Independent Mutations within the Agouti Gene Underlie Different Aspects of Pigmentation Phenotype

Linnen et al. found that the light pigmentation phenotype of light habitat-dwelling deer mice was actually composed of several distinct independently-varying traits (including dorsal lightening, ventral lightening, the placement of the dorsal-ventral boundary, and the coloration of the tail), suggesting an independent genetic basis for each trait. This was confirmed by subsequent sequencing and mapping of the Agouti gene: several SNPs in equilibrium within Agouti contributed to different traits. Implications of this study include a.) that what appears to be a large-effect QTL may actually be a cluster of QTL of small- to moderate-effect; and, b.) that similar seeming phenotypic traits controlled by the same gene may not actually the product of pleiotropy.