ARL13B regulates juxtaposed cilia-cilia elongation in BBSome dependent manner in Caenorhabditis elegans

The interaction of cilia with various cellular compartments, such as axons, has emerged as a new form of cellular communication. Cilia often extend in proximity to cilia from neighboring cells. However, the mechanisms driving this process termed juxtaposed cilia-cilia elongation (JCE) remain unclear. We use fluorescence-based visualization to study the mechanisms of coordinated cilia elongation in sensory neurons of <i>Caenorhabditis elegans</i>. Conducting a selective gene-based screening strategy reveals that ARL-13/ARL13B and MKS-5/RPGRIP1L are essential for JCE. We demonstrate that ARL-13 modulates JCE independently of cilia length. Loss of NPHP-2/inversin along with HDAC-6 enhances the cilia misdirection phenotype of <i>arl-13</i> mutants, while disruption of the BBSome complex, but not microtubule components, partially suppresses the JCE defects in <i>arl-13</i> mutants. We further show changes in the phospholipid compositions in <i>arl-13</i> mutants. We suggest that ARL-13 contributes to JCE, in part, through the modulation of the ciliary membrane.