Biomedical subjects

Stefan Glaser

Publications and source records attributed to Stefan Glaser.

4 recordsLinked to original sources

PubMed2006

Enforced expression of the homeobox gene Mixl1 impairs hematopoietic differentiation and results in acute myeloid leukemia.

Mixl1, the sole murine homologue of the Xenopus Mix/Bix family of homeobox transcription factors, is essential for the patterning of axial mesendodermal structures during early embryogenesis. Gene targeting and overexpression studies have implicated Mixl1 as a regulator of hematopoiesis arising in differentiating embryonic stem cells. To assess the role of Mixl1 in the regulation of adult hematopoiesis, we overexpressed Mixl1 in murine bone marrow using a retroviral transduction/transplantation model. Enforced expression of Mixl1 profoundly perturbed hematopoietic lineage commitment and differentiation, giving rise to abnormal myeloid progenitors and impairing erythroid and lymphoid differentiation. Moreover, all mice reconstituted with Mixl1-transduced bone marrow developed fatal, transplantable acute myeloid leukemia with a mean latency period of 200 days. These observations establish a link between enforced Mixl1 expression and leukemogenesis in the mouse.

Animals↗

PubMed2006

Multiple epigenetic maintenance factors implicated by the loss of Mll2 in mouse development.

Epigenesis is the process whereby the daughters of a dividing cell retain a chromatin state determined before cell division. The best-studied cases involve the inheritance of heterochromatic chromosomal domains, and little is known about specific gene regulation by epigenetic mechanisms. Recent evidence shows that epigenesis pivots on methylation of nucleosomes at histone 3 lysines 4, 9 or 27. Bioinformatics indicates that mammals have several enzymes for each of these methylations, including at least six histone 3 lysine 4 methyltransferases. To look for evidence of gene-specific epigenetic regulation in mammalian development, we examined one of these six, Mll2, using a multipurpose allele in the mouse to ascertain the loss-of-function phenotype. Loss of Mll2 slowed growth, increased apoptosis and retarded development, leading to embryonic failure before E11.5. Using chimera experiments, we demonstrated that Mll2 is cell-autonomously required. Evidence for gene-specific regulation was also observed. Although Mox1 and Hoxb1 expression patterns were correctly established, they were not maintained in the absence of Mll2, whereas Wnt1 and Otx2 were. The Mll2 loss-of-function phenotype is different from that of its sister gene Mll, and they regulate different Hox complex genes during ES cell differentiation. Therefore, these two closely related epigenetic factors play different roles in development and maintain distinct gene expression patterns. This suggests that other epigenetic factors also regulate particular patterns and that development entails networks of epigenetic specificities.

Alleles↗

PubMed2005

Current issues in mouse genome engineering.

The mouse is the foremost vertebrate experimental model because its genome can be precisely and variously engineered. Now that the mouse genome has been sequenced and annotated, the task of mutating each gene is feasible, and an international cooperation is providing mutated embryonic stem cells and mice as readily available resources. Because these resources will change biomedical research, decisions about their nature will have far-reaching effects. It is therefore timely to consider topical issues for mouse genome engineering, such as the background genotype; homologous, site-specific and transpositional recombination; conditional mutagenesis; RNA-mediated interference; and functional genomics with embryonic stem cells.

Animals↗

PubMed2004

A reliable lacZ expression reporter cassette for multipurpose, knockout-first alleles.

Alteration of the mouse genome through homologous recombination in embryonic stem (ES) cells is the most accurate and versatile way to dissect gene function in a vertebrate model. Most often, a selectable marker is used to create a knockout allele by replacing an essential part of the gene. However, knockout strategies are limited because the mutation is present constitutively. Conditional approaches based on the Cre-loxP site-specific recombination (SSR) system address this limitation; however, it requires that all parts of the targeted gene remain in ES cells. Here we report success with a "knockout-first" strategy that ablates gene function by insertion of RNA processing signals without deletion of any of the target gene. Incorporation of site-specific recombination target sites creates a multipurpose allele for both knockout and conditional applications.

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