In the bone marrow, CXCL12 and IL-7 are essential for B cell differentiation, whereas hematopoietic stem cell (HSC) maintenance requires SCF and CXCL12. Peri-sinusoidal stromal (PSS) cells are ...the main source of IL-7, but their characterization as a pro-B cell niche remains limited. Here, we characterize pro-B cell supporting stromal cells and decipher the interaction network allowing pro-B cell retention. Preferential contacts are found between pro-B cells and PSS cells, which homogeneously express HSC and B cell niche genes. Furthermore, pro-B cells are frequently located in the vicinity of HSCs in the same niche. Using an interactome bioinformatics pipeline, we identify Nidogen-1 as essential for pro-B cell retention in the peri-sinusoidal niche as confirmed in Nidogen-1−/− mice. Finally, human pro-B cells and hematopoietic progenitors are observed close to similar IL-7+ stromal cells. Thus, a multispecific niche exists in mouse and human supporting both early progenitors and committed hematopoietic lineages.
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•Murine peri-sinusoidal stromal cells co-express HSC and early B cell niche genes•HSCs and early B cells form specific interaction networks with PSS cells•Nidogen-1 is involved in pro-B cell retention in the peri-sinusoidal niche•Stromal cells with similar characteristics are present in human bone marrow
Balzano et al. show that bone marrow peri-sinusoidal stromal cells, which form the hematopoietic stem cell niche, also express B cell niche genes including IL-7 and Nidogen-1. Loss of Nidogen-1 expression specifically affects access of pro-B cells to IL-7, resulting in impaired expansion and differentiation of early B cells.
Biomarkers and novel therapeutic targets are urgently needed in colorectal cancer (CRC). The pseudo tyrosine kinase receptor 7 (PTK7) is involved in planar cell polarity and it is deregulated in ...various malignancies, including CRC. Yet, little is known about its protein expression in human CRC, or about a possible correlation of its expression with clinical endpoints. Using a clinically annotated Tissue MicroArray (TMA) produced from from 192 consecutive CRC patients treated by initial surgery, we examined PTK7 expression by immunohistochemistry in tumoral tissue and matched normal mucosae, and correlated its expression with clinico-pathological features and patient outcome. PTK7 depletion by specific shRNA in HCT116 and HCT15 CRC cell lines was found to affect cell proliferation, resistance to drugs and cell migration. Tumor growth and metastatic phenotype were investigated in vivo using a xenograft mouse model of CRC cells with modulated expression of PTK7 levels. PTK7 was significantly up-regulated in CRC tissue as compared to matched healthy mucosae, and significant overexpression was found in 34% of patients. PTK7 overexpression was significantly associated with a reduced metastasis-free survival in non-metastatic patients. In HCT116 and HCT15 cells, shRNA PTK7 reduced migration but did not affect cell proliferation and resistance to drugs. In a xenograft mouse of HCT15 cells, downregulation of PTK7 led to reduced tumor growth, whereas its overexpression in PTK7-negative cancer cells led to increased metastatic events. PTK7 expression thus represents a potential prognostic biomarker and a novel therapeutic target in CRC.
Spermatogenesis is a dynamic process that is regulated by adhesive interactions between germ and Sertoli cells. Germ cells express the Junctional Adhesion Molecule-C (JAM-C, encoded by Jam3), which ...localizes to germ/Sertoli cell contacts. JAM-C is involved in germ cell polarity and acrosome formation. Using a proteomic approach, we demonstrated that JAM-C interacted with the Golgi reassembly stacking protein of 55 kDa (GRASP55, encoded by Gorasp2) in developing germ cells. Generation and study of Gorasp2-/- mice revealed that knock-out mice suffered from spermatogenesis defects. Acrosome formation and polarized localization of JAM-C in spermatids were altered in Gorasp2-/- mice. In addition, Golgi morphology of spermatocytes was disturbed in Gorasp2-/- mice. Crystal structures of GRASP55 in complex with JAM-C or JAM-B revealed that GRASP55 interacted via PDZ-mediated interactions with JAMs and induced a conformational change in GRASP55 with respect of its free conformation. An in silico pharmacophore approach identified a chemical compound called Graspin that inhibited PDZ-mediated interactions of GRASP55 with JAMs. Treatment of mice with Graspin hampered the polarized localization of JAM-C in spermatids, induced the premature release of spermatids and affected the Golgi morphology of meiotic spermatocytes.
The junctional adhesion molecules Jam‐b and Jam‐c interact together at interendothelial junctions and have been involved in the regulation of immune response, inflammation, and leukocyte migration. ...More recently, Jam‐c has been found to be expressed by hematopoietic stem and progenitor cells (HSPC) in mouse. Conversely, we have reported that Jam‐b is present on bone marrow stromal cells and that Jam‐b‐deficient mice have defects in the regulation of hematopoietic stem cell pool. In this study, we have addressed whether interaction between Jam‐b and Jam‐c participates to HSPC mobilization or hematopoietic reconstitution after irradiation. We show that a blocking monoclonal antibody directed against Jam‐c inhibits hematopoietic reconstitution, progenitor homing to the bone marrow, and induces HSPC mobilization in a Jam‐b dependent manner. In the latter setting, antibody treatment over a period of 3 days does not alter hematopoietic differentiation nor induce leukocytosis. Results are translated to human hematopoietic system in which a functional adhesive interaction between JAM‐B and JAM‐C is found between human HSPC and mesenchymal stem cells. Such an interaction does not occur between HSPC and human endothelial cells or osteoblasts. It is further shown that anti‐JAM‐C blocking antibody interferes with CD34+ hematopoietic progenitor homing in mouse bone marrow suggesting that monoclonal antibodies inhibiting JAM‐B/JAM‐C interaction may represent valuable therapeutic tools to improve stem cell mobilization protocols. Stem Cells 2014;32:1043–1054
Acute myeloid leukemia (AML) originates from hematopoietic stem and progenitor cells that acquire somatic mutations, leading to disease and clonogenic evolution. AML is characterized by accumulation ...of immature myeloid cells in the bone marrow and phenotypic cellular heterogeneity reflective of normal hematopoietic differentiation. Here, we show that JAM-C expression defines a subset of leukemic cells endowed with leukemia-initiating cell activity (LIC). Stratification of
AML patients at diagnosis based on JAM-C-expressing cells frequencies in the blood served as an independent prognostic marker for disease outcome. Using publicly available leukemic stem cell (LSC) gene expression profiles and gene expression data generated from JAM-C-expressing leukemic cells, we defined a single cell core gene expression signature correlated to JAM-C expression that reveals LSC heterogeneity. Finally, we demonstrated that JAM-C controls Src family kinase (SFK) activation in LSC and that LIC with exacerbated SFK activation was uniquely found within the JAM-C-expressing LSC compartment.
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► JAM-B is highly expressed on Lung Microvascular Endothelial Cells. ► JAM-B/JAM-C interaction mediates melanoma cell adhesion to endothelial cells in vitro. ► JAM-B/JAM-C interaction contributes to ...B16F10 melanoma cells metastasis.
Metastasis is a major clinical issue and results in poor prognosis for most cancers. The Junctional Adhesion Molecule-C (JAM-C) expressed by B16 melanoma and endothelial cells has been involved in metastasis of tumor cells through homophilic JAM-C/JAM-C trans-interactions. Here, we show that JAM-B expressed by endothelial cells contributes to murine B16 melanoma cells metastasis through its interaction with JAM-C on tumor cells. We further show that this adhesion molecular pair mediates melanoma cell adhesion to primary Lung Microvascular Endothelial Cells and that it is functional in vivo as demonstrated by the reduced metastasis of B16 cells in Jam-b deficient mice.
In adult mammals, hematopoietic stem cells (HSCs) reside in the bone marrow (BM) and are maintained in a quiescent and undifferentiated state through adhesive interactions with specialized ...microenvironmental niches. Although junctional adhesion molecule-C (JAM-C) is expressed by HSCs, its function in adult hematopoiesis remains elusive. Here, we show that HSCs adhere to JAM-B expressed by BM stromal cells in a JAM-C dependent manner. The interaction regulates the interplay between HSCs and BM stromal cells as illustrated by the decreased pool of quiescent HSCs observed in jam-b deficient mice. We further show that this is probably because of alterations of BM stromal compartments and changes in SDF-1α BM content in jam-b−/− mice, suggesting that JAM-B is an active player in the maintenance of the BM stromal microenvironment.
Ikaros—a factor that positively or negatively controls gene transcription—is active in murine adult erythroid cells, and involved in fetal to adult globin switching. Mice with Ikaros mutations have ...defects in erythropoiesis and anemia. In this paper, we have studied the role of Ikaros in human erythroid development for the first time. Using a gene-transfer strategy, we expressed Ikaros 6 (Ik6)—a known dominant-negative protein that interferes with normal Ikaros activity—in cord blood or apheresis CD34+ cells that were induced to differentiate along the erythroid pathway. Lentivirally induced Ik6-forced expression resulted in increased cell death, decreased cell proliferation, and decreased expression of erythroid-specific genes, including GATA1 and fetal and adult globins. In contrast, we observed the maintenance of a residual myeloid population that can be detected in this culture system, with a relative increase of myeloid gene expression, including PU1. In secondary cultures, expression of Ik6 favored reversion of sorted and phenotypically defined erythroid cells into myeloid cells, and prevented reversion of myeloid cells into erythroid cells. We conclude that Ikaros is involved in human adult or fetal erythroid differentiation as well as in the commitment between erythroid and myeloid cells.
Summary
Adult stem cells are critical for maintaining cellular homeostasis throughout life, yet the effects of age on their regenerative capacity are poorly understood. All lymphoid and myeloid blood ...cell lineages are continuously generated from hematopoietic stem cells present in human bone marrow. With age, significant changes in the function and composition of mature blood cells are observed. In this study, we report that age‐related changes also occur in the human hematopoietic stem cell compartment. We find that the proportion of multipotent CD34+CD38− cells increases in the bone marrow of elderly (>70 years) individuals. CD34+CD38+CD90−CD45RA+/−CD10− and CD34+CD33+ myeloid progenitors persist at the same level in the bone marrow, while the frequency of early CD34+CD38+CD90−CD45RA+CD10+ and committed CD34+CD19+ B‐lymphoid progenitors decreases with age. In contrast to mice models of aging, transplantation experiments with immunodeficient NOD/SCID/IL‐2Rγ null (NSG) mice showed that the frequency of NSG repopulating cells does not change significantly with age, and there is a decrease in myeloid lineage reconstitution. An age‐related decrease in the capacity of CD34+ cells to generate myeloid cells was also seen in colony‐forming assays in vitro. Thus, with increasing age, human hematopoietic stem/progenitor cells undergo quantitative changes as well as functional modifications.
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