Quantitative trait locus mapping of airway responsiveness to chromosomes 6and 7 in inbred mice

Quantitative trait locus (QTL) mapping was used to identify chromosomal reg ions contributing to airway hyperresponsiveness in mice. Airway responsiven ess to methacholine was measured in A/J and C3H/HeJ parental strains as wel l as in progeny derived from crosses between these strains. QTL mapping of backcross [(A/J x C3H/HeJ) x C3H/HeJ] progeny (n = 137-227 informative mice for markers tested) revealed two significant Linkages to loci on chromosom es 6 and 7. The QTL on chromosome 6 confirms the previous report by others of a linkage in this region in the same genetic backgrounds; the second QTL , on chromosome 7, represents a novel locus. In addition, we obtained sugge stive evidence for linkage (logarithm of odds ratio = 1.7) on chromosome 17 , which lies in the same region previously identified in a cross between A/ J and C57BL/6J mice. Airway responsiveness in a cross between A/J and C3H/H eJ mice is under the control of at least two major genetic loci, with evide nce for a third locus that has been previously implicated in an A/J and C57 BL/6J cross; this indicates that multiple genetic factors central the expre ssion of this phenotype.