Experiment
From a recombinant congenic (RC) panel generated from crossing the donor strain STS/A onto the background strain BALB/cHeA two highly susceptible RC strains (CcS19/Dem and CcS11/Dem) and the two most resistant RC (CcS10/Dem And CcS20/Dem) strains to colon tumors were tested for their susceptibility to lung tumors. It was observed that, concordant with colon tumor susceptibility or resistance, CcS19 was highly susceptibly to ENU-induced lung tumors compared to Ccs20; and CcS11 was highly susceptible to ENU-induced lung tumors compared to CcS10.
To elucidate the concorndant extreme susceptibility of CcS19 and resistance of CcS10 mice to both colon and lung tumors Sluc loci were mapped in an ENU-treated intercross of 226 (CcS10 x CcS19) F2 mice. The progeny were PCR-genotyped using 23 mircosatellite markers with a maximal distance less than 10 cM between any two markers. The chromosomal regions affecting tumor load, size and number were determined by analysis of variance (ANOVA) using the indiviual microsatellite markers used in the genotyping.
Fifteen Sluc loci were detected that affect tumor size, load and number. Eight of the loci had individual effects and seven were detected only in pair wise interactions in which the effect of one Sluc locus depended on the genotype of a second interacting Sluc locus.
Five of the 15 loci were reported as novel mapping to Chrs 2, 17, 5, 15 and 19.
The authors note that the remaining 10 significant Sluc linkages map very closely or relatively closely to previoulsy published Sluc or Pas loci, Table S2; they could not rule out whether they were duplicate or novel loci.
Curator Note: Because the previoulsy published loci that were noted in Table S2 were all originally mapped in mouse populations that differ from the RC panel used here, we consider the additional 10 loci, as well as the significant interactions identified, in the current study to be novel QTL and have assigned offical nomenclature to them.
Sluc38, a main effects QTL mapped to Chromosome 8 linked with marker D8Mit36 (67.0 cM) in the STS/A donor region, between D8Mit14 (67.0) and D8Mit92 (71.4 cM), inherited from CcS10, p=0.0 01, effecting tumor size in male mice.
Sluc38a (D8Mit36, 67.0 cM) was detected in an interaction with Sluc43c (D4Mit15, 42.6 cM) p=0.04, effecting the tumor sizes in all mice.
[Table 3B, Table S2, QTL Sluc38 referred to in tables as previously mapped, overlapping QTL Sluc9].
Sluc42 mapped to Chromosome 8 with marker D8Mit17 (4.0 cM) in the STS/A donor region, between D8Mit3 (4.0 cM) and D8Mit125 (19.2 cM), inherited from CcS10.
[Table S2 notes this QTL as overlapping with the previously mapped, overlapping QTL Sluc20].
Analysis of these loci strongly indicates that most susceptibility genes for lung and colon cancer are not genetically independent but are pairwise linked.
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