Existence of a differentiation blockage at the stage of a megakaryocyte precursor in the thrombocytopenia and absent radii (TAR) syndrome.
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)
Letestu
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R
INSERM U 362, Laboratoire associé no. 5 du comité de Paris de la Ligue Nationale, Institut Gustave Roussy, Villejuif, France.
Vitrat
N
N
Massé
A
A
Le Couedic
J P
JP
Lazar
V
V
Rameau
P
P
Wendling
F
F
Vuillier
J
J
Boutard
P
P
Plouvier
E
E
Plasse
M
M
Favier
R
R
Vainchenker
W
W
Debili
N
N
D000293:Adolescent; D000328:Adult; D001853:Bone Marrow / Q000473:pathology; D002454:Cell Differentiation; D019070:Cell Lineage; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003114:Colony-Forming Units Assay; D004252:DNA Mutational Analysis; D005260:Female; D005315:Fetal Diseases / Q000235:genetics / Q000473:pathology; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D006410:Hematopoiesis / Q000235:genetics*; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D006801:Humans; D008297:Male; D008533:Megakaryocytes / Q000473:pathology*; D008875:Middle Aged; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D011884:Radius / Q000002:abnormalities*; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D013577:Syndrome; D013921:Thrombocytopenia / Q000151:congenital / Q000235:genetics* / Q000473:pathology; D013926:Thrombopoietin / Q000097:blood
D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; C082218:MPL protein, human; D013926:Thrombopoietin