Experiment
The role of secreted inflammatory factors in carcinogenesis led authors to map QTLs associated with macrophage-associated inflammatory factors in animals harboring known Sluc (susceptibility to lung cancer) loci. Crosses between mouse strains NXT-10/Dem,NXT-20/Dem, and O20/A were used. NXT-10/Dem and NXT-20/Dem are derived from donor recombinant congenic OcB-9/Dem and background strain O20/A. NXT-10/Dem differs from O20/A at approximately 10% of the genome across 6 chromosomes (chr.2,4,6,8,16,19), whileNXT-20/Dem differs from O20/A at approximately 10% of the genome across 7 chromosomes (chr.2,4,6,7,8,11,19).
Bone marrow-derived macrophages (BMMf) were cultured from 30 (NXT-10/Dem x O20/A)F2 animals and exposed to a panel of inflammation-related assays. Linkage analysis was performed using microsatellite markers covering regions of the genome that differed between NXT-10/Dem and O20/A. Significant linkage to TNF-alpha secretion, iNOS expression, and LPS-stimulated IL12p40 secretion was detected at 57cM on mouse Chromosome 4 near D4Mit60. Significant linkage to TNF-alpha secretion was detected at 10 cM on mouse Chromosome 8 near D8Mit3, and suggestive linkage to iNOS expression, and LPS-stimulated IL12p40 secretion was detected at 15 cM on mouse Chromosome 19 near D19Mit60. Significant linkage between sex and iNOS expression was also observed.
The loci mapped in the above cross were examined in 35 (NXT-20/Dem x O20/A)F2 intercross animals for confirmation. BMMf from these animals were exposed to inflammation-related assays and typed for microsatellite markers. Significant linkage to TNF-alpha secretion mapped to 19.5 cM on mouse Chromosome 8 near D8Mit125 and suggestive linkage to sex of the animal with various assays mapped to 66 cM on mouse Chromosome 4 near D4Mit54, thus confirming these 2 loci.
The data sets for the 2 different crosses were combined and reanalyzed. Significant linkage was observed for D4Mit54 and TNF-alpha secretion (and sex), IL12p40 secretion (and sex), iNOS expression (and sex), and LPS-stimuated IL12p40 secretion. This chromosome 4 locus is named Marif1 (macrophage-associated risk inflammatory factor 1). The Marif1 interval overlaps with several previously mapped QTLs: Sluc21 (63 cM), Idd11 (64.6 cM), Sluc6 (67 cM), Ltsd4 (67 cM), Mom1 (68 cM, now Pla2g2a), Ssic1 (67 cM), and Cdcs9 (71 cM).
Significant linkage was observed for D8Mit125 and TNF-alpha secretion (and sex), IL12p40 secretion (and sex), and iNOS expression (and sex). This chromosome 8 locus is named Marif2. TheMarif2 interval overlaps with several previously mapped QTLs: Scc8 (4 cM), Sluc20 (10 cM), Eae24 (10 cM), Ltsd3 (10 cM), Pgia4 (17 cM), Cdcs4 (21 cM), and Eae14 (21 cM).
Significant linkage was observed for D19Mit60 and IL12p40 secretion (and sex), and and LPS-stimuated IL12p40 secretion. This locus on chromosome 19 is named Marif3. The Marif3 interval overlaps with previously identified QTL Pgia23 (20 cM).
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