PKD-2 and LOV-1 constitute a putative mechanosensory transient receptor potential (TRP) channel-receptor polycystin complex that is required for male mating behaviors. PKD-2 and LOV-1 localize to cilia found at the ends of dendrites of male-specific sensory neurons, including the head CEM and the tail RnB and HOB neurons.
pkd-2 and
lov-1 mutants are defective in hermaphrodite contact response and exhibit location of vulva (Lov) defects. Mutations in the human homologs of
lov-1 and
pkd-2, PKD1 and PKD2, lead to autosomal dominant polycystic kidney disease (ADPKD). The mammalian polycystins localize to cilia on renal epithelial cells. We use C. elegans as a tool to identify molecules required for polycystin ciliary localization.
We previously screened for mutants exhibiting PKD-2::GFP mislocalization (Bae et al. 2008). In the ciliary localization (Cil) defective mutant
my16, we observe an abnormal accumulation of PKD-2::GFP in CEM cilia and along the distal dendrites of the RnB and HOB neurons. We are interested in mapping
my16 and in determining the effects of the mutation on male sensory behaviors. We are also examining genetic interactions between
my16 and other components of the PKD pathway.
With SNP and deficiency mapping,
my16 was determined to be on LGI between -2.26 cM and +0.08 cM. In conjunction with Whole Genome Sequencing, this limited
my16 to one of two ORFs. Both a fosmid and a single gene construct containing ORF1 but not ORF2 rescued the
my16 Cil phenotype. We conclude that
my16 is a missense mutation in ORF1, which we hereafter refer to as
cil-7.
cil-7 appears to encode a nematode-specific protein with orthologs in Caenorhabditis species and Pristionchus pacificus. CIL-7 has four coiled-coils, but no other distinguishing domains. Reinke et al. 2004 found
cil-7 expression to be male sex-specific. We are currently determining gene expression and protein subcellular localization of CIL-7. We hypothesize that
cil-7 affects microtubule-based ciliary transport and will determine the mechanism by which
cil-7 regulates PKD-2 ciliary localization. These studies will provide important insight into how sensory receptors, including PKD-2, localize to cilia.