Actin in the Drosophila embryo: is there a relationship to developmental cue localization?

Recent genetic manipulations have revealed that the cytoplasm of the early Drosophila embryo contains localized information that specifies the future embryonic axes. It is the restricted distribution or activity of particular gene products, either messenger RNA or protein, that is crucial for this specification. While some of the genes responsible for this information have been sequenced and the nature and distribution of their products examined, it is not known how this localization is established or maintained. The actin-based cytoskeleton is a likely candidate for the formation of a cytomatrix that would allow such distributions and yet no direct evidence has yet been found that implicates actin in positional cue localization. In this review I summarize what is known about actin filament behavior in Drosophila embryos and compare it to the distribution of positional cues. My purpose is to juxtapose these two bodies of information such that the relationship between them may be revealed.