1. Existence of a differentiation blockage at the stage of a megakaryocyte precursor in the thrombocytopenia and absent radii (TAR) syndrome
- Author
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R, Letestu, N, Vitrat, A, Massé, J P, Le Couedic, V, Lazar, P, Rameau, F, Wendling, J, Vuillier, P, Boutard, E, Plouvier, M, Plasse, R, Favier, W, Vainchenker, and N, Debili
- Subjects
Adult ,Male ,Adolescent ,DNA Mutational Analysis ,Colony-Forming Units Assay ,Bone Marrow ,Proto-Oncogene Proteins ,Humans ,Cell Lineage ,RNA, Messenger ,Receptors, Cytokine ,Child ,Cells, Cultured ,Genes, Homeobox ,Gene Expression Regulation, Developmental ,Cell Differentiation ,Syndrome ,Middle Aged ,Hematopoietic Stem Cells ,Thrombocytopenia ,Hematopoiesis ,Neoplasm Proteins ,Fetal Diseases ,Radius ,Thrombopoietin ,Child, Preschool ,Female ,Megakaryocytes ,Receptors, Thrombopoietin - Abstract
The thrombocytopenia and absent radii (TAR) syndrome is a rare disease associating bilateral radial agenesis and congenital thrombocytopenia. Here, we investigated in vitro megakaryocyte (MK) differentiation and expression of c-mpl in 6 patients. Using blood or marrow CD34(+) cells, the colony-forming unit (CFU)-MK number was markedly reduced. CD34(+) cells were also cultured in liquid medium in the presence of a combination of 3 cytokines (stem cell factor, interleukin-3, and interleukin-6) or megakaryocyte growth and development factor (PEG-rHuMGDF) with or without SCF. In the presence of PEG-rHuMGDF, the majority of mature megakaryocytes (CD41 high, CD42 high) underwent apoptosis. This phenomenon was also observed in cultures stimulated by three cytokines. However, this last combination of cytokines allowed a more complete terminal MK differentiation. Surprisingly, a homogeneous population of CD34(-)CD41(+)CD42(-) cells accumulated during the cultures. This population was unable to differentiate along the myeloid pathways. This result suggests that a fraction of MK cells is unable to differentiate in the TAR syndrome. We subsequently investigated whether this could be related to an abnormality in c-mpl. No mutation or rearrangement in the c-mpl gene was found by Southern blots or by sequencing of the c-mpl coding region and its promoter in any of the patients. Using Western blot analysis, a decreased level of Mpl was found in patient platelets. A decreased level of c-mpl messenger RNA in TAR platelets was also detected with a lower c-mpl-P to c-mpl-K ratio in comparison to adult platelets. Altogether, these results demonstrate that the thrombocytopenia of the TAR syndrome is associated with a dysmegakaryocytopoiesis characterized by cells blocked at an early stage of differentiation. (Blood. 2000;95:1633-1641)
- Published
- 2000