symmetry out, asymmetry in对称,不对称.pdf
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Symmetry 2010, 2, 1033-1054; doi:10.3390/sym2021033
OPEN ACCESS
symmetry
ISSN 2073-8994
/journal/symmetry
Review
Symmetry OUT, Asymmetry IN
Raquel Lourenço 1,2 and Leonor Saúde 1,2,*
1 Instituto de Medicina Molecular e Instituto de Histologia e Biologia do Desenvolvimento,
Faculdade de Medicina da Universidade de Lisboa, Portugal; E-Mail: ralourenco@fm.ul.pt
2 Instituto Gulbenkian de Ciência, Oeiras, Portugal
* Author to whom correspondence should be addressed; E-Mail: msaude@fm.ul.pt.
Received: 15 March 2010; in revised form: 23 April 2010 / Accepted: 18 May 2010 /
Published: 25 May 2010
Abstract: The formation of a perfect vertebrate body plan poses many questions that thrill
developmental biologists. Special attention has been given to the symmetric segmental
patterning that allows the formation of the vertebrae and skeletal muscles. These
segmented structures derive from bilaterally symmetric units called somites, which are
formed under the control of a segmentation clock. At the same time that these symmetric
units are being formed, asymmetric signals are establishing laterality in nearby embryonic
tissues, allowing the asymmetric placement of the internal organs. More recently,
a “shield” that protects symmetric segmentation from the influence of laterality cues was
uncovered. Here we review the mechanisms that control symmetric versus asymmetric
development along the left-right axis among vertebrates. We a
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