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Inductive interactions and embryonic equivalence groups in a basal metazoan, the ctenophore Mnemiopsis leidyi
Author(s) -
Henry Jonathan Q.,
Martindale Mark Q.
Publication year - 2004
Publication title -
evolution and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.651
H-Index - 78
eISSN - 1525-142X
pISSN - 1520-541X
DOI - 10.1111/j.1525-142x.2004.04001.x
Subject(s) - biology , lineage (genetic) , cilium , cell lineage , embryonic stem cell , cell division , microbiology and biotechnology , evolutionary biology , anatomy , cell , genetics , gene , cellular differentiation
Summary Ctenophores undergo locomotion via the metachronal beating of eight longitudinally arrayed rows of comb plate cilia. These cilia are normally derived from two embryonic lineages, which include both daughters of the four e 1 micromeres (e 11 and e 12 ) and a single daughter of the four m 1 micromeres (the m 12 micromeres). Although the e 1 lineage is established autonomously, the m 1 lineage requires an inductive interaction from the e 1 lineage to contribute to comb plate formation. Successive removal of the e 1 progeny at later stages of development indicates that this interaction takes place after the 32‐cell stage and likely proceeds over a prolonged period of development. Normally, the e 11 cell lies in closest proximity to the m 12 cell that generates comb plate cilia; however, either of the e 1 daughters (e 11 or e 12 ) is capable of emitting the signal required for m 1 descendants to form comb plates. Previous cell lineage analyses indicate that the two e 1 daughters generate the same suite of cell fates. On the other hand, the m 1 daughters (m 11 and m 12 ) normally give rise to different cell fates. Reciprocal m 1 daughter deletions show that in the absence of one daughter, the other cell can gene‐rate all the cell types normally formed by the missing cell. To‐gether, these findings demonstrate that the two m 1 daughters (m 11 and m 12 ) represent an embryonic equivalence group or field and that differences in the fates of the two m 1 daughters are normally controlled by cell–cell interactions. These combined properties of ctenophore development, including the utilization of deterministic cleavage divisions, inductive interactions, and the establishment of embryonic fields or equivalence groups, are remarkably similar to those present in the development of various bilaterian metazoans.