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Somatic Cell Interspecies Nuclear Transfer, Marina Julia Sansinena
Somatic Cell Interspecies Nuclear Transfer, Marina Julia Sansinena
LSU Doctoral Dissertations
The low efficiency of the nuclear transfer (NT) procedure requires large number of oocytes to produce embryos and live offspring. A series of experiments were conducted to evaluate the ability of the bovine cytoplast to reprogram nuclei from horses and llamas. In a preliminary study, equine oocytes from small (<20mm diameter) follicles were either pretreated with roscovitine or placed in maturation (IVM only) prior to NT. Roscovitine pretreatment did not improve nuclear maturation rates (roscovitine pretreatment 57% vs. IVM only 66%) and no fusion was obtained from roscovitine-pretreated oocytes after NT. Another preliminary study was conducted with the objective to produce llama NT embryos and to compare their development in two in vitro culture conditions (G1.2® vs. CR1aa). No difference was found in the number of embryos cleaved after 2 d of culture. This resulted in the first scientific report of somatic cell NT, in vitro culture and transfer of NT embryos in the llama. In the next experiment, adult horse and llama fibroblasts were injected into enucleated cow oocytes. The results showed the cow cytoplasm is capable of partially reprogramming nuclei from other species and support mitotic divisions. However, this study also showed a consistent embryonic developmental arrest at the 8- to 16- cell stage when horse or llama donor cells were used as donor nuclei. When a more closely related species of donor cell (banteng) and recipient oocyte (domestic cattle) were used for NT, no embryonic developmental arrest was found. Embryos progressed to achieve high blastocyst rates (banteng male cell line 28% vs. banteng female cell line 15%). Two banteng interspecies NT pregnancies were established and subsequently lost from the banteng male cell line. In the final study, the effect of a mixed mitochondrial population (heteroplasmy) on early embryonic development was investigated. Ooplasmic transfer performed in combination with NT procedure indicated presence of foreign mitochondria clustered in a small portion of the cytoplasm in early stages of embryo development. When goat ooplasm was transferred into interspecies (cow oocyte-goat donor cell) NT embryos, fusion and cleave rates were reduced suggesting an increased level of heteroplasmy or nuclear-ooplasmic incompatibilities.
Evolution Of Base Substitution Gradients In Primate Mitochondrial Genomes, Sameer Raina
Evolution Of Base Substitution Gradients In Primate Mitochondrial Genomes, Sameer Raina
LSU Master's Theses
The availability of large amounts of genetic data from the mitochondrial DNA of species has created an unprecedented opportunity for the study of evolutionary processes. Being our closest relatives on the evolutionary tree the primates are a prime candidate for the study of evolutionary processes. The availability of large amounts of genetic data from the primates allows us to study and compare results from different phylogenetic reconstruction methods and to study and trace rudimentary evolutionary processes within the primate lineage. The evolutionary process studied here is the response of the nucleotide frequency ratios to single-strandedness of sites during mitochondrial DNA …
Phylogenetic Influence Of Complex, Evolutionary Models: A Bayesian Approach, Neeraja M. Krishnan
Phylogenetic Influence Of Complex, Evolutionary Models: A Bayesian Approach, Neeraja M. Krishnan
LSU Master's Theses
Molecular evolution recovers the history of living species by comparing genetic information, exploring genome structure and function from an evolutionary perspective. Here we infer substitution rates and ancestral reconstructions, to better understand mutation responses to some known biochemical phenomena. Mutation processes are commonly inferred using parsimony, maximum likelihood and Bayesian. Parsimony is not explicitly model-based, and is statistically biased due to unrealistic assumptions. The model-based maximum likelihood approaches become computationally inefficient while analyzing large or high-dimensional datasets, leaving little opportunities to incorporate complex evolutionary models. We implemented a posterior probability (Bayesian) approach that evaluates evolutionary models, applying it to primate …