METB-13. A SINGLE-CELL GENETIC IN VIVO LINEAGE-TRACING PLATFORM FOR MEDULLOBLASTOMA

Abstract Comparative single-cell studies of group 3/4 medulloblastomas (MBs) and fetal brain have identified a common hierarchy glutamatergic-lineage cell types an apparent cell-of-origin in the rhombic lip. An increased understanding genetic regulators stem-cell maintenance differentiation MB would clearly be therapeutic benefit. There is significant need for lineage-tracing systems to model malignant transformation, progression, response therapy. We developed vivo organoid with readout. A high-complexity lentiviral library expressing heritable polyadenylated molecular barcodes was transduced into D283 D425 patient-derived lines. Barcoded cells were injected brains immunocompromised mice. Both preimplantation barcoded cultures resulting mature tumors profiled by RNA-sequencing (scRNA-seq). This captured both endogenous RNA barcode transcripts. While only minimal clash detected cultures, we observed clonal expansion which aligned phylogenetics analysis expressed mutations RNA. Methods assessing lineage coupling between transcriptional clusters inferring their relationship developed. Ongoing efforts recover from tumor sections via spatial transcriptomics will presented. These fill gap status quo models are needed leverage recent findings derived human tumors.