PGC-like germ cells in <i>dazl</i> mutants have the potential for feminization of gonads.

<p>(A–C) Morphology of type I germ cells observed by immunohistochemistry with OLVAS (green: germ cell) and DAPI staining (gray). Arrowheads indicate nucleoli. <i>dazl</i>–/–germ cells at hatching stage (B) are morphologically similar to wild-type PGCs at stage 30 (C) in terms of the small cell-size and a nucleolus size compared to that of wild-type type I germ cells at hatching stage (A). (D–G) <i>In situ</i> hybridization of <i>foxl3</i> and <i>meioC</i> in <i>dazl</i>–/–XX gonads at hatching stage. Arrowheads indicate <i>foxl3</i> or <i>meioC</i> negative germ cells. A black dotted line indicates the region of gonads. (H) The number of germ cells in <i>dazl</i>–/–XX and XY gonads at hatching stage (0 dph) and 10 days post hatching (10 dph). * <i>p</i><0.05, **<i>p</i><0.01 by <i>t</i>-test. (I and J) The secondary sex characteristics of medaka are defined by the shape of the dorsal and anal fins. Four of nine (4/9) ex2-Δ34 and 4/12 ex3-Δ2+7 <i>dazl</i>–/–XX were male (I), and 5/9 ex2-Δ34 and 8/12 ex3-Δ2+7 <i>dazl</i>–/–XX were female (J). (K) RT-PCR analysis of adult gonads in XX <i>dazl</i>–/–mutants. The expression pattern of germ cell-deficient gonads from <i>dazl</i>–/–XX females was similar to that of <i>dazl</i>+/–ovaries. Scale bars are 10 μm (A–G) and 1 mm (H and I).