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

Abstract

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 (x Hb ) of staumutants 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 x Hb in previous studies. Moreover, for staumutants, the upstream Bicoid (Bcd) gradients show equivalent gradient noise to that of the WT in nc12-nc14, and the downstream Evenskipped (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.

Patterning principles of morphogen gradients

“…For instance, graded expression of bmp [65] and nodal ligand transcripts in vertebrate blastula and the bicoid RNA gradient in Drosophila blastoderm [66] span about a third or more of total signal gradient range. Lastly, well-studied gradients such as Bicoid in blastoderm [48,67,68] and Dpp in wing disc [48,[67][68][69][70][71][72] provide patterning information to cells on the go (without reaching a steady state).…”