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SUMMARY:Modelling of Axonal Endoplasmic Reticulum Network by Spastic Parap
 legia Proteins   - Belgin Yalcin (Department of Genetics)
DTSTART:20160706T163000Z
DTEND:20160706T183000Z
UID:TALK66798@talks.cam.ac.uk
CONTACT:Clara Sidor
DESCRIPTION:Motor neurons control voluntary movements and have axons that 
 can be up  to 104 fold of the diameter of the cell body. Hence\, motor neu
 rons require complex machineries for maintenance and function over long ax
 onal distances. Failure of these machineries causes motor neuron  axonopat
 hies\, such as Hereditary Spastic Paraplegia (HSP)\, which is characterise
 d by spasticity and weakness of the lower limbs. To date over 50 causative
  Spastic Paraplegia Genes (SPGs) have been identified\, encoding a variety
  of proteins. Many of these proteins point at the importance of the endopl
 asmic reticulum (ER) for the function of motor neurons. Some of these prot
 ein families\, including atlastin\, spastin\, reticulon\, and REEP familie
 s\, are involved in shaping ER tubules. To investigate the role of Spastic
  Paraplegia proteins in vivo\, I first constructed tools for visualisation
  of ER in Drosophila axons. To understand the role of two proteins familie
 s\, Reticulon and REEP\, which share a partly redundant role in the format
 ion of tubular ER in yeast\, I investigated ER organisation in flies lacki
 ng these ER-shaping proteins. Loss of ReepA and ReepB (Drosophila ortholog
 ues of REEPs1-4 and REEPs  5-6 respectively)\, or of Rtnl1\, caused ER abn
 ormalities in epidermal cells. Ultrastructural evidence showed longer ER s
 heet cross-sections in larvae that lack ReepA and ReepB\, suggesting an ex
 pansion of ER sheets. Loss of ReepA and ReepB\, or of Rtnl1\, lowered ER l
 abelling in distal long motor axons. Strikingly\, triple loss of Rtnl1\, R
 eepA\, and ReepB appeared to disrupt the continuity of axonal ER\, and to 
 cause fragmentation of ER in the middle parts of long motor neurons. Loss 
 of Rtnl1 led to  accumulations of synaptic vesicles in axons\, suggesting 
 an axon transport defect. These findings suggest that disruption of axonal
  ER could be an  underlying reason for axonal degeneration in HSP. This is
  the first study to show that ER-shaping proteins can affect axonal struct
 ures\, and maintain the integrity of axonal ER.
LOCATION:Gurdon Institute Tea Room
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