MPLW515L is a novel somatic activating mutation in myelofibrosis with myeloid metaplasia. Pikman, Y., Lee, B. H, Mercher, T., McDowell, E., Ebert, B. L, Gozo, M., Cuker, A., Wernig, G., Moore, S., Galinsky, I., DeAngelo, D. J, Clark, J. J, Lee, S. J, Golub, T. R, Wadleigh, M., Gilliland, D G., & Levine, R. L PLoS Medicine, 3(7):e270, July, 2006.
MPLW515L is a novel somatic activating mutation in myelofibrosis with myeloid metaplasia [link]Paper  doi  abstract   bibtex   
BACKGROUND: The JAK2V617F allele has recently been identified in patients with polycythemia vera (PV), essential thrombocytosis (ET), and myelofibrosis with myeloid metaplasia (MF). Subsequent analysis has shown that constitutive activation of the JAK-STAT signal transduction pathway is an important pathogenetic event in these patients, and that enzymatic inhibition of JAK2V617F may be of therapeutic benefit in this context. However, a significant proportion of patients with ET or MF are JAK2V617F-negative. We hypothesized that activation of the JAK-STAT pathway might also occur as a consequence of activating mutations in certain hematopoietic-specific cytokine receptors, including the erythropoietin receptor (EPOR), the thrombopoietin receptor (MPL), or the granulocyte-colony stimulating factor receptor (GCSFR). METHODS AND FINDINGS: DNA sequence analysis of the exons encoding the transmembrane and juxtamembrane domains of EPOR, MPL, and GCSFR, and comparison with germline DNA derived from buccal swabs, identified a somatic activating mutation in the transmembrane domain of MPL (W515L) in 9% (4/45) of JAKV617F-negative MF. Expression of MPLW515L in 32D, UT7, or Ba/F3 cells conferred cytokine-independent growth and thrombopoietin hypersensitivity, and resulted in constitutive phosphorylation of JAK2, STAT3, STAT5, AKT, and ERK. Furthermore, a small molecule JAK kinase inhibitor inhibited MPLW515L-mediated proliferation and JAK-STAT signaling in vitro. In a murine bone marrow transplant assay, expression of MPLW515L, but not wild-type MPL, resulted in a fully penetrant myeloproliferative disorder characterized by marked thrombocytosis (Plt count 1.9-4.0 x 10(12)/L), marked splenomegaly due to extramedullary hematopoiesis, and increased reticulin fibrosis. CONCLUSIONS: Activation of JAK-STAT signaling via MPLW515L is an important pathogenetic event in patients with JAK2V617F-negative MF. The bone marrow transplant model of MPLW515L-mediated myeloproliferative disorders (MPD) exhibits certain features of human MF, including extramedullary hematopoiesis, splenomegaly, and megakaryocytic proliferation. Further analysis of positive and negative regulators of the JAK-STAT pathway is warranted in JAK2V617F-negative MPD.
@article{pikman_mplw515l_2006,
	title = {{MPLW515L} is a novel somatic activating mutation in myelofibrosis with myeloid metaplasia},
	volume = {3},
	issn = {1549-1676},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/16834459},
	doi = {10.1371/journal.pmed.0030270},
	abstract = {BACKGROUND: The JAK2V617F allele has recently been identified in patients with polycythemia vera (PV), essential thrombocytosis (ET), and myelofibrosis with myeloid metaplasia (MF). Subsequent analysis has shown that constitutive activation of the JAK-STAT signal transduction pathway is an important pathogenetic event in these patients, and that enzymatic inhibition of JAK2V617F may be of therapeutic benefit in this context. However, a significant proportion of patients with ET or MF are JAK2V617F-negative. We hypothesized that activation of the JAK-STAT pathway might also occur as a consequence of activating mutations in certain hematopoietic-specific cytokine receptors, including the erythropoietin receptor (EPOR), the thrombopoietin receptor (MPL), or the granulocyte-colony stimulating factor receptor (GCSFR). METHODS AND FINDINGS: DNA sequence analysis of the exons encoding the transmembrane and juxtamembrane domains of EPOR, MPL, and GCSFR, and comparison with germline DNA derived from buccal swabs, identified a somatic activating mutation in the transmembrane domain of MPL (W515L) in 9\% (4/45) of JAKV617F-negative MF. Expression of MPLW515L in 32D, UT7, or Ba/F3 cells conferred cytokine-independent growth and thrombopoietin hypersensitivity, and resulted in constitutive phosphorylation of JAK2, STAT3, STAT5, AKT, and ERK. Furthermore, a small molecule JAK kinase inhibitor inhibited MPLW515L-mediated proliferation and JAK-STAT signaling in vitro. In a murine bone marrow transplant assay, expression of MPLW515L, but not wild-type MPL, resulted in a fully penetrant myeloproliferative disorder characterized by marked thrombocytosis (Plt count 1.9-4.0 x 10(12)/L), marked splenomegaly due to extramedullary hematopoiesis, and increased reticulin fibrosis. CONCLUSIONS: Activation of JAK-STAT signaling via MPLW515L is an important pathogenetic event in patients with JAK2V617F-negative MF. The bone marrow transplant model of MPLW515L-mediated myeloproliferative disorders (MPD) exhibits certain features of human MF, including extramedullary hematopoiesis, splenomegaly, and megakaryocytic proliferation. Further analysis of positive and negative regulators of the JAK-STAT pathway is warranted in JAK2V617F-negative MPD.},
	number = {7},
	urldate = {2010-06-10},
	journal = {PLoS Medicine},
	author = {Pikman, Yana and Lee, Benjamin H and Mercher, Thomas and McDowell, Elizabeth and Ebert, Benjamin L and Gozo, Maricel and Cuker, Adam and Wernig, Gerlinde and Moore, Sandra and Galinsky, Ilene and DeAngelo, Daniel J and Clark, Jennifer J and Lee, Stephanie J and Golub, Todd R and Wadleigh, Martha and Gilliland, D Gary and Levine, Ross L},
	month = jul,
	year = {2006},
	pmid = {16834459},
	keywords = {Amino Acid Substitution, Animals, Bone Marrow Cells, Bone Marrow Transplantation, Cell Division, Cells, Cultured, Colony-Forming Units Assay, Cytokines, Disease Models, Animal, Gene Expression Regulation, Genetic Vectors, Hematologic Neoplasms, Hematopoiesis, Humans, Janus Kinases, Megakaryocytes, Mice, Mice, Inbred BALB C, Mutation, Missense, Myeloid Cells, Myeloproliferative Disorders, Oncogene Proteins, Fusion, Phosphorylation, Point Mutation, Primary Myelofibrosis, Protein Kinase Inhibitors, Protein Processing, Post-Translational, Receptor, Platelet-Derived Growth Factor alpha, Receptors, Cytokine, Recombinant Fusion Proteins, STAT Transcription Factors, Sequence Analysis, DNA, Signal Transduction, Spleen, Thrombocytosis, Transcription, Genetic, mRNA Cleavage and Polyadenylation Factors},
	pages = {e270},
}

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