Cell fate polarization in ascidian mesenchyme/muscle precursors by directed FGF signaling and role for an additional ectodermal FGF antagonizing signal in notochord/nerve cord precursors.
Asymmetric cell division plays a fundamental role in generating various types of embryonic cell. In ascidian embryos, asymmetric cell divisions occur in the vegetal hemisphere in a manner similar to those found in Caenorhabditis elegans. Early divisions in embryos of both species involve inductive events on a single mother cell that result in production of daughters with different cell fates. Here we show in the ascidian Halocynthia roretzi that polarity of muscle/mesenchyme mother precursors is determined solely by the direction from which the FGF9/16/20 signal is presented, a role similar to that of Wnt signaling in the EMS and T cell divisions in C. elegans. However, polarity of nerve cord/notochord mother precursors is determined by possible antagonistic action between the FGF signal and a signal from anterior ectoderm, providing a new mechanism underlying asymmetric cell division. The ectoderm signal suppresses MAPK activation and expression of Hr-FoxA, which encodes an intrinsic competence factor for notochord induction, in the nerve cord lineage.
Kim
Gil Jung
GJ
Faculty of Marine Bioscience and Technology, Kangnung National University, Gangneung Daehangno, Gangneung 210-702, Republic of Korea. gjkim@kangnung.ac.kr
Kumano
Gaku
G
Nishida
Hiroki
H
D000818:Animals; D019521:Body Patterning; D002454:Cell Differentiation; D002455:Cell Division; D019070:Cell Lineage; D004475:Ectoderm / Q000166:cytology / Q000502:physiology; D004789:Enzyme Activation; D005346:Fibroblast Growth Factors / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000502:physiology; D032446:Myoblasts / Q000502:physiology*; D009672:Notochord / Q000166:cytology / Q000502:physiology*; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism; D014561:Urochordata / Q000166:cytology* / Q000196:embryology
D015534:Trans-Activators; D005346:Fibroblast Growth Factors