title: The p21-activated kinase Pak1 regulates induction and migration of the neural crest in Xenopus.
abstract: Pak1 is a member of the PAK family of serine/threonine kinases that are downstream effectors of Rac1 and Cdc42 small GTPases and are implicated in cytoskeleton reorganization. Early expression of Pak1 in Xenopus embryos is tissue restricted, suggesting a role in organogenesis and in cranial neural crest (CNC) cell migration. By observing CNC in vivo and after transplantation, we show that a dominant-negative (DN) Pak1 inhibits its migration. DN-Pak1 also specifically modified the expression of several NC markers. Twist expression was decreased and Snail1 expression posteriorized, but Snail2 (Slug), Sox9 and AP2 were unaffected. DN-Pak1 inhibition of CNC migration could be rescued with Snail1 but not with Twist, which, in fact, cooperated with DN-Pak1 in inhibiting migration. The data confirm that neither Snail1 nor Snail2 expression alone is sufficient for Xenopus CNC migration. Furthermore, they show that, in this tissue, Snail1 and Snail2 expression is not interdependent, nor are these factors subject to obligatory co-regulation, and that their expression depends on signal transduction. Our results also represent the first evidence that Pak1 links extracellular signals to the genetic cascade of transcription factors necessary for CNC specification.
authors.affiliation: Laboratory of Signal Network Dynamics, Cancer Research Centre and Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine; Laval University, Québec, QC, Canada.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bisson
authors.forename: Doris
authors.initials: D
authors.lastname: Wedlich
authors.forename: Tom
authors.initials: T
authors.lastname: Moss
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002465:Cell Movement; D004627:Embryonic Induction; D009154:Mutation; D009432:Neural Crest / Q000166:cytology / Q000196:embryology / Q000201:enzymology / Q000502:physiology*; D055758:SOX9 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000378:metabolism; D051879:Twist-Related Protein 1 / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology* / Q000378:metabolism; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D055758:SOX9 Transcription Factor; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D051879:Twist-Related Protein 1; D054462:p21-Activated Kinases