Title

Global gene expression profiling of single pre-implantation bovine embryos: An analysis of the extent of nuclear reprogramming and the effects of in vitro production

Date of Completion

January 2007

Keywords

Biology, Molecular|Agriculture, Animal Culture and Nutrition

Degree

Ph.D.

Abstract

Nuclear transfer is a promising biotechnology with biomedical and agricultural applications. However, it is plagued by low efficiency, with term development less than 5% for most species. This low efficiency is thought to be due to an incomplete nuclear reprogramming process: reversing the differentiated status of the donor cell back to a totipotent state. In order to investigate the extent of nuclear reprogramming, I utilized microarray technology and analyzed the global gene expression profiles of individual, bovine, blastocyst stage, cloned embryos. I found that nuclear transfer embryos' expression profiles closely resemble the profiles of naturally produced embryos. Additionally, when compared to their respective donor cells, their profiles drastically differed. These results demonstrate that significant and largely correct nuclear reprogramming takes places by the blastocyst stage of development in the bovine. Over the four distinct groups of cloned embryos analyzed, approximately 1% differentially expressed genes were identified when compared to the in vivo embryos. These small errors in gene expression could lead to the abnormalities and mortality observed throughout gestation. Additionally, there could also be further abnormalities in gene reprogramming that occur during later differentiation. ^