Tuning of fast-spiking interneuron properties by an activity-dependent transcriptional switch

Neuronal identity is determined early during development. It is assumed that once a neuron has adopted its identity, this remains stable throughout life. However, Dehorter et al. investigated the mechanisms controlling the specification of fast-spiking interneurons. They found that the transcription factor Er81 is crucial for the normal specification of these cells by regulating the expression of a potassium channel subunit.Science, this issue p. 1216The function of neural circuits depends on the generation of specific classes of neurons. Neural identity is typically established near the time when neurons exit the cell cycle to become postmitotic cells, and it is generally accepted that, once the identity of a neuron has been established, its fate is maintained throughout life. Here, we show that network activity dynamically modulates the properties of fast-spiking (FS) interneurons through the postmitotic expression of the transcriptional regulator Er81. In the adult cortex, Er81 protein levels define a spectrum of FS basket cells with different properties, whose relative proportions are, however, continuously adjusted in response to neuronal activity. Our findings therefore suggest that interneuron properties are malleable in the adult cortex, at least to a certain extent.