Somatic cell nuclear transfer alters peri-implantation trophoblast differentiation in bovine embryos

• Published in: Reproduction (Cambridge, England) Vol. 132; no. 2; pp. 279 - 290
• Main Authors: Arnold, Daniel R, Bordignon, Vilceu, Lefebvre, Réjean, Murphy, Bruce D, Smith, Lawrence C
• Format: Journal Article
• Language: English
• Published: Colchester Society for Reproduction and Fertility 01-08-2006; BioScientifica Ltd; Portland
• Subjects: abortion (animals); Alleles; animal proteins; Animals; artificial insemination; Basic Helix-Loop-Helix Transcription Factors - genetics; Biological and medical sciences; Cattle; Cell Count; Cell Differentiation; Cloning, Organism; dysfunctional placentation; Early stages. Segmentation. Gastrulation. Neurulation; embryo (animal); Embryo Culture Techniques; Embryo Implantation; Embryology: invertebrates and vertebrates. Teratology; Embryonic Development; endometrium; Female; Fertilization in Vitro; food animals; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation, Developmental; genes; genomic imprinting; Gestational Age; in vitro fertilization; Insemination, Artificial; Interferon-gamma - genetics; messenger RNA; Nuclear Transfer Techniques; nuclear transplantation; Placenta; Placentation; Pregnancy; pregnancy complications; Pregnancy Proteins - genetics; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - analysis; Ruminantia; somatic cell nuclear transfer technique; somatic cells; trophoblast; Trophoblasts - cytology; Vertebrates: reproduction; Trophoblaste; Embryo; Fetal membrane; Ox; Somatic cell; Pregnancy; Vertebrata; Reproduction; Mammalia; Ovum implantation; Animal; Transfer; Artiodactyla; Differentiation; Ungulata
• ISSN: 1470-1626; 1741-7899
• DOI: 10.1530/rep.1.01217

Abnormal placental development limits success in ruminant pregnancies derived from somatic cell nuclear transfer (SCNT), due to reduction in placentome number and consequently, maternal/fetal exchange. In the primary stages of an epithelial–chorial association, the maternal/fetal interface is characterized by progressive endometrial invasion by specialized trophoblast binucleate/giant cells (TGC). We hypothesized that dysfunctional placentation in SCNT pregnancies results from aberration in expression of genes known to be necessary for trophoblast proliferation (Mash2), differentiation (Hand1), and function (IFN-τ and PAG-9). We, therefore, compared the expression of these factors in trophoblast from bovine embryos derived from artificial insemination (AI), in vitro fertilization (IVF), and SCNT prior to (day 17) and following (day 40 of gestation) implantation, as well as TGC densities and function. In preimplantation embryos, Mash2 mRNA was more abundant in SCNT embryos compared to AI, while Hand1 was highest in AI and IVF relative to SCNT embryos. IFN-τ mRNA abundance did not differ among groups. PAG-9 mRNA was undetectable in SCNT embryos, present in IVF embryos and highest in AI embryos. In postimplantation pregnancies, SCNT fetal cotyledons displayed higher Mash2 and Hand1 than AI and IVF tissues. Allelic expression of Mash2 was not different among the groups, which suggests that elevated mRNA expression was not due to altered imprinting status of Mash2. The day 40 SCNT cotyledons had the fewest number of TGC compared to IVF and AI controls. Thus, expression of genes critical to normal placental development is altered in SCNT bovine embryos, and this is expected to cause abnormal trophoblast differentiation and contribute to pregnancy loss.