Identification of a common mesenchymal stromal progenitor for the adult haematopoietic niche.

Microenvironment cues received by haematopoietic stem cells (HSC) are important in regulating the choice between self-renewal and differentiation. On the basis of the differential expression of cell-surface markers, here we identify a mesenchymal stromal progenitor hierarchy, where CD45Ter119CD31CD166CD146Sca1(Sca1) progenitors give rise to CD45Ter119CD31CD166CD146(CD146) intermediate and CD45Ter119CD31CD166CD146(CD166) mature osteo-progenitors. All three progenitors preserve HSC long-term multi-lineage reconstitution capability in vitro; however, their in vivo fates are different.

Evidence that β7 Integrin Regulates Hematopoietic Stem Cell Homing and Engraftment Through Interaction with MAdCAM-1.

α4β7 integrin is a cell adhesion receptor that is crucial for the migration of hematopoietic progenitors and mature effector cells in the periphery, but its role in adult hematopoiesis is controversial. We identified a subset of hematopoietic stem cells (HSCs) in the bone marrow (BM) that expressed β7 integrin. These β7(+) HSCs were capable of multilineage, long-term reconstitution and had an inherent competitive advantage over β7(-) HSCs.

Exosome-mediated microenvironment dysregulation in leukemia.

The hematopoietic stem cell (HSC) niche is composed of a complex set of stromal support cells that maintain HSCs and promote normal hematopoiesis. We now know that molecular changes within the hematopoietic niche contribute to leukemia development. Leukemia cells often reorganize the hematopoietic niche to promote and support their own survival and growth.

Evidence for direct binding between HetR from Anabaena sp. PCC 7120 and PatS-5.

HetR, master regulator of heterocyst differentiation in the filamentous cyanobacterium Anabaena sp. strain PCC 7120, stimulates heterocyst differentiation via transcriptional autoregulation and is negatively regulated by PatS and HetN, both of which contain the active pentapeptide RGSGR. However, the direct targets of PatS and HetN remain uncertain.