The genetic consequences of phenotypic loss: Transcriptomic and genome-wide analyses of pigmentation regression in cavefish.

University Of Cincinnati Main Campus, Cincinnati OH

Investigators

Abstract

Evolutionary change involves both the addition and loss of traits. Much attention has been paid to those traits that are added over time, but far less is known regarding the loss of traits. Cave-dwelling animals, such as the blind Mexican cavefish, powerfully illustrate this phenomenon since they completely lack eyes and pigmentation. This study applies cutting-edge genetic tools to understand why traits are lost in nature, and will balance our understanding of how evolution shapes and molds organisms to their environment, yielding the enormous diversity found in nature. This project includes outreach activities to engage the public with this remarkable creature. Through partnerships with local schools and the Cincinnati Zoo, the Gross lab will introduce both students and the broader community to this intriguing animal. Additionally, this research project will provide training and research opportunities at the high school, undergraduate, graduate and post-doctoral levels. Further, this project will continue to facilitate interactions with the international Astyanax research community through collaborations and scientific meetings. This work will therefore have positive societal impacts for the American public as well as the international scientific community. This project aims to uncover precise genetic changes underlying evolutionary phenotypic loss. Parallel transcriptomic and genomic approaches will evaluate genetic alterations (coding versus expression levels) implicated in pigmentation loss in a powerful cave model system, Astyanax mexicanus. This freshwater fish harbors two distinct morphotypes, an "ancestral" surface- and multiple "derived" cave-dwelling forms. Some cave populations descended from an 'older' stock, and some descended from a 'younger' stock of surface-dwelling ancestors. These natural replicate experiments allow us to investigate how genetic changes are impacted by diverse influences, such as the amount of time that has passed since the colonization of a cave environment. Recently available genetic and genomic resources now enable high-resolution studies of both known and unknown pigmentation genes for structural, expression and functional analyses. This project will inform how pleiotropy and the age of independent cave populations influence the genetic changes accompanying trait loss. Ultimately, this work will help clarify our understanding of the evolutionary mechanisms (selection versus drift) leading to regression in the natural world.