The dynamic transmission of positional information in stau- mutants during Drosophila embryogenesis

Intriguingly, the developmental patterning during Drosophila embryogenesis is highly accurate and robust despite its dynamic changes and constant fluctuations. It has been suggested that Staufen (Stau) is key in controlling the boundary variability of the gap protein Hunchback (Hb). However, its underlying mechanism is still elusive. Here, we have developed methods to quantify the dynamic 3D expression of segmentation genes in Drosophila embryos. With improved control of measurement errors, our results reveal that the posterior boundary of the Hb anterior domain (xHb) of stau- mutants shows comparable variability to that of the wild type (WT) and shifts posteriorly by nearly 12% of the embryo length (EL) to the WT position in the nuclear cycle (nc) 14. This observed large shift might contribute significantly to the apparent large variability of xHb in previous studies. Moreover, for stau- mutants, the upstream Bicoid (Bcd) gradients show equivalent gradient noise to that of the WT in nc12-nc14, and the downstream Even-skipped (Eve) and cephalic furrow (CF) show the same positional errors as the WT. Our results indicate that threshold-dependent activation and self-organized filtering are not mutually exclusive but could both be implemented in early Drosophila embryogenesis.