C. elegans vab-6 encodes a KIF3A kinesin and functions cell non-autonomously to regulate epidermal morphogenesis

Cells undergo strict regulation to develop their shape in a process called morphogenesis. Caenorhabditis elegans with mutations in the variable abnormal (vab) class of genes have been shown to display epidermal and neuronal morphological defects. While several vab genes have been well-characterized, the function of the vab-6 gene remains unknown. Here, we show that vab-6 is synonymous with a subunit of the kinesin-II heterotrimeric motor complex called klp-20/Kif3a, a motor well-understood to be involved in developing sensory cilia in the nervous system. We show that certain klp-20 alleles cause animals to develop a bumpy body phenotype that is variable but most severe in mutants containing single amino-acid substitutions in the catalytic head-domain sites of the protein. Surprisingly, animals carrying a klp-20 null allele do not show the bumpy epidermal phenotype suggesting genetic redundancy and only when mutant versions of the KLP-20 protein are present, the epidermal phenotype is observed. The bumpy epidermal phenotype was not observed in other kinesin-2 mutants, suggesting that KLP-20 is functioning independently from its role in intraflagellar transport (IFT) during ciliogenesis. Interestingly, despite having such a prominent epidermal phenotype, KLP-20 is not expressed in the epidermis, strongly suggesting a cell non-autonomous role in which it regulates epidermal morphogenesis.