Quantitative analyses reveal extracellular dynamics of Wnt ligands in Xenopus embryos
- National Institute for Basic Biology, Japan
- RIKEN, Japan
- University of Tokyo, Japan
- Kyoto University, Japan
- National Institutes of Natural Sciences, Japan
Abstract
The mechanism of intercellular transport of Wnt ligands is still a matter of debate. To better understand this issue, we examined the distribution and dynamics of Wnt8 in Xenopus embryos. While Venus-tagged Wnt8 was found on the surfaces of cells close to Wnt-producing cells, we also detected its dispersal over distances of 15 cell diameters. A combination of fluorescence correlation spectroscopy and quantitative imaging suggested that only a small proportion of Wnt8 ligands diffuses freely, whereas most Wnt8 molecules are bound to cell surfaces. Fluorescence decay after photoconversion showed that Wnt8 ligands bound on cell surfaces decrease exponentially, suggesting a dynamic exchange of bound forms of Wnt ligands. Mathematical modelling based on this exchange recapitulates a graded distribution of bound, but not free, Wnt ligands. Based on these results, we propose that Wnt distribution in tissues is controlled by a dynamic exchange of its abundant bound and rare free populations.
Data availability
Sequence data for anti-HA IgG genes have been deposited in Genbank/DDBJ under accession codes LC522514 and LC522515.
Article and author information
Author details
Funding
Japan Science and Technology Agency (JPMJPR194B)
- Yusuke Mii
Japan Society for the Promotion of Science (24870031)
- Yusuke Mii
Japan Society for the Promotion of Science (15K14532)
- Yusuke Mii
Japan Society for the Promotion of Science (18K14720)
- Yusuke Mii
Japan Society for the Promotion of Science (17K19418)
- Shinji Takada
Japan Society for the Promotion of Science (24657147)
- Yusuke Mii
- Masanori Taira
National Institutes of Natural Sciences (1311608,01311801)
- Yusuke Mii
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Ariel M Pani, University of Virginia, United States
Ethics
Animal experimentation: All experiments using Xenopus laevis were approved by the Institutional Animal Care and Use Committee, National Institutes of Natural Sciences (Permit Number 18A038, 19A062, 20A053), or the Office for Life Science Research Ethics and Safety, University of Tokyo.
Version history
- Received: January 13, 2020
- Accepted: April 23, 2021
- Accepted Manuscript published: April 27, 2021 (version 1)
- Version of Record published: May 21, 2021 (version 2)
Copyright
© 2021, Mii et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Quantitative analyses reveal extracellular dynamics of Wnt ligands in Xenopus embryos
eLife 10:e55108.
https://doi.org/10.7554/eLife.55108
Further reading
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- Developmental Biology
We previously showed that SerpinE2 and the serine protease HtrA1 modulate fibroblast growth factor (FGF) signaling in germ layer specification and head-to-tail development of Xenopus embryos. Here, we present an extracellular proteolytic mechanism involving this serpin-protease system in the developing neural crest (NC). Knockdown of SerpinE2 by injected antisense morpholino oligonucleotides did not affect the specification of NC progenitors but instead inhibited the migration of NC cells, causing defects in dorsal fin, melanocyte, and craniofacial cartilage formation. Similarly, overexpression of the HtrA1 protease impaired NC cell migration and the formation of NC-derived structures. The phenotype of SerpinE2 knockdown was overcome by concomitant downregulation of HtrA1, indicating that SerpinE2 stimulates NC migration by inhibiting endogenous HtrA1 activity. SerpinE2 binds to HtrA1, and the HtrA1 protease triggers degradation of the cell surface proteoglycan Syndecan-4 (Sdc4). Microinjection of Sdc4 mRNA partially rescued NC migration defects induced by both HtrA1 upregulation and SerpinE2 downregulation. These epistatic experiments suggest a proteolytic pathway by a double inhibition mechanism:
SerpinE2 ┤HtrA1 protease ┤Syndecan-4 → NC cell migration.
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- Developmental Biology
- Neuroscience
Human fetal development has been associated with brain health at later stages. It is unknown whether growth in utero, as indexed by birth weight (BW), relates consistently to lifespan brain characteristics and changes, and to what extent these influences are of a genetic or environmental nature. Here we show remarkably stable and lifelong positive associations between BW and cortical surface area and volume across and within developmental, aging and lifespan longitudinal samples (N = 5794, 4–82 y of age, w/386 monozygotic twins, followed for up to 8.3 y w/12,088 brain MRIs). In contrast, no consistent effect of BW on brain changes was observed. Partly environmental effects were indicated by analysis of twin BW discordance. In conclusion, the influence of prenatal growth on cortical topography is stable and reliable through the lifespan. This early-life factor appears to influence the brain by association of brain reserve, rather than brain maintenance. Thus, fetal influences appear omnipresent in the spacetime of the human brain throughout the human lifespan. Optimizing fetal growth may increase brain reserve for life, also in aging.
