Haploinsufficiency of cohesin protease, Separase, promotes regeneration of hematopoietic stem cells in mice

Abstract

Cohesin recently emerged as a new regulator of hematopoiesis and leukemia. In addition to cohesin, whether proteins that regulate cohesin's function have any direct role in hematopoiesis and hematologic diseases has not been fully examined. Separase, encoded by the ESPL1 gene, is an important regulator of cohesin's function. Canonically, protease activity of Separase resolves sister chromatid cohesion by cleaving cohesin subunit‐Rad21 at the onset of anaphase. Using a Separase haploinsufficient mouse model, we have uncovered a novel role of Separase in hematopoiesis. We report that partial disruption of Separase distinctly alters the functional characteristics of hematopoietic stem/progenitor cells (HSPCs). Although analyses of peripheral blood and bone marrow of Espl1+/Hyp mice broadly displayed unperturbed hematopoietic parameters during normal hematopoiesis, further probing of the composition of early hematopoietic cells in Espl1+/Hyp bone marrow revealed a mild reduction in the frequencies of the Lin−Sca1+Kit− (LSK) or LSK CD48+CD150− multipotent hematopoietic progenitors population without a significant change in either long‐term or short‐term hematopoietic stem cells (HSCs) subsets at steady state. Surprisingly, however, we found that Separase haploinsufficiency promotes regeneration activity of HSCs in serial in vivo repopulation assays. In vitro colony formation assays also revealed an enhanced serial replating capacity of hematopoietic progenitors isolated from Espl1+/Hyp mice. Microarray analysis of differentially expressed genes showed that Separase haploinsufficiency in HSCs (SP‐KSL) leads to enrichment of gene signatures that are upregulated in HSCs compared to committed progenitors and mature cells. Taken together, our findings demonstrate a key role of Separase in promoting hematopoietic regeneration of HSCs.

Role of chromosomal cohesion and separation in aneuploidy and tumorigenesis

“…Cohesin insufficiency can enhance self-renewal while impairing differentiation, leading to abnormal cellular plasticity, which is central to malignant transformation. This effect has been observed in hematopoietic stem cells, where cohesin insufficiency results in misexpression of critical genes involved in hematopoiesis [122,125,126,[131][132][133][134]. In mouse embryonic stem cells, cohesin depletion reduces enhancer-promoter interactions at pluripotency genes, causing a loss of the pluripotent state [137,138].…”

“…Dysfunctional cohesin affects its dynamic binding to chromatin and impairs the recruitment of RNA polymerase II, leading to transcriptional dysregulation. Cancer-associated mutations in cohesin genes can lead to aberrant DNA looping, dysregulation of crucial lineagespecific transcription factors, and misexpression of genes responsible for cellular identity and homeostasis [122,125,126,[131][132][133][134][135][136]. Cohesin insufficiency can enhance self-renewal while impairing differentiation, leading to abnormal cellular plasticity, which is central to malignant transformation.…”