Putting neurons in the right places: local interactions in the genesis of retinal architecture

Development of the nervous system can be schematically summarized as (1) making the necessary cells, (2) putting these cells in the right places, and then (3) connecting them appropriately. Each of these steps represents an enormous challenge to our understanding. Focusing on the vertebrate retina, I will consider the question of what defines the right place for a neuron to go. I will illustrate data pointing to the prominent role played by short-range cellular interactions, possibly coordinated by global factors, and will discuss how a few sets of local rules could control cell positioning and proper wiring in retinal circuits.