Position of a 'green-red' hybrid gene in the visual pigment array determines colour-vision phenotype.

The X-linked red- and green-pigment genes are arranged in a head-to-tail tandem array. The colour-vision defect of deuteranomaly (in 5% of males of European descent) is associated with a 5'-green-red-3' visual-pigment hybrid gene, which may also exist in males with normal colour vision. To explain why males with a normal red, a normal green and a green-red hybrid gene may have either normal or deutan colour vision, we hypothesized that only the first two genes are expressed and deuteranomaly results only if the green-red hybrid gene occupies the second position and is expressed preferentially over normal green-pigment genes occupying more distal positions. We used long-range PCR amplification and studied 10 deutan males (8 deuteranomalous and 2 deuteranopic) with 3 visual pigment genes (red, green and green-red hybrid) to investigate whether position of the hybrid gene in the array determined gene expression. The green-red hybrid gene was always at the second position (and the first position was always occupied by the red gene). Conversely, in two men with red, green and green-red hybrid genes and normal colour vision, the hybrid gene occupied the third position. When pigment gene mRNA expression was assessed in post-mortem retinae of three men with the red, green and green-red genotype, the green-red hybrid gene was expressed only when located in the second position. We conclude that the green-red hybrid gene will only cause deutan defects when it occupies the second position of the pigment gene array.

Defective colour vision associated with a missense mutation in the human green visual pigment gene.

All red/green colour vision defects described so far have been associated with gross rearrangements within the red/green opsin gene array (Xq28). We now describe a male with severe deuteranomaly without such a rearrangement. A substitution of a highly conserved cysteine by arginine at position 203 in the green opsins presumably accounted for his colour vision defect. Surprisingly, this mutation was fairly common (2%) in the population but apparently was not always expressed. In analogy with nonexpression of some 5'green-red hybrid genes in persons with normal colour vision, we suggest that failure of manifestation occurs when the mutant gene is located at a distal (3') position among several green opsin genes. This mutation might also predispose to certain X-linked retinal dystrophies.

The advent of the "unpatients'.

Predictive diagnosis by molecular methods will change the scientific basis of prognostics. At the same time, it will change the ethical dimensions of the relation among patients, their doctors and other providers of care.

Impact of genetic manipulation on society and medicine.

Human beings have been manipulating the genetic characteristics plants and animals since the introduction of agriculture indirect manipulation of human genes occurred with widespread use of public health and medical measures that preserve genes causing disease. The production of biologicals by DNA technology raises few ethical problems. Predictive medicine in which genetic markers (including DNA variants) are used for antenatal and preclinical diagnosis of genetic diseases and susceptibilities poses new questions of confidentiality, private versus societal goals, and self-determination. When normal DNA is used to treat the somatic cells of patients with hemoglobinopathies and other genetic diseases, no new ethical problems arise beyond those presented by an novel theory. In contrast, manipulation of DNA in human fertilized eggs would constitute a qualitative departure from previous therapies since this would affect future generations. In order to be able to make wise decisions on these matters the public must be well informed. Thus, formal and informal education in human biology and genetics must be improved at all levels.

KIE: The director of the Center for Inherited Diseases at the University of Washington reviews the current status of applications of recombinant DNA techniques to the manipulation of human genetic characteristics and considers their social and ethical implications. Motulsky distinguishes the relatively conventional dilemmas posed by gene therapy from the qualitatively different problems raised by manipulation of DNA in human fertilized eggs so as to affect future generations. He advocates strengthened formal and informal programs to educate the public about developments in molecular biology and genetics.

Brave new world?

Recent developments in biology and medicine are raising new problems in the prevention and treatment of birth defects, and in research on these diseases. The problems include immediate issues such as genetic counseling, abortion for birth defects, the withholding of complex treatments from individuals in some situations, screening for genetic and other diseases, artificial insemination, and fertilization in vitro. Other problems, such as the dysgenic effects of modern medicine and the possibilities of cloning and gene therapy, are more remote. Each of these issues should be considered on its own merits and by its immediate and remote consequences rather than by a priori absolute criteria. Ways must be found to deal with these issues in a manner acceptable to most human beings. Open discussions and freedom from coercion are the best guarantees for ultimate success. The ethical human brain is the highest accomplishment of biologic evolution. By harmonizing our scientific, cultural, and ethical capabilities, the potentially achievable results can place us at the threshold of a new era of better health and less human suffering.

Atypical cholinesterase gene E1a: rarity in Negroes and most Orientals.

Development of a rapid screening test for atypical cholinesterase in serum enabled large-scale surveys of populations. The frequency of the heterozygous trait among Greeks, Yugoslavs, and East Indians was similar to that among United States Caucasians (2.8 to 3.3 percent). In trait frequency, U.S. Negroes were intermediate (1.05 percent) between Congolese Africans (0.29 percent) and U.S. Whites (3.3 percent). The gene was absent from or very rare in populations originating in East Asia (Taiwanese, Japanese, Filipinos, and Eskimos). Prolonged apnea during anesthesia from administration of succinylcholine caused by homozygosity for this gene, is expected to be extremely rare among populations of Negroes and East Asians.

Developmental variation in the isoenzymes of human liver and gastric alchhol dehydrogenase.

The isoenzyme patterns of alcohol dehydrogenase from human liver and stomach are different in the fetal, newborn, childhood, and adult periods of life. This provides additional evidence that the fetal and adult alcohol dehydrogenases are qualitatively different. Gastric and hepatic isoenzyme patterns also differed from each other.

Negro variant of glucose-6-phosphate dehydrogenase deficiency (A-) in man.

Glucose-6-phosphate dehydrogenase in erythrocytes of the Negro type associated with enzyme deficiency (A(-)) was separated by chromatography on a carboxymethyl-Sephadex column from the electrophoretically indistinguishable Negro variant with normal enzyme activity (A(+)). Quantitative immunologic neutralization tests indicated that the A(-) enzyme had about the same enzymatic and serological activity as the A(+) and the normal (B(+)) enzymes. The enzyme activity of the A(-) variant in young erythrocytes was similar to that in young cells from normal individuals, although the activity of the A(-) variant in unfractionated red cells was 10 to 15 percent of normal. These data indicate that the basic defect in the variant enzyme (A(-)) is a structural mutation which causes more rapid degradation of the enzyme during erythrocyte aging.

Autosomal phosphogluconic dehydrogenase polymorphism in the cat (Felis catus L.).

Three patterns of 6-phosphogluconic dehydrogenase activity were obtained by starch-gel electrophoresis of blood from domestic cats. Genetic analysis indicates control of these patterns by a pair of alleles at an autosomal locus. Presence of three enzymatically active bands in heterozygotes and of single bands in homozygotes is compatible with at least a dimeric structure for the enzyme.

Predominance of hemoglobin Gower 1 in early human embryonic development.

Hemoglobin Gower 1, the structure of which is thought to be epsilon(4), is the predominant hemoglobin in early human embryonic life. This finding suggests that the production of (epsilon)-chains initially exceeds that of other known (alpha, beta, gamma, and delta) chains.

Hyperlipidemia in coronary heart disease. I. Lipid levels in 500 survivors of myocardial infarction.

Plasma cholesterol and triglyceride levels were measured after an overnight fast in 500 consecutively studied 3-mo survivors of myocardial infarction. Virtually all patients under 60 yr of age (95% ascertainment) and a randomly chosen group of older survivors admitted to 13 Seattle hospitals during an 11 mo period were included. A comparison of their lipid values with those of 950 controls demonstrated that 31% had hyperlipidemia. These lipid abnormalities were most commonly found in males under 40 yr of age (60% frequency) and in females under 50 yr of age (60% frequency). Elevation in triglyceride levels with (7.8%) or without (15.6%) an associated elevation in cholesterol levels was three times more common in survivors than a high cholesterol level alone (7.6%). These results raise the possibility that hypertriglyceridemia may be as an important a risk factor for coronary atherosclerosis as hypercholesterolemia. The identification of hyperlipidemic survivors of myocardial infarction provided a unique source of probands for family studies designed to disclose the genetic origin of hyperlipidemia in coronary heart disease.

Hyperlipidemia in coronary heart disease. II. Genetic analysis of lipid levels in 176 families and delineation of a new inherited disorder, combined hyperlipidemia.

To assess the genetics of hyperlipidemia in coronary heart disease, family studies were carried out in 2520 relatives and spouses of 176 survivors of myocardial infarction, including 149 hyperlipidemic and 27 normolipidemic individuals. The distribution of fasting plasma cholesterol and triglyceride values in relatives, together with segregation analyses, suggested the presence of five distinct lipid disorders. Three of these-familial hypercholesterolemia, familial hypertriglyceridemia, and familial combined hyperlipidemia-appeared to represent dominant expression of three different autosomal genes, occurring in about 20% of survivors below 60 yr of age and 7% of all older survivors. Two other disorders-polygenic hypercholesterolemia and sporadic hypertriglyceridemia-each affected about 6% of survivors in both age groups. The most common genetic form of hyperlipidemia identified in this study has hitherto been poorly defined and has been designated as familial combined hyperlipidemia. Affected family members characteristically had elevated levels of both cholesterol and triglyceride. However, increased cholesterol or increased triglyceride levels alone were also frequently observed. The combined disorder was shown to be genetically distinct from familial hypercholesterolemia and familial hypertriglyceridemia for the following reasons: (a) the distribution pattern of cholesterol and triglyceride levels in relatives of probands was unique; (b) children of individuals with combined hyperlipidemia did not express hypercholesterolemia in contrast to the finding of hypercholesterolemic children from families with familial hypercholesterolemia; and (c) analysis of informative matings suggested that the different lipid phenotypes owed their origin to variable expression of a single autosomal dominant gene and not to segregation of two separate genes, such as one elevating the level of cholesterol and the other elevating the level of triglyceride. Heterozygosity for one of the three lipid-elevating genes identified in this study may have a frequency in the general population of about 1%, constituting a major problem in early diagnosis and preventive therapy.

Hyperlipidemia in coronary heart disease. 3. Evaluation of lipoprotein phenotypes of 156 genetically defined survivors of myocardial infarction.

Although analysis of lipoprotein phenotypes is widely used to diagnose and classify the familial hyperlipidemias, an evaluation of this system as a method for genetic classification has hitherto not been published. The present study of 156 genetically defined survivors of myocardial infarction was therefore designed to examine the relationship between lipoprotein phenotypes and genetic lipid disorders. The lipoprotein phenotypes of each survivor was determined primarily by measurement of his plasma triglyceride and low density lipoprotein (LDL)-cholesterol concentrations; his genetic disorder was identified by analysis of whole plasma cholesterol and triglyceride levels in relatives. The mean levels of LDL-cholesterol discriminated statistically among the three monogenic lipid disorders; it was highest in survivors with familial hypercholesterolemia (261+/-61 mg/100 ml [mean +/-SD]); intermediate in those with familial combined hyperlipidemia (197+/-50); and lowest in those with familial hypertriglyceridemia (155+/-36) (P < 0.005 among the three groups). However, on an individual basis no lipoprotein pattern proved to be specific for any particular genetic lipid disorder; conversely, no genetic disorder was specified by a single lipoprotein pattern. This lack of correlation occurred for the following reasons: (a) individual LDL-cholesterol levels frequently overlapped between disorders; (b) in many instances a small quantitative change in the level of either LDL-cholesterol or whole plasma triglyceride caused qualitative differences in lipoprotein phenotypes, especially in individuals with familial combined hyperlipidemia, who showed variable expression (types IIa, IIb, IV, or V); (c) lipoprotein phenotypes failed to distinguish among monogenic, polygenic, and sporadic forms of hyperlipidemia; (d) clofibrate treatment of some survivors with genetic forms of hyperlipidemia caused their levels of triglyceride and LDL-cholesterol to fall below the 95th percentile, thus resulting in a normal phenotype; and (e) beta-migrating very low density lipoproteins (beta-VLDL), previously considered a specific marker for the type III hyperlipidemic disorder, was identified in several survivors with different lipoprotein characteristics and familial lipid distributions. These studies indicate that lipoprotein phenotypes are not qualitative markers in the genetic sense but instead are quantitative parameters which may vary among different individuals with the same genetic lipid disorder. It would therefore seem likely that a genetic classification of the individual hyperlipidemic patient with coronary heart disease made from a quantitative analysis of lipid levels in his relatives may provide a more meaningful approach than determination of lipoprotein phenotypes.

Glutathione S-transferase and epoxide hydrolase activity in human leukocytes in relation to risk of lung cancer and other smoking-related cancers.

BACKGROUND: There is considerable interindividual variation in the activity of enzymes which metabolize polycyclic aromatic hydrocarbon constituents of tobacco smoke. Low activity of enzymes which detoxify carcinogenic polycyclic aromatic hydrocarbon metabolites may be associated with increased susceptibility to cancers etiologically related to cigarette smoking. PURPOSE: We conducted a population-based, case-control study to determine whether patients with cancers related to smoking had lower activity of detoxifying isoenzymes of glutathione S-transferase (GST) and epoxide hydrolase (EH) than control subjects. METHODS: Enzyme activities were measured in leukocytes from 113 King County (Washington) residents diagnosed during 1987 with one of three smoking-related cancers (lung, oropharynx/oral cavity, or bladder), 50 King County residents with cancers believed unrelated to smoking (prostate cancer or non-Hodgkin's lymphoma), and 120 persons selected at random from the King County population. Enzyme activity measurements were made for leukocyte cytosolic GST toward transstilbene oxide (TSO), 1-chloro-2,4-dinitrobenzene, and benzo[a]pyrene-4,5-oxide (BaPO), and for microsomal EH toward BaPO. RESULTS: Overall, the distribution of activity levels of GST toward TSO and BaPO did not differ in case patients with smoking-related cancer compared with control subjects. The activities of GST toward 1-chloro-2,4-dinitrobenzene and of EH toward BaPO were somewhat lower on average in case patients with smoking-related cancers than in control subjects, but these differences were well within the limits of chance. Among the heaviest smokers, there were proportionately fewer patients with smoking-related cancers than control subjects with intermediate or high GST activity toward TSO (odds ratio = 0.6), but this difference was also plausibly due to chance (95% confidence interval = 0.3-1.1). CONCLUSIONS: While the findings of this study are compatible with a moderate protective effect of high or intermediate enzyme activity among persons heavily exposed to tobacco, as suggested by an earlier report, the data are by no means conclusive.

The glutathione S-transferase mu polymorphism as a marker for susceptibility to lung carcinoma.

Glutathione S-transferase (GST) enzymes detoxify carcinogens in tobacco smoke. Interindividual variation in GST function may be related to differences in risk for smoking-related cancer. Leukocytes from 50% of Caucasians lack GST activity toward trans-stilbene oxide (TSO), due to a deletion of the gene for the GST-mu enzyme. Presence of GST-TSO activity in leukocytes has been associated with low risk for lung cancer among cigarette smokers. We sought to determine whether GST activity in lung tissue is determined by the same gene polymorphism and whether it is associated with risk for lung cancer. Subjects were cigarette smokers, identified at the time of lung resection or autopsy in Seattle hospitals. Uninvolved lung tissue was obtained from 35 patients with lung carcinoma and 43 control patients and assayed for GST-mu activity with TSO, for the presence of the GST-mu gene product with an immunological assay, and for the GST-mu gene with Southern blotting. Mailed questionnaires were used to collect information on subjects' smoking histories and exposures which might alter enzyme activity. Interindividual results from the three assays correlated well. Smokers with high GST-TSO enzyme activity present in their lung tissue had a lower risk for lung carcinoma than did smokers with no or low activity (relative risk = 0.30; 95% confidence interval, 0.11-0.79), as did smokers with GST-mu antigen identified in lung tissue versus those with no antigen (relative risk = 0.30; 95% confidence interval, 0.11-0.79). Smokers with both maternal and paternal copies of GST-mu DNA (n = 7) had a lower cancer risk than smokers lacking GST-mu DNA (n = 30; relative risk = 0.35; 95% confidence interval, 0.06-2.10). High GST-mu activity appeared to be associated with a greater decrease in lung cancer risk among 38 heavy cigarette smokers (relative risk = 0.15; 95% confidence interval, 0.03-0.64) than among 38 light smokers (relative risk = 0.61; 95% confidence interval, 0.14-2.60). Presence or absence and number of copies of the GST-mu gene appear to determine activity of the GST-mu enzyme in lung. Smokers with the GST-mu enzyme have approximately one-third of the risk for lung carcinoma of smokers without the enzyme.

Cardiovascular disease mortality in familial forms of hypertriglyceridemia: A 20-year prospective study.

BACKGROUND: Familial combined hyperlipidemia (FCHL) and familial hypertriglyceridemia (FHTG) are 2 of the most common familial forms of hyperlipidemia. There is a paucity of prospective data concerning the risk of cardiovascular disease (CVD) in such families. The purposes of this study were to estimate 20-year total and CVD mortality risk among relatives in these families and to evaluate plasma triglyceride as a predictor of death. METHODS AND RESULTS: The study was based on lipid and medical history data from 101 families ascertained in 2 studies conducted in the early 1970s. Vital status and cause of death was determined during 1993 to 1997 for 685 family members, including first-degree relatives of the probands and spouse control subjects. Compared with spouse control subjects, 20-year CVD mortality risk was increased among siblings and offspring in FCHL (relative risk 1.7, P=0.02) after adjustment for baseline covariates. In FHTG families, the relative risk was also 1.7 but was not statistically significant (P=0.39). Baseline triglyceride was associated with increased CVD mortality risk independent of total cholesterol among relatives in FHTG families (relative risk 2.7, P=0.02) but not in FCHL families (relative risk 1.5, P=0.16) after adjustment for baseline covariates. CONCLUSIONS: This prospective study establishes that relatives in FCHL families are at increased risk for CVD mortality and illustrates the need for effective prevention strategies in this group. Baseline triglyceride level predicted subsequent CVD mortality among relatives in FHTG families, adding to the growing evidence for the importance of hypertriglyceridemia as a risk factor for CVD.

Theophylline metabolism: variation and genetics.

Variation of theophylline metabolism in 54 healthy, nonmedicated adults (13 monozygotic [MZ] twin pairs, 11 dizygotic [DZ] twin pairs, and 6 single individuals) was assessed by kinetic study. Elimination rate constant, clearance (Cl), t1/2, and apparent volume of distribution, as well as urine excretion of unchanged theophylline and of the three major metabolites (1-methyluric acid, 3-methyl-xanthine, and 1,3-dimethyluric acid) were studied. Smokers and men had increased theophylline elimination rates compared to nonsmokers and women. Identical (MZ) twins resembled each other more closely than nonidentical (DZ) twins in the various kinetic parameters, but mean intrapair differences between MZ and DZ twins for all but one of the serum and urinary parameters examined (including t1/2) were not statistically significant. Correspondingly, estimates of heritability and of intrapair correlation coefficients showed a smaller contribution of genetic factors to variation in theophylline metabolism than had been reported for other drugs investigated by twin studies. Nevertheless, in the family of the individual with the longest theophylline t1/2, the operation of a rare major gene retarding theophylline metabolism could not be excluded. A father and two out of four children had very slow Cls. This finding would be consistent with, but does not prove, monogenic inheritance.

Nutrition and genetic susceptibility to common diseases.

Genetic factors play a role in chronic disease and conditions such as coronary heart disease, hypertension, and obesity. Individual responses to nutritional factors involved in such conditions vary depending upon a person's genetic make-up. The role of individual genes is best understood for the hyperlipidemias that predispose to coronary heart disease. Until more and better information on gene-nutritional interactions is available, general population-wide recommendations regarding a prudent diet appear reasonable. At the same time, high risk screening for certain conditions such as the hyperlipidemias is appropriate.

Lipoprotein and apolipoprotein abnormalities in familial combined hyperlipidemia: a 20-year prospective study.

In order to characterize the lipoprotein abnormalities in familial combined hyperlipidemia (FCHL) and to describe factors associated with the stability of the FCHL phenotype during 20-year follow-up, 287 individuals from 48 families with FCHL originally identified in the early 1970s (baseline) were studied. Hyperlipidemia was defined as lipid-lowering medication use, or > or =age- and sex-specific 90th percentile for triglycerides or cholesterol. Triglyceride, cholesterol and medical history data were obtained at baseline and 20-year follow-up. Additional follow-up measures included HDL-C, LDL-C, LDL particle size, lipoprotein(a), apolipoprotein (apo) A-I, apoB, and apoE polymorphism. Longitudinally, two-thirds of relatives were consistently normolipidemic or hyperlipidemic, and one third were discordant for hyperlipidemic status at baseline and 20-year follow-up. Individuals with hyperlipidemia at baseline and/or follow-up had higher apoB levels than those with consistently normal lipids (P<0.05), whereas small LDL size was associated with concurrent hyperlipidemia. Among individuals who were normolipidemic at baseline, the following variables were independently associated with development of hyperlipidemia over 20 years: older age at baseline, male sex, greater increase in BMI during follow-up, and apoE alleles epsilon 2 or epsilon 4. In conclusion, apoB is associated with hyperlipidemia and apoE polymorphism is associated with later onset of hyperlipidemia in FCHL.