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- Title
AmphiFoxE4 , an amphioxus winged helix/forkhead gene encoding a protein closely related to vertebrate thyroid transcription factor-2: expression during pharyngeal development.
- Authors
Yu, Jr-Kai; Holland, Linda Z.; Jamrich, Milan; Blitz, Ira L.; Holland, Nicholas D.
- Abstract
SUMMARYThe full-length sequence and developmental expression of amphioxus AmphiFoxE4 are described. Transcripts of the gene are first detected in the pharyngeal endoderm, where the club-shaped gland is forming and sub-sequently in the definitive gland itself. AmphiFoxE4 is closely related to vertebrate genes encoding the thyroid-specific transcription factor-2 (TTF2), which plays an early developmental role in the morphogenesis of the thyroid gland and a later role in hormone-mediated control of thyroid function. In amphioxus, AmphiFoxE4 expression is not thyroid specific because the club-shaped gland, the only structure expressing the gene, is not homologous to the vertebrate thyroid; instead, the thyroid homologue of amphioxus is a specialized region of the pharyngeal endoderm called the endostyle. We propose that (a) the pharynx of an amphioxus-like ancestor of the vertebrates included a club-shaped gland that expressed FoxE4 as well as an endostyle that did not, and (b) the club-shaped gland soon disappeared in the vertebrate line of descent but (c) not before there was a homeogenetic transfer of FoxE4 expression from the club-shaped gland to the nearby endostyle. Such a transfer could have provided part of the genetic program enabling the endostyle to separate from the pharyngeal endoderm and migrate away as the rudiment of the thyroid gland.
- Subjects
DEVELOPMENTAL genetics; AMPHIOXUS; TRANSCRIPTION factors
- Publication
Evolution & Development, 2002, Vol 4, Issue 1, p9
- ISSN
1520-541X
- Publication type
Article
- DOI
10.1046/j.1525-142x.2002.01057.x