scholarly journals Nbs1 Mediates Assembly and Activity of the Mre11 complex

2019 ◽  
Author(s):  
Jun Hyun Kim ◽  
Alexander Penson ◽  
Barry S. Taylor ◽  
John H.J. Petrini

AbstractWe derived a mouse model in which a mutant form of Nbs1 (Nbs1mid8) exhibits severely impaired binding to the Mre11-Rad50 core of the Mre11 complex. TheNbs1mid8allele was expressed exclusively in hematopoietic lineages (inNbs1-/mid8vavmice). UnlikeNbs1flox/floxvavmice, which are Nbs1 deficient in the bone marrow,Nbs1-/mid8vavmice were viable.Nbs1-/mid8vavhematopoiesis was profoundly defective, exhibiting reduced cellularity of thymus and bone marrow, and stage specific blockage of B cell development. Within six months,Nbs1-/mid8mice developed highly penetrant T cell leukemias.Nbs1-/mid8vavleukemias recapitulated mutational features of human T-ALL, containing mutations inNotch1, Trp53, Bcl6, Bcor, andIkzf1, suggesting thatNbs1mid8mice may provide a venue to examine the relationship between the Mre11 complex and oncogene activation in the hematopoietic compartment. Genomic analysis ofNbs1-/mid8vavmalignancies showed focal amplification of 9qA2, causing overexpression ofMRE11andCHK1. We propose that overexpression compensates for the meta-stable Mre11-Nbs1mid8interaction, and that selection pressure for overexpression reflects the essential role of Nbs1 in promoting assembly and activity of the Mre11 complex.

2019 ◽  
Vol 116 (30) ◽  
pp. 15178-15183 ◽  
Author(s):  
Jun Hyun Kim ◽  
Alexander V. Penson ◽  
Barry S. Taylor ◽  
John H. J. Petrini

We derived a mouse model in which a mutant form of Nbn/Nbs1mid8 (hereafter Nbnmid8) exhibits severely impaired binding to the Mre11−Rad50 core of the Mre11 complex. The Nbnmid8 allele was expressed exclusively in hematopoietic lineages (in Nbn−/mid8vav mice). Unlike Nbnflox/floxvav mice with Nbn deficiency in the bone marrow, Nbn−/mid8vav mice were viable. Nbn−/mid8vav mice hematopoiesis was profoundly defective, exhibiting reduced cellularity of thymus and bone marrow, and stage-specific blockage of B cell development. Within 6 mo, Nbn−/mid8 mice developed highly penetrant T cell leukemias. Nbn−/mid8vav leukemias recapitulated mutational features of human T cell acute lymphoblastic leukemia (T-ALL), containing mutations in NOTCH1, TP53, BCL6, BCOR, and IKZF1, suggesting that Nbnmid8 mice may provide a venue to examine the relationship between the Mre11 complex and oncogene activation in the hematopoietic compartment. Genomic analysis of Nbn−/mid8vav malignancies showed focal amplification of 9qA2, causing overexpression of MRE11 and CHK1. We propose that overexpression of MRE11 compensates for the metastable Mre11−Nbnmid8 interaction, and that selective pressure for overexpression reflects the essential role of Nbn in promoting assembly and activity of the Mre11 complex.


2021 ◽  
Vol 12 ◽  
Author(s):  
Hirotaka Imada ◽  
Nobuhiro Mifune

Disease-causing parasites and pathogens play a pivotal role in intergroup behavior. Previous studies have suggested that the selection pressure posed by pathogen threat has resulted in in-group assortative sociality, including xenophobia and in-group favoritism. While the current literature has collated numerous studies on the former, strikingly, there has not been much research on the relationship between pathogen threat and in-group cooperation. Drawing upon prior studies on the function of the behavioral immune system (BIS), we argued that the BIS might facilitate cooperation with in-group members as a reactive behavioral immune response to pathogen threat. More specifically, we held that individuals might utilize cooperative behavior to ensure that they can receive social support when they have contracted an infectious disease. We reviewed existing findings pertaining to the potential role of the BIS in in-group cooperation and discussed directions for future studies.


Blood ◽  
1991 ◽  
Vol 77 (1) ◽  
pp. 64-68 ◽  
Author(s):  
ER Grumayer ◽  
F Griesinger ◽  
DS Hummell ◽  
RD Brunning ◽  
JH Kersey

Abstract In the present study we used multiparameter flow cytometry and cell sorting to evaluate fetal bone marrow, a rich source of cells early in lymphoid development. We found CD7 to be expressed on a subset of CD19+ cells, including some that had matured to cytoplasmic mu+ (pre-B) and surface mu+ (B) cells. In addition, a less mature CD7+19+ population was characterized as mu- and CD34+/-. The CD7+19+ population was clearly distinct from the mature T cells. The CD7+19+ cells were negative for nuclear TdT in contrast to CD7–19+ cells, which frequently contained TdT. CD10, which is coexpressed on the cell surface of more than 90% of CD19+ lymphocytes, was detected in a minority of CD7+19+ lymphocytes. The CD7+19+34+ cell population may be B-lineage committed, or may represent uncommitted lymphoid precursors. The biologic role of the expression of CD7 on immature and mature cells, including those of the B lineage, may indicate (1) the presence of CD7+19+ lymphoid precursor cells and/or (2) an alternate pathway of B-cell development, in which cells coexpress CD7 with other B-lineage markers.


2020 ◽  
Vol 117 (33) ◽  
pp. 20100-20108
Author(s):  
Yafeng He ◽  
Jianke Ren ◽  
Xiaoping Xu ◽  
Kai Ni ◽  
Andrew Schwader ◽  
...  

Mutation of HELLS (Helicase, Lymphoid-Specific)/Lsh in human DNA causes a severe immunodeficiency syndrome, but the nature of the defect remains unknown. We assessed here the role of Lsh in hematopoiesis using conditional Lsh knockout mice with expression of Mx1 or Vav Cre-recombinase. Bone marrow transplantation studies revealed that Lsh depletion in hematopoietic stem cells severely reduced B cell numbers and impaired B cell development in a hematopoietic cell-autonomous manner. Lsh-deficient mice without bone marrow transplantation exhibited lower Ig levels in vivo compared to controls despite normal peripheral B cell numbers. Purified B lymphocytes proliferated normally but produced less immunoglobulins in response to in vitro stimulation, indicating a reduced capacity to undergo class switch recombination (CSR). Analysis of germline transcripts, examination of double-stranded breaks using biotin-labeling DNA break assay, and End-seq analysis indicated that the initiation of the recombination process was unscathed. In contrast, digestion–circularization PCR analysis and high-throughput sequencing analyses of CSR junctions and a chromosomal break repair assay indicated an impaired ability of the canonical end-joining pathway in Lsh-deficient B cells. Our data suggest a hematopoietic cell-intrinsic role of Lsh in B cell development and in CSR providing a potential target for immunodeficiency therapy.


2007 ◽  
Vol 204 (9) ◽  
pp. 2047-2051 ◽  
Author(s):  
Simona Ferrari ◽  
Vassilios Lougaris ◽  
Stefano Caraffi ◽  
Roberta Zuntini ◽  
Jianying Yang ◽  
...  

Agammaglobulinemia is a rare primary immunodeficiency characterized by an early block of B cell development in the bone marrow, resulting in the absence of peripheral B cells and low/absent immunoglobulin serum levels. So far, mutations in Btk, μ heavy chain, surrogate light chain, Igα, and B cell linker have been found in 85–90% of patients with agammaglobulinemia. We report on the first patient with agammaglobulinemia caused by a homozygous nonsense mutation in Igβ, which is a transmembrane protein that associates with Igα as part of the preBCR complex. Transfection experiments using Drosophila melanogaster S2 Schneider cells showed that the mutant Igβ is no longer able to associate with Igα, and that assembly of the BCR complex on the cell surface is abrogated. The essential role of Igβ for human B cell development was further demonstrated by immunofluorescence analysis of the patient's bone marrow, which showed a complete block of B cell development at the pro-B to preB transition. These results indicate that mutations in Igβ can cause agammaglobulinemia in man.


Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1466-1466
Author(s):  
Christopher D Chien ◽  
Elizabeth D Hicks ◽  
Paul P Su ◽  
Haiying Qin ◽  
Terry J Fry

Abstract Abstract 1466 Pediatric acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Although cure rates for this disease are approximately 90%, ALL remains one of the leading causes cancer-related deaths in children. Thus, new treatments are needed for those patients that do not respond to or recur following standard chemotherapy. Understanding the mechanisms underlying resistance of pediatric ALL to therapy offers one approach to improving outcomes. Recent studies have demonstrated the importance of communication between cancer cells and their microenvironment and how this contributes to the progression and therapeutic resistance but this has not been well studied in the context of ALL. Since the bone marrow is presumed to be the site of initiation of B precursor ALL we set out in our study to determine how ALL cells utilize the bone marrow milieu in a syngeneic transplantable model of preB cell ALL in immunocompetent mice. In this model, intravenously injected preB ALL develops first in the bone marrow, followed by infiltration into the spleen, lymph node, and liver. Using flow cytometry to detect the CD45.2 isoform following injection into B6CD45.1+ congenic recipients, leukemic cells can be identified in the bone marrow as early as 5 days after IV injection with a sensitivity of 0.01%-0.1%. The pre-B ALL line is B220+/CD19+/CD43+/BP1+/IL-7Ralpha (CD127)+/CD25-/Surface IgM-/cytoplasmic IgM+ consistent with a pre-pro B cell phenotype. We find that increasing amounts of leukemic infiltration in the bone marrow leads to an accumulation of non-malignant developing B cells at stages immediately prior to the pre-pro B cell (CD43+BP1-CD25-) and a reduction in non-malignant developing pre B cells at the developmental stage just after to the pre-pro B cell stage (CD43+BP1+CD25+). These data potentially suggest occupancy of normal B cell developmental niches by leukemia resulting in block in normal B cell development. Further supporting this hypothesis, we find significant reduction in early progression of ALL in aged (10–12 month old) mice known to have a deficiency in B cell developmental niches. We next explored whether specific factors that support normal B cell development can contribute to progression of precursor B cell leukemia. The normal B cell niche has only recently been characterized and the specific contribution of this niche to early ALL progression has not been extensively studied. Using a candidate approach, we examined the role of specific cytokines such as Interleukin-7 (IL-7) and thymic stromal lymphopoietin (TSLP) in early ALL progression. Our preB ALL line expresses high levels of IL-7Ralpha and low but detectable levels of TLSPR. In the presence of IL-7 (0.1 ng/ml) and TSLP (50 ng/ml) phosphSTAT5 is detectable indicating that these receptors are functional but that supraphysiologic levels of TSLP are required. Consistent with the importance of IL-7 in leukemia progression, preliminary data demonstrates reduced lethality of pr-B cell ALL in IL-7 deficient mice. Overexpression of TSLP receptor (TSLPR) has been associated with high rates of relapse and poor overall survival in precursor B cell ALL. We are currently generating a TSLPR overepressing preBALL line to determine the effect on early ALL progression and are using GFP-expressing preB ALL cells to identify the initial location of preB ALL occupancy in the bone marrow. In conclusion, or model of early ALL progression provides insight into the role of the bone marrow microenvironment in early ALL progression and provides an opportunity to examine how these microenvironmental factors contribute to therapeutic resistance. Given recent advances in immunotherapy for hematologic malignancies, the ability to study this in an immunocompetent host will be critical. Disclosures: No relevant conflicts of interest to declare.


2021 ◽  
Vol 28 ◽  
Author(s):  
Alireza Hosseini ◽  
Michael R Hamblin ◽  
Hamed Mirzaei ◽  
Hamid Reza Mirzaei

: The unique features of the tumor microenvironment (TME) govern the biological properties of many cancers, including hematological malignancies. TME factors can trigger invasion, and protect against drug cytotoxicity by inhibiting apoptosis and activating specific signaling pathways (e.g. NF-ΚB). TME remodeling is facilitated due to the high self-renewal ability of the bone marrow. Progressing tumor cells can alter some extracellular matrix (ECM) components which act as a barrier to drug penetration in the TME. The initial progression of the cell cycle is controlled by the MAPK pathway (Raf/MEK/ERK) and Hippo pathway, while the final phase is regulated by the PI3K/Akt /mTOR and WNT pathways. In this review we summarize the main signaling pathways involved in drug resistance (DR) and some mechanisms by which DR can occur in the bone marrow. The relationship between autophagy, endoplasmic reticulum stress, and cellular signaling pathways in DR and apoptosis are covered in relation to the TME.


Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4191-4191
Author(s):  
Kathleen Wren Phelan ◽  
Sucha Nand ◽  
Laura C Michaelis

Abstract Abstract 4191 Background: Performance status is traditionally used to judge fitness in cancer patients. It is often a key factor in determining appropriateness for chemotherapy and entry into clinical trials. Most research on PS has been in solid tumor patients, but it is generally assumed to be valid in hematologic malignancies as well. However, PS assessment can be problematic, especially in patients who have become ill quickly or where there are conflicting parameters; e.g. patients whose function is limited but who are still actively working. We explored the role of PS in patients with AML to determine if alternative, more objectively determined parameters, could predict PS. We evaluated the relationship between PS and rates of complete remission (CR) and duration of overall survival (OS) as well as the relationship between objectively determined pretreatment parameters and these outcomes. Methods: Approval for retrospective data collection was obtained by the institutional IRB. A randomly selected cohort of 145 patients with newly diagnosed AML was identified using pharmacy records of treatment with induction agents cytarabine, daunorubicin or azacitidine. We excluded patients with acute promyelocytic leukemia. Pretreatment data was collected from the electronic medical record of each subject, including AML subtype, age, gender, PS, presence of infection at diagnosis, peripheral blood white blood cell count, peripheral blood blast percentage, hemoglobin, lactate dehydrogenase, aspartate transaminase, alanine transaminase, creatinine, albumin, left ventricular ejection fraction (LVEF), bone marrow cellularity, bone marrow blast percentage and cytogenetics. Achievement of complete remission was assessed and overall survival was calculated in months from diagnosis to either death or date of censorship. PS was obtained from physician notes and documented as a Zubrod score. In the absence of documentation, the authors reviewed medical records for presenting symptoms, mobility and functional status and made an assignment. Retrospective assignment of PS was reviewed and confirmed by at least two of the authors. Logistic regression was performed to examine the relationship between pretreatment characteristics and CR, and the effect of pretreatment characteristics and the assignment of PS, dichotomized as good (0–1) vs. poor (2–4). Linear regression analysis was used to investigate the relationship between pretreatment characteristics and OS. Results: A total of 120/145 (83%) were assigned a PS of 0, 1. Twenty patients were considered to have a PS of 2 and five patients had a PS of 3. There was a statistically significant relationship between a good PS assignment and a higher albumin level (OR 5.32, p=0.000, 95% CI 2.32, 12.22). There was no significant relationship between the remaining clinical parameters and PS assignment, including age at diagnosis. Ninety-three patients (64%) achieved a CR. There was no relationship between PS, assigned either contemporarily or retrospectively, with the achievement of CR. The median overall survival was 15 months (range 0 to 92 months). PS did not predict the duration of OS. As is well reported, CR was significantly more likely in younger (< 60 yrs) patients and patients with favorable cytogenetics. Median OS was also prolonged in these patients. No additional pretreatment characteristics were significantly related to CR or OS except LVEF. Patients with an LVEF greater than 50% were more likely to achieve a CR (P=0.0001) and had a longer OS. Conclusions: We found that, among pretreatment characteristics, a higher albumin level was associated with a good performance status. Age was not a predictor of PS. Contrary to expectations, in this population of treated AML patients, PS did not predict either CR or OS. In addition to the association of younger age and favorable cytogenetics with better outcomes, we found that a higher LVEF is also associated with higher CR rates, but this is likely explained by choice of chemotherapeutic agents. Our data calls into question the use of PS as a tool to guide therapy in routine clinical management of acute myeloid leukemia. Prospective studies should evaluate the utility of more objective and more reliably documented clinical parameters than PS for predicting patient outcome. Disclosures: No relevant conflicts of interest to declare.


Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 513-513
Author(s):  
Ling Tian ◽  
Monique Chavez ◽  
Lukas D Wartman

Abstract Loss-of-function mutations in KDM6A, an X-linked H3K27 demethylase, occur recurrently in B-cell lymphoid malignancies, including B-cell acute lymphoblastic leukemia and non-Hodgkin lymphoma. Germline inactivating mutations in KDM6A cause a neurodevelopmental disorder called Kabuki syndrome that is associated with recurrent infections and hypogammaglobulinemia.1 The role of KDM6A in normal B-cell development and function, as well as how the somatic loss of KDM6A contributes to B-cell malignancies, has not been completely defined. To address this issue, we generated a conditional knockout mouse of the KDM6A gene (with LoxP sites flanking the 3rd exon) and crossed these mice with Vav1-Cre transgenic mice to selectively inactivate KDM6A in hematopoietic stem/progenitor cells. We characterized normal hematopoiesis from young (6 to 8 week old) and aged (50 to 55 week old) male and female KDM6A conditional KO mice. We found a significant shift from lymphoid to myeloid differentiation in the bone marrow and peripheral blood of these mice. Young, female KDM6A-null mice had mild splenomegaly. Their spleens had an increased number of neutrophils (Gr-1+CD11b+ cells) and erythrocyte progenitors (CD71+Ter119+ cells) and a decreased number of B-cells (B220+ cells). These changes became more pronounced with age and were specific to the female, homozygous KDM6A knockout mice. Furthermore, analysis of B-cell maturation showed that the loss of KDM6A was associated with decreased immature (B220+IgM+ cells) and mature, resting B-cells (B220+IgD+ cells) in the spleen. Similar changes were present in the bone marrow (decreased B220+IgM+ cells and B220+CD19+ cells) and peripheral blood (decreased B220+IgM+, B220+IgD+ and B220+CD19+ cells). Early B-cell development is also altered in KDM6A-null mice. Flow cytometry showed a decrease in multipotent progenitor cells (MPPs) with a decrease in both common lymphoid progenitors (CLPs) and B cell-biased lymphoid progenitors (BLPs) in young, female KDM6A-null mice bone marrow. Next, we performed flow cytometry to catergorize the Hardy fractions of early B-cell development on bone marrow isolated from young, female KDM6A-null mice. B-cell progenitor analysis (Hardy profiles) showed an increase in Fraction A with a concomitant decrease in Fraction B/C and Fraction D, which was likely indicative of an incomplete block in B-cell differentiation after the Fraction A stage. When bulk bone marrow cells isolated from young, female KDM6A-null mice were plated in methylcellulose supplemented with interleukin-7, we observed a significantly decreased colony formation compared with bone marrow cells isolated from wildtype littermates. This pre-B lymphoid progenitor cell plating phenotype was expected given the flow cytometry results of decreased B-cell progenitors outlined above. We examined the effect of the loss of KDM6A expression on germinal center (GC) formation in the spleen following immunization with NP-CGG (4-Hydroxy-3-nitrophenylacetyl-Chicken Gamma Globulin, Ratio 16). Two weeks after NP-CGG immunization, we observed a significant decrease in follicular B-cells (FO) and a significant increase in GC B-cells as compared to wildtype littermates (Figure 1). The result is significant as GC B-cells are thought to be the cell-of-origin of follicular and DLBCL. To determine if inactivation of KDM6A affected antibody production, we measured IgM, IgG, IgE and IgA levels by ELISA from serum isolated from young, female KDM6A-null mice. Results revealed higher levels of IgM and lower levels of IgG in serum from KDM6A-null mice, which is suggestive of a class switch recombination (CSR) defect. Concordant with this result, we observed that the loss of KDM6A impaired CSR to IgG1 in splenic B cells after in vitro stimulation for three days with lipopolysaccharide (LPS), an anti-CD180 antibody and interleukin-4. Moreover, we observed a striking defect in the production of plasma cells from KDM6A-null B-cells after LPS stimulation. Taken together, our data shows that KDM6A plays an important, but complex, role in B-cell development and that loss of KDM6A impedes the B-cell immune response in a specific manner that may contribute to infection and B-cell malignancies.Stagi S, et al. Epigenetic control of the immune system: a lesson from Kabuki syndrome. Immunol Res. 2016; 64(2):345-359. Disclosures No relevant conflicts of interest to declare.


Blood ◽  
1988 ◽  
Vol 71 (1) ◽  
pp. 256-258
Author(s):  
H Hirai ◽  
M Okada ◽  
H Mizoguchi ◽  
H Mano ◽  
Y Kobayashi ◽  
...  

The relationship between chromosomal abnormality and oncogene activation was investigated during leukemic progression in two patients with myelodysplastic syndrome (MDS). Both patients had partial or complete deletion of chromosome 5 in metaphase cells obtained throughout the progression to leukemia. Analysis with specific oligonucleotide probes revealed that bone marrow cells containing an activated N-ras oncogene proliferated in a dominant manner during the process of leukemic conversion in both patients. These observations suggest that the chromosomal abnormality may precede activation of the N-ras gene in these patients, and that both the chromosomal abnormality and the activated N-ras oncogene contribute to the development of leukemia.


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