Neuron
Volume 71, Issue 6, 22 September 2011, Pages 1014-1021
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Development of Cell Type-Specific Connectivity Patterns of Converging Excitatory Axons in the Retina

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Summary

To integrate information from different presynaptic cell types, dendrites receive distinct patterns of synapses from converging axons. How different afferents in vivo establish specific connectivity patterns with the same dendrite is poorly understood. Here, we examine the synaptic development of three glutamatergic bipolar cell types converging onto a common postsynaptic retinal ganglion cell. We find that after axons and dendrites target appropriate synaptic layers, patterns of connections among these neurons diverge through selective changes in the conversion of axo-dendritic appositions to synapses. This process is differentially regulated by neurotransmission, which is required for the shift from single to multisynaptic appositions of one bipolar cell type but not for maintenance and elimination, respectively, of connections from the other two types. Thus, synaptic specificity among converging excitatory inputs in the retina emerges via differential synaptic maturation of axo-dendritic appositions and is shaped by neurotransmission in a cell type-dependent manner.

Highlights

► Bipolar cells identify laminar targets first, establish synaptic specificity later ► Specificity is generated by differential conversion of appositions to synapses ► Bipolar cell axons and ganglion cell dendrites can form multisynaptic appositions ► Neurotransmission regulates synaptic differentiation in a cell type-specific manner

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Present address: Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA