Abstract

Placental abnormalities and failed implantation are characterized phenotypes that occur in many species as a result of somatic cell cloning. This study examines a number of genes, critical for early placental development and reports aberrant expression patterns in a number of cloned bovine blastocysts, thus implicating a role of these genes in failed implantation. Messenger RNA (mRNA) expression of eight genes critical for early placental and preimplantation development including Acrogranin, Cdx2, Eomes, ErbB3, ERR2, Hand1, MRJ, and Rex1 were analyzed in single, in vivo, in vitro, and cloned bovine blastocysts (produced by hand-made cloning (HMC) and serial hand-made cloning (SHMC)) following complementary DNA (cDNA) amplification with a SMART cDNA synthesis kit. Aberrant expression of Acrogranin, Cdx2, and ERR2 was detected in a number of blastocysts produced by SHMC. Other genes, Eomes and Hand1, were not detectable in, in vivo bovine blastocysts, suggesting a differential expression pattern between bovine and murine embryos. A number of control marker genes including Oct4, IFN-tau, and PolyA were expressed in all single blastocysts analyzed. This is the first study to report that failure of implantation may be due to aberrant expression of genes in the preimplantation cloned embryo, which are crucial for the early regulation and differentiation of the placenta.