Evidence That the Laminar Fate of LGE/CGE-Derived Neocortical Interneurons Is Dependent on Their Progenitor Domains

Neocortical interneurons show tremendous diversity in terms of their neurochemical marker expressions, morphology, electrophysiological properties, and laminar fate. Allocation of interneurons to their appropriate regions and layers in the neocortex is thought to play important roles for the emergence of higher functions of the neocortex. Neocortical interneurons mainly originate from the medial ganglionic eminence (MGE) and the caudal ganglionic eminence (CGE). The diversity and the laminar fate of MGE-derived interneurons depend on the location of their birth and birthdate, respectively. However, this relationship does not hold for CGE-derived interneurons. Here, using the method of in utero electroporation, which causes arbitrary occurrence of labeled progenitor domains, we tracked all descendants of the lateral ganglionic eminence (LGE)/CGE progenitors in mice. We provide evidence that neocortical interneurons with distinct laminar fate originate from distinct progenitor domains within the LGE/CGE. We find layer I interneurons are predominantly labeled in a set of animals, whereas other upper layer neurons are predominantly labeled in another set. We also find distinct subcortical structures labeled between the two sets. Further, interneurons labeled in layer I show distinct neurochemical properties from those in other layers. Together, these results suggest that the laminar fate of LGE/CGE-derived interneurons depends on their spatial origin.