Biomedical subjects

William M Rideout

Publications and source records attributed to William M Rideout.

4 recordsLinked to original sources

PubMed2005

Global loss of imprinting leads to widespread tumorigenesis in adult mice.

Loss of imprinting (LOI), commonly observed in human tumors, refers to loss of monoallelic gene regulation normally conferred by parent-of-origin-specific DNA methylation. To test the function of LOI in tumorigenesis, we developed a model by using transient demethylation to generate imprint-free mouse embryonic stem cells (IF-ES cells). Embryonic fibroblasts derived from IF-ES cells (IF-MEFs) display TGFbeta resistance and reduced p19 and p53 expression and form tumors in SCID mice. IF-MEFs exhibit spontaneous immortalization and cooperate with H-Ras in cellular transformation. Chimeric animals derived from IF-ES cells develop multiple tumors arising from the injected IF-ES cells within 12 months. These data demonstrate that LOI alone can predispose cells to tumorigenesis and identify a pathway through which immortality conferred by LOI lowers the threshold for transformation.

Animals↗

PubMed2004

Nuclear transplantation, embryonic stem cells and the potential for cell therapy.

Nuclear transfer experiments in mammals have shown that the nucleus of an adult cell has the ability to direct the development of an entire organism, id est its genome is totipotent. However, these experiments did not conclusively demonstrate that the nuclei of terminally differentiated adult cells remain totipotent. It is possible that rare adult stem cells served as donors for the few surviving clones. To address this question, we have generated monoclonal mice from terminally differentiated lymphocytes that carry a single antigen receptor rearrangement in all tissues. Nuclear transfer technology may provide a powerful method for obtaining autologous cells for replacement therapy. We have demonstrated the feasibility of this concept by combining nuclear transfer with gene and cell therapy to treat the immune deficiency of Rag2 mutant mice, thus establishing a paradigm for 'therapeutic cloning'. Moreover, we will discuss the potential use of nuclear transfer to study the role of reversible genomic (epigenetic) modifications during tumorigenesis.

Animals↗

PubMed2003

Cyclin E ablation in the mouse.

E type cyclins (E1 and E2) are believed to drive cell entry into the S phase. It is widely assumed that the two E type cyclins are critically required for proliferation of all cell types. Here, we demonstrate that E type cyclins are largely dispensable for mouse development. However, endoreplication of trophoblast giant cells and megakaryocytes is severely impaired in the absence of cyclin E. Cyclin E-deficient cells proliferate actively under conditions of continuous cell cycling but are unable to reenter the cell cycle from the quiescent G(0) state. Molecular analyses revealed that cells lacking cyclin E fail to normally incorporate MCM proteins into DNA replication origins during G(0)-->S progression. We also found that cyclin E-deficient cells are relatively resistant to oncogenic transformation. These findings define a molecular function for E type cyclins in cell cycle reentry and reveal a differential requirement for cyclin E in normal versus oncogenic proliferation.

Animals↗

PubMed2002

Correction of a genetic defect by nuclear transplantation and combined cell and gene therapy.

Immune-deficient Rag2(-/-) mice were used as nuclear donors for transfer into enucleated oocytes, and the resulting blastocysts were cultured to isolate an isogenic embryonic stem cell line. One of the mutated alleles in the Rag2(-/-) ES cells was repaired by homologous recombination, thereby restoring normal Rag2 gene structure. Mutant mice were treated with the repaired ES cells in two ways. (1) Immune-competent mice were generated from the repaired ES cells by tetraploid embryo complementation and were used as bone marrow donors for transplantation. (2) Hematopoietic precursors were derived by in vitro differentiation from the repaired ES cells and engrafted into mutant mice. Mature myeloid and lymphoid cells as well as immunoglobulins became detectable 3-4 weeks after transplantation. Our results establish a paradigm for the treatment of a genetic disorder by combining therapeutic cloning with gene therapy.

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