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SUMMARY:The development and evolution of vertebrate oxygen-sensing cells -
  Dorit Hockman (University of Oxford)
DTSTART:20150121T130000Z
DTEND:20150121T140000Z
UID:TALK55869@talks.cam.ac.uk
CONTACT:Marcia Kishida
DESCRIPTION:When oxygen levels in the blood or surrounding air/water drop 
 below a set point (hypoxia)\, oxygen-sensing cells release neurotransmitte
 rs to stimulate afferent glossopharyngeal and/or vagal nerve endings\, tri
 ggering increased ventilation via the respiratory reflex. In amniotes\, th
 ese comprise carotid body glomus cells and ‘pulmonary neuroendocrine cel
 ls’ in the lung airway epithelium. In anamniotes\, they comprise ‘neur
 oepithelial cells’ (NECs) in the gill and orobranchial epithelia (includ
 ing the lung epithelium of air-breathing ray-finned fishes\, lobe-finned l
 ungfishes and amphibians)\, plus the carotid labyrinth of amphibians. It i
 s currently assumed that carotid body glomus cells\, which are neural cres
 t-derived and develop in association with the third pharyngeal arch artery
 \, evolved from gill NECs\, which also develop in association with pharyng
 eal arch arteries. However\, this has never been tested. Using vital dye l
 abelling\, neural fold grafts\, genetic lineage-tracing and analysis of ze
 brafish mutants lacking all neural crest cells\, I show that the serotoner
 gic NECs in the gill and orobranchial epithelia of zebrafish\, frog and la
 mprey are not neural crest-derived\, hence cannot be homologous to carotid
  body glomus cells. Instead\, NECs are most likely homologous to pulmonary
  neuroendocrine cells\, which are endoderm-derived. In neonatal mammals\, 
 neural crest-derived adrenal chromaffin cells are sensitive to hypoxia\, a
 nd at least some hypoxia-responsive chromaffin cells persist in the adult.
  I propose that carotid body glomus cells evolved from scattered chromaffi
 n cells associated with the large blood vessels of the pharyngeal arches\,
  first reported a century ago in lamprey\, whose existence we have confirm
 ed by tyrosine hydroxylase expression.
LOCATION:Part II Lecture Theatre\, Department of Zoology
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