Sticky transmission

Nerve cells restrict neurotransmitter release to their synapses. That restriction, say Markus Missler (Georg-August Universität, Göttingen, Germany), Thomas Sudhof (University of Texas Southwestern, Dallas, TX), and colleagues, is provided in part by the synaptic proteins α-neurexins. These cell adhesion proteins promote calcium channel activity, and thus fusion of neurotransmitter vesicles, at the synaptic junctions.

The polymorphism and adhesion properties of neurexins led researchers to suspect a synapse-forming function. But Missler and coworkers found that mice lacking all three α-neurexins had ultrastructurally normal synapses. The mice breathed with difficulty and died on the first day after birth. In the brain stem, where breathing rhythms are generated, synapses showed reduced frequency of spontaneous transmission— a possible sign of presynaptic problems. Reduced amplitudes of synaptic responses were also evident after stimulation of neurons in the...