Mapping Quantitative Trait Loci for Circadian Behavioral Rhythms in SMXA Recombinant Inbred Strains

SM/J and A/J inbred strain of mice have different characteristics in circadian behaviors such as free-running period (τ), phase relationship (ψ) between light-dark cycles and activity rhythms, and amount of wheel-running activity. To determine the genes which affect these behaviors, a quantitative trait locus (QTL) analysis using SMXA recombinant inbred strains derived from SM/J and A/J mice was performed. Concerning τ, two regions on chromosomes (Chrs) 7 and 18 surpassed the genome-wide suggestive level. As for ψ, one suggestive QTL was detected on Chr 7. The QTLs which affect daily activity counts under light-dark cycles and constant darkness were mapped to the same chromosomal regions on Chrs 1 and 17, respectively. The provisional QTLs detected in the present study might be useful for understanding the complex mechanism regulating circadian behaviors.