Setdb1 regulates proper differentiation of adult intestinal stem cells via restraining permissive chromatin structure and transcriptional variability

The histone methylase Setdb1 plays a pivotal role in embryonic stem cell maintenance and developmental lineage specification. However, its function in adult stem cells remains elusive. Here we show that conditional inactivation of Setdb1 in Lgr5 ⁺ intestinal stem cells alters the transcriptional programs of the progeny cell types and results in increased cell-to-cell transcriptional variability. Loss of Setdb1 blocked differentiation towards the absorptive enterocyte lineage, while the secretory cell types were only marginally affected due to the activation of alternative developmental trajectories. Setdb1 inactivation did not alter H3K9 methylation at large heterochromatin domains but led to reduced localized modifications at islands of gene-rich areas around transposase-accessible chromatin regions, which doubled in number, became broader and more heterogeneous in size. The results demonstrate that Setdb1 regulates intestinal stem cell differentiation by fine-tuning chromatin accessibility in open euchromatin regions thereby controlling transcriptional variability between cells.