Using an Animal Model to Understand Sex-Dependent Mechanisms Underlying Pregnancy Outcomes caused by Fetal and Maternal Genomic Instability
Principal Investigator: John Schimenti
DESCRIPTION (provided by applicant):
Adverse pregnancy outcomes can be the consequence of defects in several factors, such fetal or maternal genetics, environmental exposures, uterine dysfunction, preeclampsia, nutrition, infection, inflammation, and placental insufficiency. Development of a healthy placenta from trophectoderm precursors enables proper nutrient, gas and waste exchange between the fetus and mother. Additionally, maternal and placenta-intrinsic inflammation at the interface must be controlled to protect the fetus. This project addresses how genomic instability (GIN) during oogenesis and embryogenesis can cause sexually dimorphic pregnancy outcomes, and how the placenta may be especially susceptible to this condition. Research into this underappreciated cause of adverse pregnancy outcomes is motivated by findings that female mouse embryos are dramatically more prone to lethality when bearing certain GIN-causing mutations of DNA replication or repair genes. In one such model that will be utilized in this project, the female-biased lethality was due to increased susceptibility to inflammation, whereas male embryos were protected by the anti-inflammatory effects of testosterone. Preliminary data implicate the placenta as the sensitive tissue underlying the embryonic death. Remarkably, this sex-biased lethality occurred only if the dam also had a GIN genotype. The goals of this project are to understand the tissue(s), cells, and mechanisms driving GIN-induced lethal inflammation. This will be accomplished using the power of mouse genetics, genomics, and embryo manipulation. Aim 1 will test whether the placenta, the embryo, or both, are responsible for female-biased lethality. We hypothesize that the highly polyploid trophoblast giant cells may be especially sensitive to compromised DNA replication and GIN, triggering innate inflammation. Aim 2 addresses why oocytes must come from high GIN mothers for the sex bias to occur in fetuses bearing the mutant lethal genotype. Preliminary experiments implicate that such dams produce oocytes with compromised mitochondria, and this hypothesis will be tested using mitochondrial augmentation and-omics analyses. Aim 3 seeks to identify the molecular basis of lethal embryonic inflammation, with a focus on triggers of innate immunity. A combination of genetic and molecular assays will be used to test the hypothesis that nuclear GIN leads to mitochondrial RNA and DNA leakage, activating a pathway(s) that stimulates transcription of inflammation-driving interferon genes.
Overall, if successful, the results will be relevant for interpreting and addressing individual cases of recurrent pregnancy loss that may have a basis in intrinsic inflammation during gestation, and provide insights into underappreciated mechanisms causing adverse pregnancy outcomes including miscarriage and intrauterine growth retardation.