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The Influence of Nuclear Content on Developmental Competence of Gaur x Cattle Hybrid In Vitro Fertilized and Somatic Cell Nuclear Transfer Embryos¹

Department of Biomedical Sciences,³ Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G 2W1 Centre de recherche en reproduction animale,⁴ Faculté de Médecine Vétérinaire, Université de Montréal, St. Hyacinthe, Québec, Canada J2S 7C6

ABSTRACT

In nondomestic and endangered species, the use of domestic animal oocytes as recipients for exotic donor nuclei causes the normal pattern of cytoplasmic inheritance to be disrupted, resulting in the production of nuclear-cytoplasmic hybrids. Evidence suggests that conflict between nuclear and cytoplasmic control elements leads to a disruption of normal cellular processes, including metabolic function and cell division. This study investigated the effects of nuclear-cytoplasmic interactions on the developmental potential of interspecies embryos produced by in vitro fertilization and somatic cell nuclear transfer: cattle x cattle, gaur x cattle, hybrid x cattle. Cattle control and hybrid embryos were examined for development to the blastocyst stage and blastocyst quality, as determined by cell number and allocation, apoptosis incidence, and expression patterns of mitochondria-related genes. These analyses demonstrated that a 100% gaur nucleus within a domestic cattle cytoplasmic environment was not properly capable of directing embryo development in the later preimplantation stages. Poor blastocyst development accompanied by developmental delay, decreased cell numbers, and aberrant apoptotic and related gene expression profiles, all signs of disrupted cellular processes associated with mitochondrial function, were observed. Developmental potential was improved when at least a portion of the nuclear genome corresponded to the inherited cytoplasm, indicating that recognition of cytoplasmic components by the nucleus is crucial for proper cellular function and embryo development. A better understanding of the influence of the cytoplasmic environment on embryonic processes is necessary before interspecies somatic cell nuclear transfer can be considered a viable alternative for endangered species conservation.

assisted reproductive technology, embryo, in vitro fertilization

¹Supported by grants from the Natural Sciences and Engineering Research Council of Canada, Ontario Graduate Scholarships, and the Canada Research Chair Program.

Correspondence: ²FAX: 519 767 1450; e-mail: waking{at}uoguelph.ca