Eutherians have 11 retrotransposon Gag-like (RTL)/sushi-ichi homolog (SIRH) genes presumably derived from a certain retrovirus. Accumulating evidence indicates that the RTL/SIRH play variety of roles in current mammalian developmental system, such as placenta, brain, and innate immune eutherian-specific manner. It has been shown functional role Paternally Expressed 10 (PEG10) placental formatio...