ABSTRACT
An Amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
The bone marrow microenvironment has a key role in regulating haematopoiesis, but its molecular complexity and response to stress are incompletely understood. Here we map the transcriptional landscape of mouse bone marrow vascular, perivascular and osteoblast cell populations at single-cell resolution, both at homeostasis and under conditions of stress-induced haematopoiesis. This analysis revealed previously unappreciated levels of cellular heterogeneity within the bone marrow niche and resolved cellular sources of pro-haematopoietic growth factors, chemokines and membrane-bound ligands. Our studies demonstrate a considerable transcriptional remodelling of niche elements under stress conditions, including an adipocytic skewing of perivascular cells. Among the stress-induced changes, we observed that vascular Notch delta-like ligands (encoded by Dll1 and Dll4) were downregulated. In the absence of vascular Dll4, haematopoietic stem cells prematurely induced a myeloid transcriptional program. These findings refine our understanding of the cellular architecture of the bone marrow niche, reveal a dynamic and heterogeneous molecular landscape that is highly sensitive to stress and illustrate the utility of single-cell transcriptomic data in evaluating the regulation of haematopoiesis by discrete niche populations.
Subject(s)
Bone Marrow/blood supply , Cellular Microenvironment , Hematopoiesis , Hematopoietic Stem Cells , Single-Cell Analysis , Stem Cell Niche , Adaptor Proteins, Signal Transducing/metabolism , Adipocytes/cytology , Adipocytes/metabolism , Animals , Calcium-Binding Proteins/metabolism , Cell Differentiation , Cell Lineage , Endothelium, Vascular/cytology , Female , Gene Expression Regulation , Hematopoiesis/genetics , Hematopoietic Stem Cells/cytology , Hematopoietic Stem Cells/metabolism , Male , Mice , Myeloid Cells/cytology , Myeloid Cells/metabolism , Osteoblasts/cytology , Osteoblasts/metabolism , RNA-Seq , Receptors, Notch/metabolism , Stem Cell Niche/genetics , Stress, Physiological/genetics , Transcriptome/geneticsABSTRACT
Background: The nuclear factor I-A (NFIA) transcription factor promotes glioma growth and inhibits apoptosis in glioblastoma (GBM) cells. Here we report that the NFIA pro-survival effect in GBM is mediated in part via a novel NFIA-nuclear factor-kappaB (NFκB) p65 feed-forward loop. Methods: We examined effects of gain- and loss-of-function manipulations of NFIA and NFκB p65 on each other's transcription, cell growth, apoptosis and sensitivity to chemotherapy in patient-derived GBM cells and established GBM cell lines. Results: NFIA enhanced apoptosis evasion by activating NFκB p65 and its downstream anti-apoptotic factors tumor necrosis factor receptor-associated factor 1 (TRAF1) and cellular inhibitor of apoptosis proteins (cIAPs). Induction of NFκB by NFIA was required to protect cells from apoptosis, and inhibition of NFκB effectively reversed the NFIA anti-apoptotic effect. Conversely, NFIA knockdown decreased expression of NFκB and anti-apoptotic genes TRAF1 and cIAPs, and increased baseline apoptosis. NFIA positively regulated NFκB transcription and NFκB protein level. Interestingly, NFκB also activated the NFIA promoter and increased NFIA level, and knockdown of NFIA was sufficient to attenuate the NFκB pro-survival effect, suggesting a reciprocal regulation between NFIA and NFκB in governing GBM cell survival. Supporting this, NFIA and NFκB expression levels were highly correlated in human GBM and patient-derived GBM cells. Conclusions: These data define a previously unknown NFIA-NFκB feed-forward regulation that may contribute to GBM cell survival.
