Putting together a stable yet versatile network such as the mammalian central nervous system poses a formidable developmental challenge. While all neurons must acquire a common set of properties, such as the ability to form synapses and fire action potentials, there is a tremendous degree of additional specialization in each of the thousands of neuronal subtypes differing in size, shape, location and neurotransmitter phenotypes (Killackey et al., 1989; Wise and Jones, 1977). Moreover, remarkable architectural integrity is required both at the cellular and system-wide level over the course of the animal’s lifetime; yet the system must retain the ability to reshape some of its connections based on experience so that learning can occur (Kandel, 2012; Engert and Bonhoeffer, 1999).
