Fig. 2.

Establishment and maintenance of expression of terminal differentiation genes required to define a specific type of sensory neuron in a nematode. A series of gene regulatory events (not shown) produces, transiently, an activator depicted as a blue ball. That activator binds to the establishment cis-regulatory sequence (blue cube), and activates transcription of a terminal selector gene. The latter, another transcription activator, then maintains transcription of its own gene as it activates genes required for specific functions of the neuron. (Reprinted from ref. 16, Copyright 2011, with permission from Elsevier.)