Presenter: Sophie Sichel
Mentor: William Cresko and Kristin Alligood, Biology
Poster: 58
Major: Biology
In vertebrates the development of the cranial skeleton is imperative because it provides structure and support for a number of critical organs. Cranial structures vary immensely across vertebrates, but how did these different mechanisms of morphogenesis evolve at the developmental and cellular level? To elucidate the molecular mechanisms controlling variation in morphogenesis, I used the opercle bone of threespine stickleback fish as a model. Threespine stickleback are used as a model to investigate vertebrate evolution because of rapid changes between ancestral oceanic and derived freshwater forms of this fish. The opercle bone is a neural crest-derived dermal bone that is critical for respiration, foraging and communication in stickleback, undergoes morphogenesis during development, and varies among populations. Neural crest cells form the facial skeleton of vertebrates through intramembranous ossification. After the initial condensation, bone shaping is hypothesized to be dependent on the recruitment of new osteoblasts in a space and time dependent manner, and variation in bone morphogenesis would therefore be linked to differences in osteoblast recruitment. To test this hypothesis, I conducted in situ hybridizations using a probe to col10a1, which is a gene present in the cartilaginous precursor of mature dermal bone, on stickleback embryos at various times during embryonic development. This probe allowed me to visualize the developing opercle and a proliferation assay to visualize proliferating cells thought to be contributing to the developing bone. I quantified the number of proliferating cells and determined their distribution near the developing edge of the opercle in two different populations of stickleback: a population that exhibits an ancestral phenotype and a population representing the derived phenotype. I will present results describing how the number of cells recruited varies among populations. Determining the molecular and genetic factors that underlie opercle development and how they differ between ancestral and derived populations could provide evidence for how development and evolution interact on a larger scale.