Using this congenic strain, Lightweight heterozygotes were confirmed to be modestly hyperactive (Figure 4A inset, P<0.01, Student's t-test) and to weigh less than their wild-type littermates [F1,104(genotype) = 87.0, P<0.001] (Figure 4C). To rule out the possibility that a polymorphism in the D2 strain influences these phenotypes, the congenic B6.D2.12D (“Control”) strain (see Figure 2) [30] was also examined. This non-mutagenized, congenic strain harbors a distal portion of the D2 chromosome 12 encompassing all of the genes introgressed in the Lightweight congenic, controlling for all strain-specific polymorphisms in Lightweight animals. Importantly, no difference was observed between Control/+ mice and their wild-type littermates in locomotor activity (P = 0.75, Student's t-test) (Figure 4B) or weight [F1,56(genotype) = 0.45, P = 0.51] (Figure 4D). Taken together, these data strongly support the conclusion that the unc-79 mutation, and not some other lesion or polymorphism, is responsible for the observed phenotypes.
