A switch in collagen expression regulates cessation of distal tip cell migration in C. elegans.

Development of the C. elegans gonad requires precise regulation of cell migration. The distal tip cell (DTC) guides the elongation of the gonad into its final U-shaped structure before halting in adulthood. How cessation of elongation is regulated remains unknown. Here, we analyze an RNA-seq data set isolated from stage-specific DTCs to uncover the temporal gene expression dynamics underlying this process. Collagens emerged as the most enriched gene family during the transition from migratory larval stages to adulthood. We identify distinct temporal waves of collagen expression, culminating in a core adult-specific module that coincides with migration cessation. Functional analysis by RNAi depletion and analysis of mutant alleles revealed that many collagens are required for timely migration arrest, while others affect gonad shape. Perturbation of collagen remodeling enzymes phenocopied these defects. Our findings uncover a stage-specific collagen expression program in the DTC and suggest that basement membrane and cuticle collagens contribute to the termination of gonad elongation.