BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Deciphering the onychophoran ‘segmentation gene cascade’: infe
 rences about the evolution of segmentation - Ralf Janssen (Uppsala Univers
 ity)
DTSTART:20131113T130000Z
DTEND:20131113T140000Z
UID:TALK48166@talks.cam.ac.uk
CONTACT:Jeremy Solly
DESCRIPTION:The question of the origin of segmentation has troubled scient
 ists’\nminds for far more than a century\, and the question still remain
 s open. Three animal phyla are usually described as being unambiguously se
 gmented. These are the vertebrates\, to which we belong\, the annelids and
  the arthropods. That means that we find ‘segmented’ animals in each o
 f the main groups of animals\, i.e. deuterostomes\, lophotrochozoan protos
 tomes\, and ecdysozoan protostomes. At the same time\, however\, most othe
 r animal phyla are clearly non-segmented\, or only show very superficial s
 igns of ‘segmentation’.\n\nOne approach to shed light on the origin of
  segmentation was believed to lie in the investigation of developmental me
 chanisms. The idea was that if segmentation had evolved only once or twice
 \, conserved mechanisms should be found that might indicate this. Converse
 ly\, if segmentation had evolved independently in the different groups\, d
 ifferent molecular mechanisms would be expected to underlie their segment 
 formation.\n\nA first step in the investigation of such molecular mechanis
 ms is\ntypically the analysis of gene expression patterns\, and this stand
 ard\nmethod allows a quick first glance at what role a certain gene may ha
 ve during development. During the last few decades of gene expression patt
 ern analysis\, remarkable discoveries have been made\, such as the involve
 ment of Notch/Delta signaling in arthropod segmentation and the strong con
 servation of the segment-polarity gene network in arthropods and annelids.
  Such findings fuelled a vigorous discussion about the origin of segmentat
 ion and suggested a common origin to some. However\, as we believe we know
  today\, many of these patterns may be the result of convergent evolution\
 , or in other words\, may have evolved (and/or have been recruited) indepe
 ndently.\n\nIn order to understand the level of conservation of arthropod 
 segmentation\, I first analyzed segmentation genes (as known from\n_Drosop
 hila_) in the myriapod _Glomeris marginata_\, and later expanded this appr
 oach towards the onychophorans. The latter represent the likely sister-gro
 up to the arthropods\, and are therefore of special interest for the under
 standing of arthropod segmentation. Data from onychophorans allow for the 
 polarization of characters found in arthropods\, and at the same time offe
 r a deeper insight into the origin of conserved arthropod segmentation mec
 hanisms.\n\nIn my talk I will present my current work on onychophoran segm
 entation genes and discuss my findings in terms of what they may mean (or 
 not mean) for the origin of segmentation.
LOCATION:Part II Lecture Theatre\, Department of Zoology
END:VEVENT
END:VCALENDAR