Past Winner
2008 NSERC André Hamer Postgraduate Prize

Luke Harrison

Doctoral Level

McGill University

It took more than just a bit of ambition for early fish to ditch their fins and grow some limbs, but what that extra something might have been is an important question that has yet to be answered. Luke Harrison, a PhD student in Evolutionary Developmental Biology at the Redpath Museum at McGill University, is currently at work on a thesis that seeks to determine the answer to this 370 million-year-old question.

Harrison, who received an NSERC André Hamer Postgraduate Prize for his research, believes that changes in gene regulatory networks (GRN) during development may be responsible for the transition from fins to limbs in the earliest amphibians. GRNs are like wiring diagrams that represent the interactions between different genes during development in organisms. Previous studies have suggested that changes in the expression of several limb-patterning genes during development are responsible for the growth of limbs as opposed to fins, but the underlying genetic mechanisms causing those changes remain unknown. By combining aspects of paleontology and bioinformatics with lab work, Harrison will test his hypothesis that modifications which occurred in GRN architecture can provide the answer.

Harrison will determine the most likely GRNs that underlie fin and limb development, on either side of the transition, by using lungfish and frogs as models for prehistoric fish and amphibians. He will also use data from zebrafish, chicken and mice to supplement his research when needed.

Once he has estimated the GRNs involved with fin-to-limb evolution, Harrison can form a hypothesis that might explain how expression changes within the limb-patterning genes may have occurred. Based on these hypothesized changes, Harrison will then experimentally manipulate gene expression in the GRN to test his hypothesis that an alteration in GRNs is responsible for guiding the fin-to-limb transition.

This will be the first extensive examination of the evolution of gene networks during a significant vertebrate evolutionary transition. Harrison hopes his research will further validate the concept that GRN-based studies can play a valuable role in explaining the mechanisms of large-scale evolutionary change in vertebrates.