Single-cell RNA-seq of Drosophila neuroblast tumors induced by the knockdown of prospero, E(z) and trx

COMPASS and Polycomb complexes are antagonistic chromatin complexes that are frequently inactivated in cancers, but how their inactivation affects the cellular hierarchy, composition and growth of tumors is unclear. Such characteristics can be systematically investigated in Drosophila neuroblast tumors in which cooption of temporal patterning induces a developmental hierarchy that confers cancer stem cell (CSC) properties to a subset of neuroblasts retaining an early larval temporal identity. Here, using single-cell transcriptomics, we reveal that the trithorax/MLL1/2-COMPASS-like complex guides the developmental trajectory at the top of the tumor hierarchy. Consequently, trithorax inactivation drives larval-to-embryonic temporal reversion and the dramatic expansion of CSCs that remain locked in a spectrum of early temporal states. Surprisingly, this phenotype is amplified by concomitant inactivation of Polycomb Repressive Complex 2 genes, unleashing tumor growth. This study exemplifies how inactivation of specific COMPASS and Polycomb complexes cooperates to impair tumor hierarchies and induce CSC plasticity and heterogeneity. Droplet Based Single Cell RNA sequencing library were generated for a Drosophila melanogaster tissue using the 10x Genomics Chromium Platform and sequenced on the Illumina Nextseq 500