Biomedical subjects

Owen Williams

Publications and source records attributed to Owen Williams.

6 recordsLinked to original sources

PubMed2006

The mechanism of hematopoietic progenitor cell immortalization by MLL-ENL.

The t(11;19) translocation gives rise to the MLL-ENL fusion protein and is frequently found in infant myeloid and lymphoid leukemias. Immortalized myeloid cell lines can be generated by expression of MLL-ENL in murine hematopoietic progenitors. By establishing myeloid cell lines with conditional expression of MLL-ENL, we recently demonstrated that MLL-ENL is necessary to maintain immortalization and sustain the expression of a characteristic pattern of Hox genes. The cell lines can be induced to undergo terminal differentiation by inhibition of MLL-ENL expression or by treatment with G-CSF. Expression of Hoxa genes is reduced in cells differentiating as a result of MLL-ENL loss, but is maintained in G-CSF treated cells. Thus, although aberrant maintenance of Hoxa gene expression may play an important role in MLL-ENL induced leukemia, the contribution of this pathway to immortalization is critically dependent on the cytokine environment of the immortalized myeloid cells.

Animals↗

PubMed2005

Continuous MLL-ENL expression is necessary to establish a "Hox Code" and maintain immortalization of hematopoietic progenitor cells.

The t[(11;19)(p22;q23)] translocation, which gives rise to the MLL-ENL fusion protein, is commonly found in infant acute leukemias of both the myeloid and lymphoid lineage. To investigate the molecular mechanism of immortalization by MLL-ENL we established a Tet-regulatable system of MLL-ENL expression in primary hematopoietic progenitor cells. Immortalized myeloid cell lines were generated, which are dependent on continued MLL-ENL expression for their survival and proliferation. These cells either terminally differentiate or die when MLL-ENL expression is turned off with doxycycline. The expression profile of all 39 murine Hox genes was analyzed in these cells by real-time quantitative PCR. This analysis showed that loss of MLL-ENL was accompanied by a reduction in the expression of multiple Hoxa genes. By comparing these changes with Hox gene expression in cells induced to differentiate with granulocyte colony-stimulating factor, we show for the first time that reduced Hox gene expression is specific to loss of MLL-ENL and is not a consequence of differentiation. Our data also suggest that the Hox cofactor Meis-2 can substitute for Meis-1 function. Thus, MLL-ENL is required to initiate and maintain immortalization of myeloid progenitors and may contribute to leukemogenesis by aberrantly sustaining the expression of a "Hox code" consisting of Hoxa4 to Hoxa11.

Animals↗

PubMed2004

TEL-AML1 promotes development of specific hematopoietic lineages consistent with preleukemic activity.

The t(12;21)(p13;q22) translocation is the most common chromosomal abnormality yet identified in any pediatric leukemia and gives rise to the TEL-AML1 fusion product. To investigate the effects of TEL-AML1 on hematopoiesis, fetal liver hematopoietic progenitor cells (HPCs) were transduced with retroviral vectors expressing this fusion protein. We show that TEL-AML1 dramatically alters differentiation of HPCs in vitro, preferentially promoting B-lymphocyte development, enhancing self-renewal of B-cell precursors, and leading to the establishment of long-term growth factor-dependent pre-B-cell lines. However, it had no effect on myeloid development in vitro. Further experiments were performed to determine whether TEL-AML1 also demonstrates lineage-specific activity in vivo. TEL-AML1-expressing HPCs displayed a competitive advantage in reconstituting both B-cell and myeloid lineages in vivo but had no effect on reconstitution of the T-cell lineage. Despite promoting these alterations in hematopoiesis, TEL-AML1 did not induce leukemia in transplanted mice. Our study provides a unique insight into the role of TEL-AML1 in leukemia predisposition and a potential model to study the mechanism of leukemogenesis associated with this fusion.

Animals↗

PubMed2004

Flow cytometry-based methods for apoptosis detection in lymphoid cells.

Apoptosis is an active form of cell death that plays a critical role in lymphocyte development, selection and homeostasis. This process is characterized by the activation of biochemical pathways that lead to changes in cellular morphology (including cell shrinkage, membrane blebbing and nuclear condensation), DNA fragmentation, perturbation of mitochondrial membrane function and changes in the plasma membrane. Each of these cellular alterations can be rapidly quantitated in lymphocyte apoptosis using flow cytometry.

Apoptosis↗

PubMed2004

Factors related to serious injury in post-NCAP European cars involved in frontal crashes.

ABSTRACT This study examined the relationship between EuroNCAP ratings for body region protection and real world injury risk for 653 belted drivers in frontal crashes. It was also able to comment on further improvements in crash protection for post-EuroNCAP cars. Protection for the head and lower leg appeared good. In terms of life threatening injury, results showed a need to prioritise chest protection, whilst for impairment, protection for the upper leg and ankle/foot should be considered. The EuroNCAP body region scoring system reflects trends in real crash injury risks to all body regions, except for the chest, where there is no clear trend. More generally, further development in the testing regime could usefully concentrate on a restraint system test and the use of smaller dummies seated appropriately, rather than an increase of the test speed.

Accidents, Traffic↗

PubMed2002

Inefficient clustering of tyrosine-phosphorylated proteins at the immunological synapse in response to an antagonist peptide.

Interactions of T cells with MHC plus peptide in the peripheral lymphoid system are important for their survival. In this study we investigated further the molecular consequences of such interactions using F5 TCR transgenic mice and peptides previously shown to induce either negative or positive selection in the thymus. Following TCR ligation with the negatively selecting agonist peptide, mature CD8(+) cells proliferated and up-regulated the activation marker CD69. Interestingly, ligation of this TCR with MHC molecules loaded with high concentrations of the positively selecting peptide also resulted in the aforementioned changes, but with slower kinetics. Analysis of the biochemical changes that occur following stimulation with these peptides showed that phosphorylation of key signaling molecules, such as ZAP-70, CD3zeta, Vav, SLP-76, LAT, and ERK-1 and 2, could be detected after exposure to agonist but not antagonist peptide. Confocal microscopy, however, revealed infrequent phosphorylation 'patches' at the site of contact between T cells and APC presenting the antagonist peptide. Our data suggest that peptides capable of inducing positive selection in the thymus can be recognized by mature T cells and cause proliferation, up-regulation of CD69 and accumulation of phosphorylated proteins at the immunological synapse with low efficiency; however no phosphorylation of signaling molecules can be detected using conventional biochemical assays.

Animals↗