The transition from maternal to embryonic control in the 2-cell mouse embryo.

Abstract

The development of the early 2‐cell mouse embryo to the late 2‐cell stage is marked by the appearance between 23 and 26 h post‐insemination of a complex of polypeptides of mol. wt. approximately 67 K. Addition of alpha‐amanitin between 18 and 21 h post‐insemination prevents or reduces the subsequent appearance of these polypeptides. Addition of alpha‐amanitin after 21 h does not obviously affect the appearance of the approximately 67 K polypeptides. A major change in synthetic profile occurs between 29 and 32 h post‐insemination involving many polypeptides. Addition of alpha‐amanitin to 2‐cell embryos prior to 29 h post‐insemination prevents the appearance of the new polypeptides observed during this major change but does not prevent the disappearance of the old polypeptides. In contrast, addition of alpha‐amanitin after this time does not affect the appearance of the new polypeptides. This result, together with other evidence presented, suggests that during the 2‐cell stage the embryonic genome shows transcriptional activity in two phases at 18‐21 and 26‐29 h post‐insemination, that these transcripts are utilized soon after their synthesis, and that most maternal transcripts used before the second phase of embryonic transcription become ineffective soon afterwards.

Igf2r and Igf2 gene expression in androgenetic, gynogenetic, and parthenogenetic preimplantation mouse embryos: absence of regulation by genomic imprinting.

“…The Igf2T mRNA abundance declined sharply by the two-cell stage and then increased 15-fold by the eight-cell stage. This trend-a decrease between the egg and two-cell stage, followed by an increase by the eight-cell stage-is characteristic of a number of genes that are expressed following zygotic gene activation, which occurs during the two-cell stage in the mouse (Flach et al 1982;Bensaude et al 1983;. Actin, which is not an imprinted gene, is such an example (Fig.…”

Transitioning from egg to embryo: Triggers and mechanisms of egg activation

“…The length of time varies between species, from 1 day in mouse (until the 2-cell stage), to 2 hr in Drosophila (until nuclear cycle 13), and 6 hr in Xenopus (until the midblastula stage; McKnight and Miller, 1976;Newport and Zalokar, 1976;Kirschner, 1982;Flach et al, 1982). During this period, development is driven largely by mRNAs and proteins deposited in the mature oocyte by the mother (Fig.…”

Metazoan oocyte and early embryo development program: a progression through translation regulatory cascades

“…In Xenopus, after 12 rapid synchronous cleavages, when the developing embryo is composed of ∼4000 cells, the mid-blastula transition occurs and is characterized by lengthening of the cell cycle, inclusion of G1 and G2, and activation of zygotic transcription (Newport and Kirschner 1982a,b). In mouse and human, induction of transcription in the embryo occurs at the two-cell, and four-to eight-cell stages, respectively (Clegg and Piko 1982;Flach et al 1982;Braude et al 1988). Despite the earlier occurrence of zygotic transcription, activation of maternally inherited mRNAs in mammals seems to use translation mechanisms similar to those in other vertebrates (Richter 1999;Oh et al 2000).…”