Experiment
Linkage analysis was performed on 275 animals from a (NMRI8/Fbn x DBA/2OlaHsd)F2 intercross to identify QTLs associated with multiple body composition traits between 2- to 6-weeks of age. Parental strain NMRI8/Fbn is 2.5 times heavier than parental strain DBA/OlaHsd, and also exhibits 2-fold increased muscle and inner organ weight at age 6 weeks, and 4.2 times the amount of reproductive fat of DBA/2OlaHsd. Ninety-three microsatellite markers at a resolution of 14.1 cM were used for the genome scan.
Significant linkage to body weight at 3-6 weeks of age mapped to 43 cM on mouse Chromosome 1. This locus spans 36 cM - 50 cM and overlaps with QTLs previously identified by the same authors: Bwnd4wk1 (46 cM) and Bwnd5wk1 (46 cM). These symbols have been merged into Mtgq1 (multiple trait growth QTL 1). NMRI8/Fbn-derived alleles at Mtgq1 confer increased body weight. A second locus at 71 cM is linked to body weight at age 6 weeks, muscle weight, liver weight, kidney weight, and spleen weight. This locus is the previously identified QTL Bwnd6wk1 and has been renamed Mtgq5. NMRI8/Fbn-derived at Mtgq5 also confer increased body weight.
Body weight at age 2-6 weeks showed linkage to mouse Chromosome 2 at 54 cM. This locus spans 45 cM - 80 cM and overlaps with previously identified body weight QTLs Bwnd2wk1, Bwnd4wk2, Bwnd5wk2, and Bwnd6wk2. These QTLs have been merged into Mtgq2 (multiple trait growth QTL 2). NMRI8/Fbn-derived alleles at Mtgq2 confer increased body weight with a dominant mode of inheritance. Thislocus is also associated with abdominal fat weight and percentage, liver weight, and kidney weight.
Previously identified QTL Bwnd2wk3 was detected in this study at 70.5 cM on chromosome 3 and has been renamed Mtbcq1 (multiple trait body composition QTL 1). This locus spans 44.5 cM - 83.5 cM and is linked to body weight at age 2-3 weeks. Linkage to liver weight was detected at 39.5 cM. This QTL is named Lvwtq1. NMRI8/Fbn-derived alleles confer increased body weight at Mtbcq1, and increased liver weightat Lvwtq1.
Linkage to body weight at age 6 weeks, abdominal fat weight and percentage, muscle weight, liver weight, and spleen weight mapped to 67.1 cM on mouse Chromosome 4. This locus spans 63.1 cM -74.1 cM and is named Mtbcq2 (multiple trait body composition QTL 2). NMRI8-derived alleles at Mtbcq2 confer increased body composition traits.
Linkage to 6-week body weight was detected at 68 cM on mouse Chromosome 5 and is named Mtbcq3 (multiple trait body composition QTL 3). The QTL interval spans 66cM- 74 cM. NMRI8/Fbn-derived alleles at Mtbcq3 confers increased body weight. The same interval is also linked to spleen weight and is named Swqnd2 (spleen weight QTL 2). NMRI8/Fbn-derived alleles at Swqnd2 confer decreased spleen weight.
An intervalonmouse Chromosome 7 from 17.5 cM - 35.5 cM showed linkage to body weight at 2, 4, 5, and 6 weeks of age (peak at 29.5 cM). These QTLs were previously identified as Bwnd2wk4, Bwnd4wk3, Bwnd5wk4, and Bwnd6wk3. They have been merged into Mtgq3 (multipletrait growth QTL 3). NMRI8/Fbn-derived alleles at Mtgq3 confer increased body weight. Linkage to body weight at age 6-weeks, abdominal fat weight and percentage, muscle weight, and liver weight mapped to 6.5 cM. This locus spans 1.5 cM - 12.5 cM and is namedMtbcq4 (multiple trait body composition QTL 4). NMRI8/Fbn-derived alleles at Mtbcq4 confer increased body composition traits.
An interval on mouse Chromosome 9 from 27 cM - 35 cM showed linkage to body weight at 2, 4, 5, and 6 weeks of age. These QTLs are the same as Bwnd2wk6 (27 cM), Bwnd4wk5 (33 cM), Bwnd5wk5 (30 cM), and Bwnd6wk4 (28 cM). (Suggestive linkage to body weight at 3 weeks of age was also observed.) The QTLs have been merged into the new symbol Mtbcq8 (multiple trait body composition QTL 8). NMRI8/Fbn-derived alleles at Mtbcq8 confer increased body weight.
Linkage to spleen weight mapped to 22 cM on mouse Chromosome 12. The QTL interval spans 17 cM - 40 cM and is named Swqnd1 (spleen weight QTL 1). NMRI8/Fbn-derived alleles confer decreased spleen weight at this locus.
Linkage to muscle weight was detected at 27 cM on mouse Chromosome 13. This QTL spans 16 cM - 39 cM and is named Mswtq1 (muscle weight QTL 1). NMRI8/Fbn-derived alleles confer decreased muscle weight at this locus.
Significant linkage to body weight at 2-5-weeks of age mapped to 23 cM on mouse Chromosome 14. Linkage to abdominal fat weight and percentage, muscle weight, liver weight, kidney weight, and spleen weight was also observed. This locus spans 19 cM - 27 cM andoverlaps with previously identified body weight QTLs Bwnd3wk2, Bwnd4wk6, Bwnd5wk6, and Bwnd6wk5. These QTLs have been merged into Mtgq4 (multiple trait growth QTL 4). NMRI8/Fbn-derived alleles at Mtgq4 confer decreased body weight, organ and fat weights.
Linkage to body weight at age 2-5 weeks mapped to 40.4cM on mouse Chromosome 15. The QTL interval spans 27.4 cM - 53.4 cM. Linkage to abdominal fat percentage, kidney weight, and spleen weight was detected at 57.4 cM. This locus is named Mtbcq5 (multiple trait body composition QTL 5). NMRI8-derived alleles at Mtbcq5 confer decreased body weight and decreased organ and fat weights.
Significant linkage to body weight, abdominal fat weight and percentage, liver weight, and kidneyweight mapped to 27.5cM on mouse Chromosome 17. The QTL interval spans 17.5 cM - 32.5 cM and is named Mtbcq6 (multiple trait body composition QTL 6). NMRI8-derived alleles at Mtbcq6 confer decreased body composition trait values.
Significant linkage to abdominal fat weight and percentage and muscle weight mapped to 34 cM on mouse Chromosome 19. The QTL interval spans 22 cM - 47 cM and is named Mtbcq7 (multiple trait body composition QTL 7). NMRI8/Fbn-derived alleles at Mtbcq7 confer increased fat weight but decreased muscleweight.
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