Multiple-trait quantitative trait loci analysis using a large mouse sibship

Quantitative trait loci influencing several phenotypes were assessed using a genetically heterogeneous mouse population. The 145 individuals were prod uced by a cross between (BALB/cJ X C57BL/6J)F-1 females and (C3H/HeJ X DB/2 J)F-1 males. The population is genetically equivalent to full siblings deri ved from heterozygous parents, with known linkage phase. Each individual in the population represents a unique combination of alleles from the inbred grandparents. Quantitative phenotypes for eight T cell measures were obtain ed at 8 and 18 mo of age. Single-marker locus, repeated measures analysis o f variance identified nine marker-phenotype associations with an experiment wise significance level of P < 0.05. Six of the eight quantitative phenotyp es could be associated with at least one locus having experiment-wide signi ficance. Composite interval, repeated measures analysis of variance identif ied 13 chromosomal regions with comparisonwise (nominal) significance assoc iations of P < 0.001. The heterozygous-parent cross provides a reproducible , general method for identification of loci associated with quantitative tr ait phenotypes or repeated phenotypic measures.