Fig. 1.

rec8a is required for female meiosis. (A and B) Periodic acid–Schiff (PAS) staining of 2.5-mo-old wild-type (A, n = 3) and rec8a^∆22−/− (B, n = 2) XX gonads. Magnified images of zygotene (A′ and B′), pachytene (A′′ and B′′), and diplotene (A′′′) oocytes, indicated by arrowheads, are shown in the Insets. Bouquet chromosomal structure and paired bivalents were observed in zygotene and pachytene oocytes, respectively. Asterisks in A and B indicate the ovarian cavity, a typical ovarian structure of medaka. (Scale bars: 100 μm [A and B], 10 μm (A′, A′′ A′′′, B′, and B′′). (C–H) Immunohistochemistry (IHC) of 10-dph rec8a^∆22+/− (C–E, n = 5) and rec8a^∆22−/− (F–H, n = 4) XX ovaries. In the Top, samples were stained for a synapsis marker SYCP1 (green) and a germ cell marker OLVAS (blue) with DAPI staining (gray). Gray scale images of SYCP1 signals are shown in the Bottom. Germ cells indicated by dotted lines represent zygotene (C and F), pachytene (D), diplotene (E), and pachytenelike stages (G and H) characterized by cellular sizes and chromosomal structures. (Scale bar: 10 μm.) (I and J) Immunostaining of XX adult ovaries of wild-type (I, n = 3) and rec8a^∆8−/− fish (J, n = 3) for cleaved CC-3 (green) and a female mitotic germ cell marker FOXL3 (blue) with DAPI staining (gray). Arrowheads in J indicate CC-3-positive germ cells with DAPI-dense DNA fragments. (Scale bar: 50 μm.) (K) Percentage of CC-3-positive germ cells in pachytenelike oocytes (length of long axis: 15–25 µm, SI Appendix, Table S1) in wild-type and rec8a^−/− XX ovaries. Values are means ± SD from three ovaries. P value was calculated by two-tailed Student’s t test. Exact values are shown in SI Appendix, Table S2.