| 1. |
- Alsén, Samuel, et al.
(författare)
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Antigen-Presenting B Cells Program the Efferent Lymph T Helper Cell Response
- 2022
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- B cells interact with T follicular helper (Tfh) cells in germinal centers (GCs) to generate high-affinity antibodies. Much less is known about how cognate T-B-cell interactions influence Th cells that enter circulation and peripheral tissues. Therefore, we generated mice lacking MHC-II expressing B cells and, by thoracic duct cannulation, analyzed Th cells in the efferent lymph at defined intervals post-immunization. Focusing on gut-draining mesenteric lymph nodes (MLNs), we show that antigen-specific alpha(4)beta(+)(7) gut-homing effector Th cells enter the circulation prior to CXCR5(+)PD-1(+) Tfh-like cells. B cells appear to have no or limited impact on the early generation and egress of gut-homing Th cells but are critical for the subsequent appearance of Tfh-like cells that peak in the lymph before GCs have developed. At this stage, antigen-presenting B cells also reduce the proportion of alpha(4)beta(+)(7) Th cells in the MLN and efferent lymph. Furthermore, cognate B-cell interaction drives a broad transcriptional program in Th cells, including IL-4 that is confined to the Tfh cell lineage. The IL-4-producing Tfh-like cells originate from Bcl6(+) precursors in the LNs and have gut-homing capacity. Hence, B cells program the efferent lymph Th cell response within a limited window of time after antigenic challenge.
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| 2. |
- Dudenhöffer-Pfeifer, Monika, et al.
(författare)
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Immunoediting is not a primary transformation event in a murine model of MLL-ENL AML
- 2018
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Ingår i: Life Science Alliance. - : Life Science Alliance, LLC. - 2575-1077. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Although it is firmly established that endogenous immunity can prevent cancer outgrowth, with a range of immunomodulatory strategies reaching clinical use, most studies on the topic have been restricted to solid cancers. This applies in particular to cancer initiation, where model constraints have precluded investigations of immunosurveillance and immunoediting during the multistep progression into acute myeloid leukemia (AML). Here, we used a mouse model where the chimeric transcription factor MLL-ENL can be conditionally activated in vivo as a leukemic “first-hit,” which is followed by spontaneous transformation into AML. We observed similar disease kinetics regardless of whether AML developed in WT or immunocompromised hosts, despite more permissive preleukemic environments in the latter. When assessing transformed AML cells from either primary immunocompetent or immunocompromised hosts, AML cells from all sources could be targets of endogenous immunity. Our data argue against immunoediting in response to selective pressure from endogenous immunity as a universal primary transformation event in AML.
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| 3. |
- Morcos, M. N. F., et al.
(författare)
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Continuous mitotic activity of primitive hematopoietic stem cells in adult mice
- 2020
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 217:6
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Tidskriftsartikel (refereegranskat)abstract
- The proliferative activity of aging hematopoietic stem cells (HSCs) is controversially discussed. Inducible fluorescent histone 2B fusion protein (H2B-FP) transgenic mice are important tools for tracking the mitotic history of murine HSCs in label dilution experiments. A recent study proposed that primitive HSCs symmetrically divide only four times to then enter permanent quiescence. We observed that background fluorescence due to leaky H2B-FP expression, occurring in all H2B-FP transgenes independent of label induction, accumulated with age in HSCs with high repopulation potential. We argue that this background had been misinterpreted as stable retention of induced label. We found cell division-independent half-lives of H2B-FPs to be short, which had led to overestimation of HSC divisional activity. Our data do not support abrupt entry of HSCs into permanent quiescence or sudden loss of regeneration potential after four divisions, but show that primitive HSCs of adult mice continue to cycle rarely.
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| 4. |
- Okeyo-Owuor, T., et al.
(författare)
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The efficiency of murine MLL-ENL-driven leukemia initiation changes with age and peaks during neonatal development
- 2019
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Ingår i: Blood Advances. - : American Society of Hematology. - 2473-9529 .- 2473-9537. ; 3:15, s. 2388-2399
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Tidskriftsartikel (refereegranskat)abstract
- MLL rearrangements are translocation mutations that cause both acute lymphoblastic leukemia and acute myeloid leukemia (AML). These translocations can occur as sole clonal driver mutations in infant leukemias, suggesting that fetal or neonatal hematopoietic progenitors may be exquisitely sensitive to transformation by MLL fusion proteins. To test this possibility, we used transgenic mice to induce one translocation product, MLL-ENL, during fetal, neonatal, juvenile and adult stages of life. When MLL-ENL was induced in fetal or neonatal mice, almost all died of AML. In contrast, when MLL-ENL was induced in adult mice, most survived for >1 year despite sustained transgene expression. AML initiation was most efficient when MLL-ENL was induced in neonates, and even transient suppression of MLL-ENL in neonates could prevent AML in most mice. MLL-ENL target genes were induced more efficiently in neonatal progenitors than in adult progenitors, consistent with the distinct AML initiation efficiencies. Interestingly, transplantation stress mitigated the developmental barrier to leukemogenesis. Since fetal/neonatal progenitors were highly competent to initiate MLL-ENL-driven AML, we tested whether Lin28b, a fetal master regulator, could accelerate leukemogenesis. Surprisingly, Lin28b suppressed AML initiation rather than accelerating it. This may explain why MLL rearrangements often occur before birth in human infant leukemia patients, but transformation usually does not occur until after birth, when Lin28b levels decline. Our findings show that the efficiency of MLL-ENL-driven AML initiation changes through the course of pre- and postnatal development, and developmental programs can be manipulated to impede transformation.
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| 5. |
- Säwen, Petter, et al.
(författare)
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Murine HSCs contribute actively to native hematopoiesis but with reduced differentiation capacity upon aging
- 2018
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Ingår i: Elife. - 2050-084X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- A hallmark of adult hematopoiesis is the continuous replacement of blood cells with limited lifespans. While active hematopoietic stem cell (HSC) contribution to multilineage hematopoiesis is the foundation of clinical HSC transplantation, recent reports have questioned the physiological contribution of HSCs to normal/steady-state adult hematopoiesis. Here, we use inducible lineage tracing from genetically marked adult HSCs and reveal robust HSC-derived multilineage hematopoiesis. This commences via defined progenitor cells, but varies substantially in between different hematopoietic lineages. By contrast, adult HSC contribution to hematopoietic cells with proposed fetal origins is neglible. Finally, we establish that the HSC contribution to multilineage hematopoiesis declines with increasing age. Therefore, while HSCs are active contributors to native adult hematopoiesis, it appears that the numerical increase of HSCs is a physiologically relevant compensatory mechanism to account for their reduced differentiation capacity with age.
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| 6. |
- Takahashi, M., et al.
(författare)
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Reconciling Flux Experiments for Quantitative Modeling of Normal and Malignant Hematopoietic Stem/Progenitor Dynamics
- 2021
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Ingår i: Stem Cell Reports. - : Elsevier BV. - 2213-6711. ; 16:4, s. 741-753
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoiesis serves as a paradigm for how homeostasis is maintained within hierarchically organized cell populations. However, important questions remain as to the contribution of hematopoietic stem cells (HSCs) toward maintaining steady state hematopoiesis. A number of in vivo lineage labeling and propagation studies have given rise to contradictory interpretations, leaving key properties of stem cell function unresolved. Using processed flow cytometry data coupled with a biology-driven modeling approach, we show that in vivo flux experiments that come from different laboratories can all be reconciled into a single unifying model, even though they had previously been interpreted as being contradictory. We infer from comparative analysis that different transgenic models display distinct labeling efficiencies across a heterogeneous HSC pool, which we validate by marker gene expression associated with HSC function. Finally, we show how the unified model of HSC differentiation can be used to simulate clonal expansion in the early stages of leukemogenesis. © 2021 The Authors
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| 7. |
- Velasco-Hernandez, Talia, et al.
(författare)
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Hif-1 alpha Deletion May Lead to Adverse Treatment Effect in a Mouse Model of MLL-AF9-Driven AML
- 2019
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Ingår i: Stem Cell Reports. - : Elsevier BV. - 2213-6711. ; 12:1, s. 112-121
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Tidskriftsartikel (refereegranskat)abstract
- Relapse of acute myeloid leukemia (AML) remains a significant clinical challenge due to limited therapeutic options and poor prognosis. Leukemic stem cells (LSCs) are the cellular units responsible for relapse in AML, and strategies that target LSCs are thus critical. One proposed potential strategy to this end is to break the quiescent state of LSCs, thereby sensitizing LSCs to conventional cytostatics. The hypoxia-inducible factor (HIF) pathway is a main driver of cellular quiescence and a potential therapeutic target, with precedence from both solid cancers and leukemias. Here, we used a conditional knockout Hif-1 alpha mouse model together with a standard chemotherapy regimen to evaluate LSC targeting in AML. Contrary to expectation, our studies revealed that Hif-1 alpha-deleted-leukemias displayed a faster disease progression after chemotherapy. Our studies thereby challenge the general notion of cancer stem cell sensitization by inhibition of the HIF pathway, and warrant caution when applying HIF inhibition in combination with chemotherapy in AML.
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| 8. |
- Yang, W., et al.
(författare)
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Enhancing Hematopoiesis from Murine Embryonic Stem Cells through MLL1-Induced Activation of a Rac/Rho/Integrin Signaling Axis
- 2020
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Ingår i: Stem Cell Reports. - : Elsevier BV. - 2213-6711. ; 14:2, s. 285-299
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Tidskriftsartikel (refereegranskat)abstract
- The Mixed Lineage Leukemia (MLL1, KMT2A) gene is critical for development and maintenance of hematopoietic stem cells (HSCs), however, whether this protein is limiting for HSC development is unknown due to lack of physiologic model systems. Here, we develop an MLL1-inducible embryonic stem cell (ESC) system and show that induction of wild-type MLL1 during ESC differentiation selectively increases hematopoietic potential from a transitional c-Kit(+)/Cd41(+) population in the embryoid body and also at sites of hematopoiesis in embryos. Single-cell sequencing analysis illustrates inherent heterogeneity of the c-Kit(+)/Cd41(+) population and demonstrates that MLL1 induction shifts its composition toward multilineage hematopoietic identities. Surprisingly, this does not occur through increasing Hox or other canonical MLL1 targets but through an enhanced Rac/Rho/integrin signaling state, which increases responsiveness to Vla4 ligands and enhances hematopoietic commitment. Together, our data implicate a Rac/Rho/integrin signaling axis in the endothelial to hematopoietic transition and demonstrate that MLL1 actives this axis.
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| 9. |
- Yuan, Ouyang, et al.
(författare)
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A somatic mutation in moesin drives progression into acute myeloid leukemia
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:16
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Tidskriftsartikel (refereegranskat)abstract
- Acute myeloid leukemia (AML) arises when leukemia-initiating cells, defined by a primary genetic lesion, acquire subsequent molecular changes whose cumulative effects bypass tumor suppression. The changes that underlie AML pathogenesis not only provide insights into the biology of transformation but also reveal novel therapeutic opportunities. However, backtracking these events in transformed human AML samples is challenging, if at all possible. Here, we approached this question using a murine in vivo model with an MLL-ENL fusion protein as a primary molecular event. Upon clonal transformation, we identified and extensively verified a recurrent codon-changing mutation (Arg(295)Cys) in the ERM protein moesin that markedly accelerated leukemogenesis. Human cancer-associated moesin mutations at the conserved arginine-295 residue similarly enhanced MLL-ENL-driven leukemogenesis. Mechanistically, the mutation interrupted the stability of moesin and conferred a neomorphic activity to the protein, which converged on enhanced extracellular signal-regulated kinase activity. Thereby, our studies demonstrate a critical role of ERM proteins in AML, with implications also for human cancer.
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