More than any other species, humans have difficulty reproducing. As recent studies show that human infertility is ever increasing, much efforts are needed towards the understanding of our low fecundity. While aneuploidy is the leading cause of spontaneous pregnancy loss in humans, we still know surprisingly little about the developmental consequences of chromosomal abnormalities. We have here used a mouse model that spontaneously incites chromosomal primary aneuploidy in female haploid oocytes and find that after fertilization, these primary aneuploid cells become cytological unstable, generating diverse karyotypic mosaic embryos. The mosaic aneuploid embryos can develop and implant into the female uterine tissue and initiate the gastrulation process (E6.5) but quickly degrade and succumb by E8.0. We find that loss of embryo viability due to chromosomal mosaicism is caused by the activation of a spatially and temporally controlled p53-independent apoptotic mechanism and does not result from a failure to progress through mitosis. We conclude that an initial state of primary aneuploidy within an embryo results in a rapid evolution of mosaicism and early embryonic death. This gestational loss due to aneuploid mosaicism could account for the large proportion of human pregnancy loss prior to clinical recognition.
The application of cytokines for immunotherapy is frequently hampered by undesirable side effects. To avoid systemic effects, cytokines can be directly expressed in the target cells by using gene transfer. However, the uncontrolled cellular secretion of cytokines could still exert some undesirable bystander effects. Therefore, it is important to develop additional methods for a more restricted administration of cytokines. Recently, using the murine granulocytemacrophage colony-stimulating factor (mGM-CSF), we have demonstrated that cytokines can be targeted to different subcellular compartments as stable and biologically active proteins. This model could be used as a method of highly restricted administration of cytokines. Here, as model for the proof of principle, we have used a cell line (DA-3) strictly dependent on mGM-CSF for growth and demonstrated that these cells acquired autonomous growth after gene modification with plasmids encoding either extracellular or intracellular forms of mGM-CSF. Cell lines expressing secreted forms of mGM-CSF displayed the highest rates of autonomous growth and released substantial amounts of mGM-CSF. However, cell lines expressing intracellular forms of mGM-CSF also acquired autonomous growth induced by a mechanism of restricted autocrine stimulation and did not release detectable mGM-CSF to the extracellular medium. Cocultivation experiments of DA-3 cell lines expressing intracellular mGM-CSF with unmodified cells showed that there was no activation of the bystander cells. Taken together, these results support the concept that genes encoding intracellular cytokines may be used to provide the desired effect of cytokines on the target cells while avoiding the side effects of their uncontrolled secretion.
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