Micrornas in the Drosophila Egg and Early Embryo

Posttranscriptional regulation plays a very important role in animal oocytes and embryos. Maternally synthesized mRNAs and proteins control early animal development up until the maternal-to-zygotic transition (MZT). This is the point when the zygotic genome takes control. The maternally deposited mRNAs are posttranscriptionally regulated right from the time they are produced during oogenesis, through egg activation, and in the embryo. microRNAs (miRNAs) are posttranscriptional regulators that have been shown to play a role in both RNA stability and translation. I examined miRNA abundance in Drosophila stage 14 oocytes, activated unfertilized eggs, and embryos and have grouped all the then known Drosophila miRNAs into four distinct temporal classes. Class I and III appear to be maternally deposited, while Class II appears to be both maternally and zygotically transcribed, and Class IV appears to be strictly zygotically transcribed. Follow-up experiments validated three of the four classes. miRNAs of Class IV have previously been shown to play a role in maternal transcript destabilization, and I further show that this is through a SMAUG (SMG) dependent mechanism.