title: Bi-modal strategy of gastrulation in reptiles.
abstract: BACKGROUND
  Amniote gastrulation is often described with respect to human, mouse and chick development by the presence of the primitive streak, a posterior-to-anterior midline morphological cell ingression feature that has come to define Amniote gastrulation. How this midline, ingression-based strategy of gastrulation evolved from the ancestral blastopore, a circumferential involution event in Anamniotes, is unknown. However, within the Amniote clade there exists a more diverse range of gastrulation strategies than just the primitive streak. Investigating gastrulation in a wider range of Amniotes provides a way to understand evolutionary transition from blastopore to the primitive streak.
  
  
  RESULTS
  We analysed early to late gastrulation stages of Chamaeleo calyptratus, showing their unique morphology through confocal imaging of F-actin and laminin-stained embryos to visualise cell morphology and assess basal lamina integrity. We analysed the expression pattern of core mesodermal markers Brachyury and Fgf8 and complimented this analysis with that of the turtle, Trachemys scripta.
  
  
  CONCLUSIONS
  Our analysis suggests that reptile gastrulation is bi-modal; primary internalization occurs anteriorly by means of an incomplete blastopore-like opening, while posteriorly the cells undergo ingression in the Brachyury-expressing blastoporal plate. This strategy stands mid-way between Anamniotes and Avians/Mammals, suggesting that blastoporal plate is a precursor of the avian primitive streak. Developmental Dynamics 244:1144-1157, 2015. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Le Gros Clark Building, South Parks Road, Oxford, United Kingdom.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Stower
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri, USA.
authors.forename: Raul E
authors.initials: RE
authors.lastname: Diaz
authors.affiliation: Instituto de Biomedicina y Biotechnologia de Cantabria-CSIC-Universidad de Cantabria-Sodercan, Santander, Spain.
authors.forename: Lucia Carrera
authors.initials: LC
authors.lastname: Fernandez
authors.affiliation: Southeastern Louisiana University, Hammond, Louisiana.
authors.forename: Mary White
authors.initials: MW
authors.lastname: Crother
authors.affiliation: Southeastern Louisiana University, Hammond, Louisiana.
authors.forename: Brian
authors.initials: B
authors.lastname: Crother
authors.affiliation: Estacion Biologica Doñana-CSIC, C/ Américo Vespudio s/n, Seville, Spain.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Marco
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri, USA.|Department of Anatomy, and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Trainor
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Le Gros Clark Building, South Parks Road, Oxford, United Kingdom.
authors.forename: Shankar
authors.initials: S
authors.lastname: Srinivas
authors.affiliation: Instituto de Biomedicina y Biotechnologia de Cantabria-CSIC-Universidad de Cantabria-Sodercan, Santander, Spain.
authors.forename: Federica
authors.initials: F
authors.lastname: Bertocchini
keywords: blastopore; chameleon; gastrulation ingression; involution; laminin; turtle