title: A novel N-terminal motif is responsible for the evolution of neural crest-specific gene-regulatory activity in vertebrate FoxD3.
abstract: The neural crest is unique to vertebrates and has allowed the evolution of their complicated craniofacial structures. During vertebrate evolution, the acquisition of the neural crest must have been accompanied by the emergence of a new gene regulatory network (GRN). Here, to investigate the role of protein evolution in the emergence of the neural crest GRN, we examined the neural crest cell (NCC) differentiation-inducing activity of chordate FoxD genes. Amphioxus and vertebrate (Xenopus) FoxD proteins both exhibited transcriptional repressor activity in Gal4 transactivation assays and bound to similar DNA sequences in vitro. However, whereas vertebrate FoxD3 genes induced the differentiation of ectopic NCCs when overexpressed in chick neural tube, neither amphioxus FoxD nor any other vertebrate FoxD paralogs exhibited this activity. Experiments using chimeric proteins showed that the N-terminal portion of the vertebrate FoxD3 protein is critical to its NCC differentiation-inducing activity. Furthermore, replacement of the N-terminus of amphioxus FoxD with a 39-amino-acid segment from zebrafish FoxD3 conferred neural crest-inducing activity on amphioxus FoxD or zebrafish FoxD1. Therefore, fixation of this N-terminal amino acid sequence may have been crucial in the evolutionary recruitment of FoxD3 to the vertebrate neural crest GRN.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ono
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
authors.forename: Zbynek
authors.initials: Z
authors.lastname: Kozmik
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529, Taiwan; Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Jr-Kai
authors.initials: JK
authors.lastname: Yu
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan. Electronic address: hwada@biol.tsukuba.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Wada
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D009432:Neural Crest / Q000502:physiology*; D012097:Repressor Proteins / Q000502:physiology; D014158:Transcription, Genetic; D014714:Vertebrates / Q000196:embryology*
chemical_list: D051858:Forkhead Transcription Factors; D012097:Repressor Proteins
keywords: Amphioxus; FoxD3; Neural crest