title: Establishing the pre-placodal region and breaking it into placodes with distinct identities.
abstract: Specialized sensory organs in the vertebrate head originate from thickenings in the embryonic ectoderm called cranial sensory placodes. These placodes, as well as the neural crest, arise from a zone of ectoderm that borders the neural plate. This zone separates into a precursor field for the neural crest that lies adjacent to the neural plate, and a precursor field for the placodes, called the pre-placodal region (PPR), that lies lateral to the neural crest. The neural crest domain and the PPR are established in response to signaling events mediated by BMPs, FGFs and Wnts, which differentially activate transcription factors in these territories. In the PPR, members of the Six and Eya families, act in part to repress neural crest specific transcription factors, thus solidifying a placode developmental program. Subsequently, in response to environmental cues the PPR is further subdivided into placodal territories with distinct characteristics, each expressing a specific repertoire of transcription factors that provide the necessary information for their progression to mature sensory organs. In this review we summarize recent advances in the characterization of the signaling molecules and transcriptional effectors that regulate PPR specification and its subdivision into placodal domains with distinct identities.
authors.affiliation: Department of Basic Science and Craniofacial Biology, New York University, College of Dentistry, 345 East 24th Street, New York City, NY 10010, USA. Electronic address: jsj4@nyu.edu.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Saint-Jeannet
authors.affiliation: Department of Anatomy and Regenerative Biology, The George Washington University, School of Medicine and Health Sciences, 2300 I (eye) Street, NW, Washington, DC 20037, USA. Electronic address: samoody@gwu.edu.
authors.forename: Sally A
authors.initials: SA
authors.lastname: Moody
mesh_terms: D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D004475:Ectoderm / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D009432:Neural Crest / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D054258:Neural Plate / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D015398:Signal Transduction; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D051153:Wnt Proteins; D004815:Epidermal Growth Factor
keywords: BMP; Cranial sensory placodes; Eya; FGF; Gene regulatory network; Pax; Pre-placodal ectoderm; Six; Wnt