Timing of first embryonic cleavage is a positive indicator of the in vitro developmental potential of porcine embryos derived from in vitro fertilization, somatic cell nuclear transfer and parthenogenesis.
Evidence in many species has suggested that those embryos that cleave earliest after fertilization are more developmentally competent than those that cleave relatively later after fertilization. Herein we document this phenomenon in porcine in vitro-fertilized (IVF), somatic cell nuclear transfer (SCNT), and parthenogenetic (PA) embryos. In vitro-matured pig oocytes were used to generate IVF, SCNT, and PA embryos. At 24 hr post-activation (or insemination; hpa/hpi), embryos were visually assessed, and cleaved embryos were moved into a new culture well. This process was repeated at 30 and 48 hpa/hpi. All embryos were allowed to develop 7 days in culture. For IVF embryos, 39.9%, 24.6%, and 10.5% of fast-, intermediate-, or slow-cleaving embryos, respectively, developed into blastocysts by day 7. For SCNT embryos, 31.8% of fast-, 5.7% of intermediate-, and 2.9% of late-cleaving embryos achieved the blastocyst stage of development. For PA embryos, the percentages of those cleaved embryos that developed to blastocyst were 59.3%, 36.7%, and 7.5% for early-, intermediate-, and late-cleaving embryos, respectively. Using RNA collected from early-, intermediate-, and late-cleaving embryos, real-time PCR was performed to assess the transcript levels of 14 different genes of widely varied function. The qPCR results suggest that maternal mRNA degradation may not proceed in an appropriate pattern in slow-cleaving embryos. These findings (1) confirm that, as observed in other species, earlier-cleaving porcine embryos are more successful at developing in culture than are slower-cleaving embryos, and (2) implicate mechanisms of maternal transcript destruction as potential determinants of oocyte/embryo quality.
Division of Animal Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA. clay.isom@usu.edu
S Clay
SC
Isom
Rong Feng
RF
Li
Kristin M
KM
Whitworth
Randall S
RS
Prather
D000377:Agnosia; D000818:Animals; D001755:Blastocyst / Q000502:physiology; D002970:Cleavage Stage, Ovum / Q000502:physiology*; D046149:Embryo Culture Techniques; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D053652:Nuclear Transfer Techniques; D010312:Parthenogenesis / Q000502:physiology*; D013552:Swine