First published online September 5, 2008
Development 135, 1901e (2008)
© The Company of Biologists Limited
Liver organogenesis: location matters
During embryogenesis, mesodermal signals induce the morphogenesis of
endodermal organs. But what establishes the correct spatial relationship
between the mesodermal signal-producing cells and the target endoderm? On
p. 3209, Huang and
colleagues report that, during zebrafish liver organogenesis, the expression
of myosin phosphatase targeting subunit 1 (Mypt1, a protein that regulates
myosin) in the lateral plate mesoderm (LPM) ensures that the liver primordium
receives the mesodermal signals needed for its development by setting the
relative positions of these two tissues. The authors identify a liverless
mutant, sq181, that has an inactivating mutation in mypt1.
Hepatoblasts form in this mutant but proliferate poorly and are lost by
apoptosis. Other experiments indicate that the mutation alters the
morphogenesis of the LPM, which leads to the mispositioning of
bmp2a-expressing LPM cells relative to the liver primordium; this
mispositioning of Bmp signals probably causes the sq181 phenotype.
Thus, Mypt1 function (and myosin contractility) may establish the spatial
interaction between mesoderm and endoderm that is essential for liver
organogenesis in zebrafish.

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Related articles in Development:
- Mypt1-mediated spatial positioning of Bmp2-producing cells is essential for liver organogenesis
- Honghui Huang, Hua Ruan, Meng Yuan Aw, Alamgir Hussain, Lin Guo, Chuan Gao, Feng Qian, Thomas Leung, Haiwei Song, David Kimelman, Zilong Wen, and Jinrong Peng
Development 2008 135: 3209-3218.
[Abstract]
[Full Text]