AmphiFoxE4, an amphioxus winged helix/forkhead gene encoding a protein closely related to vertebrate thyroid transcription factor‐2: expression during pharyngeal development

Publisher Website
Google Scholar
Abstract
SUMMARYThe full‐length sequence and developmental expression of amphioxusAmphiFoxE4are 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.AmphiFoxE4is 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,AmphiFoxE4expression 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 expressedFoxE4as 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 ofFoxE4expression 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.

This publication has 36 references indexed in Scilit: