Epigenetic Characteristics and Development of Embryos Cloned from Donor Cells Treated by Trichostatin A or 5-aza-2-deoxycytidine

Development to blastocyst following nuclear transfer is dependent on the donor cellʹs ability to reprogram its genome to that of a zygote. This reprogramming step is inefficient and may be dependent on a number of factors, including chromatin organization. Trichostatin A (TSA; 0–5 µM), a histone deacetylase inhibitor, was used to increase histone acetylation and 5-aza-2ʹ-deoxycytidine (5-aza-dC; 0–5 (mu)M), a DNA methyltransferase inhibitor, was used to decrease methylation of chromatin in donor cells in an attempt to improve their reprogrammability. Adult fibroblast cells treated with 1.25 or 5 (mu)M TSA had elevated histone H3 acetylation compared to untreated controls. Cells treated with 0.3 (mu)M 5-aza-dC had decreased methylation compared to untreated controls. Both drugs at 0.08 (mu)M caused morphological changes of the donor cells. Development to blastocysts by embryos cloned from donor cells after 0.08 or 0.3 µM 5-aza-dC treatments was lower than in embryos cloned from untreated control cells (9.7% and 4.2%, respectively, vs. 25.1%), whereas 0.08 (mu)M TSA treatment of donor cells increased blastocyst development compared to controls (35.1% vs. 25.1%). These results indicate that partial erasure of preexisting epigenetic marks of donor cells improves subsequent in vitro development of cloned embryos.