The spatial and temporal origin of chandelier cells in mouse neocortex.

Diverse γ-aminobutyric acid-releasing interneurons regulate the functional organization of cortical circuits and derive from multiple embryonic sources. It remains unclear to what extent embryonic origin influences interneuron specification and cortical integration because of difficulties in tracking defined cell types. Here, we followed the developmental trajectory of chandelier cells (ChCs), the most distinct interneurons that innervate the axon initial segment of pyramidal neurons and control action potential initiation. ChCs mainly derive from the ventral germinal zone of the lateral ventricle during late gestation and require the homeodomain protein Nkx2.1 for their specification. They migrate with stereotyped routes and schedule and achieve specific laminar distribution in the cortex. The developmental specification of this bona fide interneuron type likely contributes to the assembly of a cortical circuit motif.