Response of Drosophila embryonic cells to tumor promoters

Drosophila MelanogasterEmbryo Cultures: AnIn VitroTeratogen Assay

An in vitro teratogen assay has been developed that uses Drosophila embryo cell cultures. The endpoints selected in assessing the teratogenic potential of any agent (physical or chemical) involves detection of interference with normal muscle and/or neuron differentiation, induction of heat stock (stress) proteins, and inhibition of normal neurotransmitter levels. Current studies involve use of reporter gene technology (protein fusions) to identify teratogenicity. Results so far suggest that the Drosophila assay is capable of accurately establishing if a particular agent tested can act as a teratogen by a variety of appropriate endpoints (morphological, biochemical, molecular). Furthermore, this assay can be used not only as a teratogen screen, but also in mechanistic studies of abnormal development, gene involvement in teratogenic resistance, and the possible role of heat shock proteins in preventing birth defects.

Activation of mitogen-activated protein kinase by heat shock treatment in Drosophila

Heat shock treatment of Drosophila melanogaster tissue culture cells causes increased tyrosine phosphorylation of several 44 kDa proteins, which are identified as Drosophila mitogen-activated protein (MAP) kinases. Tyrosine phosphorylation occurs within 5 min, and is maintained at high levels during heat shock. It decreases to basal levels during recovery, concurrent with the repression of heat shock transcription and heat-shock-protein synthesis. The increased MAP kinase tyrosine phosphorylation is parallelled by increased MAP kinase activity. At least two MAP kinases, DmERK-A and DmERK-B, are identified whose tyrosine phosphorylation increases during heat shock. Thus MAP kinase activation is an immediate early response to heat shock, and its increased activity is maintained throughout heat shock treatment. Protracted MAP kinase activation may contribute to heat shock transcription factor phosphorylation and the numerous metabolic alterations that constitute the heat-shock response.