Quantitative microinjection of Drosophila embryos.

INTRODUCTIONThe quantitative microinjection of drugs, antibodies, toxins, and manipulated RNAs and proteins into Drosophila embryos--the "pharmacological approach"--provides a unique opportunity to analyze cellular functions in the developing embryo, and provides spatial and temporal resolution that is not readily available through genetic studies. These studies require that the observed effects reflect a dose-response relationship so that the data can be accurately interpreted. Quantitative microinjections can be readily achieved with the addition of a fluorescent tracer to the solution to be injected. Analysis of the resulting integrated fluorescent intensity following injection can then be used to determine the volume and hence the concentration of the solution injected. This protocol outlines the procedures for the microinjection and quantification of aqueous solutions during high-resolution observation of early development in the Drosophila embryo.