A PCR based method to determine the Kalow allele of the cholinesterase gene: the E1k allele frequency and its significance in the normal population

The Kalow allele for cholinesterase is a quantitative variant of the usual gene and has been shown to result from a single base pair change in the DNA. A new method based on the polymerase chain reaction to distinguish Kalow alleles of the cholinesterase gene was developed. Using the amplification refractory mutagenesis system, two different reactions distinguished the presence of a guanine (normal E1u allele) from that of an adenine (Kalow E1k allele) at nucleotide 1615 within the coding sequences of the gene. The frequency of the Kalow allele in our sample of 51 persons was determined to be 20%. The mean total cholinesterase activity in heterozygotes was 90% of that in persons who typed as E1uE1u homozygotes. Two E1kE1k homozygotes were identified and their cholinesterase activities were the two lowest measured.

Human major histocompatibility complex contains several leukemia susceptibility genes

In mice, homozygosity for the Mhc haplotype H-2k is associated with increased susceptibility to spontaneous and virus-induced leukemia, lymphoma and other neoplasms in the predisposed host. The influence of the Mhc on malignant development in these models is to shorten the latency after virus inoculation. Here, we present evidence that a similar phenomenon results in early-onset of human leukemia. A molecular analysis of the MHC in 112 CML patients showed that those who developed the disease when aged less than 35 years (early-onset group) had higher homozygosity rates for the DOA1, HSP70 and C4 alleles of the DR53 group of ancestral haplotypes, for a subtype of HLA-A3, and a higher allele frequency of BfFb compared to the late-onset group. The oldest patient (n = 13) homozygous for DR53 was 52-years-old (p = 0.004), and all HLA-A3 homozygous patients (n = 4) were in the early-onset group (p = 0.01). The relative risk for early-onset CML yielded by HLA-A3 homozygosity was 17.6. The well-known serological HLA-Cw4 association was not confirmed at the DNA level and thought to be due to linkage disequilibrium with BfFb. The factor B association was sex-limited. The DR52 group haplotypes appeared to be protective. The HLA-identical sibling frequency was increased only in the early-onset group (p < 0.01). Our findings agree with the concept of an MHC influence on the development of malignancies. The similarity in the location of the susceptibility loci and the serological cross-reaction between H-2Ek and DR53 raise the possibility that the mouse and human MHC share the same leukemia susceptibility genes.

Smoking and plasma lipoproteins in man: effects on low density lipoprotein cholesterol levels and high density lipoprotein subfraction distribution

In a survey of a healthy population (n = 197), LDL cholesterol, plasma triglycerides and VLDL triglycerides were found to be substantially increased and plasma HDL cholesterol decreased in smokers. The lipid-associated atherogenic risk in smokers as assessed by the LDL/HDL ratio was significantly higher [2.89 (SD 1.18, n = 63)] than in non-smokers [2.38 (SD 0.98, n = 86) P < 0.01]. The lower HDL level found in smokers was explained by a lower HDL-2 subfraction as determined by analytical ultracentrifugation. HDL 2b, 2a and 3a, measured by gradient gel electrophoresis, were all lower in the smokers but this was only significant for HDL 2a. Smoking had no effect on Lp(a) levels. HDL cholesterol and HDL-2 were strongly negatively correlated whereas LDL cholesterol and LDL/HDL ratio were strongly positively correlated with the plasma triglyceride concentration. There was a small but significant reduction in plasma CETP activity [non-smokers 49% t/microliter (SD 17, n = 90), smokers 43% t/microliter (SD 17, n = 66) P < 0.05] but CETP activity was not correlated with any measure of HDL in this population. Smoking was found to be an important independent contributor to the variation in plasma triglyceride, HDL, HDL-2 and LDL/HDL ratio. After correcting for sex, age, BMI, alcohol consumption, oral contraceptive use and plasma triglycerides smoking was still found to be significantly associated with HDL and the LDL/HDL ratio. Upon adjustment for covariant factors the mean differences between smokers and non-smokers for HDL cholesterol, HDL-2 and LDL/HDL were 0.15 mM, 16 mg dl-1 and 0.39 respectively. There appeared to be important sex differences in the influence of smoking on plasma lipoproteins. In women the main impact of smoking was on triglyceride levels and they in turn affected LDL and HDL. In contrast, in men, smoking had little impact on triglycerides and affected HDL more directly. We conclude that smoking cigarettes has an important effect on plasma lipoprotein metabolism through multiple mechanisms.

The ins/del polymorphism in the signal sequence of apolipoprotein B has no effect on lipid parameters

The 'ins/del' polymorphism in the signal sequence of apolipoprotein B alters the hydrophobicity of the signal sequence and therefore would be expected to affect the rate of production of apolipoprotein B (apo B) and the plasma concentrations of lipoproteins containing this apolipoprotein. We sought evidence for an association with plasma lipid levels and this polymorphism in two studies, one using a normal randomly selected population (N = 188) and another using a mildly hypercholesterolaemic group of men aged 45-64 (N = 360). The frequency of the rarer, 'del' allele, was the same in both groups. Likewise no differences in serum cholesterol, serum triglycerides, very low density lipoprotein, low density lipoprotein or high density lipoprotein were seen comparing homozygotes for the signal sequence allele within either group.

Frequency of the XbaI, EcoRI, PvuII and MspI polymorphisms of the apolipoprotein B gene in relation to hypercholesterolaemia in the general population

In this study the frequencies of the genotypes of four restriction fragment length polymorphisms in the apolipoprotein B gene (XbaI, EcoRI, PvuII and MspI) are compared between groups of normolipidaemic and diet resistant hypercholesterolaemic individuals as possible markers for the influence of this gene on plasma cholesterol levels. In the first part of the study genotypes of all four markers were determined in 92 normolipidaemic (mean cholesterol 5.6 + 0.8 mmol/l) and 79 diet resistant hypercholesterolaemic (mean cholesterol 7.8 + 0.7 mmol/l) individuals seen in a local health centre screening programme for coronary heart disease risk factors. No significant difference was seen in the frequencies of the EcoRI and PvuII genotypes between the two groups. There was significant enrichment of both the XbaI X2 (presence of cutting site) allelic frequency and of the MspI M1M2 (M2 absence of cutting site, rarer allele) genotype frequency in the hypercholesterolaemic group. In the second part of the study an independent larger group of individuals, seen in a multicentre screening programme across the city of Glasgow, were genotyped for the two potentially significant polymorphic sites (XbaI and MspI). From this second screening programme 188 age matched normolipidaemic males (mean cholesterol 5.0 +/- 0.8 mmol/l) were compared with 186 males who were still hypercholesterolaemic (mean 8.2 +/- 0.6 mmol/l) after three months dietary intervention. The hypercholesterolaemic individuals in this second study did not show a significant enrichment of the XbaI X2 allele but again showed a highly significant enrichment of the MspI M1M2 genotype. This genetic effect may relate directly to the charge change from arginine to glutamine at amino acid 3611 caused by the MspI mutation or to an as yet unknown functionally significant mutation in linkage disequilibrium with this site.

DNA-based presymptomatic diagnosis of Wilson disease

Investigation using DNA markers in a family with Wilson disease revealed that an apparently normal child of 10 years of age with non-diagnostic copper biochemistry had the disease. The procedure used linked restriction fragment length polymorphic markers. Demonstration of increased liver copper concentration from a liver biopsy confirmed the diagnosis and the child was started on chelation therapy. Two other asymptomatic siblings were shown, using the same techniques, not to have the disease. Similar analysis was carried out on another family with just one index case.

Synonymous polymorphism in the coding sequence of human 3-beta hydroxysteroid-5-ene dehydrogenase (HSD)

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Restriction fragment length polymorphisms in the Apo B gene in relation to coronary heart disease in a southern Asian population

We have examined DNA polymorphisms associated with the apolipoprotein B gene in 95 Sri Lankan males with ischaemic heart disease and 95 matched controls. For polymorphisms detected using the XbaI or MspI enzymes the allele frequency in Sri Lankans contrasted markedly from that in Caucasians. Overall, there was no significant association of any allele studied with coronary disease cases in this sample. There was, however, a significant difference observed between the XbaI allele frequency in normotriglyceridaemic or normocholesterolaemic CHD cases compared with the allele frequency in the controls.

Genetic variation in the cholesteryl ester transfer protein and apolipoprotein A-I genes and its relation to coronary heart disease in a Sri Lankan population

The influence of variation in the genes for cholesteryl ester transfer protein and apolipoprotein A-I was investigated in 95 patients with coronary heart disease and 95 matched control subjects of South East Asian extraction. Restriction fragment length polymorphisms (RFLPs) linked to the cholesteryl ester transfer protein gene TaqIA and TaqIB, and to the apolipoprotein A-I gene SstI, were examined to investigate the extent of genetic variation at these loci. None of the alleles defined by these RFLPs were associated with increased coronary risk. Analysis of the data by division of high density lipoprotein-cholesterol levels into tertiles showed a trend of a higher frequency of B1 allele (presence of the TaqIB site) with reduced high density lipoprotein levels. The B1 allele was more frequent in control subjects, with low high density lipoprotein levels (P less than 0.02), but not in coronary heart disease patients. The differences became significant for both groups (P less than 0.05) when the data of non-smokers were analysed separately.

The Xba1 polymorphism of the apolipoprotein B gene influences the degradation of low density lipoprotein in vitro

This study examines the influence of variation in the apolipoprotein B (apoB) gene, the major protein of low-density lipoprotein (LDL), on the LDL degradation rate in vitro. Previously we have shown (Demant et al. (1988) J. Clin. Invest. 82, 797-802) that there is an association between the fractional catabolic rate of LDL in vivo and the apoB polymorphism detected using the Xba1 restriction enzyme. Subjects with genotype X1X1 (X1 = absence of cutting site) cleared LDL more rapidly from the plasma compartment than those with the X2X2 genotype. In this study, the LDL degradation rate on dermal fibroblasts was measured for 33 individuals of genotype X1X1 or X2X2. These were subdivided into three groups: (1) young normolipidaemic, (2) older normolipidaemic and (3) older hypercholesterolaemic subjects, because age is known to markedly affect the plasma LDL concentration and may independently influence the population of LDL particles under study. In all experiments, the degradation rate of one type of LDL was compared directly in the cell culture dish with that from an individual of the alternate genotype by labelling them separately with the two iodine isotopes 125I and 131I. In the group of young normals (mean cholesterol 5.03 mmol/l, mean age 31 years), no significant difference was observed between the degradation rates of LDL derived from X1X1 individuals versus X2X2. However, in the older group of normals (mean cholesterol 5.4 mmol/l, mean age 48 years), LDL from subjects with X1X1 genotype was catabolised 17% faster than that from X2X2 subjects (P less than 0.001). A similar result was seen in hypercholesterolaemics (mean cholesterol 8.3 mmol/l, mean age 57 years) with LDL isolated from X1X1 subjects being degraded 22% more rapidly than that from X2X2 subjects. This in vitro evidence adds further weight to the hypothesis that genetic variation in the apoB gene leads to structural changes in LDL than alter its potential for degradation via the LDL receptor.

An StuI RFLP at the human cholesteryl ester transfer protein (CETP) locus

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Genetic influences on GABA-related seizures

Genetic differences in susceptibility to chemically induced seizures were examined in various populations of mice. Three inbred strains: C57BL, DBA, and C3H and a heterogenous stock (HS) of mice were tested for sensitivity to seizures induced by 3-mercaptopropionic acid (MP) and flurothyl. Dose response curves were constructed for each population of mice with each agent by quantitating latencies to specific stages of seizures. Significant strain and sex differences were observed in sensitivity to MP-induced seizures. Rank order from least sensitive to most sensitive was C57BL, HS, DBA, and C3H. Sensitivity to flurothyl-induced seizures was also strain dependent, but the rank order of sensitivity was different than for MP. The least sensitive strain was C57BL followed by HS, C3H, and DBA. Analysis of GABA receptors in seven brain regions obtained from C57BL and DBA using 3H-muscimol to measure high affinity GABA binding did not reveal significant differences in receptor number between these two strains. It thus appears that different genetic factors influence susceptibility to MP-induced seizures than to flurothyl-induced seizures. Furthermore, there is probably little correlation between the number of high affinity GABA receptors and sensitivity to seizures.

The consensus sequence YGTGTTYY located downstream from the AATAAA signal is required for efficient formation of mRNA 3' termini

Our previous DNA sequence comparisons of 3' terminal portions from equivalent herpes simplex virus type 1 (HSV-1) and HSV-2 genes identified a conserved sequence (consensus YGTGTTYY; Y = pyrimidine) located approximately 30bp downstream from the AATAAA signal. We report here that this signal is located downstream from 67% of the mammalian mRNA 3' termini examined. Using constructions with the bacterial chloramphenicol acetyl transferase (CAT) gene linked to an HSV 'terminator' fragment, we show that deletions in the 'terminator' reduce CAT activities and the levels of CAT mRNA 3' termini. Specifically: (1) deletions of downstream sequences which extend up to the consensus YGTGTTYY signal reduce CAT levels to values 35% of those obtained with undeleted plasmids, (2) a deletion of a further 14bp, which removes the YGTGTTYY consensus but not the poly A site, reduces CAT activities to 1%-4%. The levels of CAT mRNA 3' termini reflect the reductions in CAT activities however, levels of mRNA 5' termini are unaffected by these deletions. The RNA produced in the absence of the YGTGTTYY signal is present in the cytoplasm although no CAT activity is detectable.

Latex agglutination test for detection of Clostridium difficile toxin in stool samples

A total of 163 stool specimens were tested for detection of Clostridium difficile and its toxin by cytotoxicity assay with tissue culture, latex agglutination test, and isolation of the organism. From 33 specimens which were positive for toxin by cytotoxicity, 30 were positive by the latex agglutination test; the organism was isolated from 21. The total number of samples which were positive with the latex agglutination test was 44. The predictive value of a positive latex agglutination result relative to the cytotoxicity test was 68%, and the predictive value of a negative result was 97.5%. The specificity and sensitivity of the latex agglutination test relative to the cytotoxicity assay and the low cost and simple facilities required indicate that the latex agglutination test is a useful procedure for screening for C. difficile toxins, provided that positive latex results are confirmed by cytotoxicity assay.

Regulation of the F conjugation genes studied by hybridization and tra-lacZ fusion

Hybridization experiments and tra-lacZ fusions were used to obtain further insight into the complex series of control systems that affect F conjugation. We confirmed that the regular IncF FinOP control system represses transcription of traJ, and found that the traJ product is required for transcription of traM as well as of the traY-Z operon. The chromosomal sfrA gene product may be required to prevent premature termination of traJ transcription, while the sfrB gene product prevents premature termination at two sites within the traY-Z operon. The FinQ inhibition system determined by several IncI plasmids caused termination at three different sites in the operon, and that of JR66a at one further site. JR66a and R485 strongly inhibit F transfer, but have weak, or no (respectively) effects on transcription: they may inhibit function of one or more transfer gene products.