Sequence and developmental expression of AmphiDll, an amphioxus Distalless gene transcribed in the ectoderm, epidermis and nervous system: insights into evolution of craniate forebrain and neural crest

Citations Over TimeTop 10% of 1996 papers

Abstract

The dynamic expression patterns of the single amphioxus Distal-less homolog (AmphiDll) during development are consistent with successive roles of this gene in global regionalization of the ectoderm, establishment of the dorsoventral axis, specification of migratory epidermal cells early in neurulation and the specification of forebrain. Such a multiplicity of Distal-less functions probably represents an ancestral chordate condition and, during craniate evolution, when this gene diversified into a family of six or so members, the original functions evidently tended to be parcelled out among the descendant genes. In the amphioxus gastrula, AmphiDll is expressed throughout the animal hemisphere (presumptive ectoderm), but is soon downregulated dorsally (in the presumptive neural plate). During early neurulation, AmphiDll-expressing epidermal cells flanking the neural plate extend lamellipodia, appear to migrate over it and meet mid-dorsally. Midway in neurulation, cells near the anterior end of the neural plate begin expressing AmphiDll and, as neurulation terminates, these cells are incorporated into the dorsal part of the neural tube, which forms by a curling of the neural plate. This group of AmphiDll-expressing neural cells and a second group expressing the gene a little later and even more anteriorly in the neural tube demarcate a region that comprises the anterior three/fourths of the cerebral vesicle; this region of the amphioxus neural tube, as judged by neural expression domains of craniate Distal-less-related genes, is evidently homologous to the craniate forebrain. Our results suggest that craniates evolved from an amphioxus-like creature that had the beginnings of a forebrain and possibly a precursor of neural crest - namely, the cell population leading the epidermal overgrowth of the neural plate during early neurulation.

Related Papers

• → Histological and ultrastructural studies on the origin of caudal neural crest cells in mouse embryos(1984)39 cited
• → Identification of transcripts potentially involved in neural tube closure using RNA sequencing(2018)10 cited
• → The spatial and temporal pattern of C-Lmx1 expression in the neuroectoderm during chick neurulation(1999)24 cited
• → Genetic Regulation of Early Nervous System Development(2005)
• Characterization of an individual neural crest-like cell lineage in the invertebrate chordate Ciona intestinalis(2008)