Figure 7.

Congenic lines demonstrate an effect of the chromosome 18 genotype on wheel running phenotype. (A) Portions of chromosome 18 have been transferred from the CAST to the B6 background in congenic strains. The early runner phenotype was previously linked to a locus between marker D18Mit122 and D18Mit162 on chromosome 18 (Era1) by QTL analysis (upper panel reproduced from ref.15). Era1 is here aligned with the physical map of chromosome 18 and the genetic markers that have been genotyped as homozygous B6 (black in schematic representations of chromosome 18) or homozygous CAST (white in schematic representation of chromosome 18) in B6.CAST.18P and B6.CAST.18M mice. Marker and genotype information were adopted from Davis et al¹⁷ with modification of the B6.CAST.18M genotypes according to our more detailed genotyping results. The current proximal flanking marker is D18Mit181 and the proximal internal marker is D18Mit51. Wheel running data from one male B6.CAST.18P mouse (B) and one male B6.CAST.18M mouse (C) were double-plotted in percentile actogram format over 20 days (10 days in LD12:12 using 83 lux green light and 10 days in constant dark). Time spent in darkness is indicated by gray shading. (D) Phase angle of entrainment is altered in both congenic strains. Group mean ± SEM values of phase angle of entrainment are derived from DD data. ANOVA, F = 28.69, P < 0.001. ***P < 0.001 vs. B6, Student t. (E) Free running period length is (surprisingly) longer in congenic mice relative to B6. Group mean ± SEM values are shown. ANOVA, F = 34.47, P < 0.001. **P < 0.01; ***P < 0.001 vs. B6, Student t for unpaired measures. B6, B6.CAST.18P and B6.CAST.18M mice also differed significantly from CAST, P < 0.001, Student t for unpaired measures.