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From Zygote to Implantation: Morphological and Molecular Dynamics during Embryo Development in the Pig
Author(s) -
Oestrup O,
Hall V,
Petkov SG,
Wolf XA,
Hyldig S,
Hyttel P
Publication year - 2009
Publication title -
reproduction in domestic animals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.546
H-Index - 66
eISSN - 1439-0531
pISSN - 0936-6768
DOI - 10.1111/j.1439-0531.2009.01482.x
Subject(s) - epiblast , biology , microbiology and biotechnology , embryonic stem cell , primitive streak , gastrulation , germ layer , homeobox protein nanog , blastocyst , reprogramming , embryogenesis , zygote , inner cell mass , somatic cell , embryoid body , mesoderm , embryo , genetics , induced pluripotent stem cell , cell , gene
Content The increasing focus on the pig as a biomedical model calls for studies which investigate morphological and molecular mechanisms during initial embryonic development in this species. In the pig, the paternal genome is actively demethylated in the zygote, whereas the maternal genome remains methylated. The major genome activation occurs at the four‐cell stage, when prominent ribosome‐synthesizing nucleoli develop in the blastomeres, allowing for trophectoderm and inner cell mass (ICM) differentiation. Unlike in mice, the pluripotency gene OCT4 is initially expressed in both compartments. The ICM differentiates into epiblast and hypoblast approximately at the time of hatching from the zona pellucida, and subsequently the loss of the Rauber’s layer results in an uncovered epiblast establishing the embryonic disc again in contrast to mice. This particular and protracted ICM/epiblast biology may contribute to the lack of success in culturing porcine embryonic stem cells. The embryonic disc subsequently becomes polarized by a posterior thickening, which includes ingression of the first extra‐embryonic mesoderm. Thereafter, the primitive streak forms and gastrulation results in formation of the somatic germ layers and germline, i.e. the primordial germ cells. The latter remain pluripotent for a period and may be isolated and cultured as embryonic germ cells in vitro .