NSF Award
0078131
0078131<br/>Sackerson<br/><br/>The Drosophila body plan is organized into reiterating units called segments. Segmentation occurs early in embryogenesis, and is critically dependent on the proper expression of the transcription factor, even-skipped (eve). In the complete absence of eve function, all segmentation is lost. The segmentation function of eve is carried out through its expression in seven circumferential bands ("stripes") at the blastoderm stage; the seven stripes mark the positions of the future odd-numbered parasegments, and through this positioning, directly and indirectly determine the positions of the fourteen segments. even-skipped stripe 1 (eve stripe 1) is of special interest, since it occurs between the segments which will become head and those which will become trunk; eve stripe 1 also is required for the formation of the cephalic furrow, a transient invagination at the boundary between the head and trunk that occurs early in gastrulation. The position of eve stripe 1 is presumed to be set by an interaction between the patterning systems of the head and trunk.<br/><br/>The objective of this work is to elucidate the mechanisms by which eve stripe 1 is positioned. It is expected that novel insights into gene regulatory mechanisms in the Drosophila embryo will be obtained, since models for the positioning of the other eve stripes in the trunk cannot be extrapolated in a simple way to explain the formation of eve stripe 1. The availability of transgenic flies which express the reporting gene, lacZ, at the position of eve stripe 1, along with clones and the DNA sequence of the eve stripe 1 enhancer, open up the opportunity for a detailed examination of eve stripe 1 expression.<br/><br/>This question will be approached by examining the effects of mutations in early developmental regulators on the expression of eve stripe 1 from the transgenes and from the endogenous locus. The maternal coordinate gene bicoid, and the traditional zygotic gap genes will be examined. In addition, the head-specific gap genes and certain pair-rule and homeotic genes will also be examined for effects. From this data a model will be proposed which will then be tested by the production of further transgenic lines. In this second phase of the work, the mutation of putative cis-regulatory sequences and the misexpression of putative trans-regulatory proteins will both be used to further elucidate the regulatory network involved in eve stripe 1 regulation. It is expected that an understanding of eve stripe 1 regulation will contribute to our understanding of head development in Drosophila, pattern formation, and the spatial control of gene expression.
