Extending Jak2V617F and MplW515 Mutation Analysis to Single Hematopoietic Colonies and B and T Lymphocytes

Abstract

JAK2V617F and MPLW515L/K are myeloproliferative disorder (MPD)-associated mutations. We genotyped 552 individual hematopoietic colonies obtained by CD34؉ cell culture from 16 affected patients (13 JAK2V617F and 3 MPLW515L/K) to determine (a) the proportion of colonies harboring a particular mutation in the presence or absence of cytokines, (b) the lineage distribution of endogenous colonies for each mutation, and (c) the differences (if any) in the pattern of mutation among the various MPDs, as established by genotyping of individual colonies. Genotyping analysis revealed cohabitation of mutation-negative and mutationpositive endogenous colonies in polycythemia vera as well as other MPDs. Culture of progenitor cells harboring MPLW515L/K yielded virtually no endogenous erythroid colonies in contrast to JAK2V617F-harboring progenitor cells. The mutation pattern (i.e., relative distribution of homozygous, heterozygous, or wild-type colonies) was not a distinguishing feature among the MPDs, and MPLW515 mutations were detected in B and/or T lymphocytes in all three patients tested. These observations suggest that clonal myelopoiesis antedates acquisition of JAK2V617F or MPLW515L/K mutations and that the latter is acquired in a lympho-myeloid progenitor cell. STEM CELLS 2007;25: 2358 -2362 Disclosure of potential conflicts of interest is found at the end of this article.

Clinical correlates of JAK2V617F presence or allele burden in myeloproliferative neoplasms: a critical reappraisal

“…Jamieson et al 21 have demonstrated that the mutation was present in flow cytometrypurified populations of hematopoietic stem cells, common myeloid progenitors, granulocyte/macrophage progenitors and megakaryocytic/erythroid progenitors. Similar findings in different hematopoietic cell lineages have been reported in PV and PMF patients [22][23][24][25][26] although lymphoid cells were involved in only a proportion of the patients; 27 furthermore, the occurrence of the mutation in a myelo-lymphoid progenitor in patients with PV and PMF has been demonstrated. 28 Mitotic recombination of the short arm of chromosome 9, resulting in homozygosity for the V617F allele at the single cell level, happens in about 30% of patients with PV and PMF as compared to only 2-4% of those with ET.…”

Low JAK2V617F allele burden in primary myelofibrosis, compared to either a higher allele burden or unmutated status, is associated with inferior overall and leukemia-free survival

“…However, we are intrigued by the possibility that a low JAK2V617F allele burden is a surrogate for the coexistence of a more dominant JAK2V617F-negative clone with a higher propensity to undergo clonal evolution. Such a contention is supported by increasing evidence that point to JAK2V617F as a secondary event in the clonal hierarchy of myeloproliferative neoplasms 27 and is consistent with the development of mutation-negative leukemic transformation in mutation-positive patients. 28 Also in support of the scenario for competing clones, we have previously shown the concurrent occurrence of JAK2V617F and MPLW515L/K in some patients with PMF 29 and clonal dominance by the latter in such an instance.…”

Differences in the JAK2 and MPL Mutation Status in the Cell Lineages of the bcr/abl-negative Chronic Myeloproliferative Neoplasm Subtypes

“…The present study examined two ET patients and found that the cell lineages involved with the JAK2-V617F mutation were different from those with the MPL-W515L mutation (3,4). Whether acquisition of the JAK2-V617F mutation is an early event or not in the pathogenesis of MPNs is one of the important issues to be resolved.…”

“…The mutations of the Janus Kinase 2 (JAK2) gene and thrombopoietin receptor (c-MPL) gene are detected in bcr/abl negative chronic myeloproliferative neoplasm (MPN), which primarily includes polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis with regard to the conclusions that can be drawn from these findings (3,4).…”