Development of a larval nervous system in the sea urchin.

This review reports recent findings on the specification and patterning of neurons that establish the larval nervous system of the sea urchin embryo. Neurons originate in three regions of the embryo. Perturbation analyses enabled construction of gene regulatory networks controlling the several neural cell types. Many of the mechanisms described reflect shared features of all metazoans and others are conserved among deuterostomes. This nervous system with a very small number of neurons supports the feeding and swimming behaviors of the larva until metamorphosis when an adult nervous system replaces that system.