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SUMMARY:Formation and disease relevance of axonal endoplasmic reticulum\, 
 a "neuron within a neuron”. - Dr Cahir O’Kane\, Department of Genetics
 \, University of Cambridge
DTSTART:20171019T130000Z
DTEND:20171019T140000Z
UID:TALK75451@talks.cam.ac.uk
CONTACT:Caroline Newnham
DESCRIPTION:Axons contain a smooth tubular endoplasmic reticulum (ER) netw
 ork that appears to be continuous with ER throughout the neuron. Its conti
 nuity is unique for intracellular membranous organelles and makes it poten
 tially a channel for regional and long-distance communication in neurons\,
  and it has been termed a "neuron within a neuron".\n\nThe mechanisms that
  form this axonal ER network are unknown. Mutations affecting reticulon or
  REEP proteins\, with intramembrane hairpin domains that model ER membrane
 s\, cause an axon degenerative disease\, hereditary spastic paraplegia (HS
 P). We show that Drosophila axons have an extensive axonal ER network\, wh
 ich these proteins help to model. Loss of HSP hairpin proteins causes ER s
 heet expansion\, partial loss of ER from distal motor axons\, and occasion
 al discontinuities in axonal ER. Ultrastructural analysis reveals an exten
 sive ER network in axons\, which shows larger and fewer tubules in larvae 
 that lack reticulon and REEP proteins\, consistent with loss of membrane c
 urvature. Live imaging reveals an ER network with both stable and dynamic 
 features\, suggesting mechanisms that continually regulate its density and
  continuity.\n\nTherefore HSP hairpin-containing proteins are required for
  shaping and continuity of axonal ER\, thus suggesting roles for ER modeli
 ng in axon maintenance and function. A role for sporadic gaps in the ER ne
 twork in HSP diseases is an attractive hypothesis for the susceptibility o
 f longer axons to the disease\, and identification of new HSP genes by hum
 an exome and genome sequencing may reveal additional components of the mac
 hinery that maintains ER organisation and function in axons. We have only 
 scratched the surface of how axonal ER is formed\, and its physiological f
 unction\; a combination of human and Drosophila genetics promises to revea
 l more answers to these questions.\n
LOCATION:Biffen Lecture Theatre\, Department of Genetics\, Downing Site
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