Influence of genotype-dependent effects of covariates on the outcome of segregation analysis of the body mass index.
- 1 September 1993
- journal article
- Vol. 53 (3), 676-87
Abstract
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.This publication has 27 references indexed in Scilit:
- The transmission probability model is useful to prevent false inference.1993
- COMBINED LINKAGE AND SEGREGATION ANALYSIS USING REGRESSIVE MODELS1988
- Familial resemblance in energy intake: contribution of genetic and environmental factorsThe American Journal of Clinical Nutrition, 1988
- Genetic Analysis of Human Obesity in an Italian SampleHuman Heredity, 1987
- Three limitations of the body mass indexThe American Journal of Clinical Nutrition, 1986
- ROBUSTNESS AND POWER OF THE UNIFIED MODEL IN THE ANALYSIS OF QUANTITATIVE MEASUREMENTS1986
- Morbid Obesity and Related Health RisksAnnals of Internal Medicine, 1985
- Complications of ObesityAnnals of Internal Medicine, 1985
- Health implications of obesity: an NIH Consensus Development Conference.1985
- GENETIC ANALYSIS OF THE STANFORD LRC FAMILY STUDY DATAAmerican Journal of Epidemiology, 1981