QTL Hotspot on Mouse Distal Chromosome 1 dataset. We thank Drs. Aldons J. Lusis and Eric Schadt for access to the B6C3HF2 datasets. We thank Drs. Markus Dettenhofer, Philip Leder and their colleagues for providing brains from Fmn2+/+, Fmn2+/2, and Fmn22/2 mice. We thank Michael Hawrylycz and Ed Lein for their assistance with analysis on the Allen Brain Atlas. Finally, we thank Feng Jiao and Shu Hua Qi for technical assistance. Author Contributions Conceived and designed the experiments: LL RWW. Performed the experiments: KM DCC TS. Analyzed the data: KM DCC TS XW RWW. Contributed reagents/materials/analysis tools: LL RWW. Wrote the paper: KM. References 1. DeFries JC, Gervais MC, Thomas EA (1978) Response to 30 generations of selection for open-field activity in laboratory mice. Behav Genet 129: 1432–1435. 2. Caldarone B, Saavedra C, Tartaglia K, Wehner JM, Dudek BC, et al. (1997) Quantitative trait loci analysis affecting contextual conditioning in mice. Nat Genet 17: 335–337. 3. 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