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Biomedical subjects

R Anwar

Publications and source records attributed to R Anwar.

At least 19 recordsLinked to original sources
PubMed2003

CTLA-4 (CD152) expression in peripheral blood T cells in Kawasaki disease.

Kawasaki disease (KD) is an acute febrile illness of early childhood caused by vasculitis. Whether or not peripheral blood T cells are activated in acute KD remains uncertain, as some reports have presented evidence of peripheral blood T cell activation, whereas others suggest that the level of peripheral blood T cell activation is low during acute KD. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4, CD152) is a surface molecule of activated T cells. We therefore investigated intracellular CTLA-4 expression in the peripheral blood T cells of patients with acute KD as a marker of T cell activation. We collected blood samples from 20 patients with KD and six with Epstein-Barr virus infectious mononucleosis (EBV-IM) who were admitted to our hospital, as well as 13 healthy children. We determined the intracellular expression of CTLA-4 in T cells by flow cytometry. We demonstrated that the intracellular expression of CTLA-4 is up-regulated in peripheral blood CD3+ T cells, CD4+ T cells and CD8+ T cells at the early part of the acute stage in KD. However, the mean percentages of intracellular T cells expressing CTLA-4 in EBV-IM patients were about fourfold higher than those in T cells from patients with acute KD. Our results suggested that the level of activation of peripheral blood T cells is very low during acute KD.

Abatacept↗
PubMed2001

Identification of a new Leu354Pro mutation responsible for factor XIII deficiency.

We report a new homozygous CTG-->CCG (Leu-->Pro) mutation at codon 354 in the factor XIIIA gene of a patient suffering from FXIII deficiency. Leu354 lies in a pocket within the core domain of the FXIIIA molecule, with its side chain pointing into the structure of the barrel 1 domain. Replacement of leucine with a proline residue gives rise to steric hindrance between the proline ring and the surrounding residues, and rearrangement of these residues would be necessary for proline to be accommodated at this position. Using PCR-RFLP, we have demonstrated the absence of this mutation from 220 normal alleles. Together, these data suggest that Leu354Pro is likely to be the disease-causing mutation in this factor XIII deficient family.

Adult↗
PubMed2000

Genetic screening in a large family with juvenile onset primary open angle glaucoma.

AIMS: A number of genetic loci have been implicated in the pathogenesis of primary open angle glaucoma (POAG). The aim of this study was to identify the genetic cause of POAG in a large Scottish family and, if possible, offer genetic screening and advice to family members. METHODS: Family members were examined to determine their disease status. Base excision sequence scanning was carried out in order to test for the presence of a POAG causing mutation at known genetic loci. Direct DNA sequencing was performed in order to determine the mutation sequence. RESULTS: All family members of known affected disease status and two family members of unknown disease status were found to have a mutation in the TIGR gene. The mutation resulted in the substitution of a glycine residue with an arginine residue at codon 252 (Gly252Arg). No other sequence variations were present in any members of the family. CONCLUSION: The Gly252Arg mutation in the TIGR gene results in the development of POAG in this family. It was possible to identify younger, currently unaffected, members of the family who carry the mutation and who are therefore at a very high risk of developing POAG themselves. This is the first demonstration that Gly252Arg can be a disease causing mutation rather than a benign polymorphism. The possible pathogenic mechanisms and wider implications of the mutation are considered.

Adolescent↗
PubMed2000

Factor XIII deficiency causing mutation, Ser295Arg, in exon 7 of the factor XIIIA gene.

Inherited factor XIII (FXIII) deficiency is an autosomal recessive disorder which results in a serious bleeding diathesis, problems with wound healing and a very high risk of recurrent miscarriage in deficient females. We have analysed the molecular basis of factor XIII deficiency in two patients and their parents, who originate from the North of Pakistan. Four sequence changes were identified: an AGC-->AGG (Ser-->Arg) FXIII deficiency-causing mutation in codon 295; G-->A at position -246 upstream of exon 1; T-->C and C-->T at positions -23 and -24, respectively, in intron 9. Using molecular modelling we predict that the Ser295Arg mutation would prevent the FXIIIA molecule from folding correctly and thus result in an unstable FXIIIA mutant polypeptide. The sequence changes -246G-->A, -23T-->C and -24C-->T are normal polymorphisms. RT-PCR analysis demonstrates that the intronic sequence changes do not appear to affect the accuracy of FXIIIA RNA processing.

Child↗
PubMed1999

Genotype/phenotype correlations for coagulation factor XIII: specific normal polymorphisms are associated with high or low factor XIII specific activity.

Factor XIII is a transglutaminase essential for normal hemostasis. We have studied the plasma FXIII levels and FXIII activity in 71 individuals and found these to be normally distributed. FXIII specific activity is also normally distributed. However, we show that FXIII activity is not directly dependent on FXIII levels, and individuals with low FXIII levels may have high FXIII activity and vice versa. We have determined the FXIIIA genotype in these individuals to assess whether the variation observed in FXIII specific activity is dependent on specific polymorphisms in the FXIIIA gene. Our data show that the Leu34 and Leu564 variants give rise to increased FXIII specific activity, while the Phe204 variant results in lower FXIII specific activity. We also report preliminary evidence that the Phe204 polymorphism may be associated with recurrent miscarriage. Overall, we have identified 23 unique FXIIIA genotypes. Certain specific FXIIIA genotypes consistently give rise to high, low, or median FXIII specific activity levels, while others appear to have little or no consistent influence on the FXIII phenotype. These genotype to phenotype relationships are discussed in light of the growing interest in the role of FXIII in clinical problems involving an increased thrombotic tendency.

Abortion, Habitual↗
PubMed1998

Identification of a large deletion, spanning exons 4 to 11 of the human factor XIIIA gene, in a factor XIII-deficient family.

Inherited deficiency of factor XIIIA subunit (FXIIIA) is an autosomal recessive disorder that is characterized by a life-long bleeding tendency and complications in wound healing. Molecular genetic studies have shown the deficiency can be due to small sequence changes within the FXIIIA gene, such as point mutations or microdeletions. On molecular analysis of the FXIIIA gene in an FXIII-deficient patient, of United Kingdom origin, we identified a putative homozygous missense mutation, Arg408Gln. However, the father of this patient is homozygous normal for arginine at codon 408. Having proved paternity in this pedigree by microsatellite analysis, we examined the FXIIIA RNA of the patient by reverse transcriptase-polymerase chain reaction and found the paternal allele to lack exons 4 through 11 inclusive. Hence, a huge deletion extending from intron 3 to intron 11 and the Arg408Gln mutation are jointly responsible for FXIIIA deficiency in this family. This is the first finding of such a large deletion in the FXIIIA gene.

Adult↗
PubMed1998

PAX 6 is normal in most cases of Peters' anomaly.

Mutations in the PAX 6 gene are known to cause many cases of inherited and sporadic aniridia. Although embryologically similar to aniridia, the cause of Peters' anomaly has received far less attention. Two reports have been published demonstrating mutations in the PAX 6 gene in Peters' anomaly. We have analysed the PAX 6 gene in 15 individuals with Peters' anomaly (7 familial, 8 sporadic). This is the largest cohort of Peters' anomaly described. The PAX 6 gene was screened using a combination of single-strand conformational polymorphism gel electrophoresis and direct sequencing. No mutations were found in the coding region of the PAX 6 gene. We feel that Peters' anomaly is a heterogeneous condition and that for the majority of cases PAX 6 is not the 'Peters' anomaly gene'.

Anterior Eye Segment↗
PubMed1998

Splicing and missense mutations in the human FXIIIA gene causing FXIII deficiency: effects of these mutations on FXIIIA RNA processing and protein structure.

We have investigated the molecular basis of factor XIII (FXIII) deficiency in a family from the north-west region of the U.K. and identified two sequence changes in the FXIII subunit A (FXIIIA) gene. We report a novel Asn to Lys mutation at codon 541, and a g-->a mutation at the intron 5/exon 6 splice junction in the FXIIIA gene. The splicing mutation results in two abnormal FXIIIA transcripts. The Asn541 residue is important for stabilizing an external fold in the FXIIIA barrel 1 domain. The Asn541Lys mutation is expected to result in inappropriate folding and therefore an unstable FXIIIA molecule.

Adult↗
PubMed1998

New splicing mutations in the human factor XIIIA gene, each producing multiple mutant transcripts of varying abundance.

Coagulation factor XIII, a transglutaminase which stabilises blood clots by covalently cross-linking fibrin, is essential for normal haemostasis. FXIII deficiency results in a life-long bleeding disorder with added complications in wound healing and tissue repair. Sequence changes in the human FXIIIA gene, largely missense mutations, are primarily responsible for inherited FXIII deficiency. We have carried out molecular analysis of the FXIIIA gene in two unrelated FXIII deficient individuals and identified three splice site mutations; a g-->a at the exon 6 acceptor splice site, a g-->a at the exon 7 donor splice site and a coding sequence T-->G at the exon 8 donor splice site. We have also examined the FXIIIA mRNA in these patients and find that each mutation gives rise to multiple transcripts which vary in their relative abundance. The precise molecular mechanisms which result in these variant transcripts, and their relative abundance in our FXIII deficient patients, are discussed.

Adolescent↗
PubMed1997

Male pseudohermaphroditism resulting from a novel mutation in the human steroid 5 alpha-reductase type 2 gene (SRD5A2).

The enzyme steroid 5 alpha-reductase, via NADPH, catalyses the conversion of testosterone to dihydrotestosterone, which is required for the embryonic differentiation of the external male genitalia and the prostate. An impairment of this reaction causes a form of male pseudohermaphroditism in which genetic males differentiate predominantly as phenotypic females. Molecular analysis of the 5 alpha-reductase type 2 gene in a patient with confirmed biochemical 5 alpha-reductase deficiency has resulted in the identification of a novel mutation, GAA to AAA, at codon 200. This mutation produces an amino acid change from glutamic acid to lysine, and may affect the ability of the enzyme to bind its co-factor.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1997

A new mutation in the human lipoprotein lipase gene causing familial hyperchylomicronaemia.

Lipoprotein lipase plays a major role in the regulation of lipid metabolism. The enzyme acts to hydrolyse triglycerides, providing free fatty acids for energy generation or storage, thus affecting the maturation of circulating lipoproteins. Biochemical and molecular analyses were performed on two siblings of consanguineous Pakistani origin, presenting with hyperchylomicronaemia, which revealed that the disorder resulted from lipoprotein lipase deficiency. Molecular analysis of the lipoprotein lipase gene has revealed a novel homozygous mutation, leucine to proline at amino acid residue 303, within the amino terminal domain of the protein.

Child↗
PubMed1996

Molecular analysis of the presenilin 1 (S182) gene in "sporadic" cases of Alzheimer's disease: identification and characterisation of unusual splice variants.

Mutations of the presenilin 1 (PS-1) gene at the Alzheimer's disease (AD) FAD3 locus on chromosome 14q24.3 are responsible for the majority of familial early-onset AD. As genes responsible for familial forms of AD are obvious candidates for further investigation in "sporadic" disease, we performed a molecular analysis of PS-1 transcripts extracted from brain tissues of a series of histologically confirmed cases of "sporadic" AD (n=10) and also from histologically "normal" (non-Alzheimer) age-matched brain controls (n=5). No sequence changes in the PS-1 coding sequence were detected after analysis by reverse transcription-PCR. This suggests that the frequency of mutations in the PS-1 (S182) coding region in "sporadic" Alzheimer's disease in very low. However, we demonstrated that the PS-1 gene is highly variably spliced. One splice variant involves the 5' untranslated region of the PS-1 gene only and hence encodes for normal PS-1. Six further splice variants involve coding regions of the PS-1 gene and result in truncated proteins lacking specific transmembrane domains. Most of these variants do not coincide with recognized sites of introns in the PS-1 gene. One of these variants, resulting in the loss of transmembrane domain TM-VII, was found only in an AD patient.

Alternative Splicing↗
PubMed1995

Molecular basis of inherited factor XIII deficiency: identification of multiple mutations provides insights into protein function.

Factor XIII (FXIII) is a zymogen essential for normal haemostasis. In inherited FXIII deficiency the majority of cases show absence of the FXIIIa subunit. Molecular analysis of PCR-amplified FXIIIa subunit exonic regions, and of RT-PCR amplified cDNA from six patients with FXIIIa subunit deficiency, from five unrelated families, has revealed 10 sequence changes: three mutations resulting in abnormal splicing of pre-mRNA, one nonsense mutation, one deletion/insertion change, three point mutations producing Val34Leu, Asn60Lys and Arg408Gln changes, and two silent mutations. In three families the patients are homozygous for a specific deficiency causing mutation, and patients from the remaining two families are compound heterozygotes. Understanding the molecular pathology of the disorder provides insights into the structure-function relationships of the various domains within the FXIII protein. From a clinical point of view, it enables direct diagnosis at the DNA level and may aid the development of FXIII analogues to promote wound healing.

Base Sequence↗