Cortical hem-like progenitors contribute pyramidal neurons to the neocortex and hippocampus

The cortical hem is a signaling center at the midline of the embryonic telencephalon that provides instructive cues to the adjacent cortical primordium and serves as the hippocampal organizer, inducing multiple distinct hippocampal field identities. The cortical hem consists of neuroepithelial progenitors, and gives rise to diverse neuronal and non-neuronal cell types, including Cajal-Retzius cells, hippocampal pyramidal neurons, and choroid plexus epithelial cells. Here, we use two independent Cre drivers, Wnt3aCre and Lmx1aCre, to examine the lineages from the cortical hem. We report that these lineages also contribute pyramidal neurons to the neocortex, and we describe their spatiotemporal distribution. Together, our results extend the known lineages of the cortical hem.