Role of Cohesin-Resolving Protease, Separase, In Hematopoiesis.

Cohesin is an evolutionarily conserved protein complex that forms during the replication of sister chromatids. It is a multi-protein complex that consists of four proteins, Smc1, Smc3, Rad21, and Scc3. Resolution of sister chromatid cohesion at the onset of anaphase depends on Separase, an endopeptidase that separates sister chromatids by cleaving cohesion Rad21. A recent study suggests a new role of Cohesin proteins in gene expression and development with implications in hematopoiesis. Our data indicates that cohesin-resolving protease Separase may play a critical role in hematopoiesis. HYPOTHESIS: We hypothesize that Separase plays a role in hematopoiesis by increasing the quantity of hematopoietic stem cells (HSC). METHODS: Our experimental approach was to isolate murine long-term HSC from WT mice and mice with one mutated copy of Separase (i.e. Separase heterozygotes). In addition, in vivo competitive long term repopulation assays were used assess the function of HSC in Separase heterozyotes. RESULTS: Separase heterozygote have increased HSC numbers (p<0.05) as compared to WT mice. In addition, an improved engraftment in a competitive repopulation assay (p < 0.001) was seen in the Separase heterozyotes. Analysis of the engrafted cells demonstrated no difference between the wild type and Separase heterozygote animals, indicating the increased engraftment may be due to unique features in the primitive hematopoietic stem cells. CONCLUSION: Investigation of the mechanism for improved HSC engraftment in Separase heterozygote mice will significantly contribute to our understanding of marrow engraftment and function. Elucidating the mechanisms of hematopoietic dysregulation will provide insights into the development of life-threatening disorders such as leukemia and, in the setting of bone marrow transplant, engraftment failure.

No relevant conflicts of interest to declare.