title: [Placental developmental defects in cloned mammalian animals].
abstract: The cloning technique, also called somatic cell nuclear transfer (SCNT), has been successfully established and gradually applied to various mammalian species. However, the developmental rate of SCNT mammalian embryos is very low, usually at 1% to 5%, which limits the application of SCNT. Placental developmental defects are considered as the main cause of SCNT embryo development inhibition. Almost all of SCNT-derived mammalian placentas exhibit various abnormalities, such as placental hyperplasia, vascular defects and umbilical cord malformation. Mechanistically, these abnormalities result from failure of establishment of correct epigenetic modification in the trophectoderm genome, which leads to erroneous expression of important genes for placenta development-related, particularly imprinted genes. Consequently, aberrant imprinted gene expression gives rise to placental morphologic abnormalities and functional defects, therefore decreases developmental competence of cloned embryos. Currently, although numerous methods that can improve the developmental ability of SCNT-derived embryos have been reported, most of them are unable to substantially enhance the success rate of SCNT due to failure to eliminate the placental development defects. In this review, we summarize placental abnormalities and imprinted gene expression in mammalian cloning, and propose directions for the future research aiming to improve the cloning efficiency.
authors.affiliation: National Engineering Research Center for Swine Breeding Industry, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Ao
authors.affiliation: National Engineering Research Center for Swine Breeding Industry, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
authors.forename: De-wu
authors.initials: DW
authors.lastname: Liu
authors.affiliation: National Engineering Research Center for Swine Breeding Industry, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Geng-yuan
authors.initials: GY
authors.lastname: Cai
authors.affiliation: National Engineering Research Center for Swine Breeding Industry, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Zhen-fang
authors.initials: ZF
authors.lastname: Wu
authors.affiliation: National Engineering Research Center for Swine Breeding Industry, College of Animal Science, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Zi-cong
authors.initials: ZC
authors.lastname: Li
mesh_terms: D000818:Animals; D004622:Embryo, Mammalian; D047108:Embryonic Development; D005260:Female; D018392:Genomic Imprinting; D053652:Nuclear Transfer Techniques; D010920:Placenta / Q000002:abnormalities* / Q000098:blood supply; D011247:Pregnancy; D014470:Umbilical Cord / Q000002:abnormalities