REGULATION OF GENE ACTIVITY IN XENOPUS EARLY DEVELOPMENT

The long term aim of this work is to understand the molecular mechanisms of
gene regulation in the early vertebrate embryo. The cis-acting sequences essential for embryonic gene expression will be
determined by microinjection of cloned genes into fertilized frog eggs.
Following identification of the cis-acting elements, gel retardation and
DNase footprinting techniques will be used to detect and characterize the
DNA-binding proteins that interact with the regulatory elements. The frog
system is ideal for these studies, not only because of the ease of
microinjection, but also because the availability of very large numbers of
embryos will provide an ample source of material for the isolation of DNA-
binding factors. Using this approach, the experiments outlined in this
proposal will investigate gene regulation at two important stages in
embryonic development. Firstly, the regulation of the first genes to be expressed from the zygotic
genome will be examined. The trans-acting factors that regulate these
genes are expected to be maternal and the experiments in this proposal seek
to isolate and characterize these maternal regulatory factors. It is
important to understand how maternal factors regulate zygotic gene
transcription because this step is critical for the success of all
subsequent embryonic development. Secondly, the regulation of genes expressed during neurogenesis will be
examined. Neural induction is one of the classic problems of developmental
biology but almost nothing is known of its mechanism. The experiments in
this proposal will identify the cis and trans-acting factors responsible
for the temporal and tissue-specific regulation of the neural cell adhesion
molecule, (N-CAM), which is one of the first genes to be transcribed in
response to neural induction. These studies will lead to a better understanding of transcriptional
regulation in vertebrate embryos. In particular, basic information on the
regulation of neural genes will contribute to a complete picture of
neurogenesis, and this in turn will be important for understanding the
neurogenic defects that result in anencephaly and spina bifida.