251
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Affiliation(s)
- H D Madhani
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA.
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252
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Longley BJ, Reguera MJ, Ma Y. Classes of c-KIT activating mutations: proposed mechanisms of action and implications for disease classification and therapy. Leuk Res 2001; 25:571-6. [PMID: 11377682 DOI: 10.1016/s0145-2126(01)00028-5] [Citation(s) in RCA: 220] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Mutations causing constitutive activation of KIT have been shown to be causative in some forms of mastocytosis, and several types of mutations have been associated with myeloproliferative disorders (MPDs), acute myelogenous leukemia (AML), sinonasal lymphomas, and gastrointestinal stromal tumors (GIST). We divide these activating mutation into two types - 'regulatory type' mutations, which affect regulation of the kinase molecule, and 'enzymatic pocket type' mutations, which alter the amino acid sequence directly forming the enzymatic site. KIT inhibitors have been suggested as therapeutic drugs for these conditions, but different types of activating mutations respond differentially to KIT inhibitors, so classification of individuals on the basis of specific mutations is necessary to guide therapy.
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Affiliation(s)
- B J Longley
- Department of Dermatology and Pathology, Columbia University, 630 West 168th Street, VC-15-202, New York, NY 10031, USA
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253
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Russell LD, Warren J, Debeljuk L, Richardson LL, Mahar PL, Waymire KG, Amy SP, Ross AJ, MacGregor GR. Spermatogenesis in Bclw-deficient mice. Biol Reprod 2001; 65:318-32. [PMID: 11420255 PMCID: PMC3049812 DOI: 10.1095/biolreprod65.1.318] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Bclw is a death-protecting member of the Bcl2 family of apoptosis-regulating proteins. Mice that are mutant for Bclw display progressive and nearly complete testicular degeneration. We performed a morphometric evaluation of testicular histopathology in Bclw-deficient male mice between 9 days postnatal (p9) through 1 yr of age. Germ cell loss began by p22, with only few germ cells remaining beyond 7 mo of age. A complete block to elongated spermatid development at step 13 occurred during the first wave of spermatogenesis, whereas other types of germ cells were lost sporadically. Depletion of Sertoli cells commenced between p20 and p23 and continued until 1 yr of age, when few, if any, Sertoli cells remained. Mitochondria appeared to be swollen and the cytoplasm dense by electron microscopy, but degenerating Bclw-deficient Sertoli cells failed to display classical features of apoptosis, such as chromatin condensation and nuclear fragmentation. Macrophages entered seminiferous tubules and formed foreign-body giant cells that engulfed and phagocytosed the degenerated Sertoli cells. Leydig cell hyperplasia was evident between 3 and 5 mo of age. However, beginning at 7 mo of age, Leydig cells underwent apoptosis, with dead cells being phagocytosed by macrophages. The aforementioned cell losses culminated in a testis-containing vasculature, intertubular phagocytic cells, and peritubular cell "ghosts." An RNA in situ hybridization study indicates that Bclw is expressed in Sertoli cells in the adult mouse testis. Consequently, the diploid germ cell death may be an indirect effect of defective Sertoli cell function. Western analysis was used to confirm that Bclw is not expressed in spermatids; thus, loss of this cell type most likely results from defective Sertoli cell function. Because Bclw does not appear to be expressed in Leydig cells, loss of Leydig cells in Bclw-deficient mice may result from depletion of Sertoli cells. Bclw-deficient mice serve as a unique model to study homeostasis of cell populations in the testis.
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Affiliation(s)
- Lonnie D. Russell
- Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901-6512
| | - Jeff Warren
- Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901-6512
| | - Luciano Debeljuk
- Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901-6512
| | - Laura L. Richardson
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996
| | - Patryce L. Mahar
- Center for Molecular Medicine, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Katrina G. Waymire
- Center for Molecular Medicine, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Scott P. Amy
- Center for Molecular Medicine, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Andrea J. Ross
- Center for Molecular Medicine, Emory University School of Medicine, Atlanta, Georgia 30322
- Graduate Program in Biochemistry, Cell and Developmental Biology, Emory University, Atlanta, Georgia 30322
| | - Grant R. MacGregor
- Center for Molecular Medicine, Emory University School of Medicine, Atlanta, Georgia 30322
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254
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Ning ZQ, Li J, Arceci RJ. Signal transducer and activator of transcription 3 activation is required for Asp816 mutant c-Kit–mediated cytokine-independent survival and proliferation in human leukemia cells. Blood 2001; 97:3559-67. [PMID: 11369651 DOI: 10.1182/blood.v97.11.3559] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Activating mutations of c-kit at codon 816 (Asp816) have been implicated in a variety of malignancies, including acute myeloid leukemia (AML). The mutant c-Kit receptor confers cytokine-independent survival of leukemia cells and induces tumorigenicity. Changes in the signal transduction pathways responsible for Asp816 mutant c-Kit–mediated biologic effects are largely undefined. The results of this study show that Asp816 mutant c-Kit induces constitutive activation of signal transducer and activator of transcription 3 (STAT3) and STAT1, and up-regulates STAT3 downstream targets, Bcl-xL and c-myc. The phosphatidylinositol-3-kinase (PI-3K)/Akt pathway, but not the Ras-mediated mitogen-activated protein (MAP) kinase pathway, is also constitutively activated by Asp816 mutant c-Kit. Suppression of STAT3 activation by a dominant negative molecule in MO7e leukemia cells transduced with mutant c-kit inhibits stem cell factor (SCF)-independent survival and proliferation, accompanied by the down-regulation of Bcl-xL and c-myc. However, activated STAT3 does not appear to be the sole mediator that is responsible for the phenotypic changes induced by Asp816 mutant c-Kit, because expression of constitutively activated STAT3 in MO7e cells does not completely reconstitute cytokine independence. Activation of other signaling components by mutant c-Kit, such as those in the PI-3K/Akt pathway, is demonstrated and may also be needed for the mutant c-Kit–mediated biologic effects. The investigation of altered signal transduction pathways and the resulting functional consequences mediated by Asp816 mutant c-Kit should provide important information for the characterization of subsets of leukemia and potential molecular pathways for therapeutic targeting.
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Affiliation(s)
- Z Q Ning
- Division of Hematology/Oncology, Children's Hospital Medical Center, Cincinnati, OH, USA
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255
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Yan W, Kero J, Huhtaniemi I, Toppari J. Stem cell factor functions as a survival factor for mature Leydig cells and a growth factor for precursor Leydig cells after ethylene dimethane sulfonate treatment: implication of a role of the stem cell factor/c-Kit system in Leydig cell development. Dev Biol 2000; 227:169-82. [PMID: 11076685 DOI: 10.1006/dbio.2000.9885] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The significance of the interaction between Sertoli cell-produced stem cell factor (SCF) and its receptor, c-kit, on Leydig cells (LCs) during LC development and differentiation is unknown. In the present study, we investigated the potential role of the SCF/c-kit system in LC apoptosis and precursor LC proliferation after ethylene dimethane sulfonate (EDS) treatment in rats. A function-blocking anti-c-kit antibody, ACK-2, was used to block SCF/c-kit interaction at four time points, corresponding to the peak of LC apoptosis and three waves of proliferation of precursor LCs. Blockade of SCF/c-kit interaction by ACK-2 accelerated LC apoptosis and inhibited proliferation of precursor LCs during the first two waves of precursor LC proliferation around days 3-4 and day 10, but not the third wave of precursor LC proliferation around day 20 after EDS treatment. The data suggest that the soluble SCF might act as a survival factor for mature LCs and a growth factor for precursor LCs after EDS-induced LC depletion. This is also supported by a close correlation between the oscillating levels of soluble SCF mRNA and the profiles of LC apoptosis and regeneration. Since regeneration of the LC population after EDS treatment resembles the development of adult-type LCs during prepubertal life, the present findings imply that soluble SCF might participate in regulation of the formation of the LC population during testicular development. Our data also support a model in which delicate and reciprocal regulation exists between soluble SCF production by Sertoli cells, testosterone production by LCs, and pituitary gonadotropins.
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Affiliation(s)
- W Yan
- Department of Physiology, University of Turku, Kiinamyllynkatu 10, 20520 Turku, Finland
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256
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Abstract
The tyrosine-kinase receptor c-kit and its ligand, stem cell factor (SCF), are essential for the maintenance of primordial germ cells (PGCs) in both sexes. However, c-kit and a post-meiotic-specific alternative c-kit gene product play important roles also during post-natal stages of spermatogenesis. In the adult testis, the c-kit receptor is re-expressed in differentiating spermatogonia, but not in spermatogonial stem cells, whereas SCF is expressed by Sertoli cells under FSH stimulation. SCF stimulates DNA synthesis in type A spermatogonia cultured in vitro, and injection of anti-c-kit antibodies blocks their proliferation in vivo. A point mutation in the c-kit gene, which impairs SCF-mediated activation of phosphatidylinositol 3-kinase, does not cause any significant reduction in PGCs number during embryonic development, nor in spermatogonial stem cell populations. However males are completely sterile due to a block in the initial stages of spermatogenesis, associated to abolishment of DNA-synthesis in differentiating A1-A4 spermatogonia. With the onset of meiosis c-kit expression ceases, but a truncated c-kit product, tr-kit, is specifically expressed in post-meiotic stages of spermatogenesis, and is accumulated in mature spermatozoa. Microinjection of tr-kit into mouse eggs causes their parthenogenetic activation, suggesting that it might play a role in the final function of the gametes, fertilization.
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Affiliation(s)
- P Rossi
- Dipartimento di Sanità Pubblica e Biologia Cellulare, Università Tor Vergata, Roma, Italy.
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257
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Grootegoed JA, Siep M, Baarends WM. Molecular and cellular mechanisms in spermatogenesis. BAILLIERE'S BEST PRACTICE & RESEARCH. CLINICAL ENDOCRINOLOGY & METABOLISM 2000; 14:331-43. [PMID: 11097779 DOI: 10.1053/beem.2000.0083] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Mammalian spermatogenesis shows a strict control of many specific molecular and cellular events. This control involves Sertoli cell-germ cell interaction, as well as a programmed performance of changes in chromatin structure and gene expression in the developing germ cells. In recent years, much knowledge about the functions of defined genes in spermatogenesis has been gained by making use of mouse transgenic and gene knockout models. Several of these models are discussed in this brief overview, with an emphasis on genes encoding proteins involved in the control of gene transcription, mRNA translation, DNA repair and protein ubiquitination. A better understanding of the molecular and cellular biology of spermatogenesis in the mouse may provide concepts that can improve our understanding of human male infertility and may also lead to the identification of novel targets for contraceptive intervention.
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Affiliation(s)
- J A Grootegoed
- Department of Endocrinology and Reproduction, Erasmus University Rotterdam, 3000 DR Rotterdam, TheNetherlands
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258
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Feng LX, Ravindranath N, Dym M. Stem cell factor/c-kit up-regulates cyclin D3 and promotes cell cycle progression via the phosphoinositide 3-kinase/p70 S6 kinase pathway in spermatogonia. J Biol Chem 2000; 275:25572-6. [PMID: 10849422 DOI: 10.1074/jbc.m002218200] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stem cell factor (SCF)/c-kit plays an important role in the regulation of hematopoiesis, melanogenesis, and spermatogenesis. In the testis, the SCF/c-kit system is believed to regulate germ cell proliferation, meiosis, and apoptosis. Studies with type A spermatogonia in vivo and in vitro have indicated that SCF induces DNA synthesis and proliferation. However, the signaling pathway for this function of SCF/c-kit has not been elucidated. We now demonstrate that SCF activates phosphoinositide 3-kinase (PI3-K) and p70 S6 kinase (p70S6K) and that rapamycin, a FRAP/mammalian target of rapamycin-dependent inhibitor of p70S6K, completely inhibited bromodeoxyuridine incorporation induced by SCF in primary cultures of spermatogonia. SCF induced cyclin D3 expression and phosphorylation of the retinoblastoma protein through a pathway that is sensitive to both wortmannin and rapamycin. Furthermore, AKT, but not protein kinase C-zeta, is used by SCF/c-kit/PI3-K to activate p70S6K. Dominant negative AKT-K179M completely abolished p70S6K phosphorylation induced by the constitutively active PI3-K catalytic subunit p110. Constitutively active v-AKT highly phosphorylated p70S6K, which was totally inhibited by rapamycin. Thus, SCF/c-kit uses a rapamycin-sensitive PI3-K/AKT/p70S6K/cyclin D3 pathway to promote spermatogonial cell proliferation.
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Affiliation(s)
- L X Feng
- Department of Cell Biology, Georgetown University Medical Center, Washington, DC. 20007, USA
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259
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Goding CR. Mitf from neural crest to melanoma: signal transduction and transcription in the melanocyte lineage. Genes Dev 2000. [DOI: 10.1101/gad.14.14.1712] [Citation(s) in RCA: 192] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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260
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