Presynaptic establishment of the synaptic cleft extracellular matrix is required for post-synaptic differentiation.
Formation and regulation of excitatory glutamatergic synapses is essential for shaping neural circuits throughout development. In a Drosophila genetic screen for synaptogenesis mutants, we identified mind the gap (mtg), which encodes a secreted, extracellular N-glycosaminoglycan-binding protein. MTG is expressed neuronally and detected in the synaptic cleft, and is required to form the specialized transsynaptic matrix that links the presynaptic active zone with the post-synaptic glutamate receptor (GluR) domain. Null mtg embryonic mutant synapses exhibit greatly reduced GluR function, and a corresponding loss of localized GluR domains. All known post-synaptic signaling/scaffold proteins functioning upstream of GluR localization are also grossly reduced or mislocalized in mtg mutants, including the dPix-dPak-Dock cascade and the Dlg/PSD-95 scaffold. Ubiquitous or neuronally targeted mtg RNA interference (RNAi) similarly reduce post-synaptic assembly, whereas post-synaptically targeted RNAi has no effect, indicating that presynaptic MTG induces and maintains the post-synaptic pathways driving GluR domain formation. These findings suggest that MTG is secreted from the presynaptic terminal to shape the extracellular synaptic cleft domain, and that the cleft domain functions to mediate transsynaptic signals required for post-synaptic development.
Rohrbough
Jeffrey
J
Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37235, USA.
Rushton
Emma
E
Woodruff
Elvin
E
Fergestad
Tim
T
Vigneswaran
Krishanthan
K
Broadie
Kendal
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D017931:DNA Primers / Q000235:genetics; D004330:Drosophila / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D017344:Genes, Insect; D006025:Glycosaminoglycans / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009154:Mutation; D009469:Neuromuscular Junction / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D017470:Receptors, Glutamate / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure
D002352:Carrier Proteins; D017931:DNA Primers; D029721:Drosophila Proteins; D006025:Glycosaminoglycans; D017470:Receptors, Glutamate