Meeting Abstract

19.5  Thursday, Jan. 3  Population genetics of the HoxA2 enhancer in killifish (Teleostei: Fundulus) RAINCROW, J.D.*; CHIU, C.H.; Rutgers University; Rutgers University raincrow@biology.rutgers.edu

Hox genes encode transcription factors that play an important role in body axis formation and are likely to have a major influence on the development and evolution of body plans. Hox genes are clustered together on chromosomes along with their cis-regulatory elements. All derived teleost fishes (Class Actinopterygii) examined to date possess at least seven Hox clusters. This extra duplication is not observed in the cartilaginous fishes (sharks), lobe-finned fishes (coelacanth, tetrapods) and basal ray-finned fishes (bichir), i.e. taxa that flank the teleost clade. The discovery of additional Hox clusters in teleosts is intriguing since they are by far the most diverse and morphologically quite disparate group of vertebrates with about 25,000 extant species. One enigmatic feature of teleost Hox clusters is that cis-regulatory sequences show evidence of ongoing evolution within the teleost lineage, creating variation between closely related taxa. What are the mechanisms that could account for this variation over relatively short evolutionary time scales? Are these sequences the target of natural selection? In this study, I investigate the problem using a population genetics approach on populations of sister killifish species (Fundulus olivaceus and F. notatus). I focus on the HoxA2a and HoxA2b enhancers because its variation between paralogs and among teleost species makes it an ideal candidate to test for evidence of selection.