Ribosomal protein mutation suppresses gonadal leader cell migration defects in mig-17/ADAMTS mutants in Caenorhabditis elegans

The migration of the gonadal distal tip cells (DTCs) in Caenorhabditis elegans provides an excellent model for studying the migration of epithelial tubes during organogenesis. Mutations in the mig-17/ADAMTS gene cause misdirected migration of DTCs during gonad formation, resulting in deformed gonad arms. An amino-acid substitution in RPL- 20 corresponding to the mammalian RPL18a/eL20, a component of the 60S ribosomal large subunit, showed a slow growth phenotype and strongly suppressed the mig-17 gonadal defects. Slow-growing mutants clk-1 and clk-2 also suppressed mig-17, although weaker than rlp-20 mutants. MIG-17 recruits FBL-1C/fibulin-1C to the gonadal basement membrane to regulate DTC migration. Reducing the gene dosage of fbl-1 by half partially compromised the suppressor activity of the mutant rpl-20 gene on mig-17. Analysis using the mNeonGreen-FBL-1 reporter revealed that its localization to the gonadal basement membrane was significantly reduced in mig-17, whereas it was recovered to the wild-type levels in mig-17; rpl-20 double mutants. These results indicate that the rpl-20 mutation suppresses mig-17 gonadal defects through dual mechanisms: deceleration of growth rate and enhancement of FBL-1C recruitment to the gonadal basement membrane.