Species-specific determinants of bison somatic cell nuclear transfer embryo development

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Somatic cell nuclear transfer (SCNT) technology provides a unique alternative for the preservation of genetic material from valuable individuals and species. The use of interspecies SCNT for the production of embryos in non-domestic species is necessary due to insufficient quantities of oocytes from rare or exotic animals as recipients for the exotic donor nucleus. Poor development of these embryos to term-gestation suggests that they are developmentally compromised. Incompatibility between the donor nucleus and recipient cytoplasm is thought to play an important role in the decreased development. Our research interest lies in elucidating the mechanisms that are disrupted during interspecific nuclear-cytoplasmic interactions to identify the reasons for decreased developmental competence in the absence of technique-related problems. Studies to date have documented the importance of cytoplasmic composition and organization in SCNT embryo success. Mitochondria play a central role in cellular pathways (energy production, apoptosis) that are necessary for proper cell function. Dysregulation of mitochondrial biogenesis, function and distribution results in alterations in mtDNA copy number, ATP levels and rates of apoptosis, all of which have been associated with early embryo arrest and death. Interactions between the cytoplasm and the nuclear genome and centrosomes, components inherited from the unrelated donor cell, are critical for maintaining normal mitochondrial activity. The proposed research will examine whether nuclear-cytoplasmic interactions involved in mitochondrial distribution and function are disrupted in interspecific SCNT embryos from evolutionarily similar cattle species. Bison (Bison bison) and domestic cattle (Bos taurus) gametes and somatic cells will be used to produce hybrid embryos using in vitro fertilization (IVF) and SCNT techniques. Analysis of these unique hybrids will give us a better understanding of the basic differences in nuclear and cytoplasmic contribution to embryo development. This is essential for the development and optimization of in vitro embryo production protocols for non-domestic species.