Lineage Recording in Human Brain Organoids with iTracer.

Induced pluripotent stem cell (iPSC)-derived organoids provide models to study human organ development. Single-cell transcriptomics enables highly resolved descriptions of cell states within these systems; however, approaches are needed to directly determine the lineage relationship between cells. Here we provide a detailed protocol (Fig. 1) for the application of iTracer (He Z, Maynard A, Jain A, et al., Nat Methods 19:90-99, 2022), a recently published lineage recorder that combines reporter barcodes with inducible CRISPR-Cas9 scarring and is compatible with single-cell and spatial transcriptomics. iTracer is used to explore clonality and lineage dynamics during brain organoid development. More broadly, iTracer can be adapted to any iPSC-derived culture system to dissect lineage dynamics during normal or perturbed development.