The
vab-10 gene encodes cytoskeletal linker proteins called spectraplakins, and the
vab-10(
tk27) mutant exhibits abnormal gonad formation due to the defective migration of gondal distal tip cells (DTCs). We found that
vab-10(
tk27) lacks DTC-specific VAB-10B isoform(s). When wild type DTCs turn dorsally, their nuclei are first relocated to the dorsal side of the cells. Although the DTCs are attracted dorsally by the UNC-6/netrin guidance in this mutant, their nuclei stayed at the anterior or posterior ends rather than were relocated to the dorsal side. The actin and microtubul e (MT) cytoskeletons exhibited filamentous structures in the wild type DTCs which are often aligned along the migratory axis. In
vab-10(
tk27) , although the alignment of F-actins was affected mildly, that of MTs was severely disorganized. Interestingly, a
vab-10 mini gene encoding only the actin-binding and the MT-binding domains was sufficient to rescue the mutant phenotype. Because UNC-83 interacts with UNC-84 in the nuclear membrane and recruits kinesin-1 to regulate nuclear migration in
hyp7 cells (Meyerzon et al., 2009), we examined migration of the DTC nuclei in the
unc-83 and
unc-84 mutants. We found that nuclear relocation in the DTCs at the first turn is compromised as in the
vab-10(
tk27) mutants. We propose that VAB-10B/spectraplakin acts to regulate the alignment of MTs by linking F-actins and MTs in DTCs, which may facilitate proper alignment of MTs along which the nuclei are translocated in a kinesin-dependent manner.