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Nature. 2019 Jan;565(7740):480-484. doi: 10.1038/s41586-018-0865-9. Epub 2019 Jan 16.

Molecular control of macroscopic forces drives formation of the vertebrate hindgut.

Author information

1
Department of Genetics, Harvard Medical School, Boston, MA, USA. nln2113@columbia.edu.
2
Department of Biomedical Engineering, Columbia University, New York, NY, USA. nln2113@columbia.edu.
3
Department of Genetics and Development, Columbia University Medical Center, New York, NY, USA. nln2113@columbia.edu.
4
Department of Genetics, Harvard Medical School, Boston, MA, USA.
5
School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
6
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
7
Department of Physics, Harvard University, Cambridge, MA, USA.
8
Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, MA, USA.
9
Department of Genetics, Harvard Medical School, Boston, MA, USA. tabin@genetics.med.harvard.edu.

Abstract

The embryonic gut tube is a cylindrical structure from which the respiratory and gastrointestinal tracts develop1. Although the early emergence of the endoderm as an epithelial sheet2,3 and later morphogenesis of the definitive digestive and respiratory organs4-6 have been investigated, the intervening process of gut tube formation remains relatively understudied7,8. Here we investigate the molecular control of macroscopic forces underlying early morphogenesis of the gut tube in the chick embryo. The gut tube has been described as forming from two endodermal invaginations-the anterior intestinal portal (AIP) towards the rostral end of the embryo and the caudal intestinal portal (CIP) at the caudal end-that migrate towards one another, internalizing the endoderm until they meet at the yolk stalk (umbilicus in mammals)1,6. Migration of the AIP to form foregut has been descriptively characterized8,9, but the hindgut is likely to form by a distinct mechanism that has not been fully explained10. We find that the hindgut is formed by collective cell movements through a stationary CIP, rather than by movement of the CIP itself. Further, combining in vivo imaging, biophysics and mathematical modelling with molecular and embryological approaches, we identify a contractile force gradient that drives cell movements in the hindgut-forming endoderm, enabling tissue-scale posterior extension of the forming hindgut tube. The force gradient, in turn, is established in response to a morphogenic gradient of fibroblast growth factor signalling. As a result, we propose that an important positive feedback arises, whereby contracting cells draw passive cells from low to high fibroblast growth factor levels, recruiting them to contract and pull more cells into the elongating hindgut. In addition to providing insight into the early gut development, these findings illustrate how large-scale tissue level forces can be traced to developmental signals during vertebrate morphogenesis.

PMID:
30651642
PMCID:
PMC6397660
[Available on 2019-07-16]
DOI:
10.1038/s41586-018-0865-9

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