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  • Title: [Overcoming the "2-cell block" in mouse embryos in aggregation chimeras].
    Author: Sekirina GG, Neganova IE.
    Journal: Ontogenez; 1996; 27(5):361-70. PubMed ID: 8999390.
    Abstract:
    The embryos of the inbred mouse strain BALB/c are predisposed to so-called "two-cell block" after explantation from the maternal organism before the late two-cell stage and cultivation in a standard synthetic medium. Hybrid embryos (CBA x C57B1) F2 are competent to complete preimplantation development in vitro. The BALB/c embryo predisposed to block ("blocking") at the early two-cell stage was aggregated using phytohemagglutinin with four to five two- and eight-cell BALB/c embryos capable of reaching the blastocyst stage in vitro ("non-blocking"). This aggregate successfully developed until the blastocyst stage for 72 h. The aggregation of the early two-cell BALB/c embryos with each other did not prevent the block. After the aggregation of the blocking and non-blocking embryos at the two-cell stage, a common integrated blastocyst developed. In aggregates with eight-cell embryos, the blocking embryo formed a separate blastocyst, although it preserved contacts with non-blocking embryos during the entire period of cultivation. Ultrastructural analysis has shown that two-cell embryos aggregated using phytohemagglutinin form adhesive contacts up to several microns long. Possible mechanisms of cooperation between the competent and deficient partners in aggregates with two-cell embryos are discussed.
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