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Fat-free mass (FFM) consists mostly of skeletal muscle and bone tissues, and identification of the genes and molecular mechanisms involved in the control of FFM would have implications for the understanding of sarcopenia and potentially osteoporesis associated with aging, as well as the response to starvation, refeeding, anorexia, and any other conditions in which lean body mass is important. A genome-wide search for genes related to body leanness has been completed in the Quebec Family Study (QFS). Microsatellite markers (N = 292) from the 22 autosomal chromosomes were typed. The mean spacing of the markers was 11.9 centimorgans (cM) (range, <0.1 to 41). FFM was calculated from percent body fat, derived from underwater weighing, and body weight and was adjusted by regression for age and sex effects before analysis. A maximum of 336 sib pairs or 609 pairs of extended relatives were analyzed using single-point Haseman-Elston regression (SIBPAL and RELPAL) and multipoint variance component (SEGPATH) linkage analyses. Significant linkages were observed on chromosomes 15q25-q26 for a CA repeat within the insulin-like growth factor 1 receptor (IGF1R) gene (Lod score = 3.56) and at 18q12 with D18S877 (Lod score = 3.53) and D18S535 (Lod score = 3.58), 2 markers located 10 cM apart. A moderately significant linkage was also observed on chromosome 7p15.3 with the marker D7S1808 (Lod score = 2.72). The most obvious candidate genes within the regions identified by these linkages include the IGF1R on 15q and neuropeptide Y (NPY) and growth hormone-releasing hormone (GHRH) receptor on 7p. On 18q, the melanocortin receptor 4 (MC4R) is not likely the candidate gene for the observed linkage. This study represents the first genome-wide search for genes that may be involved in the regulation of the lean component of body mass in humans.

Linkage and association studies between three exonic polymorphisms in the leptin receptor gene and body composition variables in the HERITAGE Family Study were undertaken. Polymorphisms K109R, Q223R, and K656N have been analyzed with body mass index (BMI), sum of height skinfolds (SF8), fat mass (FM), percent body fat (%FAT), fat free mass, and plasma leptin level. Single-point linkage analysis and covariance analysis across genotypes were performed, by race, on phenotypes adjusted for age and sex. Blacks (88 parents; 231 adult offspring) from 115 nuclear families (72-119 sibpairs) and Caucasians (192 parents; 330 adult offspring) from 99 nuclear families (319-364 sibpairs) were used for these analyses. In Caucasians, BMI and FM showed suggestive linkages with K109R (P = 0.02 and P = 0.05, respectively) and associations with Q223R (P = 0.005 and P = 0.03, respectively). In blacks, no statistically significant linkage or association was observed. In Caucasians, associations with Q223R were observed in parents, but not in offspring, for BMI, FM, and %FAT (0.04< or =P< or =0.0001). Males, not females, showed differences across genotypes for the same phenotypes plus SF8 and leptin (0.03< or = P< or =0.0002). Carriers of the R223 allele showed higher values than noncarriers for BMI (+4 U, P = 0.0001), SF8 (+30 mm, P = 0.01), FM (+7 kg, P = 0.0004), %FAT (+5%, P = 0.0002), and leptin (+4 ng/mL, P = 0.0006). These results indicate a significant effect of leptin receptor on adiposity in middle-aged Caucasian males.

The familial aggregation of resting systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) was assessed in 98 white families, who participated in the HERITAGE Family Study, and were selected to be sedentary, and primarily nonobese and normotensive. In the present study, 522 family members were sedentary at baseline examination, and resting SBP, DBP, and HR measured during this examination were investigated. If physical activity level is a potent environmental factor, then we expected that the relative contribution of environmental factors to the familial aggregation of blood pressure (BP) would be somewhat reduced, because activity was controlled for in this study. Using a familial correlation model, maximal heritabilities were estimated to be 54%, 41%, and 32% for resting SBP, DBP, and HR, respectively, in these families; and they were 51%, 42%, and 34% for resting SBP, DBP, and HR, respectively, when the data were adjusted for body mass index. The estimates are somewhat higher for BP but similar for HR to those reported in previous family studies, suggesting that the distribution of the underlying etiologic factors in these sedentary families may be similar to those in the general population. There was substantial spouse resemblance in this study, which may be explained by a higher concordance for correlated lifestyle factors including diet, similar activity levels, or by assortative mating for relative weight or dietary preferences.

We discuss the Genetic Analysis Workshop 11 analyses of data from the Collaborative Study on the Genetics of Alcoholism from a methodological perspective, concentrating on approaches and issues relevant to linkage and association studies of complex human phenotypes. Genome screening by parametric linkage, nonparametric linkage, association, and combined linkage/association methods are discussed. Issues particular to complex disease include etiologic heterogeneity, multivariate phenotype modeling, and parent-of-origin effects. Other methodological topics discussed are new and enhanced methods, ascertainment, weighting of nonindependent sib pairs, and data cleaning and validation.

In cases where sibship data are collected for a quantitative trait locus (QTL) linkage study without access to parental genotypes, the proportion of genes shared identical by descent must be estimated using the marker allele frequencies. No systematic study has been conducted to date to evaluate the effect of misspecification of these frequencies on a test of quantitative trait linkage. Analysis of both simulated and actual data on quantitative traits was carried out under various sets of allele frequency estimates. While correctly specifying the allele frequency distribution led to a slightly more powerful test and higher lod scores, the differences were small and would not likely alter the conclusion of a study. These results suggest that, at least for QTL analysis, there is a great deal of tolerance for misspecifying marker allele frequencies with little, if any, appreciable effect on the linkage test. However, the observed variations may be sufficiently large to alter the priority on might give to a positive finding for follow up.

Background: A positive interaction between high plasma lipoprotein(a) [Lp(a)] and unfavorable plasma lipid levels has been reported to result in very high risk for premature coronary artery disease (CAD). We further examined this issue for men and women with early onset CAD. We also examined potential interactions between Lp(a) and non-lipid risk factors., Methods and Results: In 338 men and women with early onset CAD (most with a positive family history of early CAD) and 480 general population controls, we measured Lp(a), lipids and other risk factors. In univariate analysis, relative odds for CAD was 1.7 (P = 0.002) for plasma Lp(a) >50 mg/dl. Elevated Lp(a) level was found to interact with adjusted plasma total/high density lipoprotein (HDL) cholesterol such that when Lp(a) was over 50 mg/dl and adjusted plasma total/HDL cholesterol >5.8, relative odds for CAD were 8.0-9.6 (P<0.0001) in multiple logistic regression. Non-lipid risk factors were generally found to multiply the risk associated with Lp(a) (as predicted by logistic regression) without evidence for interaction., Conclusions: We find evidence that Lp(a) does interact positively with adjusted plasma total/HDL cholesterol ratio. Aggressive risk factor intervention, especially for lipids, in those with elevated Lp(a) therefore appears indicated.

The genetics of human fatness has been the subject of many recent studies, motivated by the increased morbidity and mortality associated with obesity, as well as the increasing prevalence of overweight and obesity. The body-mass index (BMI) and fat mass (FM), measured by underwater weighing, were assessed for 1,630 individuals from approximately 300 families from phase 1 of the Quebec Family Study. The two phenotypes are highly correlated ( approximately .8) in adults, and previous segregation analysis revealed evidence for a recessive major gene for each trait. In our study, we utilized bivariate segregation analysis to determine the source(s) of phenotypic correlation-namely, a pleiotropic major gene, shared familial factors/polygenes, or shared nontransmitted environmental factors. Analysis was performed by use of the Pedigree Analysis Package, with extensions to the bivariate case. Tests of hypotheses provided evidence for two pleiotropic recessive loci, together accounting for 64% and 47% of the variance in BMI and FM, respectively. Under the model, all sources of phenotypic correlation were significant: 73% of the covariance was attributed to the pleiotropic major loci, 8% to residual familial effects, and 19% to nontransmitted environmental factors. The high degree of genetic identity between the two traits is not surprising, since the BMI often is used as a surrogate for FM; however, simultaneous analysis of both phenotypes enabled the detection of a second major locus, which apparently does not affect extreme overweight (as does the primary major locus) but which affects variation in the "normal" range.

Background: Polymorphisms of the renin-angiotensin system are associated with cardiovascular pathology. Therefore, the association of the insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene and the T235 (methionine to threonine substitution) polymorphism of the angiotensinogen (AGT) gene with intima-media thickness of the carotid artery was investigated., Methods and Results: Subjects were randomly selected from two centers participating in both the Atherosclerosis Risk in Communities (ARIC) and NHLBI Family Heart Studies. Probands were 45-64 years of age who were free of cardiovascular disease and had B-mode ultrasound measured carotid intima-media thickness. Multiplex polymerase chain reaction amplification was used to evaluate the ACE I/D and AGT T235 polymorphisms: genotype information was available on 495 and 475 participants, respectively. The frequencies of the ACE D and AGT T alleles were 0.56 and 0.52, respectively; 30% were homozygous for the ACE D allele, and 29% were homozygous for the AGT T allele. After adjustment for systolic blood pressure, antihypertensive medication use, diabetes, age, sex and LDL cholesterol, the mean intima-media thickness was 0.729, 0.732 and 0.721 mm in the ACE DD, ID, and II genotypes, respectively (partial F test 1.53, P = 0.22), and 0.727, 0.732 and 0.724 mm in the AGT MM, MT, and TT genotypes, respectively (partial F test 0.91, P = 0.40). Combining the genotypes for ACE and AGT, there were also no differences in intima-media thickness across the eight joint genotypes., Conclusion: We found no evidence that the ACE I/D and AGT T235 polymorphisms of the renin-angiotensin system were associated with carotid intima-media thickness in this population-based sample of middle-aged adults with no history of cardiovascular disease. The lack of an association between these variants and intima-media thickness may indicate that early atherosclerosis is mediated by factors other than these RAS polymorphisms.

The body mass index (BMI) is a complex phenotype representing the amount of fat mass, lean mass, body build and proportions, and it is likely to be affected by various metabolic processes, hormonal effects, energy intake and expenditure, and interactions within and among these broad categories of etiologic factors. Nonetheless, several previous studies have reported evidence for major gene segregation for the BMI in various populations. Data on a random sample of Caucasian families participating in the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study were analyzed to document the extent of familial resemblance and to investigate whether a similar monogenic inheritance pattern could be detected. Genetic analysis was carried out on age- and sex-adjusted BMI values. Familial correlations were significant implying a maximal heritability, including all genetic and environmentally inherited additive factors, of 41% to 59%. Segregation analysis revealed the presence of two maximum likelihood solutions, one characterized as a recessive Mendelian gene and the other as a major effect with an ambiguous transmission pattern. The presence of two such solutions is consistent with detection of two separate factors, each influencing the BMI distribution in a substantive manner. The evidence also supports a multifactorial background for BMI and suggests that the frequencies of these two factors, one of which appears to be a gene, may vary among diverse populations in the United States.

Objectives: Abdominal visceral fat (AVF) is considered a risk factor for diabetes, atherogenic lipid profiles and hypertension. However, little is known about the genetic contribution to AVF as compared to total body fat., Design: AVF was assessed by computerized tomography, and total body fat (fat mass) was assessed by underwater weighing in 86 families participating in the Heritage Family Study. All family members were sedentary at baseline examination. The familial factors underlying the variability in age-adjusted AVF, age-fat mass-adjusted AVF and age-adjusted fat mass, were assessed using a familial correlation model., Results: The maximal heritability (including genetic and familial environmental effects) for AVF was comparable before (47%) and after (48%) adjusting for fat mass, and was 55% for fat mass itself in these sedentary families. Spouse correlations were significant for fat mass and for AVF prior to, but not after, adjustment for fat mass., Conclusions: These results confirm the only previous study which investigated the familial aggregation of AVF (both in pattern and magnitude), suggesting that the factors underlying AVF in these sedentary families may be similar to those in the population at large. Although both genetic and familial environmental factors probably influence each of fat mass and AVF, there appears to be a predominantly genetic etiology for the visceral component which is independent of total body fat. These findings imply that some individuals are more at risk then others because of an inherited tendency to store abdominal fat viscerally rather than subcutaneously.

Purpose: In studies conducted in several different populations, the M235T substitution in the angiotensinogen (AGT) locus has been associated with hypertension., Methods: A case-control study was initiated in an attempt to replicate this finding. Persons with hypertension, age- and sex-matched normotensive controls, and randomly sampled individuals were probands from the Family Heart Study of the National Heart, Lung, and Blood Institute. Subjects were recruited from the Atherosclerosis Risk in Communities study (ARIC) in North Carolina and Minneapolis, MN, and from the Framingham Heart Study in Massachusetts. Genotypes were determined for the M235T substitution in the AGT locus and for the insertion/deletion polymorphism in the angiotensin-converting enzyme (ACE) locus. Simple association tests as well as logistic regression analyses were performed., Results: The association of AGT-T235 with hypertension was replicated in the Framingham sample (odds ratio, 1.60; 95% confidence interval, 1.11-2.30), but not in the ARIC white or black subjects. However, logistic regression analysis suggested a significant association of AGT with hypertension in both the ARIC white and Framingham samples when the effects of body mass index, triglycerides, and the presence of significant coronary heart disease were controlled. These analyses further suggested that, in the ARIC data, the relationship with the AGT locus is stronger in women than men and that there may be interaction (epistasis) between homozygotes for T235 and ACE-DD in the Framingham data. While the small sample size precluded logistic regression analysis, the frequency of the T235 allele in the black random sample was much higher than in the comparable white sample., Conclusions: These results are compatible with the presence of a genetic risk factor for hypertension in or near the angiotensinogen locus.

Angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) are major components of the renin-angiotensin systems. An association between myocardial infarction (MI) and the ACE DD genotype of the insertion/deletion (ID) polymorphism in intron 16 of the ACE gene has been reported. However, other similarly designed studies have not found such an association. Angiotensin II, the product of AGT, has a direct effect on vascular tone; and a variant in the AGT gene has been found to be associated with MI in the Japanese. This case-control study was initiated to investigate whether the ACEI/D and AGT M235T polymorphisms are associated with an increased risk for coronary heart disease (CHD) and MI. Our study groups were composed of participants in the National Heart Lung Blood Institute (NHLBI) Family Heart Study (FHS) selected from three population-based studies: two Atherosclerosis Risk in Communities (ARIC) centers (Forsyth County, NC, and Minneapolis, MN), and the Framingham Heart Study. In multivariate analysis within ARIC Caucasians, a significant positive association was found between CHD (controls = 230, cases = 232) and the AGT TT genotype (P = 0.022; OR = 1.84, 1.09-3.10 95% CI). When we restricted the analysis to a low-risk group for CHD (controls = 70, cases = 35) an interaction between the ACE DD and AGT TT genotypes was significant (P = 0.025; OR = 5.02 1.22-20.6 95% CI). After further subsetting low-risk cases to those with a definite MI (controls = 74, cases = 16), we found that the associations with the ACE DD genotype was also significant (P = 0.013, OR = 3.94, 1.28-12.2 95% CI). Comparable tests in the Framingham sample failed to support an association of these markers with CHD. In conclusion, within selected groups the ACE D and AGT 235T alleles are statistically associated with CHD and MI, and there is a synergistic interaction between the two alleles. These results and those from previous studies together suggest that the association of these two loci is neither strong nor consistent and involves a complex interaction among risk factors and genotypes.

We investigated the power of the affected sibpair method for detecting a disease locus when the disease is inherited through two bi-allelic loci. The power was computed for all possible values of the gene frequencies and penetrances that lead to a given population prevalence and a given sibling relative risk. A method to generate rapidly all possible models that give a specific population prevalence and relative risk is provided. We applied it to the case of a two-locus disease with a prevalence of 10% and a low sibling relative risk of 1.5. For this particular example, regardless of the true underlying model, a sample size (N = 450 for alpha = 0.05, N = 1,500 for alpha = 0.0001) may be determined such that one would expect enough power (0.80) to detect at least one of the two disease genes. In addition to the general case, we examined a special class of models in which the marginal penetrances at each locus are either recessive or dominant. In this instance, the gene frequencies were excellent predictors of the power afforded by a particular sample size. These methods have been implemented in a C program called SIBPOWER which is freely available from the first author. With this program, investigators can perform their own power calculations for any two-locus model of their choice thus avoiding the need to use single-locus approximations that may grossly underestimate the necessary sample size.

An assumption-free algorithm has been applied to compute the probabilities of all possible identity-by-descent (IBD) configurations when the parents have not been genotyped. These probabilities can be used to determine the amount of information that a particular sibship will bring to a nonparametric linkage analysis. It is shown that the number of possible configurations can be extremely large even when the markers are closely spaced and are rather polymorphic. Further, it is not always possible to reduce this number to a manageable one simply by consideration of the relative probabilities of the configurations.

There is general consensus that linkage with a quantitative trait locus cannot be detected with a reasonable number of sibpairs unless that trait has a very high heritability or the pairs are highly selected. However, the latter may require the screening of a very large number of pairs before a relatively small number of highly informative pairs is attained. At the same time, it is known that, for the same number of typed individuals, larger sibships tend to provide more linkage information than do independent sibpairs. We thus compared the efficiency of two sampling schemes, (1) random and (2) single ascertainment via an individual with an extreme phenotype, for sibship sizes ranging from two to five. The results demonstrate the clear trade-off between sibship size and the stringency of the ascertainment scheme.

We compare the results of genomic scans conducted with the Haseman-Elston sib-pair method using either (1) the average marker information from several adjacent loci or (2) each marker individually. Under smoothing, the squared sib-pair trait difference is regressed on the average number of alleles shared identical by descent averaged at several adjacent loci. This results in a significant decrease in the number of false-positives when compared to the individual marker approach. Linkage of Q4 to MG4 was found only with smoothing but not the individual marker approach. Overall, smoothing resulted in the loss of two true linkages.

In an effort to safeguard against false inference of a major gene in segregation analysis, it has become common practice to require nonrejection of the Mendelian-transmission hypothesis (Mendelian tau's) and rejection of the no-transmission hypothesis (equal tau's). However, it is not known how often one would actually infer a major gene, when one exists, by using these criteria. A simulation study was undertaken to investigate this issue. Segregation of a Mendelian gene under a variety of models was simulated in families with both parents and three children. The data were analyzed by using POINTER; the assumptions under the generating and analysis models were identical. By design, the power to reject the no-major-effect hypothesis (q = 0) was > 60% for all models considered; tests on the transmission probabilities were carried out only when q = 0 was rejected, using alpha = 0.05 for all tests. The rates of Mendelian inference were mostly in the range of 22%-50% under recessive inheritance, versus 60%-99% under dominant inheritance. Notably, it was not possible to resolve the transmission (from among Mendelian tau's, equal tau's, and general unconstrained tau's) in approximately 20%-70% of the cases under recessive models, versus 3%-15% under dominant models. Therefore, while tests on transmission probabilities can serve to reduce rates of false inference of a major gene, it is also possible to fail to infer a major gene when one indeed exists, especially under recessive inheritance.

Regional fat distribution is related to higher risks of cardiovascular morbidity and mortality, independent of general obesity. In particular, a centralized pattern of fat deposition, characterized by greater abdominal stores relative to extremity stores, is associated with a higher propensity to metabolic complications. Motivated by these considerations, we have initiated a systematic investigation of several measures of regional fat distribution aimed at the identification of possible major gene effects. Two measures approximate the size of subcutaneous fat stores: the sum of six skinfold thicknesses (SF6 = abdominal + suprailiac + subscapular + calf + triceps + biceps), and the sum of three trunk skinfold thicknesses (TSF3 = abdominal + suprailiac + subscapular). Both of these phenotypes are highly correlated with total fat mass, 0.83 and 0.78 for SF6 and TSF3, respectively. The trunk to extremity ratio [TER = TSF3/ (calf + triceps + biceps)] is perhaps the most important of these phenotypes insofar as it is an index of centralized obesity; it is modestly correlated with fat mass (r = 0.18). Each of these phenotypes was adjusted for total fat mass by regression prior to analysis so that we could examine genetic effects on these measures of regional fat distribution without the confounding influence of the determinants of fat mass itself. Segregation analysis of SF6 and TSF3 controlled for total fat mass suggests the presence of a major effect underlying the observed phenotypic distribution; however, tests on the transmission probabilities did not substantiate the segregation of a Mendelian gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Fulker and Cardon's interval mapping extension of Haseman and Elston's sib-pair linkage method was used to map loci affecting the quantitative phenotypes presented as part of Problem 2, both adjusted and not adjusted for covariates: Q1 was adjusted for age and the environmental factor (EF); Q2 and Q3 for EF; and Q4 for age, sex, and EF. Adjusted Q2 and Q4 were also log-transformed. The effect of candidate locus C5 (D5G28) on Q1 was detected by a test of association--apparently, allele 1 of C5 is protective (leading to lower values of Q1), allele 2 has no effect, and allele 3 contributes to elevated levels of Q1. C5 accounted for 5.2% of the variation in Q1; it was included as an additional concomitant in the adjustment procedure. Analysis of the correlational structure among the variables revealed that Q4 was not associated with either affected status or Q1 after controlling for the effects of age, and we concluded that Q4 probably does not itself play a role in the etiology of the disease. Mapping studies using a significance level of 0.05 lead to the detection of all the genes, but also resulted in a high frequency of false positive results. On the other hand, using a 0.0005 significance level resulted in the detection of D2G10-11 for both Q1 and Q3, and D1G2 was detected for Q2. One false positive was detected using this significance level and the effects of D1G2 on Q1 and D5G22-23 on Q4 were missed. There was no systematic effect of adjustment for covariates on the detection of loci, although in general, analysis of adjusted phenotypes yielded substantially higher rates of false positives. Finally, this mapping approach correctly located D1G2 and D2G10-11 for Q1 using the nonadjusted phenotype, and D1G10-11 for Q3 using the adjusted phenotype. The maximum difference between the estimated map location from the true location was 1.5 cM. It would be important to estimate the error interval around these inferred locations in order to assess the utility of this method for fine mapping over small (e.g,. 2 cM) intervals.

The familial resemblance for immunoglobulin A, D, E, G, and M levels was investigated with family data collected in Canada and the U.S., entertaining both multifactorial and single gene hypotheses. Significant familial effects were found for each of the immunoglobulins, and there was significant support for a major gene hypothesis for IgA and IgD levels. Whereas there have been several reports suggesting a major gene determinant for IgE levels, including that from our own Canadian study, analysis of the U.S. sample suggested that a multifactorial component parsimoniously explained the observed familial resemblance.

This paper reports the results of commingling and genetic segregation analyses performed on a quantitative reading phenotype in 125 families ascertained through normal, nondisabled readers. Commingling analysis using SKUMIX suggested that the reading phenotype best fit a skewed, single distribution model. Complex segregation using POINTER was then performed on the power adjusted data. While there were some analytical ambiguities and complexities, the segregation analysis indicated that there was familial transmission of the phenotype and that a significant percentage of the variance in this phenotype could be attributed to a major gene with dominance. Because the estimated frequency of the putative dominant allele is .35, 57% of the population would carry at least one copy of this allele. This common allele, with low penetrance, accounted for 54% of the phenotypic variance in reading scores. These findings are considered in the context of our earlier report of major gene influence ona qualitative dyslexic phenotype in a sample of 133 dyslexic proband families that were originally matched to the present sample of control families (Pennington et al., 1991). The applicability of a classic single gene, multifactorial-polygenic, and oligogenic or QTL models for reading ability/disability is discussed.

In the present investigation, we have attempted to identify regions of the genome in which "obesity genes" potentially reside using robust sib-pair linkage analysis. Data were collected on 1,628 individuals in 301 nuclear families residing in the environs of Québec City during the period 1978-1981. In addition to traditional blood group antigens and enzyme polymorphisms, several phenotypes in the obesity domain that are associated with increased morbidity were assessed, including measures relating to heaviness (i.e., the body mass index), body composition and nutrient partitioning (i.e., % body fat), and regional fat distribution without and with standardization for total fat mass (i.e., the sum of six skinfold thicknesses, and the ratio of the sums of trunk to extremity skinfold thicknesses). Three consistent patterns of potential linkage relationships with obesity phenotypes were revealed in these data, involving the marker loci adenosine deaminase, the Kell blood group antigen, and esterase D, which identify chromosomal regions 20q13, 7q33, and 13q14, respectively. Other potential linkages also were identified in the short arm of chromosome 1, interesting because of the presence of the db and fa loci on homologous regions of chromosome 1 in mouse and rat models of obesity, respectively. Each of the tentative linkage relationships reported here warrant follow-up using alternative methods and require replication in independent studies.

Background: Several studies indicate that endogenous hormones play a role in the etiology of coronary artery disease, either as independent risk factors or indirectly, via an effect on lipids, lipoproteins, or other heart disease risk factors., Methods and Results: The relation between endogenous hormone levels and premature (< 56-year-old patients) myocardial infarction was assessed in a retrospective study involving 49 male survivors of premature myocardial infarction and 49 age-matched, volunteer male controls. Serum samples were obtained for each subject the morning after a > or = 12-hour fast and frozen at -70 degrees C for subsequent hormonal analysis. Among the male patients, the average duration between the most recent myocardial infarction and blood sampling was 3.4 years (range, 0.7 to 19.2 years). Individuals reporting the use of any medications with the potential to alter lipid, lipoprotein, or hormone levels were excluded from these analyses. Dehydroepiandrosterone sulfate levels were significantly lower in the patients than in the control subjects. This association remained statistically significant even after accounting for the effects of total cholesterol, triglycerides, the ratio of total to high-density lipoprotein (HDL) cholesterol, HDL, apolipoprotein A-I, apolipoprotein A-II, apolipoprotein B, and body mass index. There were no significant differences in the levels of estradiol, testosterone, or free testosterone or the ratio of estradiol to testosterone between patients and control subjects., Conclusions: Our conclusions are limited by the retrospective nature of this study. However, these data indicate that serum dehydroepiandrosterone sulfate levels are inversely related to premature myocardial infarction in males and that this association is independent of the effects of several known risk factors for premature myocardial infarction.

The power to detect major gene effects by rejection of the "no major gene" null hypothesis against a mixed model alternative was determined in random samples of nuclear families over a variety of conditions. Benchmarks have been developed using a varying number of families whose structure includes both parents and three children. Phenotypes were simulated assuming a Mendelian major gene under either recessive or dominant inheritance, with 0-30% residual polygenic heritability. Three trait prevalences--5, 10, and 20%--were considered in combination with increasing displacement between homozygous means, spanning a range of 14 to 36% of the phenotypic variance attributable to the major gene effect. All other assumptions of the traditional mixed model were adopted in the generating models. Segregation analysis was carried out on the simulated data sets and the proportion of samples out of 200 replications in which the null hypothesis q = 0 was rejected is reported as the power. Thus, failure to detect a major gene effect in this context is solely due to sampling variation, since no other perturbations were introduced. In general, there appears to be greater power to detect dominant major gene effects as opposed to recessive ones using otherwise comparable parameter values, and the effect of varying sibship size under dominant models appears to be greater as well. The use of joint vs. conditional likelihood calculations also was evaluated: substantial drops in power were observed when using conditional likelihoods under recessive inheritance, while the differences in power appeared to be nominal under dominant inheritance. The results of this investigation are offered as a guide to assist in the design of family studies whose aim is to detect major gene effects.

Dehydroepiandrosterone sulfate (DHEAS) was examined in random (control) and nonrandom (case) families participating in the Cincinnati Myocardial Infarction and Hormone (CIMIH) family study. The case families were ascertained through white men who survived a myocardial infarction (MI) before the age of 56, whereas control families were recruited through advertisements and through an adolescent boy maturation study. Both familial correlations and genetic effects of DHEAS were investigated. First, maximum likelihood estimates of the sex-specific familial correlations (corrected for nonrandom ascertainment) suggested that there was significant heterogeneity between the two sampling types. This heterogeneity was isolated to the male sibling correlation, which was higher in the case than control families. Post hoc analyses suggested that the sibling group heterogeneity may be in part a function of age, since the control sample offspring were on average much younger than those in case families. No sex differences other than those for the siblings were noted in the familial correlations. Second, heritability was investigated in control families using a simple path model (TAU) that allowed for sex differences. The only significant model parameter was the sex-specific familiarity (combined polygenic and familial environmental effects), which was larger in females (74%) than in males (29%). In general, these analyses suggested that (1) DHEAS may play only a limited role in the increased risk for premature MI, and (2) the degree of heritable (familial) variation may be dependent on sex.

Familial correlations for total testosterone and free testosterone were examined in both random and nonrandom families participating in the Cincinnati Myocardial Infarction and Hormone Family Study (CIMIH). The non-random families were ascertained through Caucasian males who had survived a myocardial infarction (MI) prior to age 56 years, while random families were recruited largely through an adolescent boy maturation study. Eight sex-specific familial correlations were estimated (father-mother, father-son, father-daughter, mother-son, mother-daughter, son-son, daughter-daughter, and son-daughter) for each of the MI and random samples using maximum likelihood methods with appropriate ascertainment correction. These familial correlations were examined for differences between the random and MI samples, as well as for sex-specific familial patterns. The results suggest that total testosterone levels may have a limited role in determining MI risk, as evidenced by the overall heterogeneity between samples, and lower serum levels in MI than random probands. The pattern of correlations for both androgens suggests that a simple genetic model appears unlikely; however, familiarity cannot be ruled out. Although possible covariate effects such as age and sex may have masked some potentially significant results, especially in males, familiarity in females is suggested (correlations ranging from .3-.9). The relative stability of these hormones in females as compared to that in males may have contributed to its identification, and suggests the familial transmissibility may be associated with adrenal production and/or metabolic clearance of testosterone.

Several recent studies of the body mass index (BMI) have provided support for a recessive major gene influencing heaviness in humans. Segregation analysis of the BMI was carried out recently in a series of randomly sampled French-Canadian families to determine whether we could replicate the major gene finding by using a residual phenotype adjusted for the effects of age and sex. The best model included a recessive major effect for high BMI values with residual familial resemblance; however, Mendelian transmission could not be confirmed, and the no-transmission hypothesis (where all the tau's are constrained to be equal) was not rejected. Considering that the BMI is a complex phenotype affected by many factors and that there are known variations in body composition during growth and aging, we undertook a reanalysis of the data, using a model that allowed the estimation of genotype-specific age and gender effects. New tests on the transmission parameters satisfy the criteria for interfering Mendelian segregation. The results suggest that individuals with the "high" recessive genotype show the greatest degree of heaviness at birth, with a subsequent trend toward lower values throughout life, while individuals with the dominant "normal" genotypes show no appreciable trends with age. In addition, the "high" genotype appears to confer a greater degree of heaviness in females as compared with males. These results, along with other observations from the data, suggest that, while a recessive single gene influence may be discernible, the phenotypic expression of the BMI is likely to be complicated by genotype x environment interactions and, possibly, by the action of other loci. Further, the data also are consistent with the hypothesis that modifying factors may include the adoption of a more prudent life-style by individuals genetically predisposed to heaviness and a secular increase in the incidence, prevalence, and potency of environmentally based triggers leading to a higher penetrance of the "heavy" genotype in the young.

Interest in a single gene etiology for obesity, as assessed by the body mass index (BMI), has been spurred recently by reports of a putative recessive major gene for extreme values, which accounts for as much as 40% of the variance. The major gene hypothesis was evaluated here in the Québec Family Study, a random sample of 375 French-Canadian volunteer families. This report represents one component in a more complete investigation of obesity in these families. In contrast to the recent studies, a major gene hypothesis for BMI was not verified here. Although there was a major effect, it did not conform to a Mendelian pattern of transmission. A multifactorial component (i.e., polygenic and/or common environmental factors) accounted for 42% of the phenotypic variance. In addition, evidence of heterogeneity between the generations was found. The heterogeneity was traced to the major non-Mendelian component (which accounted for 0.01% of the variance in parents and over 40% in offspring) rather than to the multifactorial one. These results would suggest that a simple recessive gene mixed model may not be sufficient to explain the familial distribution of the BMI. Several factors which may have contributed to these results include temporal trends and surrogate effects such as those related to variation in body composition and energy balance components.

Segregation patterns of three body composition measures which were derived from underwater weighing were evaluated in a random sample of 176 French-Canadian families. Two of the variables can be considered as primary partitions of weight (fat mass [FM] and fat-free mass [FFM]), while the remaining variable (percent body fat [%BF]) is a derived index combining the measures of both fat and fat-free weight. This study represents the first report investigating major gene effects for these measures. Segregation analyses revealed that a major locus hypothesis could not be rejected for two of the three phenotypes. The single exception was FFM, for which nearly 60% of the variance was accounted for by a non-Mendelian major effect, which may reflect environmentally based commingling or may be in part a function of gene-environment interactions or correlations. In contrast to the results for FFM, the results for each of FM and %BF were similar and suggested a major locus which accounted for 45% of the variance, with an additional 22%-26% due to a multifactorial component. Given the similarity of the major gene characteristics for these two phenotypes, the possibility that the same gene underlies both measures warrants investigation. A reasonable hypothesis is to consider genes that may influence nutrient partitioning, as the family of candidate genes to receive the major attention.

Regional fat distribution is related to higher risk of diabetes and cardiovascular morbidity and mortality, independent of excess body mass for height. In particular, the male (android) pattern of fat deposition, which is characterized by greater truncal and abdominal fat stores relative to extremity fat levels, is associated with a higher propensity to metabolic complications. Motivated by these considerations, we have initiated a systematic investigation of several measures of regional fat distribution aimed at the detection of possible single gene effects. In this paper, we assess the evidence for commingling in the distributions of these variables in a large French-Canadian study. Two measures approximating the size of subcutaneous fat stores relative to total body fat were considered: the sum of six skinfolds (SF6 = abdominal + supra-iliac + subscapular + calf + tricep + bicep), and the sum of three trunk skinfolds (TSF3 = abdominal + supra-iliac + subscapular). In addition, two measures assessing the distributional pattern of subcutaneous fat were considered: the ratio of TSF3 to the sum of the three extremity skinfolds (TER), and a relative fat pattern index [RFPI = subscapular/(subscapular + supra-iliac)]. All four measures were assessed both prior to and after adjusting for total fat mass, which was measured using underwater weighing. Significant distributional heterogeneity was observed for some of these measures, either between generations and/or between the sexes. In general, however, fat mass adjustment tended to eliminate the heterogeneity; the exception was for RFPI, for which sex differences were noted both prior to and after the adjustment. The finding of commingling of distributions for almost all phenotypes is consistent with (but not evidence for) major gene effects. However, for some of the measures the effect of a putative major locus genotype may be mediated by covariates such as age and/or sex.

Human body mass and composition are heterogeneous phenotypes resulting from the combined effects of genes, environmental factors, and their interactions. In order to gain an understanding of the individual genetic determinants leading to obesity, we have initiated a systematic analysis of several measures of fatness and its phenotypes including: the body mass index (wt/ht2), fat mass, fat-free (lean) mass, the ratio of fat mass over fat-free mass, percent body fat, and a fat mass index (fat mass/ht). In this report, we examine the distributions of these age and sex adjusted variables in a large family study from Québec in terms of evidence for commingling and skewness, and evaluate the inter-relationships among the measures. Fat mass, fat-free mass and the fat mass index conceptually represent primary variables in that they are quantitative measures of relevant components of total body weight; the hypothesis of a single distribution was inferred for each of these primary measures, with significant residual skewness except for fat mass. In general, offspring (8-26 years old) distributions were more positively skewed than parent (30-60 years old) distributions. The remaining variables (body mass index, fat mass to fat-free mass ratio, and percent body fat) are indexes combining information on fat and fat-free mass into single measures. Although offspring data were consistent with a single skewed distribution, commingling was found in the parents in each case. The prominent heterogeneity between generations suggests that there may be significant developmental (genetic or environmental) effects in the transition during growing years to adult pattern phenotypes, particularly for the complex indicators of body composition.

Characterizing the distribution of parameters of iron metabolism by hemochromatosis genotype remains an important goal vis-à-vis potential screening strategies to identify individuals at genetic risk, since a specific marker to detect the abnormal gene has not been identified as yet. In the present investigation, we analyze serum iron values in ascertained families using a method which incorporates both segregation of the clinical affection status and the HLA linkage information to identify the underlying genotypes. The analysis is performed using an extension of the model presented by Bonney et al., comprising regressive models for segregation analysis and the multipoint linkage strategy implemented in LINKAGE. The gene was found to be completely recessive with respect to both clinical manifestations and serum iron abnormalities, with significant differences in expression by sex. Clinical manifestations were present for all male homozygotes in this data set, suggesting that the recessive hemochromatosis genotype is fully penetrant at all ages in males. This was not the case for younger females. Significant genotype-specific age and sex effects were found for serum iron values. It is interesting that deletion of the HLA marker information did not affect our ability to resolve the genetic model when we analyzed a bivariate phenotype. This serves as a reminder that a search for relevant biological markers can be equally important in discerning the genetic etiology of a disease trait, as a search for linked genetic markers.

The segregation of genetic hemochromatosis was analyzed by using percent transferrin saturation (TS) as a phenotypic marker of the disease. Homozygotes for the disease were readily discernable with the added information provided by the quantitative indicator. However, there was no evidence of partial expression of TS abnormalities in heterozygotes, contrary to previous studies.

A bivariate segregation analysis of genetic hemochromatosis with serum ferritin concentration was undertaken to examine the pleiotropic effect of the hemochromatosis locus on each of the two phenotypes, in an ascertained sample of families from Brittany, France. The gene was recessive with respect to both phenotypes, and the estimated gene frequency in the general population was 0.054. Although the ferritin concentration was corrected for the linear relationship with age among controls, there was a residual correlation with age among male family members, consistent with the progressive increase in body iron stores among hemochromatosis homozygotes. This genotype-specific relationship with age illustrates the importance of incorporating interaction effects into analytic models, and suggests that even as a better indicator of progress of disease, rather than liability to disease, serum ferritin concentration serves well to distinguish hemochromatosis homozygotes from alternate genotypes in a family study.

Commingling and segregation of age-sex-adjusted systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial blood pressure (MBP) were examined in 1,560 individuals from 374 French-Canadian nuclear families. After correction for skewness, evidence in favor of two commingled distributions was found for SBP in the combined data (parents and offspring) and in parents, but not in offspring. Segregation analysis (using the computer program POINTER) suggested that a multifactorial contribution to all three phenotypes was greater in offspring than in parents, which could be the result of either polygenic or shared environmental components relevant to sibships, or both. Statistical evidence was found for a major effect on SBP. However, Mendelian transmission of the major effect was rejected, and no transmission of the major effect (equal tau's) was not. This is just the opposite to what would be expected if the major effect was due to a major gene, and it would ordinarily be considered as sufficient evidence to refute a major gene effect on SBP. However, the commingling in parents but not in offspring (who are all below 26 years of age), and the finding of equal transmission probabilities (nearly equal to 1), are compatible with an alternative interpretation. It is possible that there is a real major gene effect on SBP but that the genotype for elevated SBP has not yet expressed itself in the offspring as they have not yet gone through the risk period. Accordingly, this possibility needs to be evaluated further in additional studies involving older offspring.

Evidence for a sex-linked determinant of immunoglobulin M levels was sought using correlational and commingling analyses in a sample of 174 randomly selected nuclear families. While mean IgM levels in females were approximately 25% higher than that in males, the pattern of familial correlations did not follow the expectations under a sex-linked model, and there was no commingling in the distribution of IgM levels as expected when a trait is under the influence of a major gene.

Path analysis is one of several methods available for quantitative genetic analysis, providing for both tests of hypotheses and estimates of relevant parameters. Central to the theory is the assumption that the observations follow a multivariate normal distribution within families. The purpose of the present investigation is to assess the effects of a certain type of departures from multivariate normality using quantitative family data on lipid and lipoprotein levels. The results show that even large departures produce reasonably unbiased parameter estimates. Whereas moderate departures lead to few inferential errors in hypothesis testing, gross departures from multivariate normality may have considerable effects on likelihood ratio tests.

Six laboratory measures of iron metabolism were studied in a control sample, and a family sample was ascertained on the basis of probands with clinically diagnosed genetic hemochromatosis. The respective distribution of each variable evidenced a mixture of components, presumably arising from the segregation of an HLA-linked locus for hemochromatosis. There were significant differences in the distributional characteristics with respect to sex and genotype-specific variances. These aspects of the data have important implications for subsequent segregation and linkage analyses, which traditionally assume homoscedasticity and homogeneity of the genetic effect.

A single 51-member kindred, ascertained on the basis of a normotriglyceridemic proband with depressed high-density lipoprotein cholesterol (HDL-C) and myocardial infarctions at ages 40 and 42, was studied with respect to quantitative variation in HDL-C and apolipoprotein (apo) AI and AII levels. The results of bivariate segregation analysis suggest that the etiology of depressed HDL-C involves one or possibly two major loci: one has a pleiotropic effect on apo AI and apo AII levels and, possibly another one that affects apo AI levels. Both the major loci were characterized as having a dominant allele leading to depression of the respective trait(s). In addition, analysis of the cosegregation of HDL-C and apo AI levels gave evidence of residual nonfamilial factors common to both traits, leading to a positive covariance between them. This could reflect the role of apo AI in the transformation of nascent HDL-C particles into mature ones via its cofactor activity to lecithin cholesterol acyltransferase. The proposed two-locus model represents one possible etiology for the heterogeneous disorder of hypoalphalipoproteinemia. This analysis of a single pedigree does not completely define the genetic mechanism, but it does illustrate a useful new analytic approach.

Discriminant analysis was used to explore multivariate associations with ABO blood types in a biracial sample of 898 Bogalusa youths. Dependent variables included blood pressure (systolic and diastolic), serum lipid and lipoprotein levels (total cholesterol, alpha-, beta-, and pre-beta-lipoprotein cholesterol, and triglycerides), and anthropometric variables (height, weight, right arm length, triceps skinfold thickness, and a computed ponderal index). Analyses performed within race showed that several variables including beta-lipoprotein cholesterol, systolic blood pressure, and the ponderal index were sufficient to discriminate between individuals possessing the B antigen (B and AB) and those not possessing the B antigen (A and O) in the White subsample. However, height in itself can account for the detected difference, B individuals being taller than non-B individuals by a mean value of 2.4 cm. A concordant, but not significant effect was found in the Black subsample. Further tests support the conclusion that the strongest association is between ABO blood type and height.

Complex segregation analysis under the unified mixed model of inheritance (major gene and multifactorial) is performed on families ascertained through 23 probands with hypoalphalipoproteinemia (depressed HDL-cholesterol, denoted HDL-c). Evidence for segregation of a recessive major gene for depressed HDL-c with frequency q = 0.116, in addition to multifactorial transmission (H = 0.572), is found in these families. Reanalysis of a subset of families with severely depressed HDL-c confirms the conclusions based on the original analysis, except that different definitions of "affection" give rise to different estimates of gene frequency. Our finding of a recessive mode of inheritance differs from previous claims for a dominant gene because previous analyses did not use a mixed model for segregation analysis of hypoalphalipoproteinemia. When the significant multifactorial background is neglected, we also find evidence for the invalid claim of a dominant gene. This demonstrates the necessity of using mixed models for determining the mode of inheritance of a given phenotype.

A genetic analysis of the segregation of hereditary hemochromatosis, indexed by the measurement of latent capacity of transferrin (LCAP), was undertaken in an ascertained sample of 147 pedigrees from Brittany, France. There were no mean differences by sex in the distribution of LCAP in the control sample, although in the family data there was a higher representation of males with low values than of females with low values, consistent with the higher proportion of affected males. The results of bivariate segregation analysis revealed no systematic evidence for heterozygous expression either in the biochemical domain of LCAP abnormalities or in increased liability to overt symptomatic disease. Joint consideration of the quantitative variable with hemochromatosis affection status allowed clear resolution of a recessive single-gene inheritance pattern in these families.

Palmar pattern ridge counts were subjected to segregation analysis in an attempt to identify possible major gene effects on these dermatoglyphic traits. The phenotypes considered were total palmar pattern ridge count, and ridge counts for the right interdigital III and IV and left interdigital IV individual palmar areas (sample sizes were too small for the other palmar areas). Evidence of familial resemblance was found for all of the phenotypes studied, and initial evidence for a major effect was found for all but the right palm interdigital III ridge count. However, this initial evidence could be attributed to nongenetic effects in each case, including skewness in the trait distribution. Tests for agreement with Mendelian transmission frequencies were found to be very useful in discriminating between a non-Mendelian major effect and a major gene. We concluded against a major gene effect for any of these traits, and multifactorial inheritance remains a plausible alternative explanation for the familial resemblance.

Genetic and environmental influences in causing a disease are difficult to measure because of lack of precision in identification of relevant nongenetic variables. The Household Relationships Interview and Schedule was developed to measure shared common environment in families (Common Environment Index) and to take into account developmental stages throughout the life cycle and separation/disruption. Seven trained persons interviewed three individuals who reported fictitious interrelated life histories varying in length and complexity. Discrepancies between the recorded data and the true data were analyzed. Overall 96.1% of the items were recorded correctly. Thus, the method has shown good face and construct validity and reliability for measuring quantity of time shared by relatives in a common household. Common environment as measured by this instrument should be a particularly useful tool in behavior-genetic studies.

Atopic disease is generally recognized to be familial, although specific genetic components have yet to be identified. High levels of a unique class of immunoglobulins, immunoglobulin E (IgE), have been shown to be associated with allergies. Several investigators have reported evidence indicating a recessive regulatory locus where an individual with the homozygous recessive genotype has persistently elevated levels of IgE. Willcox and Marsh [1978] have proposed a hypothesis relating IgE production and liability to become allergic. A test of this hypothesis was carried out in the present study. Bivariate segregation analysis of IgE levels and allergy was performed on 173 nuclear families, and the results indicate that an IgE regulatory locus contributes to the familial transmission of allergy. The results are further discussed in the context of the Willcox and Marsh hypothesis.

Sixteen kindreds were ascertained through probands clinically determined to have primary hypoalphalipoproteinemia, characterized by bottom decile high-density lipoprotein cholesterol (HDL-c), but otherwise normolipidemic. Age- and sex-adjusted, standardized HDL-c levels on 64 individuals in 14 nuclear families in which the proband was a parent were analyzed using the unified mixed model of segregation analysis as implemented in the computer program POINTER. The analysis proceeded by using the likelihood of offspring conditional on the parental phenotypes (conditional likelihood), which appears to overcome the limitation of possible heterogeneity in the selection criteria and provides an appropriate correction for the ascertainment. In these families, the multifactorial contribution to the phenotype appears to be small and significant only in the offspring generation. Although it was not possible to resolve the dominance pattern at the major locus since none of a recessive, additive, or dominant hypothesis could be firmly rejected, these families provided clear evidence for a major gene. Genetic heterogeneity is still a possibility, even within "primary" hypoalphalipoproteinemia.

The inheritance of palmar pattern ridge counts for individual palmar areas, combined distal areas, and all ten areas combined was investigated in families belonging to two strictly endogamous Brahmin castes of peninsular India. Ridge count phenotypes were obtained by the method proposed by Malhotra et al. (1981a), however, zero observations (indicating patterns not circumscribed by triradii) were excluded from analysis. Path analytic methods were applied in order to determine the relative influences of polygenes, intrauterine environment, and residual environment. The proportion of genetic variation was, in general, consistently greater in one population than the other, and significant intrauterine environmental effects were detected for the population with lower heritabilities. The results of this investigation suggest that a simple polygenic model may not be sufficient to explain the inheritance of ridge counts in the interdigital IV configurational area. Distal pattern ridge counts do not appear to be influenced by more or less uterine environmental effects than all areas considered together. The proportion of genetic variation for the total palmar pattern ridge count was 52% in both populations.