Special Topics in Neuroscience
Pre- and postsynaptic membranes at the
neuromuscular synapse are highly specialized
Schwann cell
nerve terminal
muscle cell
postjunctional folds
Pre- and postsynaptic membranes at the
neuromuscular synapse are highly specialized
Muscle pre-patterning
The synaptic basal lamina contains signals for
presynaptic and postsynaptic differentiation
MBL:myofiber basal lamina
Presynaptic and postsynaptic differentiation are
defective in mice lacking MuSK
Acetylcholine receptor (AChR) genes are expressed selectively by
myofiber synaptic nuclei, leading to enrichment of AChR mRNA in
the central, synaptic region of the muscle
Muscle from transgenic mice harboring a
gene fusion between the regulatory
region from the AChR d subunit gene and
human growth hormone (hGH) gene
α-BGT :α-bungarotoxin AChR
MCK:muscle creatine kinase
diaphragm muscle
in situ hybridization
Model for the assembly of central synapses
synaptic vesicles
postsynaptic
scaffolding
molecules
APV:active-zone precursor vesicles
Synapse-organizing function of the postsynaptic
adhesion molecule neuroligin
HEK293 cell fi broblasts
neuroligin
A simplified model for transsynaptic interactions that may
coordinate assembly of presynaptic and postsynaptic elements
of glutamatergic synapses and recruitment of NMDA- and AMPAtype glutamate receptors
VGCC:voltage-gated calcium channels
homophilic interactions
Heterophilic interactions
Model for lamina-specific synaptic connectivity
through homophilic adhesion molecules
Synapse Elimination
Evidence of synapse elimination at the
neuromuscular junction
In the developing nervous system synapse number
is increasing while axonal convergence is falling
Changes in fan-in and fan-out at developing
circuits
First, axons disconnect from many target cells reducing their fan-out or divergence.
Second, this rearrangement leads to less fan-in or convergence.
Third, at the same time as axons disconnect from some target cells they are
strengthening their connection with other target cells by increasing the number of
synapses at their remaining targets
Time-lapse imaging shows how axonal branches are lost
during synapse elimination at the neuromuscular junction
transgenic mouse that expresses YFP(green)motor axon
a-bungarotoxin (red)AChR
retraction bulb