Manipulating the Mitochondrial Genome To Enhance Cattle Embryo Development

The mixing of mitochondrial DNA (mtDNA) from the donor cell and the recipient oocyte in embryos and offspring derived from somatic cell nuclear transfer (SCNT) compromises genetic integrity and affects embryo development. We set out to generate SCNT embryos that inherited their mtDNA from the recipient oocyte only, as is the case following natural conception. Whilst SCNT blastocysts produced from Holstein (Bos Taurus) fibroblasts depleted of their mtDNA and oocytes derived from Angus (Bos Taurus) cattle possessed oocyte mtDNA only, the co-existence of donor cell and oocyte mtDNA resulted in blastocysts derived from non-depleted cells. Moreover, the use of the reprogramming agent, Trichostatin A (TSA), further improved the development of embryos derived from depleted cells. RNA-seq analysis highlighted 35 differentially expressed genes from the comparison between blastocysts generated from non-depleted cells and blastocysts from depleted cells, both in the presence of TSA. The only differences between these two sets of embryos were the presence of donor cell mtDNA and a significantly higher mtDNA copy number for embryos derived from non-depleted cells. Furthermore, the use of TSA on embryos derived from depleted cells positively modulated the expression of CLDN8, TMEM38A and FREM1, which affect embryonic development. In conclusion, SCNT embryos produced by mtDNA depleted donor cells have the same potential to develop to the blastocyst stage without the presumed damaging effect resulting from the mixture of donor and recipient mtDNA.

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