FIGURE 4.

Nuclear staining of the defective gonad in pat-3(Y804E) and him-4 mutant animals. (A) A linker cell migration trajectory of N2 male gonad. Male gonad initiates migration on the surface of ventral muscle (Hedgecock et al., 1987). The linker cell (arrow end) at the anterior tip of male gonad navigates the elongation of gonad tube, initiating its anterior migration at early L2 larval stage. Later it turns toward the dorsal muscle, starts to migrate posteriorly, slides down obliquely to the ventral side, and finally fuses to a rectal cell at the posterior end of the body. At the posterior end of the gonad, the distal tip cell (solid dot end) stays in the midbody. (B) A diagram of a pat-3(Y804E) or him-4 mutant gonad. The mutant gonad displays abnormal turns. The linker cell (arrow) fails to make dorsal turns and loops around the ventral half instead. In many cases, distal tip (solid dot) appears extended toward the posterior end of the body. (C) Nuclear staining of pat-3(+) male, showing a typical male gonad appearance. From the anterior, the turning gonad arm is filled with undifferentiated germ cell nuclei. (D) Nuclear staining of pat-3(Y804E), unlike the pat-3(+) male gonad in panel (C), this gonad displayed sperm nuclei located anteriorly to undifferentiated germ cell nuclei. Small arrows indicate ectopic sperm. (E,F) Alleles of him-4 mutants; nuclear staining patterns are similar to that of pat-3(Y804E). (G) pat-3(Y792/804F); him-4(e1267) lon-2(e678), showing the gonad with rescued morphology. This gonad displayed sperm nuclei located posterior to undifferentiated germ cells. Ventral side was determined by the location of male tail fan opening and ventral nerve cord staining. Sperm nuclei (small puncta, open arrow heads) are located posterior to undifferentiated germ cell nuclei (closed arrow heads). Worms were fixed with methanol and stained with 0.1 μg/ml DAPI in M9 buffer (see section “Materials and Methods”). The solid triangles on the left indicate the anterior end of animals. Bar = 100 μm.