Cilia are microtubule-based cellular protrusions with diverse biological functions, including fluid
movement, cellular locomotion, environmental sensing, and signal transduction. Traditionally,
most cilia are classified based on differences in ciliary ultrastructure, biological function, and ciliary
motility, with primary cilia and motile cilia as the major categories. The primary cilia functions as
solitary sensory hubs to transduce extracellular stimuli into intracellular signaling pathways, and
the motile cilia exhibited coordinated beating to generate directional fluid movement. Choroid
plexus epithelial cells contain multi-sensory cilia that regulate the production of cerebrospinal fluid
(CSF) to support neuronal development and physiology. Using serial transmission electron
microscopy (TEM) and focus ion beam scanning electron microcopy (FIB-SEM), our preliminary
results suggest that the multi-sensory cilia of choroid plexus represent a distinct type of cilia,
exhibiting unique ultrastructural features, while resembling aspects of both primary cilia and motile
cilia. Defective ciliogenesis in choroid plexus causes hydrocephalus, at least in part, due to CSF
overproduction. Choroid plexus cilia are likely to play an important role in Shh signaling, as FoxJ1
deficient choroid plexus cilia no longer respond to Shh treatment in explant culture. We discovered
a functional connection between Shh signaling and Aqp1 expression. Hence, we hypothesize that
choroid plexus cilia are a unique type of multi-sensory that mediate Shh signaling to regulate CSF
production, at least in part, by regulating the expression of water channels and ion transporters.
Here, using a combined approach of advanced imaging techniques, mouse genetics, imaging
studies, cell biology and molecular biology, we propose to study the ciliary ultrastructures,
ciliogenesis mechanisms and biological functions of the multi-sensory cilia of choroid plexus. First,
using electron microscopy, FIB-SEM and super-resolution imaging, we will characterized the
ultrastructure of choroid plexus cilia, and define their developmental dynamics at different
developmental stages. Second, we will employ mouse genetics and genomics studies to identify
and characterize the ciliogenesis machineries of choroid plexus cilia. Finally, we will elucidate the
molecular mechanisms through which dynamic choroid plexus cilia mediate the Shh signaling to
regulate CSF production. Taken together, the proposed studies will structurally and functionally
define a new type of multi-sensory cilia in choroid plexus, and will generate important insights on
the molecular basis for the regulation of CSF production.