Faster embryonic segmentation through elevated Delta-Notch signalling

David J Jörg,Andrew C Oates,Bo-Kai Liao

doi:10.1038/ncomms11861

Abstract

An important step in understanding biological rhythms is the control of period. A multicellular, rhythmic patterning system termed the segmentation clock is thought to govern the sequential production of the vertebrate embryo's body segments, the somites. Several genetic loss-of-function conditions, including the Delta-Notch intercellular signalling mutants, result in slower segmentation. Here, we generate DeltaD transgenic zebrafish lines with a range of copy numbers and correspondingly increased signalling levels, and observe faster segmentation. The highest-expressing line shows an altered oscillating gene expression wave pattern and shortened segmentation period, producing embryos with more, shorter body segments. Our results reveal surprising differences in how Notch signalling strength is quantitatively interpreted in different organ systems, and suggest a role for intercellular communication in regulating the output period of the segmentation clock by altering its spatial pattern.

Highlights

An important step in understanding biological rhythms is the control of period
The venus-yellow fluorescent protein (YFP) tag was inserted to facilitate cellular-level imaging of DeltaD protein in vivo, which will be reported elsewhere; here we focus on the phenotypic effects of this transgene
The mRNA patterns from the transgenic loci are indistinguishable from WT deltaD expression (Fig. 1a–f)

Summary

Introduction

An important step in understanding biological rhythms is the control of period. A multicellular, rhythmic patterning system termed the segmentation clock is thought to govern the sequential production of the vertebrate embryo’s body segments, the somites. DeltaD mutants, known as after eight (aei)[16,17], form their first 10 segments B20% slower than wildtype (WT) and the length of these segments is correspondingly larger; other loss-of-function mutations and pharmacological treatments affecting this pathway show a similar phenotype[18] During this developmental interval the wave pattern has a longer wavelength in the anterior PSM in mind bomb mutants than in WT siblings. We ask whether an appropriately directed increase in Delta-Notch signalling causes a change in segmentation period We approach this by engineering zebrafish with extra copies of a transgene containing the deltaD locus within its full genomic regulatory region to drive the correct spatiotemporal expression pattern. Beyond its previously described role in synchronizing oscillators, these findings suggest that Delta-Notch signalling can affect the wavelength of the tissue’s spatial pattern and thereby alter its output period

Methods

Results

Conclusion