Difference in megakaryocyte expression of GATA-1, IL-6, and IL-8 associated with maintenance of platelet counts in patients with plasma cell neoplasm with dysmegakaryopoiesis.

Dysmegakaryopoiesis is a diagnostic criterion for myelodysplastic syndrome (MDS), which accompanies thrombocytopenia. Recently, dysmegakaryopoiesis was reported in patients with plasma cell neoplasm (PCN). Although these patients maintained normal platelet counts, disease progressed, with most bone marrow cells being replaced by plasma cells. Several studies reported that dysmegakaryopoiesis was induced by inflammatory mechanisms; however, the exact mechanism underlying dysmegakaryopoiesis remains unknown. This study aimed to investigate whether changes in the megakaryocytic expression of GATA-1, pro-inflammatory cytokines (interleukin [IL]-6 and IL-8), and CD9 affect platelet counts and dysmegakaryopoiesis in patients with PCN and MDS. A total 114 patients were examined and categorized into four groups: MDS with dysmegakaryopoiesis (34 patients), PCN without dysmegakaryopoiesis (36 patients), PCN with dysmegakaryopoiesis (19 patients), and lymphoma without bone marrow infiltration (25 patients). Expression of GATA-1, IL-6, IL-8, and CD9 in megakaryocytes was assessed by immunohistochemical (IHC) staining of paraffin-embedded bone marrow sections. Localized expression of transcription factor and cytokines was observed in megakaryocytes. Furthermore, expression of GATA-1, IL-6, and IL-8 significantly differed (all p values < 0.05). Decreased GATA-1 expression was identified in MDS. Decreased IL-6 expression was observed in PCN and MDS. Moreover, decreased IL-8 expression was associated with dysmegakaryopoiesis, regardless of whether platelet counts were maintained. In conclusion, PCN patients with dysmegakaryopoiesis had normal platelet counts, and their megakaryocytes showed decreased IL-6 and IL-8 expression and normal GATA-1 expression. The differences in the megakaryocytic expression of cytokines in PCN and MDS with dysmegakaryopoiesis may be applicable to future therapeutic strategies.

Transient abnormal myelopoiesis in neonates: GATA get the diagnosis.

Transient abnormal myelopoiesis occurs exclusively in patients with Down syndrome (constitutional trisomy 21), manifests in the neonatal period, and is characterized by circulating megakaryoblasts with varied degrees of multisystem organ involvement. In most cases, this process resolves spontaneously by 3 to 6 months of age, but for some, the disease can be fatal. Affected patients are particularly prone to develop acute megakaryoblastic leukemia in early childhood. Somatic GATA1 mutations are believed to be pivotal in the development of transient abnormal myelopoiesis and have proven to be a marker of clonal identity in its evolution to megakaryoblastic leukemia. We describe a study case of transient abnormal myelopoiesis and review the clinical manifestations, laboratory features, natural history, molecular genetics, and postulated disease pathogenesis of this disorder.

Abnormal P-selectin localization during megakaryocyte development determines thrombosis in the gata1low model of myelofibrosis.

Patients with primary myelofibrosis have increased risk for bleeding and thrombosis. It is debated whether propensity to thrombosis is due to increased numbers of platelet microparticles and/or to pathological platelet-neutrophil interactions. Platelet neutrophil interactions are mediated by P-selectin and even though the megakaryocytes of myelofibrosis patients express normal levels of P-selectin, it remains abnormally localized to the demarcation membrane system rather than being assembled into the α-granules in platelets. Mice carrying the hypomorphic Gata1(low) mutation express the same megakaryocyte abnormalities presented by primary myelofibrosis patients, including abnormal P-selectin localization to the DMS and develop with age myelofibrosis, a disease that closely resembles human primary myelofibrosis. Whether these mice would also develop thrombosis has not been investigated as yet. The aim of this study was to determine whether Gata1(low) mice would develop thrombosis with age and, in this case, the role played by P-selectin in the development of the trait. To this aim, Gata1(low) mice were crossed with P-sel(null) mice according to standard genetic protocols and Gata1(low)P-sel(wt), Gata1(low)P-sel(null) and Gata1(WT)P-sel(null) or Gata1(wt)P-sel(wt) (as controls) littermates obtained. It was shown that platelet counts, but not hematocrit, are reduced in Gata1(low) mice. Moreover, platelet microparticles are reduced in Gata1(low) mice and P-selectin positive platelet microparticles were not found. To determine the phenotypic implications of the different mutations, bleeding time was estimated by a tail cut procedure. Mutant mice were sacrificed and presence of thrombosis was determined by immunohistological staining of organs. Gata1(low) mice with or without the P-selectin null trait had a prolonged bleeding time compared to wild type mice. However, in Gata1(low) mice significantly higher frequency of thrombotic events was seen in adult and old Gata1(low) mice compared to Gata1(low)P-sel(null) mice. Thus, presence of the P-selectin null trait rescued Gata1(low) mice from the thrombotic phenotype, but did not change the level of platelet microparticles. Taken together these data indicate that abnormal localization of P-selectin, induced by the Gata1(low) mutation, and thus, increased pathological interactions with leucocytes, is responsible for the increased presence of thrombosis seen in these mice.

The IL1RN promoter rs4251961 correlates with IL-1 receptor antagonist concentrations in human infection and is differentially regulated by GATA-1.

IL-1R antagonist (IL-1Ra) is required for adequate host defense in invasive pneumococcal disease (IPD). The minor allele of an IL1RN gene (C/T) promoter polymorphism (rs4251961) has been shown to be associated with decreased IL-1Ra production in healthy adults. We genotyped 299 children with IPD, and examined 19 IL1RN haplotype-tagging single-nucleotide polymorphisms. Human embryonic kidney HEK293(T) cells were transfected with the promoter reporter plasmid pGL3p containing either allelic variant C (pGL3pCC) or T (pGL3pTT) with or without cotransfection with an expression construct overexpressing the globin transcription factor GATA-1. Plasma IL-1Ra concentrations were significantly higher in nonsurvivors compared with survivors (p < 0.0005), and the C allele of rs4251961 was associated with a significant increase in plasma IL-1Ra concentrations (p = 0.01) during the acute illness of IPD. These findings were validated in a cohort of 276 treatment-naive HIV-infected adults, with borderline significance (p = 0.058). Functional analyses demonstrated that the activity of the promoter constructs containing the T allele increased ~6-fold as compared with basal activity, and that containing the C allele by ~9-fold (p < 0.001) in the presence of GATA-1. Our findings suggest that the IL-1Ra single-nucleotide polymorphism rs4251961 plays a key role in the pathophysiology of IPD and in other human infections.

Long-term outcome of hemizygous and heterozygous carriers of a germline GATA1 (G208R) mutation.

The transcriptional regulator GATA1 is crucially involved in megakaryocytopoiesis and erythropoiesis. Mutations of the gene which is located on the X chromosome have been associated with platelet and red blood cell abnormalities. We identified a family with a GATA1 (G208R) mutation in whom a low male birth rate and frequent miscarriages among heterozygous females suggested increased fetal death in male hemizygotes. Female mutation carriers had normal or near normal hemoglobin levels and platelet counts ranging from normal to severely reduced, probably reflecting skewed X chromosome inactivation. Platelets were dimorphous, and thrombocytopenia was associated with erythroblastosis. The only living male mutation carrier had severe macrothrombocytopenia with life-threatening bleeding episodes, moderate to severe anemia, eosinopenia, skeletal abnormalities, and abundant extramedullary hematopoiesis. Long-term sequelae in the 50-year-old patient included unilateral nephrectomy following misinterpretation of paraspinal hematopoiesis as renal cancer, spinal stenosis which was possibly favored by progressive bone marrow expansion, and severe secondary gout.