Mapping Data

Experiment

• Experiment
  TEXT-QTL
• Chromosome
  8
• Reference
  J:276689 Gray MM, et al., Genetics of Rapid and Extreme Size Evolution in Island Mice. Genetics. 2015 Sep;201(1):213-28
• ID
  MGI:6850656

Genes

Gene	Assay Type
Bw55	visible phenotype
Grq6	visible phenotype

Notes

• Experiment
  Organisms on islands provide a revealing window into the process of adaptation. Populations that colonize islands often evolve substantial differences in body size from their mainland relatives. Although the ecological drivers of this phenomenon have received considerable attention, its genetic basis remains poorly understood. The authors use house mice (subspecies: Mus musculus domesticus) from remote Gough Island to provide a genetic portrait of rapid and extreme size evolution. In just a few hundred generations, Gough Island mice (GI/Wisc) evolved the largest body size among wild house mice from around the world. Through comparisons with a smaller-bodied wild-derived strain from the same subspecies (WSB/EiJ), the authors demonstrate that GI/Wisc mice achieve their exceptional body weight primarily by growing faster during the 6 weeks after birth.
  
  The authors use genetic mapping in large F2 intercrosses between GI/Wisc mice and WSB/EiJ to identify quantitative trait loci (QTL) responsible for the evolution of 16-week weight trajectories. The authors generated a total of 1374 F2 mice: 497 from cross A (WSB/EiJ x GI/Wisc = 279 and GI/Wisc x WSB/EiJ = 218; maternal strain denoted first) and 877 from cross B (WSB/EiJ x GI/Wisc = 494 and GI/Wisc x WSB/EiJ = 383).
  
  Weekly weights were collected for all mice from 1 week through 16 weeks of age, unless they were paired for breeding.
  
  All mice were genotyped on the Mega Mouse Universal Genotyping Array (MegaMUGA; http://www.neogen.com/Agrigenomics/pdf/Slicks/MegaMUGAFlyer.pdf). The MegaMUGA is an Illumina Infinium array that contains ~77,800 markers. Markers are spaced at ~33 kb across the genome and are mostly single nucleotide polymorphisms (SNPs) with a few structural variants and transgenic markers.
  
  QTL analysis was performed by Haley-Knott regression (Haley and Knott 1992) on a 0.5-cM grid across the genome. The authors used conditional genotype probabilities (given the available marker data) calculated assuming a genotyping error rate of 0.2% and the Carter-Falconer map function. While the authors considered data on 11,833 markers, QTL calculations were ultimately based on a fixed grid of 2665 pseudomarkers. Smoothed body weights and estimated growth rates were analyzed separately.
  
  Single-QTL analysis was performed at each of the 16 time points, individually, including indicators for each F1 mother (to account for sibship differences) and sex as fixed additive covariates. The results across time points were combined by averaging the LOD scores across time points at each genomic position to give SLOD scores (Kwak et al. 2014). Thresholds for statistical significance were calculated using a permutation test.
  
  Genetic mapping analysis identified 19 QTL for body weight and growth rate (genome coordinates relative to GRCm38/mm10):
  
  Bw52 (body weight QTL 52) maps to Chr 1: 42.4 - 136.9 Mb with a peak LOD score at 78.9 Mb.
  
  Bw53 (body weight QTL 53) maps to Chr 6: 3.4 - 23.5 Mb with a peak LOD score at 17.9 Mb.
  
  Bw54 (body weight QTL 54) maps to Chr 7: 86.1 - 121.9 Mb with a peak LOD score at 118.9 Mb.
  
  Bw55 (body weight QTL 55) maps to Chr 8: 69.1 - 106.1 Mb with a peak LOD score at 81.5 Mb.
  
  Bw56 (body weight QTL 56) maps to Chr 9: 42.7 - 97.5 Mb with a peak LOD score at 47.3 Mb.
  
  Bw57 (body weight QTL 57) maps to Chr 10: 58.6 - 77.4 Mb with a peak LOD score at 68.1 Mb.
  
  Bw58 (body weight QTL 58) maps to Chr 10: 119.0 - 129.6 Mb with a peak LOD score at 128.1 Mb.
  
  Bw59 (body weight QTL 59) maps to Chr 11: 31.5 - 81.5 Mb with a peak LOD score at 51.5 Mb.
  
  Grq1 (growth rate QTL 1) maps to Chr 1: 73.0 - 92.9 Mb with a peak LOD score at 84.3 Mb.
  
  Grq2 (growth rate QTL 2) maps to Chr 4: 103.1 - 141.6 Mb with a peak LOD score at 104.6 Mb.
  
  Grq3 (growth rate QTL 3) maps to Chr 6: 17.0 - 27.3 Mb with a peak LOD score at 17.9 Mb.
  
  Grq4 (growth rate QTL 4) maps to Chr 7: 38.6 - 86.9 Mb with a peak LOD score at 80.1 Mb.
  
  Grq5 (growth rate QTL 5) maps to Chr 7: 125.4 - 137.0 Mb with a peak LOD score at 118.9 Mb.
  
  Grq6 (growth rate QTL 6) maps to Chr 8: 32.4 - 92.7 Mb with a peak LOD score at 45.9 Mb.
  
  Grq7 (growth rate QTL 7) maps to Chr 10: 16.9 - 88.7 Mb with a peak LOD score at 66.3 Mb.
  
  Grq8 (growth rate QTL 8) maps to Chr 10: 123.3 - 129.6 Mb with a peak LOD score at 125.3 Mb.
  
  Grq9 (growth rate QTL 9) maps to Chr 13: 111.2 - 119.3 Mb with a peak LOD score at 116.5 Mb.
  
  Grq10 (growth rate QTL 10) maps to Chr 15: 19.6 - 42.2 Mb with a peak LOD score at 36.4 Mb.
  
  Grq11 (growth rate QTL 11) maps to Chr 16: 3.5 - 29.8 Mb with a peak LOD score at 26.4 Mb.
  
  Additive effects indicate that GI/Wisc alleles increase weight at most QTL and at most ages.