A Quantitative Trait Locus for Body Fat on Chromosome 1q43 in French Canadians: Linkage and Association Studies

Objective: To explore a quantitative trait locus (QTL) on human chromosome 1q affecting BMI, adiposity, and fat‐free mass phenotypes in the Quebec Family Study cohort. Research Methods and Procedures: Non‐parametric sibpair and variance component linkage analyses and family‐based association studies were performed with a dense set of chromosome 1q43 microsatellites and single‐nucleotide polymorphism markers in 885 adult individuals. Results: Linkage was observed between marker D1S184 and BMI ( p = 0.0004) and with body fat mass or percentage body fat ( p ≤ 0.0003), but no linkage was detected with fat‐free mass. Furthermore, significant linkages ( p < 0.0001) were achieved with subsamples of sibpairs at both ends of phenotype distributions. Association studies with quantitative transmission disequilibrium tests refined the linkage to a region overlapping the regulator of G‐protein signaling 7 ( RGS7 ) gene and extending to immediate upstream gene loci. Discussion: The present study indicates that the QTL on chromosome 1q43 specifically affects total adiposity and provides a genetic mapping framework for the dissection of this adiposity locus.