MISEXPRESSION OF THE DROSOPHILA ARGOS GENE, A SECRETED REGULATOR OF CELL DETERMINATION

I have examined the effects on cells in the developing eye of over-exp ressing the argos gene. Transgenic flies carrying argos expressed unde r hsp70 and sevenless control sequences were analysed. All cell types in the developing eye (except bristles) are sensitive to argos concent ration: over-expression leads to too few cells forming, the opposite p henotype to that seen in argos loss-of-function mutants. This effect w as only seen with HS-argos dies: sev-argos hiss, which over-express th e protein at a lower level are not affected, suggesting that a conside rable over-expression is required to disrupt cell fate, However, sev-a rgos is able to rescue argos eye mutations completely, indicating that the normal expression pattern is not critical for wild-type eye devel opment. By transfecting argos into tissue culture cells, I show that t he protein is secreted in a soluble form.