Choroid Plexus Multi-Sensory Cilia Regulate Production of Cerebrospinal Fluid

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.