Fig. 2. Developmental expression and localization of XCds1. (A) Expression of XCds1 during oogenesis from stage I to VI. (B) Expression of XCds1 during oocyte maturation. Immature oocytes (IM) were treated with progesterone to induce maturation and GVBD occurred at about 2 hours. Metaphase arrest of meiosis II occurred at about 4 hours after GVBD. (C) Expression of XCds1 during embryogenesis. Embryos were staged according to Nieuwkoop and Faber (Nieuwkoop and Faber, 1956). (D) Embryos were untreated (-) or treated with hydroxyurea (HU) or aphidicolin (APH) as early as stage 8 to inhibit DNA replication and then sampled at stage 9, post-MBT. Note that mobility shift of XCds1 (upper arrow) was detectable in hydroxyurea- or aphidicolin-treated post-MBT embryos, while it was undetectable in untreated post-MBT embryos (-), as in stage-6 untreated embryos (pre-MBT). Oocytes or embryos were subjected to western blot analysis with anti-XCds1 antibody. Each lane was loaded with proteins equivalent to one oocyte or embryo. (E) Nuclear localization of XCds1 in immature Xenopus oocytes. An immature oocyte was dissected into cytoplasmic (C) and nuclear (N) fractions. Proteins were resolved by SDS-PAGE and visualized by western blot with anti-XCds1 (top) or anti-XChk1 (bottom) antibodies. Proteins equivalent to one quarter of the cytoplasmic or nuclear fraction were analyzed.