Elsevier

Developmental Biology

Volume 237, Issue 2, 15 September 2001, Pages 270-281
Developmental Biology

Regular Article
Amphioxus Evx Genes: Implications for the Evolution of the Midbrain–Hindbrain Boundary and the Chordate Tailbud

https://doi.org/10.1006/dbio.2001.0375Get rights and content
Under an Elsevier user license
open archive

Abstract

Evx genes are widely used in animal development. In vertebrates they are crucial in gastrulation, neurogenesis, appendage development and tailbud formation, whilst in protostomes they are involved in gastrulation and neurogenesis, as well as segmentation at least in Drosophila. We have cloned the Evx genes of amphioxus (Branchiostoma floridae), and analysed their expression to understand how the functions of Evx have evolved between invertebrates and vertebrates, and in particular at the origin of chordates and during their subsequent evolution. Amphioxus has two Evx genes (AmphiEvxA and AmphiEvxB) which are genomically linked. AmphiEvxA is prototypical to the vertebrate Evx1 and Evx2 genes with respect to its sequence and expression, whilst AmphiEvxB is very divergent. Mapping the expression of AmphiEvxA onto a phylogeny shows that a role in gastrulation, dorsal–ventral patterning and neurogenesis is probably retained throughout bilaterian animals. AmphiEvxA expression during tailbud development implies a role for Evx throughout the chordates in this process, whilst lack of expression at the homologous region to the vertebrate Midbrain-Hindbrain Boundary (MHB) is consistent with the elaboration of the full organiser properties of this region being a vertebrate innovation.

Keywords

Amphioxus
Evx genes
chordates
gastrulation
neurogenesis
Midbrain–Hindbrain Boundary
tailbud development

Cited by (0)

1

Present address: Division of Zoology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, England.

2

Present address: Centre d'Investigacions en Bioquı́mica i Biologia Molecular, Hospital de la Vall d'Hebrón, Pg. Vall d'Hebrón 119–129, 08035 Barcelona, Spain.

3

To whom correspondence should be addressed. Fax: +34 934110969. E-mail: [email protected].