Timing factors affecting blastocyst development in equine somatic cell nuclear transfer.
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
In nuclear transfer (NT), exposure of donor cell chromatin to the ooplast cytoplasm may aid reprogramming; however, the length of exposure feasible is limited by the developmental life span of the oocyte. We examined the effect of duration of nucleus-cytoplasmic exposure before activation and of in vitro maturation (IVM) in equine NT. In experiment 1, 24 h IVM and a delay of 2, 5, or 8 h between reconstruction and activation yielded 4%, 15%, and 11% blastocysts, respectively. In experiment 2, a 5-h activation delay yielded 17% and 22% blastocysts with two donor cell lines. In experiment 3, using a 5-h activation delay, the blastocyst rate was significantly higher using oocytes after 20 h IVM than after 24 h IVM; however, only 28% of oocytes were in metaphase II (MII) at 20 h. In experiment 4, oocytes were denuded of cumulus at 20 h, and those in metaphase I (MI) were returned to culture for 3 h (20+3H treatment); blastocyst rates were 30% and 27%, respectively (8-h and 5-h delay to activation, respectively). Four live foals resulted from the transfer of 17 blastocysts (24%) produced using MII oocytes and a 5- or 8-h activation delay. Use of equine oocytes immediately after reaching MII, combined with a longer delay from reconstruction to activation, increased developmental competence after equine NT.
