Abstract 339 – Transcriptome changes of peripheral blood related to delayed implantationin brown bears and polar bears

Asuka Nishijima, Yojiro Yanagawa, Naoya Matsumoto, Kyogo Hagino, Hideyuki
Sakamoto, Youichi Irie, Chihiro Sochi, Kanako Ushio, Hiroko Tanaka, Takashi Hayakawa

Mating and giving birth in a suitable condition is essential for mammals, those living in seasonal
areas. Embryonic diapause, which is known as delayed implantation in mammals, is a reversible
embryo dormancy before implantation. This interesting phenomenon allows mammals to
regulate the timing of mating and parturition. Ursids are one of the few families in which all
species are most likely to have delayed implantation. Ursids also have other unique
reproduction characteristics, such as pseudopregnancy, denning, and giving birth to unmatured
cubs. However, those unique reproduction characteristics make it difficult to detect their
pregnancy status. Our previous study showed that pregnant female brown bears’ peripheral
blood transcriptome was changed between estrus and delayed implantation period. In this
study, we collected peripheral blood from five individual male brown bears and three individual
pseudo-pregnant female brown bears in different periods. These bears’ peripheral blood
transcriptomes were compared with pregnant brown bears to identify pregnant female-specific
transcriptome changes. Pregnant brown bears’ peripheral blood transcriptome changes were
also compared with pregnant polar bears to verify those changes were common in other bear
species. Pregnant female-specific transcriptome changes related to delayed implantation could
be used as markers for an early pregnancy test in bears. Pregnancy test in bears could improve
their reproduction success in captives and contribute to ex-situ conservation.