XB-IMG-131813
Xenbase Image ID: 131813
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Fig. 1. Diagram illustrating the segmentation of the paraxial
mesoderm in different vertebrate embryos. The paraxial mesoderm
on the left side of the diagram represents somitogenesis in Xenopus
embryos (Hamilton, 1969) while that on the right represents
somitogenesis in higher vertebrates, such as in a chick or mouse
embryo. In all vertebrates, anterior region of the presomitic
mesoderm appears to be first pre-patterned into somitomeres
(Jacobson and Meier, 1986; Meier, 1979). In Xenopus, however, a
somite forms when a group of myotomal cells segregates, rotate 90°,
and orients parallel to the A-P axis. Each somite consists entirely of
mononucleated myotomal cells while the dermatome does not
undergo segmentation or rotation (Hamilton, 1969). In mouse or
chick embryos, each somite forms when a group of mesenchymal
cells forms an epithelial ball, that then undergoes a further
subdivision into sclerotome, myotome and dermatome. We have
aligned the events of segmentation in the diagram by equating the
segregation of myotomal cells in Xenopus to the formation of an
epithelial ball in chick or mouse. However, what structures are
analogous in the segmentation of different species is not known. Image published in: Jen WC et al. (1997) Copyright © 1997. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. Larger Image Printer Friendly View |