; R o o t E n t r y F , C o m p O b j b W o r d D o c u m e n t O b j e c t P o o l = > ? @ A B C D E F G F Microsoft Word 6.0 Document MSWordDoc Word.Document.6 ; (((( :ll: hl =P u P Z Bookman Old Style (Light) (TT) BriemScript (TT) Playbill (TT) Book Antiqua (TT) Braggadocio (TT) Peignot Medium (Medium) (TT) Arial Narrow (TT) Bookman Old Style (DemiBold Italic) (TT) Parade (TT) Times Bell MT (TT) Onyx (TT 9513550 Small A central question in modern biology is how genetic information establishes body form in higher eukaryotes. In Drosophila, the establishment of the body plan involves the coordinate activities of a hierarchy of segmentation genes, which establish a template of reiterated segments along the anterior-posterior axis, and homeotic genes, which specify the identity of each segment. At every step in the segmentation hierarchy, there are significant refinements in patterns of gene expression that culminate in the expression of the segment polarity genes in patterns of fourteen transverse rows of single cells that will give rise to the future border cells of the segments. The most dramatic example of such a refinement is seen in the transition from the broad expression domains of the gap genes to the metameric striped patterns of the pair-rule genes. Recent molecular analyses suggest that this transition involves direct DNA binding of the protein products encoded by the gap genes to the cis regulatory regions (enhancers) of the pair-rule genes. Although much effort has been expended eluc idating the structure of the enhancers involved in these interactions, relatively little is known about the trans control of the patterns. However, it has been hypothesized that gap proteins may act as graded morphogens to control pair-rule gene activity in a concentration dependent manner. The gap genes also play a crucial role in establishing the positions of expression of the homeotic genes, which are important for specifying the identity of individual segments later in development. This proposal outlines a series of experiments designed to directly test the gradient model of morphogenesis for gap genes during segmentation, and the role of the homeotic genes in segmental specification. In these studies, a combination of genetic analyses and indirect misexpression techniques will be performed to precisely alter gap and homeotic gene expression patterns in the blastoderm. The misexpression experiments will use the well characterized stripe 2 enhancer from the even-skipped gene to control the position and timing of ectopic expression. By manipulating known binding sites in this enhancer, the shape and level of ectopic expression can be changed in a very precise way. Preliminary results suggest that misexpressing the gap gene, knirps causes disruptions in segmentation expression patterns that are consistent with a gradient mechanism of morphogenesis. Surprisingly, the disruptions do not cause lethality during embryogenesis, with many individual mutants surviving to late stages of puparium formation. Therefore, the experiments proposed here will not only permit the analysis of how embryonic genes interact to form more refined expression patterns, but also how these patterns control cell fate decisions important for the formation of the larval and adult body form. *** ; Oh +' 0 $ H l D h R:WWUSERTEMPLATENORMAL.DOT S u m m a r y I n f o r m a t i o n ( < 9513550 eozsaruh eozsaruh @ @ @ @ @ @ F # Microsoft Word 6.0 2 ; e = e a a j j j j j j j 4 1 e T + 4 j 4 j j j j ~ j j j j . 9513550 Small A central question in modern biology is how
