Mitochondria distribution in cloned pig embryos

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DESCRIPTION (provided by applicant): The purpose of this research is to explore mitochondrial distribution as markers for developmental potential of cloned pig embryos. Cloning of mammalian embryos has become attractive in recent years because of the high potential for biomedical and agricultural applications. Cloning of pigs as tissue and organ donors is of high interest because of the exceptional physiological compatibility with humans. However, practical applications are not yet feasible because of the low cloning efficiency (ca. 0.2% in pigs) for which causes are only little understood. One reason may be an asymmetrical mitochondria distribution that can result in reduced ATP generating capacity and an inability to support normal cell functions. We propose that specific patterns of mitochondria aggregation and microtubule organization will allow us to predict developmental potential of cloned embryos and increase cloning efficiency. Our specific aims are to analyze: 1a) whether differences in mitochondrial distribution occur among individual blastomeres in cohorts of morphologically normal cleavage stage embryos; 1b) whether changes in intracellular pH are associated with disruption of mitochondrial organization and reduced development in vitro; 2a) whether microtubule organization plays a role in mitochondrial distribution after nuclear transfer in cloned embryos; and 2b) whether unequal centrosome separation after nuclear transfer plays a role in mitochondrial distribution. The distribution of mitochondria will be examined by scanning laser confocal microscopy in fixed and live oocytes, in cleavage stage embryos, and development to the blastocyst stages. MitoTracker Green FM and Mitotracker-X-Rosamine will be used to stain mitochondria. Double and triple immunofluorescence staining with anti-tubulin and anti-centrosome antibodies will determine the relationship between mitochondria and microtubule organization. We will correlate survival to the blastocyst stages with characteristic mitochondria fluorescence patterns. These experiments will provide new information on mitochondria distribution and microtubule organization after nuclear cloning and allow future research aimed at selecting embryos that are most likely to survive and increase live birth of cloned animals. Pilot data from this RO3 small grants program research will be used to apply for funding through the RO1 mechanism.