We have designed a system for targeted gene expression that allows the selective activation of any cloned gene in a wide variety of tissue- and cell-specific patterns. The gene encoding the yeast transcriptional activator GAL4 is inserted randomly into the Drosophila genome to drive GAL4 expression from one of a diverse array of genomic enhancers. It is then possible to introduce a gene containing GAL4 binding sites within its promoter, to activate it in those cells where GAL4 is expressed, and to observe the effect of this directed misexpression on development. We have used GAL4-directed transcription to expand the domain of embryonic expression of the homeobox protein even-skipped. We show that even-skipped represses wingless and transforms cells that would normally secrete naked cuticle into denticle secreting cells. The GAL4 system can thus be used to study regulatory interactions during embryonic development. In adults, targeted expression can be used to generate dominant phenotypes for use in genetic screens. We have directed expression of an activated form of the Dras2 protein, resulting in dominant eye and wing defects that can be used in screens to identify other members of the Dras2 signal transduction pathway.

Targeted gene expression as a means of altering cell fates and generating dominant phenotypes.

Notch signaling defines an evolutionarily ancient cell interaction mechanism, which plays a fundamental role in metazoan development. Signals exchanged between neighboring cells through the Notch receptor can amplify and consolidate molecular differences, which eventually dictate cell fates. Thus, Notch signals control how cells respond to intrinsic or extrinsic developmental cues that are necessary to unfold specific developmental programs. Notch activity affects the implementation of differentiation, proliferation, and apoptotic programs, providing a general developmental tool to influence organ formation and morphogenesis.

http://science.sciencemag.org/content/sci/284/5415/770.full.pdf

Notch Signaling: Cell Fate Control and Signal Integration in Development

Cellular Motility Driven by Assembly and Disassembly of Actin Filaments

Publisher Summary This chapter describes techniques concerned with classical and molecular genetics, cell biology, and biochemistry that can be used with Schizosaccharomyces pombe . Conjugation and sporulation cannot take place in S. pombe except under conditions of nutrient starvation. ME medium is generally used for genetic crosses. To cross two strains, a loopful of h – and a loopful of h + are mixed together on a ME plate. The cross is left to dry and is then incubated below 30°, as conjugation is severely reduced above this temperature. Fully formed four-spore asci can be seen after 2–3 days of incubation. A 2 day-old cross is usually used for tetrad analysis. Using a 3-day-old cross, one can check for the presence of asci under the light microscope. Random spore analysis allows many more spores to be examined than in tetrad analysis, and in this way recombination mapping and strain construction can be carried out. Diploid cells arise spontaneously in most S. pombe strains, this characteristic can be used to isolate homozygous diploids of any strain. For mutagenesis of yeast strains, ethylmethane sulfonate (EMS) and nitrosoguanidine is used.

Molecular genetic analysis of fission yeast Schizosaccharomyces pombe.

Wnt proteins are now recognized as one of the major families of developmentally important signaling molecules, with mutations in Wnt genes displaying remarkable phenotypes in the mouse, Caenorhabditis elegans, and Drosophila. Among functions provided by Wnt proteins are such intriguing processes as embryonic induction, the generation of cell polarity, and the specification of cell fate. Until recently, our knowledge of the molecular mechanism of Wnt signaling was very limited, but over the past year, several major gaps have been filled. These include the identification of cell-surface receptors and a novel mechanism of relaying the signal to the cell nucleus. In addition, several components of Wnt signaling are implicated in the genesis of human cancer. These insights have come from different corners of the animal kingdom and have converged on a common pathway. At this junction in this rapidly evolving field, we review our current understanding of Wnt function and signaling mechanisms, doing so in a comparative approach. We have put emphasis on the latest findings, highlighting novelty and underscoring questions that remain. For additional literature, we refer to several previous reviews (McMahon 1992; Nusse and Varmus 1992; Klingensmith and Nusse 1994; Miller and Moon 1996; Moon et al. 1997). We have limited the number of references, particularly in the tables. Fully referenced forms of these tables can be found on the Wnt homepage (http://wwwleland.stanford.edu/∼rnusse/wntwindow.html).

/pdf/wnt-signaling-a-common-theme-in-animal-development-4ifaxai8dj.pdf

Wnt signaling: a common theme in animal development

A P-element vector has been constructed and used to generate lines of flies with single autosomal P-element insertions. The lines were analyzed in two ways: (1) the identification of cis-acting patterning information within the Drosophila genome, as revealed by a lacZ reporter gene within the P element, and (2) the isolation of lethal mutations. We examined 3768 independent lines for the expression of lacZ in embryos and looked among these lines for lethal mutations affecting embryonic neurogenesis. This type of screen appears to be an effective way to find new loci that may play a role in the development of the Drosophila nervous system.

/pdf/searching-for-pattern-and-mutation-in-the-drosophila-genome-5d8a9pa9o0.pdf

Searching for pattern and mutation in the Drosophila genome with a P-lacZ vector.

Flamingo, a seven-pass transmembrane cadherin, regulates planar cell polarity under the control of Frizzled.

Control of Actin Reorganization by Slingshot, a Family of Phosphatases that Dephosphorylate ADF/Cofilin

https://www.cell.com/cell/pdf/0092-8674(87)90518-6.pdf

Tadashi Uemura

Papers

Searching for pattern and mutation in the Drosophila genome with a P-lacZ vector.

Flamingo, a seven-pass transmembrane cadherin, regulates planar cell polarity under the control of Frizzled.

Control of Actin Reorganization by Slingshot, a Family of Phosphatases that Dephosphorylate ADF/Cofilin

DNA topoisomerase II is required for condensation and separation of mitotic chromosomes in S. pombe.

numb, a gene required in determination of cell fate during sensory organ formation in Drosophila embryos