Comprehensive spatiotemporal mapping of single-cell lineages in developing mouse brain by CRISPR-based barcoding

A fundamental interest in developmental neuroscience is to map the complete single-cell lineages within the brain. We developed a CRISPR editing-based lineage specific tracing (CREST) method for clonal tracing in Cre mice. We combined two complementary strategies to map the comprehensive single-cell lineage landscape in developing mouse brain. Applying snapCREST (snapshotting CREST) in mouse ventral midbrain (vMB), we constructed a spatiotemporal lineage landscape spanning the major developmental stage of vMB. Specifically, we identified six progenitor archetypes that could represent principal clonal fate of individual vMB progenitors, whose progenies showed restricted and graded distribution along the dorsal-ventral axis. We uncovered subregion-specific relationship between glutamatergic and GABAergic neurons and identified three distinct clonal lineages in the floor plate that specified glutamatergic neurons, dopaminergic neurons, or both neuronal types. We further created pandaCREST (progenitor and derivative associating CREST) by combining CREST, ex vivo organoid culture, and clonal splitting strategy to associate the transcriptome of progenitor cells in vivo with their differentiation potentials. Using pandaCREST, we identified multiple developmental origins of dopaminergic neurons and demonstrated that the fate potential of a transcriptome-defined progenitor type reflects the composite potentials of individual progenitors, each with distinct clonal fate and molecular signatures. Thus, the CREST method and strategies allow comprehensive single-cell lineage analysis that could offer new insights into the molecular programs underlying neural specification. Overall design: We performed scRNA-seq at different time points to investigate single-cell lineage in developing mouse ventral midbrain. CREST barcodes from mouse embryonic fibroblasts and different mouse tissues were enriched from genomic DNA or scRNA-seq cDNA libraries for CREST characterization and lineage analyses.