| Popis: |
The control and function of the msh-class (muscle segment homeobox) genes, Msx-1 and Msx-2, was investigated during vertebrate embryonic development. Experiments were performed on the limbs of mouse and chicken embryos. The limb was chosen as a model developmental system in which it was possible to analyse patterns of Msx gene expression, to relate these patterns to developmental processes known to be occurring and hence to elucidate potential roles for the genes. It was also possible to examine the potential for functional redundancy between the genes. The studies provided evidence that the Msx genes were involved in a wide range of developmental decisions in several tissues, although the actual molecular role of the genes is still uncertain. There was a correlation between the expression of the Msx genes in the limb and the reported expression of bone morphogenetic protein-4 (BMP-4). I performed experiments to show that BMP-4 was an in vivo upstream activator of the Msx genes in the limb. It was therefore possible to suggest elements of the genetic pathways which may be involved in epithelial-mesenchymal interactions at disparate sites around the body, and to suggest a scenario for the evolution of Msx gene expression patterns. The control of Msx-1 was further investigated using a reporter gene consisting of 4.7kb of Msx-1 5' sequence in frame with the lacZ coding sequence. An assay was developed, by means of which the reporter construct could be introduced into cells in culture by microinjection, then grafted into the developing chicken limb in ovo, using X-Gal staining to visualise expression of the gene. The primary aim was to find sequences in Msx-1's promoter which were responsible for induction of Msx-1 in response to the signal from the apical ectodermal ridge (AER.) of the limb. |
