Heterodimerization of AML1/ETO with CBFß is required for leukemogenesis but not for myeloproliferation.

The AML1/Runx1 transcription factor and its heterodimerization partner CBFß are essential regulators of myeloid differentiation. The chromosomal translocation t(8;21), fusing the DNA binding domain of AML1 to the corepressor eight-twenty-one (ETO), is frequently associated with acute myeloid leukemia and generates the AML1/ETO (AE) fusion protein. AE represses target genes usually activated by AML1 and also affects the endogenous repressive function of ETO at Notch target genes. In order to analyze the contribution of CBFß in AE-mediated leukemogenesis and deregulation of Notch target genes, we introduced two point mutations in a leukemia-initiating version of AE in mice, called AE9a, that disrupt the AML1/CBFß interaction (AE9aNT). We report that the AE9a/CBFß interaction is not required for the AE9a-mediated aberrant expression of AML1 target genes, while upregulation/derepression of Notch target genes does require the interaction with CBFß. Using retroviral transduction to express AE9a in murine adult bone marrow-derived hematopoietic progenitors, we observed that both AE9a and AE9aNT lead to increased myeloproliferation in vivo. However, both development of leukemia and long-term replating capacity are only observed with AE9a but not with AE9aNT. Thus, deregulation of both AML1 and Notch target genes is required for the development of AE9a-driven leukemia.

[B-cell content after bone marrow transplantation--molecular basis of the limited antibody diversity]. / A csontveló-átültetés után kialakuló B-sejt-készlet--a korlátozott ellenanyag-sokféleség molekuláris alapjai.

Despite B-cell counts and serum immunoglobulin levels usually normalized by one year, humoral immunity and the incidence of bacterial infections continue to be abnormal even after years following bone marrow transplantation. This immunodeficiency could be partially caused by B-cell repertoire restriction similar to that observed early in ontogeny. Immune reconstitution after haematopoietic stem cell transplantation really follows many established ontogenetic patterns relating to the appearance of particular membrane markers, immunoglobulin classes and subclasses, and onset of antigen receptor rearrangements. The sequence of events that occur during successful bone marrow transplantation can be regarded as a blueprint for immune reconstitution in other clinical settings as well. However, the repertoire does not resemble a fetal one, because it displays adult-size IgH CDR3s, adult-type immunoglobulin gene utilization and no evidence of bias towards any particular VH-gen family. Therefore, in the description and interpretation of these events, it is important to realize that immune reconstitution does not appear to recapitulate human fetal ontogeny. In terms of B lymphocyte diversity, the inadequacy of the recovering immune system is more likely to be explained by a combination of other factors--such as clonal dominance and the delayed occurrence of somatic hypermutation.

Thalassaemia in Bombay: The role of medical genetics in developing countries

This study of 200 families with thalassaemic children in Bombay showed that these children's treatment and needs place a significant, unavoidable and increasing demand on the public health services. At the same time, owing to the potentially large number of patients and the difficulties of long-term management, the situation is characterized by evasion of the problem, failure of planing, no provisions for prevention, and inadequate treatment leading to premature death among the affected children. The burden on such families is greater in developing than in developed countries because, besides caring for the chronically sick child, their lives are dominated by the high cost of treatment, often amounting to 20-30 per cent of the income for many families. Seven mothers with no healthy children and 27 with only one healthy child had been sterilized; 90 per cent of reproductive-age couples felt that prenatal diagnosis was a necessity. Also, ignorance and prejudice in the community led to social isolation for the forty families

The experience in Europe shows that improved treatment is the key step in controlling thalassaemia. A well-organized day-transfusion service is cost-effective, soon restoring the children to health and leading to increased optimism. The formulation of associations by parents could mobilize ...(AU)