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SUMMARY:Setting up embryonic polarity in the hydrozoan Clytia hemisphaeric
 a - Evelyn Houliston\, Developmental Biology Unit\, CNRS/Université Pierr
 e et Marie Curie\, Villefranche-sur-mer\, France
DTSTART:20111109T130000Z
DTEND:20111109T140000Z
UID:TALK33886@talks.cam.ac.uk
CONTACT:25357
DESCRIPTION:Setting up embryonic polarity in the hydrozoan Clytia hemispha
 erica.\n\nEvelyn Houliston. \nDevelopmental Biology Unit\, CNRS/Universit
 é Pierre et Marie Curie\, Villefranche-sur-mer\, France. \n\nThe characte
 ristic oral-aboral polarity of cnidarian larvae was long thought to emerge
  progressively during embryonic development\, rather than to be directed b
 y localised maternal determinants as is commonly the case for axis specifi
 cation in bilaterian animals. In recent years\, the results of experimenta
 l manipulations in  variety of cnidarian species have changed this percept
 ion\, indicating that cnidarian axis specification\, as well as germ layer
  formation though gastrulation\, is directed by maternal localised determi
 nants. Furthermore\, accumulating molecular evidence has shown that Wnt si
 gnalling plays a key role in regulating axial properties and gastrulation 
 in cnidarians\, as it commonly does in bilaterians. The common eumetazoan 
 ancestor may thus have exhibited embryonic patterning based on maternal mR
 NA localisation acting upstream of regionlised Wnt signalling. \nUsing an 
 emerging experimental model from the Hydrozoa\, Clytia hemisphaerica1\, we
  have identified embryonic axis determinants at the molecular level as loc
 alised maternal mRNAs\, coding for a Wnt ligand and two Frizzled-family re
 ceptors with antagonistic activities2\,3.  These mRNAs become translated f
 ollowing fertilisation\, initiating a sequence of interactions that restri
 cts Wnt-beta catenin signalling to the future oral territory of the blastu
 la. Wnt-beta catenin activity is required for transcription of many target
  genes  in the oral territory\, including two Brachyury orthologues necess
 ary for gastrulation. In parallel\, the same maternally provided Wnt ligan
 d is required to coordinate Strabismus–mediated Planar Cell Polarity alo
 ng the oral-aboral axis.  I will describe experiments that have led us to 
 this current picture\, and some ongoing efforts to identify novel players 
 in defining oral identity downstream of Wnt signalling.\n\n1) Houliston\, 
 E.\, Momose\, T. & Manuel\, M. (2010) "Clytia hemisphaerica: A jellyfish c
 ousin joins the laboratory. Trends in Genetics  26\,   159-167\n\n2 ) Mom
 ose\, T. & Houliston\, E. (2007) Two Oppositely Localized Frizzled RNAs as
  Axis Determinants in a Cnidarian embryo PLoS Biology 5 (4) E70\n\n3) Momo
 se\, T.\, Derelle\, R. & Houliston\, E. (2008) A maternally localised Wnt 
 ligand required  for axial patterning in the cnidarian Clytia hemisphæric
 a. Development 135\, 2105-2113\n
LOCATION:Part II Lecture Theatre\, Department of Zoology
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