Norioki Ohno

Reciprocal expression of Bmi1 and Mel-18 is associated with functioning of primitive hematopoietic cells

OBJECTIVE The Polycomb-group (PcG) genes regulate global gene expression in many biological processes, including hematopoiesis, by manipulating specific target genes. It is known that various PcG genes regulate self-renewal of hematopoietic stem cells (HSCs). Here we have shown that the reciprocal expression of PcG proteins regulates self-renewal and differentiation of HSCs. METHODS We used murine and human bone marrow cells and evaluated the reciprocal expression of PcG proteins on the basis of their respective intranuclear distributions. PcG-gene expression in HSCs was knocked down by small interfering RNAs. The function of each gene in HSCs was analyzed in vitro and in vivo. RESULTS Cells were either Bmi1-positive or Mel-18-positive. The Bmi1-positive cells contained very little amounts of Mel-18 and vice versa. The bmi1-knockdown marrow cells did not show HSC function, while the mel-18-knockdown marrow cells showed increased stem cell function. Results of the analysis on human cells were similar to those observed in case of murine cells. In a clinical investigation, transplantation using sources with a low Bmi1 to Mel-18 ratio was associated with early hematopoietic recovery. CONCLUSION Reciprocal expression of Bmi1 and Mel-18 regulated HSC function. Here, we observed that expression of the PcG genes-bmi1 and mel-18-is correlated with self-renewal and differentiation of HSCs. Thus, it was suggested that the balance between Bmi1 and Mel-18 regulates self-renewal of HSCs.

Successful treatment of Kasabach-Merritt syndrome with vincristine and diagnosis of the hemangioma using three-dimensional imaging.

Kasabach-Merritt syndrome is a life-threatening congenital disorder characterized by an enlarging hemangioma, thrombocytopenia, and consumption coagulopathy. We report the case of a one-month male infant who presented with a large cutaneous tumor in his right axilla with ecchymosis, thrombocytopenia, and chronic consumption coagulopathy. Three-dimensional computed tomography was useful for accurate diagnosis of the cutaneous tumor and for determining the precise vascular constitution of the hemangioma, suggesting the efficacy of this method for diagnosing Kasabach-Merritt syndrome. Although administration of a corticosteroid was not effective, additional administration of vincristine resulted in the reversal of thrombocytopenia and coagulopathy with reduction of the hemangioma.

Decreased Expression in Nuclear Factor-κB Essential Modulator Due to a Novel Splice-Site Mutation Causes X-linked Ectodermal Dysplasia with Immunodeficiency

X-linked ectodermal dysplasia with immunodeficiency (XL-ED-ID) is caused by hypomorphic mutations in NEMO, which encodes nuclear factor-kappaB (NF-κB) essential modulator. We identified a novel mutation, 769−1 G>C, at the splicing acceptor site of exon 7 in NEMO in a Japanese patient with XL-ED-ID. Although various abnormally spliced NEMO messenger RNAs (mRNAs) were observed, a small amount of wild-type (WT) mRNA was also identified. Decreased NEMO protein expression was detected in various lineages of leukocytes. Although one abnormally spliced NEMO protein showed residual NF-κB transcription activity, it did not seem to exert a dominant-negative effect against WT-NEMO activity. CD4+ T cell proliferation was impaired in response to measles and mumps, but not rubella. These results were consistent with the clinical and laboratory findings of the patient, suggesting the functional importance of NEMO against specific viral infections. The 769−1 G>C mutation is responsible for decreased WT-NEMO protein expression, resulting in the development of XL-ED-ID.

Transient pseudothrombocytopenia in a neonate: Transmission of a maternal EDTA-dependent anticoagulant

EDTA-dependent pseudothrombocytopenia (PTCP) is characterised by a low platelet count caused by autoantibodies in the serum reacting with EDTA-anticoagulated blood. EDTA-dependent PTCP is caused by a factor that retains EDTA anticoagulation activity in the serum. We report here that a neonate from a mother with PTCP presented with transient low platelet counts when EDTA was used as an anticoagulant. To confirm the transmission of a maternal serum factor to the neonate, we examined to add the maternal serum into the normal blood. Platelet count decreased significantly after adding maternal serum. Clumped platelets were also observed in the smears of mixed samples.

Significant augmentation of regulatory T cell numbers occurs during the early neonatal period

Regulatory T cells (Tregs) control immune responses by suppressing various inflammatory cells. Tregs in newborn babies may play an important role in preventing excessive immune responses during their environmental change. We examined the number and phenotype of Tregs during the neonatal period in 49 newborn babies. Tregs were characterized by flow cytometry using cord blood (CB) and peripheral blood (PB) from the early (7–8 days after birth) and late (2–4 weeks after birth) neonatal periods. CD4+forkhead box protein 3 (FoxP3+) T cells were classified into resting Tregs (CD45RA+FoxP3low), activated Tregs (CD45RA– FoxP3high) and newly activated T cells (CD45RA– FoxP3low). Compared with CB and PB during the late neonatal period, the percentage of Tregs and all Treg subpopulations in the CD4+ lymphocyte population were increased significantly during the early neonatal period. Furthermore, the proportion and absolute number of activated Tregs were increased markedly compared with other Treg subpopulations, such as resting Tregs and newly activated T cells (non‐Tregs), in the early neonatal period. Increased Tregs concomitantly expressed the suppressive molecule cytotoxic T lymphocyte antigen‐4 (CTLA‐4). The up‐regulated expression of chemokine receptor 4 (CCR4) and down‐regulated expression of CCR7 were also observed in expanded Tregs. When cord blood cells were cultured in vitro with CD3 monoclonal antibodies (mAb) for 5 days, CD4+CD45RA–FoxP3high cells were increased significantly during the culture. Thus, the presence of increased activated Tregs in early neonates may play an important role in immunological regulation by suppressing excessive T cell activation caused by the immediate exposure to ubiquitous antigens after birth.