Individual Human Cortical Progenitors Can Produce Excitatory and Inhibitory Neurons

The cerebral cortex is a cellularly-complex structure comprised of a rich diversity of neuronal and glial cell types. Cortical neurons can be broadly categorized into two classes—glutamatergic excitatory neurons and GABAergic inhibitory interneurons. Previous developmental studies in rodents have led to the prevailing model that while excitatory neurons are born from progenitors located in the cortex, cortical interneurons are born from a separate population of progenitors located outside of the developing cortex in the ganglionic eminences1-5. However, the developmental potential of human cortical progenitors has not been thoroughly explored. Here we show that in addition to excitatory neurons and glia, human cortical progenitors are also capable of producing GABAergic neurons with the transcriptional characteristics and morphologies of cortical interneurons. By developing a cellular barcoding tool called “ScRNAseq-compatible Tracer for Identifying Clonal Relationships” (STICR), we were able to perform clonal lineage tracing of 1912 primary human cortical progenitors from six specimens and capture both the transcriptional identities and clonal relationships of their resulting progeny. A subpopulation of cortically-born GABAergic neurons were transcriptionally similar to cortical interneurons born from the caudal ganglionic eminence and these cells were frequently related to excitatory neurons and glia. Thus, our results demonstrate that individual human cortical progenitors can generate both excitatory neurons and cortical interneurons, providing a new framework for understanding the origins of neuronal diversity in the human cortex. Sequencing of Synthetic Plasmid and Lentiviral STICR libraries for quantitative analysis