Real-time monitoring of an endogenous Fgf8a gradient attests to its role as a morphogen during zebrafish gastrulation

Research output: Contribution to journalResearch articleContributedpeer-review


Morphogen gradients impart positional information to cells in a homogenous tissue field. Fgf8a, a highly conserved growth factor, has been proposed to act as a morphogen during zebrafish gastrulation. However, technical limitations have so far prevented direct visualization of the endogenous Fgf8a gradient and confirmation of its morphogenic activity. Here, we monitor Fgf8a propagation in the developing neural plate using a CRISPR/Cas9-mediated EGFP knock-in at the endogenous fgf8a locus. By combining sensitive imaging with single-molecule Fluorescence Correlation Spectroscopy (FCS), we demonstrate that Fgf8a, produced at the embryonic margin, propagates by diffusion through the extracellular space and forms a graded distribution towards the animal pole. Overlaying the Fgf8a gradient curve with expression profiles of its downstream targets determines the precise input-output relationship of Fgf8a-mediated patterning. Manipulation of the extracellular Fgf8a levels alters the signaling outcome, thus establishing Fgf8a as a bona fide morphogen during zebrafish gastrulation. Furthermore, by hindering Fgf8a diffusion, we demonstrate that extracellular diffusion of the protein from the source is critical for it to achieve its morphogenic potential.


Original languageEnglish
Article numberdev201559
JournalDevelopment (Cambridge, England)
Issue number19
Publication statusPublished - 4 Sept 2023

External IDs

unpaywall 10.1242/dev.201559
ORCID /0000-0002-7133-7474/work/142251282
ORCID /0000-0003-0283-0211/work/142257357
Scopus 85174319944


Sustainable Development Goals


  • Animals, Body Patterning/genetics, Fibroblast Growth Factors/genetics, Gastrulation/genetics, Morphogenesis/genetics, Signal Transduction/genetics, Zebrafish, Zebrafish Proteins/genetics