MEX-1 first appears at low levels in mature oocytes, and increases after fertilization. MEX-1 is most abundant in the posterior half at the
late-1-cell stage, and continues in the germ line cytoplasm until P4 divides. During the early cleavage stages, MEX-1 is present in the cytoplasm of each of the germline blastomeres, and is not detected in nuclei. After each division of a germline blastomere, MEX-1 is detected initially in both daughters, but then disappears from the somatic daughter later in that cell cycle.