PEG10 (paternally expressed 10) exists in the marsupial tammar wallaby and showed virtually
exclusive monoallelic expression in 4 embryos. Paternal expression was confirmed in two embryos and
one yolk sac sample (Suzuki
S et al, 2007).
Insertion of PEG10 by retrotransposition occurred in the therian (marsupial and placental) ancestor
since it is not present in the egg-laying platypus, a prototherian mammal.