An exploratory investigation of genetic linkage with body composition and fatness phenotypes: the Québec Family Study.

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.