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- Title
Expression of <italic>six3</italic> and <italic>otx</italic> in Solenogastres (Mollusca) supports an ancestral role in bilaterian anterior‐posterior axis patterning.
- Authors
Redl, Emanuel; Scherholz, Maik; Wollesen, Tim; Todt, Christiane; Wanninger, Andreas
- Abstract
The homeodomain transcription factors <italic>six3</italic> and <italic>otx</italic> are involved in patterning the anterior body and parts of the central nervous system (CNS) in bilaterians. Their similar expression patterns have been used as an argument for homology of heads, brains, segmentation, and ciliated larvae. We investigated the developmental expression of <italic>six3</italic> and <italic>otx</italic> in the aplacophoran mollusk <italic>Wirenia argentea</italic>. <italic>Six3</italic> is expressed in subepithelial cells delimiting the apical organ of the solenogaster pericalymma larva. <italic>Otx</italic> is expressed in cells of the prototroch and adjacent regions as well as in posterior extensions of the prototrochal expression domain. Advanced larvae also show pretrochal <italic>otx</italic> expression in the developing CNS. Comparative analysis of <italic>six3</italic> and <italic>otx</italic> expression in bilaterians argues for an ancestral function in anterior‐posterior body axis patterning but, due to its presence in animals lacking a head and/or a brain, not necessarily for the presence of these morphological structures in the last common ancestor (LCA) of bilaterians. Likewise, the hypothesis that the posterior border of <italic>otx</italic> expression corresponds to the border between the unsegmented head and the segmented trunk of the LCA of protostomes is not supported, since <italic>otx</italic> is extensively expressed in the trunk in <italic>W. argentea</italic> and numerous other protostomes.
- Subjects
SOLENOGASTERS; CENTRAL nervous system; HOMOLOGY (Biochemistry); TRANSCRIPTION factors; ECTODERM
- Publication
Evolution & Development, 2018, Vol 20, Issue 1, p17
- ISSN
1520-541X
- Publication type
Article
- DOI
10.1111/ede.12245