title: The Fox and the thyroid: the amphioxus perspective.
abstract: The evolutionary origins of several vertebrate organs are still controversial. The thyroid is classically thought to derive directly from the endostyle (a pharyngeal organ found in urochordates, cephalochordates and lampreys). Several molecular and biochemical lines of evidence agree with this scenario. However, a recent paper,1 describing the expression of a FoxE ortholog in amphioxus, suggests that some molecular pathways might actually have been recruited from an adjacent region of the pharynx. Although additional data from urochordates and lamprey are needed to confirm this hypothesis; these results propose an interesting new scenario for thyroid evolution that involved the reorganisation of genetical and morphological features in the pharyngeal endoderm in order to give rise to a entirely new organ. They also give an indication that the ancestral role of the FoxE gene family was probably limited to the differentiation of part of the pharynx.
authors.affiliation: School of Animal and Microbial Sciences, The University of Reading, PO Box 228, Whiteknights, Reading, RG6 6AJ, UK. f.mazet@reading.ac.uk
authors.forename: Françoise
authors.initials: F
authors.lastname: Mazet
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D019070:Cell Lineage; D002816:Chordata, Nonvertebrate; D004707:Endoderm / Q000378:metabolism; D019143:Evolution, Molecular; D008954:Models, Biological; D010614:Pharynx / Q000378:metabolism; D013961:Thyroid Gland / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics
chemical_list: D014157:Transcription Factors