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SUMMARY:Expression of segment polarity genes in brachiopods supports a non
 -segmental ancestral role of engrailed for bilaterians - Bruno Vellutini (
 Sars International Centre for Marine Molecular Biology)
DTSTART:20161116T130000Z
DTEND:20161116T140000Z
UID:TALK68072@talks.cam.ac.uk
CONTACT:Olivia Tidswell
DESCRIPTION:The diverse and complex developmental mechanisms of segmentati
 on have been more thoroughly studied in arthropods\, vertebrates and annel
 ids—distantly related animals considered to be segmented. Far less is kn
 own about the role of “segmentation genes” in organisms that lack a se
 gmented body. I investigated the expression of the arthropod segment polar
 ity genes _engrailed_\, _wnt1_ and _hedgehog_ in the development of brachi
 opods—marine invertebrates without a subdivided trunk but closely relate
 d to the segmented annelids. I found that a stripe of _engrailed_ expressi
 on demarcates the brachiopod embryonic head/trunk boundary\, and that at l
 east in one species\, this _engrailed_ stripe is abutted by the expression
  of _wnt1_\, in a pattern similar to the parasegmental boundaries of insec
 ts. Thus\, the adjacent expression of _engrailed_/_wnt1_ is not exclusive 
 of arthropod and annelid segments\, but also occurs in a non-segmental bou
 ndary of larval brachiopods. When broadening the analysis to all bilateria
 ns\, I found that in several lineages\, including the segmented arthropods
  and annelids\, _engrailed_ is first expressed at the head/trunk distincti
 on during embryogenesis\, much like in brachiopods. This suggests that bil
 aterians share a non-segmental domain of _engrailed_ expression during ear
 ly embryogenesis\, and that such pattern might be ancestral to the group. 
 In a comparative phylogenetic context\, these findings support that _engra
 iled_ has an ancient axial patterning role—perhaps related to the establ
 ishment of the head/trunk boundary—and was secondarily recruited to the 
 segmental boundaries of arthropods and annelids. 
LOCATION:Part II Lecture Theatre\, Department of Zoology
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