Surface-expressed E-cadherin, and mitochondrial and microtubule distribution in rescue of mouse embryos from 2-cell block by aggregation

Neganova IE, Sekirina GG, Eichenlaub-Ritter U. Surface-expressed E-cadherin, and mitochondrial and microtubule distribution in rescue of mouse embryos from 2-cell block by aggregation. MOLECULAR HUMAN REPRODUCTION. 2000;6(5):454-464.E-cadherin (uvomorulin)-mediated cell interactions are essential for preimplantation development in mammals, We observed that E-cadherin is expressed at contact sites between blastomeres of 2-cell mouse embryos of non-blocking genotype (CBA x C57BL fl) explanted at 32 h post human chorionic gonadotrophin (HCG) and cultured in vitro, while blastomere rounding and reduced zones of contact and E-cadherin-staining were observed in embryos of a blocking strain (MF1) arrested at the 2-cell stage, Embryos of MF1 strain can be rescued by aggregation with four 2-cell embryos of the non-blocking genotype, An early event in rescue is E-cadherin expression at contact zones between adjacent embryos of different genotype in aggregation chimeras. E-cadherin-mediated signalling appears important for the rescue (including formation of adherens-like contacts, cell polarization and morphogenetic processes) since there is no rescue when E-cadherin-specific antibodies are present during phytohaemagglutinin-mediated aggregation and subsequent culture. In blocked embryos, the distribution of microtubules is disturbed and concomitantly mitochondria cluster around the nucleus. Rescue by aggregation retains normal mitochondrial distribution in the presence of a dense microtubular lattice in all blastomeres, Therefore, E-cadherin-mediated signalling and its downstream effects on cytoskeletal organization are essential in the rescue of blocking embryos by aggregation. Normal preimplantation development appears to be dependent on the polarized expression of surface E-cadherin and the microtubule-mediated dispersal of mitochondria

LacZ transgene expression as a cell marker to analyse rescue from the 2-cell block in mouse aggregation chimeras

Neganova IE, Augustin M, Sekirina GG, Jockusch H. LacZ transgene expression as a cell marker to analyse rescue from the 2-cell block in mouse aggregation chimeras. ZYGOTE. 1998;6(3):223-226.Embryos from certain mouse strains are arrested at the 2-cell stage in cell culture ('2-cell block'), whereas those from other strains develop to the blastocyst stage under the same conditions. It was previously shown that blocking embryos can be rescued in culture by aggregation with an excess of 2-cell stages of a non-blocking strain such as CBA x C57BL/6 F-2. Here we have employed a LacZ transgene in a blocking strain (NMRI) to follow the fate of rescued blastomeres up to the blastocyst stage. We found that rescued blastomeres can participate in both inner cell mass and trophoblast formation, thus completely overcoming the 2-cell block