Clonal multi-omics reveals Bcor as a regulator of dendritic cell development and its action at a clonal level

Despite major developments in single cell multi-omics approaches, a single stem or progenitor cell can only be tested once. Here we develop ‘clonal multi-omics’, where recent daughters of a clone act as surrogates of the parental cell allowing multiple tests of its molecular profile and/or cellular fate under different conditions. We first present SIS-seq – a novel clonal method whereby siblings are examined in parallel for gene expression by RNA-seq, or for fate after culture. We use this method to identify, then validate using CRISPR, the genes expressed in single haematopoietic progenitors that control the development of the different dendritic cell (DC) subtypes. In this way, Bcor is identified as a suppressor of plasmacytoid DC (pDC) and conventional DC subtype 2 (cDC2) numbers during Flt3 ligand-mediated ‘emergency’ DC development. Using a complementary method SIS-skew – where WT and BcorKO siblings of the same clone are examined in parallel for fate – we discover that Bcor restricts clonal expansion, especially for generation of cDC2s, and suppresses clonal fate potential, especially for pDCs. SIS-seq and SIS-skew therefore represent novel and broadly applicable clonal multi-omics approaches that could reveal the molecular and cellular mechanisms governing stem, immune, reprogrammed and cancer cell function at a single cell level, including after genetic or extrinsic factor perturbation.