The pattern of expression of two extracellular matrix proteins, tenascin and thrombospondin, is being examined during craniofacial development in mammals. These proteins are thought to be significant in musculosketetal development, in the process of ossification, in the establishment of connective tissue patterning, as well as in a number of other developmental events. Two model systems -- mice and the mini-opossum, Monodelphis domestica -- will be used to test these hypotheses. Specific studies include: the use of PCR cloning techniques to contruct a marsupial cDNA probe to tenascin; the use of these probes to map the spatial and temporal expression of tenascin in cranial skeletal tissues in the developing marsupial neonate; the comparison of the pattern of expression in Monodelphis with that in mice; the collection of pilot data for a future study involving the experimental manipulation of matrix gene expression in vivo by application of exogenous growth factors; and the mapping of expression of thrombospondin in time and space in mic embryos. This project is significant for a number of reasons. First, it will allow an examination of the processes involved in normal craniofacial development and may help illuminate the significance of two molecules thought to be of general significance in development. Second, it will make use of a new model for mammalian development, Monodelphis domestica, in which most development occurs after birth. Additionally, these studies will allow exploration of the molecular basis of heterochronies observed in marsupial and placental mammal development. Finally, in line with the goals of the Career Advancement Award, this project will provide the opportunity to extend previous research into entirely new directions.
