“Genetic Characterization of the progressive hydrocephaly (prh) Mouse Mutant”
Shawn Vuong, June Goto, Rolf Stottmann, Kenneth Campbell, and Francesco Mangano
Hydrocephalus is the most common brain malformation found at birth. Although the surgical intervention can greatly ameliorate outcomes, currently there is no medical cure for this condition. In addition, about 30% of these cases have unknown etiology. In order to identify molecular mechanisms involved in congenital hydrocephalus development, we investigated the genetic mutation responsible for progressive hydrocephaly (prh) mouse mutant, which was isolated in a previous forward genetic screening for severe neonatal onset hydrocephalus phenotype in mice. We performed a whole-genome sequencing in the mutant mouse and found a single nucleotide mutation candidate within Ccdc39 (coiled-coil domain containing protein 39) gene, one of primary ciliary dyskinesia genes critical for motile cilia functions. Western blotting and cDNA sequencing analysis show that the mutation affects proper mRNA splicing of the Ccdc39 gene and results in loss of the protein to undetectable levels. In immunohistochemistry, we found Ccdc39 is highly expressed in choroid plexus epithelium cells in the developing wild type mouse brain, but is missing from that of prh mutant. Choroid plexus is the major cerebrospinal fluid production site and has transiently motile multi-cilia in neonatal period. The transmission electron microscopy study revealed microtubule structures of choroid plexus cilia axoneme is disrupted in the prh mutant mice. In vitro trancytosis assay using primary cultured mouse choroid plexus cells showed altered fluid transferring rate in the mutant derived cells. Together, these data indicate that loss of Ccdc39 may disrupt the motility of choroid plexus cilia in the developing brain and suggest the possible involvement of choroid plexus cilia in the development of congenital hydrocephalus.