Isolation and characterisation of a variant allele of the gene for human apolipoprotein E.

Size-selected human DNA fragments enriched in the Apolipoprotein E (ApoE) gene sequence were cloned from an individual of known ApoE phenotype, E2/E2. The clone bank was screened using a human cDNA clone for the ApoE locus (1), and a single genomic clone was isolated. Sequence data obtained from appropriate subcloned fragments confirmed that the codon for Arg-158 (CGC) in the E3 allele is altered to the codon for Cys (TGC) in the E2 allele. Hybridisation data indicated the presence of at least one intron in the ApoE gene, consistent with the structure of an independently isolated human ApoE4 allele (2).

Effects of apoprotein E polymorphism on serum lipoprotein concentration.

Serum concentrations for the cholesterol and triglyceride content of very low density lipoprotein (VLDL) and the cholesterol content of intermediate density lipoprotein (IDL), low density lipoprotein (LDL), and the high density lipoprotein fractions (HDL2), HDL3) were measured in 337 men and women with the apo E phenotype who were born in the Grampian Region of North East Scotland. The subjects' ages ranged from 45 to 60 years (mean, 53 years). Cigarette smoking and alcohol consumption were recorded and were shown to have minor, but suggestive, effects on serum lipoprotein concentrations. The LDL concentration of E-3/2 subjects was compared with the commonest category, E-3/3, and was found to be about 20% lower in men and about 12% lower in women, in whom the VLDL and IDL concentrations were substantially elevated. In E-4/3 women, the serum LDL concentration was about 10% higher than in E-3/3 women, and the other differences were minor. The effect of allelic substitutions differed between the sexes. The relations between C-peptide ratios and serum lipoprotein concentration differed by gender and phenotype. A comparison with earlier estimates of LDL heritability suggests that in this population, a substantial fraction of the genetic variance of LDL is due to segregation at the apo E locus. The implications of this significant finding are discussed.

The gene for apolipoprotein C-II is closely linked to the gene for apolipo-protein E on chromosome 19.

We have used a common TaqI restriction fragment length polymorphism (RFLP) near the human apolipoprotein C-II (apoC-II) gene to study linkage with apolipoprotein E (apoE). The inheritance of the apoC-II RFLP was followed in seven families that were segregating for apoE protein variants. No recombinants were observed in 20 informative meioses, giving an overall lod score of greater than 4.0 at recombination fraction 0. We have also observed apparent linkage disequilibrium between apoE and the apoC-II RFLP. Taken together these results demonstrate that these two apolipoprotein genes are closely linked and confirm that the gene for apoC-II is on human chromosome 19.

Chromosome aberrations in divers.

The incidence of chromosome gain and loss and chromosomal aberrations has been measured in 48-h lymphocyte cultures of divers and control subjects as part of an overall research program to identify possible long-term health hazards associated with commercial diving. When the two diving groups, air divers (n = 77) and helium-oxygen divers (n = 76), are compared with two control groups, oil rig workers (n = 75) and nonoil industry controls (n = 52), 3.9% (6 out of 153) had an unusually high number of structural aberrations in a small portion of the dividing lymphocytes. Similar damage was not found in controls. The remaining 147 divers had a similar low incidence of chromosomal aberrations to the two control groups. The factors responsible for this phenomenon are not known, but several aspects of diving can effectively be ruled out. These are: direct effects of pressure, breathing mixture, radiographic exposure, and viral infection. The causative agent must be acting locally on lymphocytes after their last maturation division. Further studies are continuing on this topic in an effort to identify the causative factor or factors.

Polymorphism at the apoprotein-E locus in relation to risk of coronary disease.

The frequency of genotypes at the polymorphic locus which codes for Apoprotein-E, an important constituent of very low density serum lipoprotein, has been determined in a random sample of persons between the ages of 45 and 60 years, born in the Grampian Region of North East Scotland. Three alleles, EII, EIII and EIV occur with a frequency of respectively 0.08, 0.77 and 0.15. In a random sample of survivors of myocardial infarction, born in the same region, genotype EIVEIII occurs more and EIIIEII less frequently than expected. Also the mean age at first infarction is lower in men for genotype EIVEIII than for other genotypes. Commonly occurring genotypes at this locus apparently influence the risk of coronary disease. A prospective study is needed to show how the genetic effects are expressed.

Non-random chromosome loss in PHA-stimulated lymphocytes from normal individuals.

31773 lymphocyte metaphase cells from 280 karyotypically normal men aged 18-46 were examined for chromosome gain or loss. Chromosome loss was much more common than chromosome gain. Frequency of chromosome loss did not conform to a binomial distribution. There is a striking non-linear, inverse relationship between likelihood of loss and chromosome length. Chromosome gain shows a near binomial distribution between cells and no clear relationship to chromosome length. These facts indicate that the hypodiploid cells mostly arose as technical artefacts during slide preparation but that hyperdiploid cells were mainly due to non-disjunctional gain.

Genetics of the apolipoprotein-E isoprotein system in man.

The inheritance of the apoprotein-E isoprotein polymorphism in man has been studied by pedigree analysis. Alternative genotypes have been identified by the use of isoelectric focusing and two dimensional electrophoresis. A single locus three allele model can account for the inherited differences. In addition to the major bands there are also minor bands which may differ in charge or molecular weight or both, probably owing to post-translational modification. Their relative intensity has been compared in alternative categories of patient liable to raised serum lipoprotein concentration and only in hyperthyroid cases is there clear evidence of relative increase of post-translational activity which is reduced after restoration of the euthyroid state.

Coronary heart disease in North-East Scotland a study of genetic and environmental variation in serum lipoproteins and other variables.

1. Serum lipoprotein concentrations and other variables such as relative weight, skinfold thickness, blood pressure, serum glucose, uric acid, fibrinogen smoking habits, etc. have been recorded on about 700 persons, including about 200 survivors of myocardial infarction under age 50 years, 250 of their relatives and 250 unrelated controls. 2. Elevated levels of VLDL and LDL are several times more frequent in survivors of infarction than in controls. 3. Cigarette smoking is associated with 20 to 30 per cent increase in VLDL. 4. Relative weight and skinfold thickness together account for a quarter of the variance of VLDL in men, 9 per cent in women. 5. LDL and HDL are uncorrelated; there is a low, consistently negative correlation between HDL and VLDL and IDL. 6. Parent-offspring regression and sib correlations indicate high, intermediate and low heritability for respectively HDL, LDL and VLDL. First degree relatives of survivors of infarction have levels of VLDL, IDL and LDL but not HDL.

The effect of delipidated high density lipoprotein on human leukocyte sterol synthesis.

Sterol synthesis is increased when whole human serum is added to leukocytes in buffer. Addition to the buffer of an equivalent amount of serum from which lipid has been extracted by organic solvent leads to a greater increase in synthesis. The addition of whole high density lipoprotein to buffer has little effect on sterol synthesis whereas addition of delipidated high density lipoprotein stimulates sterol synthesis. Delipidated high density lipoprotein may be responsible for the stimulation of sterol synthesis by delipidated serum.

A comparison of delipidated sera used in studies of sterol synthesis by human mononuclear leukocytes.

Sterol synthesis in human mononuclear leukocytes is stimulated by delipidated serum. Synthesis in media containing serum delipidated by three different methods is compared. Significant differences between subjects are shown and the differences are maximized by measuring synthesis in serum delipidated by extraction with butanol-diisopropyl ether 40:60 and diethyl ether.

Human Y chromosome variation in normal and abnormal babies and their fathers.

C-banded chromosome preparations were obtained from cord blood from normal newborns and venous blood from abnormal newborns and the corresponding fathers. There is significant heterogeneity between individuals in euchromatin and especially heterochromatin lengths of the Y chromosome. The average dimensions of the Y of fathers of normal and abnormal babies do not differ. Y chromosomes from cord blood appear more condensed than from venous blood and the consequences are not removed by the use of the Y/F index. Such differences have not been considered in reported apparent variation in the size of the Y chromsome in relation to criminality.

Nerve entrapment at the elbow in rheumatoid arthritis.

Although there was some delay in the posterior interosseous branch of the radial nerve conduction time in six of the 152 rheumatoid elbows, in no case were there clinical signs attributable to entrapment of this nerve. Some delay in ulnar nerve conduction was recorded in 27 of the 152 elbows; this was marked in 12. These patients tended to be older and to have more severe disease of the elbow.

Larsen's syndrome;.

Three cases of Larsen's syndrome with retospective diagnoses have been described. All of them had both the clinical and radiographic signs characteristic for the syndrome, namely flat, hyperteloric facies, multiple dislocations of the joints, club foot deformity, and long cylindrical fingers. The radiographic findings were generalized and diagnostic in all of the cases. Our patients had additional ossification centers for the body of calcaneus.