Host: The Japanese Society of Toxicology
Name : The 50th Annual Meeting of the Japanese Society of Toxicology
Date : June 19, 2023 - June 21, 2023
While it has been reported that parthenogenesis occurred naturally in some fish, reptiles, and birds, parthenogenetic embryos in mammals are embryonic lethal due to placental defects. This was thought to be due to the lack of expression of paternally expressed imprinting genes, which have essential functions for the development of placenta. To date, we have succeeded in isolating a novel paternally expressed imprinting gene, Peg10, and by generating Peg10-deficient mice, we have shown that Peg10 has essential functions in the formation of placenta. As Peg10 encodes two ORFs, each of which is similar to GAG and POL protein encoded by Sushi-ichi retrotransposon from Fugu fish, Peg10 is apparently derived from a retrotransposon. The Peg10 retrotransposon inserted into the genome in the common ancestor of mammals and has acquired important functions in placentation during mammalian evolution. Because retrotransposons lack the envelope proteins and other features of retroviruses, they cannot infect other cells, that is that they could not be horizontally transferred to other cells. Hence, how the Peg10 retrotransposon are horizontally transferred to the mammalian genome in the common ancestor of mammals has been a mystery. More recently, we have demonstrated the existence of an exosome-mediated mechanism of horizontal gene transfer. Furthermore, since Peg10 protein has been reported to bind to its own mRNA and localize to exosomes, we would like to introduce a new hypothesis for the horizontal gene transfer that occurred in the mammalian common ancestor.
