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SUMMARY:Genetic analysis of layer specific axon targeting in the Drosophil
 a visual system - Milan Petrovic\, University of Muenster
DTSTART:20081120T110000Z
DTEND:20081120T114500Z
UID:TALK15268@talks.cam.ac.uk
CONTACT:Greg Jefferis
DESCRIPTION:The segregation of axon and dendrite projections into distinct
  synaptic layers is a fundamental principle of nervous system organization
  and the structural basis for information processing in the brain1. Layer-
 specific recognition molecules that allow projecting neurons to stabilize 
 transient contacts and initiate synaptogenesis2\, 3 have been identified. 
 However\, most of the neuronal cell-surface molecules critical for layer o
 rganization are expressed broadly in the developing nervous system4\, 5\, 
 raising the question of how these so-called permissive adhesion molecules 
 support synaptic specificity. Here we show that the temporal expression dy
 namics of the zinc-finger protein sequoia is the major determinant of Dros
 ophila photoreceptor connectivity into distinct synaptic layers. Neighbour
 ing R8 and R7 photoreceptors show consecutive peaks of elevated sequoia ex
 pression\, which correspond to their sequential target-layer innervation. 
 Loss of sequoia in R7 leads to a projection switch into the R8 recipient l
 ayer\, whereas a prolonged expression in R8 induces a redirection of their
  axons into the R7 layer. The sequoia-induced axon targeting is mediated t
 hrough the ubiquitously expressed Cadherin-N cell adhesion molecule. Our d
 ata support a model in which recognition specificity during synaptic layer
  formation is generated through a temporally restricted axonal competence 
 to respond to broadly expressed adhesion molecules. Because developing neu
 rons innervating the same target area often project in a distinct\, birth-
 order-dependent sequence\, temporal identity seems to contain crucial info
 rmation in generating not only cell type diversity during neuronal divisio
 n6 but also connection diversity of projecting neurons.\n\nSee also: http:
 //www.nature.com/nature/journal/vaop/ncurrent/abs/nature07407.html
LOCATION:MRC LMB: Neurobiology Division Seminar Room (Level 2)
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