Appearance of B Chromosomes like Structures in Apodemus Peninsulae Primary Cell Culture

B chromosomes (Bs) have been found in all major eukaryotic clades. Specimens of Korean field mouse (Apodemus peninsulae) from populations inhabiting the mainland of the Russian Far East, Sakhalin and Stenina Islands were used. Animals from wild populations and Hokkaido Island in the Japan contain Bs while ones of Russian island populations do not have Bs. Cell cultures have been established from mouse tails fibroblasts from both island populations; in 3-5 passages, Bs-like elements appear in cultures cells. CENP-A chromatin immunoprecipitation (AChIP probe) on cell culture A. peninsulae from the Stenina Island has been undertaken. CENP-A precipitated DNA and probe of mouse centromere were used to mark all the heterochromatic regions of A. peninsulae and A. agrarius species. Bs-like elements from cultured cells of A. peninsulae show the same tendency as in wild populations: there are weakly and strongly labelled by AChIP probe amongst them Bslike elements, which appear in cultured cells of island populations (Stenina, Sakhalin) and wild populations of Hokkaido Island, are more similar in morphology compared to the Bs from the animals from Russian Far East. The data obtained suggest that the mice of the three islands 7-10 thousand years ago belonged to a single population, have a similar gene pool, and differ from the gene pool of continental populations of mice from the Far East.