Experiment
Modifiers of the cystic fibrosis (CF) phenotype were mapped to mouse Chromosomes 1, 9, and 10 using allele comparison between B6;129-Cftrtm1Unc and C57BL/6J-Cftrtm1Unc. 108 polymorphic loci at an average spacing of 12 cM - 13 cM were compared betweenthe 2 strains. B6;129-Cftrtm1Unc is a mixed line composed of 95% C57BL/6J and 5% 129X1/SvJ. Although B6;129-Cftrtm1Unc carries the Cftr mutation, these animals exhibit a mild cystic fibrosis phenotype (increased survival, reduced intestinal inflammation, near normal body weight, and reduced mucus accumulation in intestinal crypts) compared to C57BL/6J-Cftrtm1Unc.
Linkage to the mild CF phenotype is linked to D1Mit36 (92.3 cM) on mouse Chromosome 1. This locus is named Cfmq1 (cystic fibrosis modifier QTL 1). Heterozygosity at Cfmq1 appears to confer milder CF traits. Potential candidate genes for Cfmq1 include Kcnj9 (94.2 cM), Kcnj10 (93.5 cM), Tnfsf4 (84.9 cM), Fasl (89 cM), Sele (86.6 cM), Sell (86.6 cM), Selp (86.6 cM), Slamf1 (93.3 cM), Cd48 (93.3 cM), Cd84 (93.3 cM), Slamf6 (89.5 cM), Slamf9, Xcl1 (87 cM), Fcgr2b (92.3 cM), Fcgr3 (92.3 cM), Fcer1g (93.3 cM), Fcer1a (94.2 cM), and Tlr5 (98 cM). Previously identified body weight QTL mapping near Cfmq1 are Cfbw1 (85 cM), Obq9 (88.4 cM), and Bw8q1 (100 cM).
Linkage to the mild CF phenotype is linked to D9Mit90 (9 cM) on mouse Chromosome 9. This locus is named Cfmq2 (cystic fibrosis modifier QTL 2). Homozygosity for 129X1/SvJ-derived alleles at Cfmq2 appears to confer milder CF traits. Potentialcandidate genes for Cfmq2 include Kcnj5 (11 cM), Mmp3 (1 cM), and Mmp7 (1 cM). Previously identified body weight QTL mapping near Cfmq2 are Lbm6 (7.7 cM) and Bwtq4 (8 cM).
Linkage to the mild CF phenotype is linked to D10Mit14 (65 cM) on mouse Chromosome 10. This locus is named Cfmq3 (cystic fibrosis modifier QTL 3). Heterozygosity at Cfmq3 appears to confer milder CF traits. Potential candidate genes for Cfmq3 include Kcnc2 (62 cM), Kitl (57 cM), Lyzs (66 cM), Ifng (67 cM), Il22 (67 cM), Stat2 (70 cM),and Stat6 (70 cM). Previously identified QTL mapping near Cfmq3 are Bgeq8 (57 cM), Pbwg5 (68 cM), and Im5 (65 cM).