Spatially varying mRNA decay contributes to sharpening the even-skipped expression pattern in the Drosophila embryo.

The regulation of mRNA decay is important for numerous cellular and developmental processes. Here, we use the even-skipped (eve) patterning gene in the early Drosophila embryo to investigate whether regulated mRNA decay contributes to shaping the mature striped expression pattern. Using mathematical models to analyze live and fixed imaging data, we show that for eve stripes 2 and 4, spatially regulated degradation rates outperform models with constant or mRNA age-dependent decay. Uniform mRNA decay rates perturb definition of eve stripes 2 and 4 in silico, and we show that altering eve mRNA numbers in vivo by changing the UTR results in dysregulation of the anterior-posterior pair-rule network and embryo segmentation defects. Overall, these data demonstrate how eve mRNA instability can function with transcriptional regulation to define sharp expression domain borders. We discuss the possibility that spatially regulated mRNA stability may be used to help sculpt other expression patterns during development.