidase deficiency and its correlation to clinical phenotype will improve prognostic prediction at diagnosis, aid in genetic counselling of families, and provide a framework to more accurately assess experimental treatment protocols. We have used the approach of single-strand conformational polymorphism analysis and direct sequencing of the alpha-L-iduronidase gene in an attempt to define the molecular basis of iduronidase deficiency in affected individuals. An initial series of 19 patients representing 35 independently segregating mutant alleles were studied. In addition to five previously identified mutations (W402X, Q70X, E274X, H82P, and P533R) two novel mutations (A75T and 474-2a-->g) were found. These seven mutations account for 71% of the mutant alleles and 53% of the genotypes in this group of patients. Analysis of a larger independently ascertained group of 103 MPS I patients, mainly of Northern European origin, revealed that together the two novel mutations account for 7% of mutant alleles and are associated with severe clinical phenotypes. These mutations are the most frequent MPS I mutations detected so far after W402X and Q70X. With the definition of these two mutations, a clear picture of the molecular heterogeneity of MPS I is emerging.

Amino Acid Sequence↗
PubMed1994

Morquio A syndrome: cloning, sequence, and structure of the human N-acetylgalactosamine 6-sulfatase (GALNS) gene.

Deficiency of the lysosomal enzyme, N-acetylgalactosamine 6-sulfatase (GALNS;EC 3.1.6.4), results in the storage of the glycosaminoglycans, keratan sulfate and chondroitin 6-sulfate, which leads to the lysosomal storage disorder Morquio A syndrome. Four overlapping genomic clones derived from a chromosome 16-specific gridded cosmid library containing the entire GALNS gene were isolated. The structure of the gene and the sequence of the exon/intron boundaries and the 5' promoter region were determined. The GALNS gene is split into 14 exons spanning approximately 40 kb. The potential promoter for GALNS lacks a TATA box but contains GC box consensus sequences, consistent with its role as a housekeeping gene. The GALNS gene contains an Alu repeat in intron 5 and a VNTR-like sequence in intron 6.

Base Sequence↗