Regulates the timing and orientation of distal tip cell migration during gonadal development. May act in parallel to cacn-1 and Rac GTPases to control the anterior and posterior migration of distal tip cells. Expressed in the nucleus of distal tip cells and in the cytoplasm of germ cells. Localized to the peripheral chromatin region of the nucleus. Expressed in distal tip cells and in germline cells. Expressed in the nucleus of distal tip cells until larval stage L4 when expression decreases onwards to late adulthood. Defective cessation of distal tip cell migration from the dorsal muscle towards the mid-body during gonadal development. RNAi-mediated knockdown of cacn-1 in mig-39 null animals results in a strong overshoot phenotype in which anterior and posterior distal tip cells. RNAi-mediated knockdown of Rac GTPase, Rac-2, in double mig-39 and either ced-10 or mig-2 (which are also Rac GTPases) null animals, suppresses the overshoot phenotype in mig-39 null animals.