In addition to this finding, the Greenberg lab also discovered NPAS4, an activity-dependent transcription factor that is required for inhibitory synapse formation through its regulation of Bdnf transcription, and other activity-dependent genes. Similar to their previous finding, the authors found a specific role for this genetic program in inhibitory circuit development, since perturbation of NPAS4 function had no effect in excitatory synapse formation or function. Thus, the activity-dependent gene program plays a key role specifically in the development of inhibitory circuits in the cortex, which are responsible for fine-tuning neuronal output and nervous system function.
