A fundamental question could be a model for the development of other sets of repeated structures. In this project, I would like to examine the basis of limb formation, limblessness and differences between forelimbs and hindlimbs using Fugu rubripes. Fugu is a Japanese pufferfish, which has the fewest vertebrae among animals with backbones, and no pelvic fins.

More specifically, I will identify genes and regulatory elements that are responsible for lack of pelvic fin in Fugu.

At present, most of our knowledge about developmental mechanisms of limb formation comes from experimental analysis of chicken and mouse embryos. In this project, I will built upon that knowledge to gain insight into the molecular genetic basis of limb loss using Fugu rubripes. Fugu is the best model to approach this problem because they lack pelvic fins, although they have complete pectoral fins and because its genome sequence is completely known. I hypothesize that Fugu has a mutation in either a gene needed for hindlimb development, or in a hindlimb-specific regulatory element of a gene necessary for limb development.

There have been few cases in which the evolution of any major morphological trait has been traced to its molecular genetic basis, especially among vertebrates. Thus, illustration of the developmental genetic origin of hindlimb loss in Fugu would be an early example of understanding of how evolution promotes developmental change.