Fig. 5. SPN-4 protein distribution. (A-J) SPN-4 and POS-1 distribution. Wild-type gonads and embryos were stained with an anti-SPN-4 antibody (red; A,B,E,H) and an anti-POS-1 antibody (green; C,F,I). (D,G,J) Merged images including DAPI-stained images (blue). Anterior is leftwards, posterior is rightwards, dorsal is upwards and ventral is downwards. Scale bars: 10 µm. (A) Oocytes. SPN-4 was detected in oocytes from adult animals. (B-D) One-cell embryo just before the first cleavage. (E-G) Two-cell stage embryo. (H-J) Four-cell stage embryo. SPN-4 was uniformly present in the cytoplasm up to the two-cell stage, then began to localize to the posterior blastomeres P₂ and EMS. Co-localization of SPN-4 and POS-1 was mainly observed in the cytoplasm of the posterior blastomeres, including the germline (D,G,J; yellow regions) and P granules (yellow dots, see Fig. 6). (K) SPN-4 in spn-4 embryo at four-cell stage.