Evolution of Gene Regulatory Networks for Development of Novel Structures in Echinoderm Embryos

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

The great diversity of animal morphology is due to genomic changes that alter the programming of development; however, the exact nature of such changes is poorly understood. For many technical reasons the genetic basis of development is extraordinarily well understood in sea urchin embryos, especially that of a cell lineage that will form the skeleton of the larva. This cell lineage is an evolutionary novelty as it is not found in the embryos of the other groups of animals related to the sea urchin (e.g. sea stars and sea cucumbers). This provides the exceptional opportunity to understand how regulatory changes have occurred during evolution to allow the development of an entirely novel morphology. All of the same (orthologous) genes, with the exception of just one, that are needed to make the sea urchin skeleton lineage are also expressed in the sea star embryo. This preliminary data demonstrates that this developmental novelty, therefore, is not due to the acquisition of new genes, but rather a change in the way in which these same genes function. This project will determine the regulatory interactions between these orthologous genes in sea star embryos in order to understand how their function has evolved in the sea urchin. Gene products will be perturbed using various molecular approaches and the effect on development and expression of other genes will be determined. A series of cross-species experiments will also be undertaken, where gene products from sea stars will be injected into the embryo of the sea urchin and vice versa. These experiments will directly determine whether there has been an evolutionary change in gene function and how any such changes alter development. This project will provide a highly mechanistic understanding of how evolutionary changes in gene function can lead to the development of novel structures and will provide intensive research experiences for several undergraduates and a woman graduate student.