scholarly journals Disruption of Sept6, a Fusion Partner Gene of MLL, Does Not Affect Ontogeny, Leukemogenesis Induced by MLL-SEPT6, or Phenotype Induced by the Loss of Sept4

2005 ◽  
Vol 25 (24) ◽  
pp. 10965-10978 ◽  
Author(s):  
Ryoichi Ono ◽  
Masafumi Ihara ◽  
Hideaki Nakajima ◽  
Katsutoshi Ozaki ◽  
Yuki Kataoka-Fujiwara ◽  
...  
Keyword(s):  
Fusion Gene ◽  
Fusion Partner ◽  
Myeloproliferative Disease ◽  
Cellular Processes ◽  
Partner Gene ◽  
Quantitative Changes ◽  
High Degree ◽  
Deficient Mice

ABSTRACT Septins are evolutionarily conserved GTP-binding proteins that can heteropolymerize into filaments. Recent studies have revealed that septins are involved in not only diverse normal cellular processes but also the pathogenesis of various diseases, including cancer. SEPT6 is ubiquitously expressed in tissues and one of the fusion partner genes of MLL in the 11q23 translocations implicated in acute leukemia. However, the roles of this septin in vivo remain elusive. We have developed Sept6-deficient mice that exhibited neither gross abnormalities, changes in cytokinesis, nor spontaneous malignancy. Sept6 deficiency did not cause any quantitative changes in any of the septins evaluated in this study, nor did it cause any additional changes in the Sept4-deficient mice. Even the depletion of Sept11, a close homolog of Sept6, did not affect the Sept6-null cells in vitro, thus implying a high degree of redundancy in the septin system. Furthermore, a loss of Sept6 did not alter the phenotype of myeloproliferative disease induced by MLL-SEPT6, thus suggesting that Sept6 does not function as a tumor suppressor. To our knowledge, this is the first report demonstrating that a disruption of the translocation partner gene of MLL in 11q23 translocation does not contribute to leukemogenesis by the MLL fusion gene.

Mechanisms of Activation of the FIP1L1-PDGFRα Fusion Kinase.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2422-2422
Author(s):  
Elizabeth H. Stover ◽  
Jan Cools ◽  
D. Gary Gilliland
Keyword(s):  
Fusion Protein ◽  
Tyrosine Kinase ◽  
Kinase Inhibitor ◽  
Hypereosinophilic Syndrome ◽  
Fusion Partner ◽  
Myeloproliferative Disease ◽  
Alternative Mode ◽  
Type Iii

Abstract We recently identified the FIP1L1-PDGFRα fusion protein as a frequent cause of hypereosinophilic syndrome (HES), a disorder characterized by persistent eosinophilia and organ dysfunction. ~60% of HES patients who are sensitive to imatinib, a selective tyrosine kinase inhibitor, harbor the FIP1L1-PDGFRα fusion. The fusion is expressed as a consequence of an interstitial chromosomal deletion of human chromosome 4 that fuses a novel protein FIP1L1 to the cytoplasmic domain of the tyrosine kinase PDGFRα, a type III receptor tyrosine kinase (RTK). The fusion protein is a constitutively active kinase and has transforming properties in vitro and in vivo that are inhibited by imatinib. In order to understand the mechanism of activation of the FIP1L1-PDGFRα fusion kinase, a series of deletions of FIP1L1 were fused to PDGFRα and the fusions were tested for transforming activity. The data suggested that the FIP1L1 moiety was in fact dispensable for PDGFRα activation. For example, substitution of FIP1L1 with the Myc-epitope fused to PDGFRA still resulted in PDGFRα autophosphorylation; transformation of Ba/F3 cells to IL-3 independent growth; and induction of a myeloproliferative disease in a murine bone marrow transplant assay. Structural analyses of other type III RTKs, such as FLT3, have identified an autoinhibitory function of the juxtamembrane (JM) domain. Thus, the lack of requirement for FIP1L1 suggests that activation of the FIP1L1-PDGFRa fusion kinase might be caused by disruption of an autoinhibitory JM domain in PDGFRα. Indeed, in patients with the FIP1L1-PDGFRα fusion, the breakpoints in PDGFRA are tightly clustered within exon 12, which encompasses the JM domain. Whereas activation of most known fusion kinases relies on enforced dimerization by a fusion partner, disruption of an autoinhibitory JM domain may be an alternative mode of fusion kinase activation.

Environmental Factors Determine Lineage Fate in a Human Model of MLL-AF9 Leukemia.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3374-3374
Author(s):  
Junping Wei ◽  
Wunderlich Mark ◽  
Catherine Fox ◽  
Jorge F. DiMartino ◽  
James C. Mulloy
Keyword(s):  
Fusion Gene ◽  
Human Model ◽  
Fusion Partner ◽  
Reciprocal Translocations ◽  
Acute Leukemias ◽  
Human Cd34 ◽  
B Lymphoid ◽  
Novel Therapeutic Strategies

Abstract The MLL gene is fused to over 30 different fusion partners by reciprocal translocations in human acute leukemias. Some fusion partners are associated almost exclusively with myeloid or lymphoid leukemias while others are found in both. The degree to which the fusion partner contributes to the lineage of the resulting leukemia remains a matter of controversy. Using a novel model system, we demonstrate that myeloid vs lymphoid differentiation of hematopoietic progenitors transformed by MLL-AF9 can be predictably driven by cytokine combinations in vitro and in vivo. The t(9;11)(p22;q23) MLL-AF9 fusion gene is commonly associated with M5 myeloid leukemia but approximately 5% of MLL-AF9 leukemia is B-lymphoid. Expression of MLL-AF9 in human CD34+ cells enables efficient modeling of acute myeloid, B-lymphoid and biphenotypic leukemia. The lineage of the resulting leukemia can be readily manipulated in vitro (by altering the growth factors) or in vivo (using B-lymphoid-biased NOD/SCID mice or myeloid-biased NOD/SCID that are transgenic for human SCF, GM-CSF and IL-3). The cytokines IL-3, IL-7 and FLT3L appear to exert the major effects on lineage fate determination in vitro. Through limiting dilution and clonality analyses, we find a complex relationship between different leukemia stem cell compartments, with some LSC demonstrating multipotentiality and others showing strict lineage commitment. Data indicate that these differences are primarily due to microenvironment effects, with the identity of the initial cell that is targeted by MLL-AF9 possibly playing a role. These results would argue against a deterministic role for the fusion partner in MLL leukemia. This human-based system should prove useful in addressing the mechanism of lineage promiscuity of MLL leukemias. It also affords us the unique ability to determine the susceptibility of the different LSC to standard chemotherapeutic compounds, in addition to identifying novel therapeutic strategies that may be effective in treating MLL leukemia.

scholarly journals Rac1 Is Crucial for Hair Follicle Integrity but Is Not Essential for Maintenance of the Epidermis

2006 ◽  
Vol 26 (18) ◽  
pp. 6957-6970 ◽  
Author(s):  
Anna Chrostek ◽  
Xunwei Wu ◽  
Fabio Quondamatteo ◽  
Rong Hu ◽  
Anna Sanecka ◽  
...  
Keyword(s):  
Hair Follicle ◽  
Hair Follicles ◽  
Small Gtpase ◽  
Epidermal Keratinocytes ◽  
Sebaceous Glands ◽  
Cellular Processes ◽  
Normal Differentiation ◽  
Deficient Mice

ABSTRACT Rac1 is a small GTPase that regulates the actin cytoskeleton but also other cellular processes. To investigate the function of Rac1 in skin, we generated mice with a keratinocyte-restricted deletion of the rac1 gene. Rac1-deficient mice lost nearly all of their hair within a few weeks after birth. The nonpermanent part of mutant hair follicles developed constrictions; lost expression of hair follicle-specific keratins, E-cadherin, and α6 integrin; and was eventually removed by macrophages. The permanent part of hair follicles and the sebaceous glands were maintained, but no regrowth of full-length hair follicles was observed. In the skin of mutant mice, epidermal keratinocytes showed normal differentiation, proliferation, cell-cell contacts, and basement membrane deposition, demonstrating no obvious defects of Rac1-deficient epidermis in vivo. In vitro, Rac1-null keratinocytes displayed a strong spreading defect and slightly impaired adhesion. These data show that Rac1 plays an important role in sustaining the integrity of the lower part of hair follicles but not in maintenance of the epidermis.

Multinucleated Osteoclast Formation In Vivo and In Vitro by P2X7 Receptor-Deficient Mice

2003 ◽  
Vol 13 (2-4) ◽  
pp. 12 ◽  
Author(s):  
Alison Gartland ◽  
Katherine A. Buckley ◽  
Robert A. Hipskind ◽  
M. J. Perry ◽  
J. H. Tobias ◽  
...  
Keyword(s):  
P2x7 Receptor ◽  
Osteoclast Formation ◽  
Deficient Mice

FcγRIII (CD16)-Deficient Mice Show IgG Isotype-Dependent Protection to Experimental Autoimmune Hemolytic Anemia

Blood ◽  
1998 ◽  
Vol 92 (11) ◽  
pp. 3997-4002 ◽  
Author(s):  
Dirk Meyer ◽  
Carsten Schiller ◽  
Jürgen Westermann ◽  
Shozo Izui ◽  
Wouter L. W. Hazenbos ◽  
...  
Keyword(s):  
Hemolytic Anemia ◽  
Autoimmune Hemolytic Anemia ◽  
Knock Out ◽  
Effector Cells ◽  
Igg Isotypes ◽  
Knock Out Mice ◽  
Deficient Mice ◽  
Experimental Autoimmune

Abstract In autoimmune hemolytic anemia (AIHA), there is accumulating evidence for an involvement of FcγR expressed by phagocytic effector cells, but demonstration of a causal relationship between individual FcγRs and IgG isotypes for disease development is lacking. Although the relevance of IgG isotypes to human AIHA is limited, we could show a clear IgG isotype dependency in murine AIHA using pathogenic IgG1 (105-2H) and IgG2a (34-3C) autoreactive anti–red blood cell antibodies in mice defective for FcγRIII, and comparing the clinical outcome to those in wild-type mice. FcγRIII-deficient mice were completely resistent to the pathogenic effects of 105-2H monoclonal antibody, as shown by a lack of IgG1-mediated erythrophagocytosis in vitro and in vivo. In addition, the IgG2a response by 34-3C induced a less severe but persistent AIHA in FcγRIII knock-out mice, as documented by a decrease in hematocrit. Blocking studies indicated that the residual anemic phenotype induced by 34-3C in the absence of FcγRIII reflects an activation of FcγRI that is normally coexpressed with FcγRIII on macrophages. Together these results show that the pathogenesis of AIHA through IgG1-dependent erythrophagocytosis is exclusively mediated by FcγRIII and further suggest that FcγRI, in addition to FcγRIII, contributes to this autoimmune disease when other IgG isotypes such as IgG2a are involved.

scholarly journals Considerations when investigating lncRNA function in vivo

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Andrew R Bassett ◽  
Asifa Akhtar ◽  
Denise P Barlow ◽  
Adrian P Bird ◽  
Neil Brockdorff ◽  
...  
Keyword(s):  
Normal Cell ◽  
Regulatory Elements ◽  
Genomic Locus ◽  
Cellular Processes ◽  
Cell Processes ◽  
Non Coding Rnas ◽  
Per Se ◽  
Dna Regulatory Elements

Although a small number of the vast array of animal long non-coding RNAs (lncRNAs) have known effects on cellular processes examined in vitro, the extent of their contributions to normal cell processes throughout development, differentiation and disease for the most part remains less clear. Phenotypes arising from deletion of an entire genomic locus cannot be unequivocally attributed either to the loss of the lncRNA per se or to the associated loss of other overlapping DNA regulatory elements. The distinction between cis- or trans-effects is also often problematic. We discuss the advantages and challenges associated with the current techniques for studying the in vivo function of lncRNAs in the light of different models of lncRNA molecular mechanism, and reflect on the design of experiments to mutate lncRNA loci. These considerations should assist in the further investigation of these transcriptional products of the genome.

scholarly journals Mice Lacking the Inhibitory Collagen Receptor LAIR-1 Exhibit a Mild Thrombocytosis and Hyperactive Platelets

2017 ◽  
Vol 37 (5) ◽  
pp. 823-835 ◽  
Author(s):  
Christopher W. Smith ◽  
Steven G. Thomas ◽  
Zaher Raslan ◽  
Pushpa Patel ◽  
Maxwell Byrne ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Kinase Activity ◽  
Thrombus Formation ◽  
Physiological Role ◽  
Src Family Kinase ◽  
Glycoprotein Vi ◽  
Collagen Receptor ◽  
Deficient Mice

Objective— Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is a collagen receptor that belongs to the inhibitory immunoreceptor tyrosine-based inhibition motif–containing receptor family. It is an inhibitor of signaling via the immunoreceptor tyrosine-based activation motif–containing collagen receptor complex, glycoprotein VI-FcRγ-chain. It is expressed on hematopoietic cells, including immature megakaryocytes, but is not detectable on platelets. Although the inhibitory function of LAIR-1 has been described in leukocytes, its physiological role in megakaryocytes and in particular in platelet formation has not been explored. In this study, we investigate the role of LAIR-1 in megakaryocyte development and platelet production by generating LAIR-1–deficient mice. Approach and Results— Mice lacking LAIR-1 exhibit a significant increase in platelet counts, a prolonged platelet half-life in vivo, and increased proplatelet formation in vitro. Interestingly, platelets from LAIR-1–deficient mice exhibit an enhanced reactivity to collagen and the glycoprotein VI–specific agonist collagen-related peptide despite not expressing LAIR-1, and mice showed enhanced thrombus formation in the carotid artery after ferric chloride injury. Targeted deletion of LAIR-1 in mice results in an increase in signaling downstream of the glycoprotein VI–FcRγ-chain and integrin αIIbβ3 in megakaryocytes because of enhanced Src family kinase activity. Conclusions— Findings from this study demonstrate that ablation of LAIR-1 in megakaryocytes leads to increased Src family kinase activity and downstream signaling in response to collagen that is transmitted to platelets, rendering them hyper-reactive specifically to agonists that signal through Syk tyrosine kinases, but not to G-protein–coupled receptors.

scholarly journals On the origin of the increased tissue iron content in graded magnesium deficiency states in the rat

1997 ◽  
Vol 77 (3) ◽  
pp. 475-490 ◽  
Author(s):  
Klaus Schumann ◽  
Annette Lebeau ◽  
Ursula Gresser ◽  
Theodor Gunther ◽  
Jürgen Vormann
Keyword(s):  
Haemolytic Anaemia ◽  
Rapid Growth ◽  
Magnesium Deficiency ◽  
Erythropoietic Activity ◽  
Mg Deficiency ◽  
Adequate Diet ◽  
Fe Content ◽  
High Degree

To investigate the mechanism of tissue Fe accumulation in graded Mg deficiency rats were fed on diets of different Mg contents (70, 110, 208, 330, and 850 mg Mg/kg) for 10, 20, and 30 d during rapid growth. There was no significant impact of Mg deficiency or high luminal Mg concentrations on intestinal59Fe transferin vitroorin vivo. Plasma Mg concentrations and body weight started to decrease after 10 d. Significant haemolytic anaemia was observed after 20 d with siderosis in liver and spleen developing in parallel. Anaemia showed no features of Fe deficiency or infiammation. Comparison between the 70 mg Mg/kg group and animals that received the same quantity of a Mg-adequate diet (850 mg Mg/kg) permitted estimation of quantities of Fe liberated by haemolysis and the increased Fe content in liver and spleen. Both variables showed a high degree of correlation, indicating that the excess of liberated haemoglobin Fe was stored in the tissue. The erythropoietic activity was high during rapid growth, i.e. at days 10 and 20 and decreased significantly after 30 d in all except the most Mg-deficient groups. However, haemolytic anaemia developed because even the high erythropoietic activity in the 70 and 110 mg Mg/kg groups was not sutlicient to recycle all haemoglobin Fe liberated by haemolysis. After 30 d of Mg-deficient feeding the erythrocyte Mg content had decreased to 40% of control values. According to the literature Mg-deficient erythrocytes have a decreased survival time which is likely to be the cause of the observed haemolysis.

Developmental regulation of heterochromatin-mediated gene silencing in Drosophila

Development ◽  
1998 ◽  
Vol 125 (12) ◽  
pp. 2223-2234 ◽  
Author(s):  
B.Y. Lu ◽  
J. Ma ◽  
J.C. Eissenberg
Keyword(s):  
Cell Cycle ◽  
Gene Silencing ◽  
Mitotic Activity ◽  
Larval Stage ◽  
Developmental Regulation ◽  
Promoter Strength ◽  
Lacz Gene ◽  
High Degree

The roles of differentiation, mitotic activity and intrinsic promoter strength in the maintenance of heterochromatic silencing were investigated during development using an inducible lacZ gene as an in vivo probe. Heterochromatic silencing is initiated at the onset of gastrulation, approximately 1 hour after heterochromatin is first visible cytologically. A high degree of silencing is maintained in the mitotically active imaginal cells from mid-embryogenesis until early third instar larval stage, and extensive relaxation of silencing is tightly associated with the onset of differentiation. Relaxation of silencing can be triggered in vitro by ecdysone. In contrast, timing and extent of silencing at both the initiation and relaxation stages are insensitive to changes in cell cycle activity, and intrinsic promoter strength also does not influence the extent of silencing by heterochromatin. These data suggest that the silencing activity of heterochromatin is developmentally programmed.

Surfactant metabolism in surfactant protein A-deficient mice

1997 ◽  
Vol 272 (3) ◽  
pp. L479-L485 ◽  
Author(s):  
M. Ikegami ◽  
T. R. Korfhagen ◽  
M. D. Bruno ◽  
J. A. Whitsett ◽  
A. H. Jobe
Keyword(s):  
Lung Tissue ◽  
Protein A ◽  
Surfactant Protein ◽  
Normal Lung ◽  
Tissue Slices ◽  
Normal Lung Function ◽  
Deficient Mice ◽  
Surfactant Metabolism

In the present study we asked if surfactant metabolism was altered in surfactant protein (SP) A-deficient mice in vivo. Although previous studies in vitro demonstrated that SP-A modulates surfactant secretion and reuptake by type II cells, mice made SP-A deficient by homologous recombination grow and reproduce normally and have normal lung function. Alveolar and lung tissue saturated phophatidylcholine (Sat PC) pools were 50 and 26% larger, respectively, in SP-A(-/-) mice than in SP-A(+/+) mice. Radiolabeled choline and palmitate incorporation into lung Sat PC was similar both in vivo and for lung tissue slices in vitro from SP-A(+/+) and SP-A(-/-) mice. Percent secretion of radiolabeled Sat PC was unchanged from 3 to 15 h, although SP-A(-/-) mice retained more labeled Sat PC in the alveolar lavages at 48 h (consistent with the increased surfactant pool sizes). Clearance of radiolabeled dipalmitoylphosphatidylcholine and SP-B from the air spaces after intratracheal injection was similar in SP-A(-/-) and SP-A(+/+) mice. Lack of SP-A had minimal effects on the overall metabolism of Sat PC or SP-B in mice.

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