Sorting sloppy Sonic

Abstract

In the classic picture of morphogen-mediated patterning, cells acquire the correct spatial arrangement of specified fates by reading a precisely distributed gradient of morphogen. Xiong et al. now provide evidence for an alternate strategy-cells of the zebrafish neural tube actively sort to their correct positions following disordered specification by Sonic hedgehog.

Figure 1. Cell Sorting in Morphogen-Mediated Patterning

Cell sorting leads to precise patterns from salt-and-pepper specification of neural progenitors. (A) In a cross-section view, the unspecified cells of the neural plate (white) overlay the presumptive notochord expressing Shh (green), creating a shallow gradient (right). (B) As the notochord forms and Shh expression increases, disordered Shh-induced specification, as observed by distinct gene expression programs in the neurectoderm (blue, red, and white cells), begins as the neural plate converges toward the midline. (C) In the neural keel, highly intermingled progenitors (far right) sort to their appropriate positions, such that in the neural rod and tube (D), the neural progenitors are correctly positioned along the dorsal ventral (DV) axis.