Transition from maternal to embryonic control of development in IVM/IVF domestic cat embryos
1997
Hoffert, K.A. | Anderson, G.B. | Wildt, D.E. | Roth, T.L.
The timing of the transition from maternal to zygotic control of development (MZT) and the initiation of transcription was studied in domestic cat embryos to determine if there is a temporal association between these phenomena and the developmental block observed in cat embryos fertilized in vitro. Embryos were derived from in vitro-matured, in vitro-fertilized (IVM/IVF) oocytes. In Experiment 1, embryos (n = 52) were cultured continuously in the presence of 10 micrograms/ml alpha manitin (a transcriptional inhibitor) from 12-hr postinsemination (hpi), and cleavage stage was evaluated every 24 hr. The proportion of embryos cleaving to at least the 5-8-cell stage in the presence of alpha-amanitin (32/52) was similar (P> 0.05) to that of controls cultured without alpha-amanitin (25/50). In contrast, only 7.7% of alpha-amanitin-treated embryos cleaved to the 9-16-cell stage, compared with 38.0% of the controls (P < 0.05), indicating that products of embryonic transcription were required for cleavage beyond the 5-8 cell stage. In Experiment 2, embryos were cultured in the presence of 20 micomolar 3H-uridine for 12 hr beginning at 24, 36, 48, or 60 hpi and subjected to autoradiography. Embryos of 5-8-cell and 9-16-cell stages (14 of 27 and 8 of 12, respectively) clearly demonstrated nuclear labeling, a finding also confirmed by computer-aided densitometry. It is concluded that embryonic transcription and the MZT occur by the 5-8-cell stage of IVM/IVF domestic cat embryo development and the MZT is not directly related to the partial morula-to-blastocyst developmental block observed in cultured IVF cat embryos.
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