Our lab is interested in uncovering the molecular mechanisms by which form and structure are generated during vertebrate development and how these processes get modified across evolutionary time to produce phenotypic variation. We combine the study of emerging model organisms, because of their diverse, naturally occurring and ecologically relevant phenotypes, with traditional model species, because of the powerful molecular and genetic tools available, to explore questions relating to patterning and the evolution of novelty in mammalian skin. I will describe how we are using the African striped mouse as a model system to understand formation and evolution of mammalian stripes. In striped mice, stripes result from underlying differences in melanocyte maturation, which give rise to spatial variation in hair color. We identified the transcription factor Alx3 as a regulator of this process. In embryonic dorsal skin, patterned expression of Alx3 foreshadows pigment stripes, and acts to directly repress Mitf, a master regulator of melanocyte differentiation, giving rise to light-colored hair. Moreover, Alx3 is also upregulated in the light stripes of chipmunks, which have independently evolved a similar coat pattern. I’ll end by discussing how we are currently using multiple approaches and additional model systems to gain mechanistic insights into the ways in which phenotypic novelty evolves.