As a class, mammals display enormous diversity in form and function. From the tiny hog-nosed bat that weighs less than 2 grams to giant 150 ton Blue Whales, mammals walk, run, jump, swim, glide, or fly through nearly every terrestrial, aquatic, or aerial habitat on the planet. This project will take advantage of an excellent model system, the developing mammalian limb, to investigate how gene regulation during development is modified by natural selection to generate biodiversity. Available evidence suggests that mammalian limb diversification has probably not occurred primarily by the evolution of new genes, but by differential regulation of existing genes shared by all mammals. However, it is not known how the regulation of these shared genes is altered to generate the great variation in limb development and form among mammals, nor which specific genes are most important to the development of species-specific limb shape and function. Without this information, it will not be possible to understand the role development has played in shaping the evolution of mammalian limbs, and therefore why mammals have evolved some limb forms and not others. To fill this gap, the project will use a molecular method called RNAseq to compare gene expression during limb development in three mammals: bat (Carollia perspicillata), opossum (Monodelphis domestica), and mouse (Mus musculus). These species are taxonomically diverse, have readily available embryonic materials, and represent extremes of mammalian limb development and adult limb structure. The project will also create new training opportunities for undergraduate and graduate students, provide resources that will advance bats and opossums as emerging model organisms for developmental studies, and identify genes that may be targets for novel therapies in the treatment of birth defects such as limb deformities.
