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Biomedical subjects

D S Millar

Publications and source records attributed to D S Millar.

At least 37 records · Page 2Linked to original sources
PubMed1995

Population differences in the frequency of the factor V Leiden variant among people with clinically symptomatic protein C deficiency.

The factor V Leiden variant, responsible for the phenomenon of activated protein C resistance, was found to be less frequent among British (0.06) and Swedish/Danish (0.15) protein C deficiency patients than previously reported in a Dutch study (0.19). In the Swedish population, a significantly increased frequency of the factor V Leiden allele was apparent in protein C deficiency patients as compared to healthy controls. However, this was not found in the British population. Coinheritance of the factor V Leiden variant is therefore unlikely to be the sole determinant of whether a person with protein C deficiency will come to clinical attention. Nevertheless, when patient data were analysed by type of protein C deficiency, it was noted that the frequency of the factor V Leiden variant was 2.8-fold higher in type II patients compared to type I patients. A possible explanation of this disparity is discussed.

Alleles↗
PubMed1994

Haemophilia A: database of nucleotide substitutions, deletions, insertions and rearrangements of the factor VIII gene, second edition.

A large number of different mutations in the factor VIII (F8) gene have been identified as a cause of haemophilia A. This compilation lists known single base-pair substitutions, deletions and insertions in the F8 gene and reviews the status of the inversional events which account for a substantial proportion of mutations causing severe haemophilia A.

Base Sequence↗
PubMed1994

Three novel missense mutations in the antithrombin III (AT3) gene causing recurrent venous thrombosis.

The polymerase chain reaction and direct sequencing were used to determine the nature of the mutations in the antithrombin III (AT3) gene in seven unrelated patients with familial antithrombin III (ATIII) deficiency and recurrent venous thrombosis. Three novel mutations were found, two associated with a type I deficiency state (Pro80-->Thr and His120-->Tyr) manifesting reduced synthesis of ATIII. The other novel lesion (Met251-->Ile) was associated with a dysfunctional ATIII protein (type II ATIII deficiency) and is predicted to interfere either with a heparin-induced conformational change in the ATIII molecule or with docking to thrombin. A novel polymorphism (Tyr158-->Cys) was also found to occur in several individuals of Scandinavian origin.

Amino Acid Sequence↗
PubMed1994

Haemophilia A: database of nucleotide substitutions, deletions, insertions and rearrangements of the factor VIII gene, second edition.

A large number of different mutations in the factor VIII (F8) gene have been identified as a cause of haemophilia A. This compilation lists known single base-pair substitutions, deletions and insertions in the F8 gene and reviews the status of the inversional events which account for a substantial proportion of mutations causing severe haemophilia A.

Base Sequence↗
PubMed1994

Screening for inversions in the factor VIII (F8) gene causing severe haemophilia A.

A total of 164 unrelated patients with severe haemophilia A were screened for partial inversions of the factor VIII (F8) gene resulting from recombination between the intronic F8A gene and one or other of two homologous upstream A gene sequences. Inversions were found in 69 (42%) patients. Most inversions (90%) involved the distal rather than the proximal A gene. This unique mutational mechanism is estimated to occur with a frequency of 7.2 x 10(-6) per gene per gamete per generation. Although two patients with an inversion possessed inhibitors (antibodies) against factor VIII, possession of inhibitors did not appear to be associated disproportionately with inversion-type mutations.

Blotting, Southern↗
PubMed1994

A homozygous deletion/insertion mutation in the protein C (PROC) gene causing neonatal Purpura fulminans: prenatal diagnosis in an at-risk pregnancy.

A novel homozygous mutation in the protein C (PROC) gene was detected in an individual with severe type I protein C deficiency who presented with neonatal Purpura fulminans. The deletion/insertion mutation found [3351del4, 3350insA] resulted in an Asn102-->Lys substitution and the removal of codon Gly103. First trimester prenatal diagnosis was performed in a subsequent pregnancy by chorionic villus sampling and PCR/direct sequencing; the foetus was shown to be heterozygous for the lesion. This diagnosis was confirmed phenotypically after the birth of a clinically healthy child.

Base Sequence↗
PubMed1993

A novel point mutation (Val 297-->Met) in the serine proteinase domain of protein C in a patient with both venous and arterial thromboembolic disease.

A novel heterozygous GTG-->ATG (Val 297-->Met) substitution was detected in an individual with probable inherited protein C deficiency and both venous and arterial thrombotic disease. The lesion occurs in a highly conserved residue within the serine protease domain. In a molecular model of protein C, Met 297 makes unfavourable interactions with neighbouring residues suggesting that the mutant protein is unable to adopt a stable/functional conformation.

Adult↗
PubMed1993

A novel dysfunctional protein C (protein C Padua 2) associated with a thrombotic tendency: substitution of Cys for Arg-1 results in a strongly reduced affinity for binding of Ca++.

A dysfunctional protein C (PC) molecule (Protein C Padua 2) was found in a 40-year-old man presenting with recurrent deep vein thrombosis/pulmonary embolism and a family history of thrombotic disease. The patient exhibited a normal PC antigen level, normal chromogenic activity (using Protac as PC activator) but markedly reduced coagulometric activity. After adsorption of patient plasma onto Al(OH)3, between 30% and 45% PC antigen/chromogenic activity but no coagulometric activity was detectable in the supernatant. The dysfunctional molecule exhibited reduced affinity for a Ca++ dependent anti-protein C monoclonal antibody as detected by specific ELISA assay. Immunoblotting experiments showed that PC Padua 2 had an increased MW (95 kD v 65 kD for normal PC). The lesion responsible was determined by PCR/direct sequencing to be a heterozygous CGT/TGT transition in exon 3 of the protein C gene resulting in the substitution of Arg by Cys at residue--1 in the pro-peptide leader sequence. The presence of a high MW PC was consistent with the fact that (part of) the propeptide (at least Cys-1) still was attached to the protein C molecule. This finding could also explain the strongly reduced affinity of PC Padua 2 for the Ca++ dependent anti-protein C monoclonals.

Adult↗
PubMed1992

A genomic sequencing protocol that yields a positive display of 5-methylcytosine residues in individual DNA strands.

The modulation of DNA-protein interactions by methylation of protein-binding sites in DNA and the occurrence in genomic imprinting, X chromosome inactivation, and fragile X syndrome of different methylation patterns in DNA of different chromosomal origin have underlined the need to establish methylation patterns in individual strands of particular genomic sequences. We report a genomic sequencing method that provides positive identification of 5-methylcytosine residues and yields strand-specific sequences of individual molecules in genomic DNA. The method utilizes bisulfite-induced modification of genomic DNA, under conditions whereby cytosine is converted to uracil, but 5-methylcytosine remains nonreactive. The sequence under investigation is then amplified by PCR with two sets of strand-specific primers to yield a pair of fragments, one from each strand, in which all uracil and thymine residues have been amplified as thymine and only 5-methylcytosine residues have been amplified as cytosine. The PCR products can be sequenced directly to provide a strand-specific average sequence for the population of molecules or can be cloned and sequenced to provide methylation maps of single DNA molecules. We tested the method by defining the methylation status within single DNA strands of two closely spaced CpG dinucleotides in the promoter of the human kininogen gene. During the analysis, we encountered in sperm DNA an unusual methylation pattern, which suggests that the high methylation level of single-copy sequences in sperm may be locally modulated by binding of protein factors in germ-line cells.

5-Methylcytosine↗
PubMed1992

Prenatal exclusion of haemophilia A and carrier testing by direct detection of a disease lesion.

A novel mutation was detected in the Factor VIII gene of a sporadic case of severe haemophilia A. The lesion, a CGA-->TGA transition, converts Arg 795 to Term and adequately accounts for the severe phenotype observed. PCR/direct sequencing was used to confirm the carrier status in the mother. Exclusion of haemophilia A in an at-risk pregnancy was then achieved by demonstration of the absence of this lesion in fetal DNA from a chorionic villus sample. The mutation was also detectable by chemical cleavage of mismatch (CCM), which both confirmed the prenatal diagnosis and established the carrier status of the proband's sister. This example therefore serves to illustrate the potential of direct gene analysis in sporadic cases of haemophilia A and/or in families uninformative for known RFLPs.

Base Sequence↗
PubMed1992

De novo splice site mutation in the antithrombin III (AT3) gene causing recurrent venous thrombosis: demonstration of exon skipping by ectopic transcript analysis.

A single basepair substitution at conserved position -1 in the exon 3a donor splice site of the liver-expressed antithrombin III (AT3) gene was detected by PCR/direct sequencing in a patient with sporadic type 1 ATIII deficiency and recurrent venous thrombosis. The lesion, a heterozygous silent AAG----AAA transition at Lys 176 occurred de novo in the proposita. Ectopic transcript analysis of lymphocyte mRNA demonstrated the presence of an abnormally sized mRNA specific to the patient which was shown by cDNA sequencing to lack exon 3a. Oligonucleotide discriminant hybridization demonstrated the absence of any detectable transcript of normal length derived from the disease allele. These findings demonstrate the utility of ectopic transcript analysis in the characterization of defects of mRNA splicing.

Antithrombin III↗
PubMed1991

Recurrent deletion in the human antithrombin III gene.

Eight unrelated patients with recurrent thromboembolism, a family history of thrombosis, and plasma antithrombin III (ATIII) activity/antigen levels consistent with a diagnosis of heterozygous type I ATIII deficiency were studied by polymerase chain reaction/direct sequencing of ATIII gene exon-coding regions. Frameshift mutations of one base and two bases, respectively, were found to have occurred in two unrelated patients at the same GAG codon (Glu 245) within exon 4 of the ATIII gene. A literature search showed six further hitherto unrecognized deletion "hotspots" in four other human genes. These deletion-prone sites exhibited sufficient sequence homology with each other to derive a consensus sequence (T G A/G A/G G A/C), suggesting that deletion in human genes may not only be non-random but also sequence-directed.

Antithrombin III↗
PubMed1991

Molecular genetic analysis of factor X deficiency: gene deletion and germline mosaicism.

A case of homozygous factor X deficiency arising from the inheritance of two non-identical gene deletions from heterozygous parents is described. One, a partial gene deletion, was localized to exons VII and VIII by a combination of Southern blotting and polymerase chain reaction (PCR) amplification of exon sequences. The other deletion, of maternal origin, probably involves the entire factor X gene. Restriction fragments associated with the exon VII + VIII deletion were present in three siblings including the homozygous proband. These fragments were however absent from the somatic cells of the father, a finding consistent with germline mosaicism.

Base Sequence↗