Recently, two heterozygous truncating mutations of the thrombopoietin (TPO) receptor MPL, coded by the c-mpl gene, were identified in a 10-year-old Japanese patient with CAMT transmitted in an autosomal recessive manner.
The <i>MPL</i> R102P mutation was first described in congenital amegakaryocytic thrombocytopenia in a homozygous state with a loss-of-function activity.
Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare, autosomal recessive disorder induced by mutations of the gene coding for thrombopoietin (TPO) receptor (c-MPL).
Mutations in the genes of hematopoietic growth factor receptors as a cause of congenital cytopenia, such as congenital amegakaryocytic thrombocytopenia (CAMT) or severe congenital neutropenia (CN), are discussed.
Previously, we identified an inherited syndrome of congenital amegakaryocytic thrombocytopenia and radio-ulnar synostosis that is associated with a point mutation in the third helix of HOXA11 homeodomain (HOXA11-DeltaH3).
We propose that a 21q22 deletion resulting in RUNX1 haploinsufficiency can produce a phenotype similar to CAMT with various associated anomalies depending on which adjacent genes are absent or disrupted.
Surprisingly, complimentary transduction of MPL into normal or CAMT iPSCs using a retroviral vector showed that MPL overexpression promoted erythropoiesis in normal CD34+ hematopoietic progenitor cells (HPCs), but impaired erythropoiesis and increased aberrant megakaryocyte production in CAMT iPSC-derived CD34+ HPCs, reflecting a difference in the expression of the transcription factor FLI1.
Congenital amegakaryocytic thrombocytopenia (CAMT) and thrombocytopenia with absent radii (TAR) share features of isolated thrombocytopenia, reduced or absent marrow megakaryocytes, impaired responsiveness to thrombopoietin (TPO), and high plasma TPO levels.
Thrombopoietin is essential for the maintenance of normal hematopoiesis in humans: development of aplastic anemia in patients with congenital amegakaryocytic thrombocytopenia.
Heterozygous mutations in <i>MECOM</i> (MDS1 and EVI1 complex locus) have been reported to be causative of a rare association of congenital amegakaryocytic thrombocytopenia and radioulnar synostosis.
Surprisingly, complimentary transduction of MPL into normal or CAMT iPSCs using a retroviral vector showed that MPL overexpression promoted erythropoiesis in normal CD34+ hematopoietic progenitor cells (HPCs), but impaired erythropoiesis and increased aberrant megakaryocyte production in CAMT iPSC-derived CD34+ HPCs, reflecting a difference in the expression of the transcription factor FLI1.
Using in vitro assays with hematopoietic progenitors from patients of both patient groups we could provide experimental evidence for a residual activity of the thrombopoietin receptor in CAMT II patients.
Most of the cases of congenital amegakaryocytic thrombocytopenia are caused by defective expression or function of the thrombopoietin receptor due to homozygous or compound heterozygous mutations in the gene MPL.
The marrow findings and a significantly elevated plasma thrombopoietin (Tpo) level were consistent with congenital amegakaryocytic thrombocytopenia; we sought a genetic mutation that could explain this phenotype.
Compound heterozygous c-Mpl mutations in a child with congenital amegakaryocytic thrombocytopenia: functional characterization and a review of the literature.