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Open Access Thesis

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Degree Program

Molecular & Cellular Biology

Degree Type

Master of Science (M.S.)

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Month Degree Awarded



According to the Knockout Mouse Project (KOMP), loss of glutamatic oxaloacetic transaminase 2 (Got2) results in lethality between embryonic day (E) 9.5 and E12.5, which is a critical period for organ and placenta development. The first aim of this project is to characterize the KOMP-generated Got2 null allele. In situ hybridization reveals that while Got2 is ubiquitous throughout much of the embryo, it is highly expressed in the liver and throughout the developing labyrinth layer of the placenta by E9.5. While Got2-/- embryos are lethal at E10.5, at E9.5 Got2-deficient embryos have pharyngeal arch defects, do not turn properly, and have oedemic hearts. Because of the widespread and high levels of Got2 in the placenta and its putative role in energy production, we hypothesized that the embryonic lethality observed was caused by placenta dysfunction. The second aim of this project is to test the hypothesis, using a conditional Got2 allele, which phenocopies the original null alleles when induced to make a full null allele, to create an epiblast-only conditional knockout (cKO). Compared to heterozygous littermates cKO Got-/- embryos are slightly delayed, but otherwise grossly normal at E9.5, are pale and smaller than littermates at E11.5 and are smaller and markedly reduced or absent liver at E12.5. Histological and molecular analysis demonstrates that the cKO embryos, like the null embryos, have a normal liver bud at E9.5. By E10.5 the cKO livers are highly reduced. Mass spectrometry of single intact E10.5 cKO embryos demonstrated that their metabolism exhibits significant changes relative to controls, with alterations in malate aspartate shuttle metabolites, as well as pyruvate and pyrimidine and purine precursor metabolites. These results suggest that placental expression of Got2 is critical for embryo development between E8.5 to E10.5 and that embryonic expression of Got2 is conspicuously required for embryonic liver development by E10.5.

First Advisor

Dr. Kimberly D. Tremblay