02301nas a2200337   4500000000100000000000100001008004100002260001200043653002400055653002900079653002200108653003000130100001900160700002300179700002000202700001700222700001700239700002100256700001800277700001500295700001800310700001500328700002000343700001800363245009300381856005400474300001200528490000800540520140100548022001401949       2019                            d  c2019-0610aCell type diversity10aGene expression analysis10aNeural patterning10aStem-cell differentiation1 aSilvia Velasco1 aAmanda J. Kedaigle1 aSean K. Simmons1 aAllison Nash1 aMarina Rocha1 aGiorgia Quadrato1 aBruna Paulsen1 aLan Nguyen1 aXian Adiconis1 aAviv Regev1 aJoshua Z. Levin1 aPaola Arlotta00aIndividual brain organoids reproducibly form cell diversity of the human cerebral cortex  uhttps://www.nature.com/articles/s41586-019-1289-x  a523-5270 v5703 aExperimental models of the human brain are needed for basic understanding of its development and disease1. Human brain organoids hold unprecedented promise for this purpose; however, they are plagued by high organoid-to-organoid variability2,3. This has raised doubts as to whether developmental processes of the human brain can occur outside the context of embryogenesis with a degree of reproducibility that is comparable to the endogenous tissue. Here we show that an organoid model of the dorsal forebrain can reliably generate a rich diversity of cell types appropriate for the human cerebral cortex. We performed single-cell RNA-sequencing analysis of 166,242 cells isolated from 21 individual organoids, finding that 95% of the organoids generate a virtually indistinguishable compendium of cell types, following similar developmental trajectories and with a degree of organoid-to-organoid variability comparable to that of individual endogenous brains. Furthermore, organoids derived from different stem cell lines show consistent reproducibility in the cell types produced. The data demonstrate that reproducible development of the complex cellular diversity of the central nervous system does not require the context of the embryo, and that establishment of terminal cell identity is a highly constrained process that can emerge from diverse stem cell origins and growth environments.  a1476-4687