The blood-brain barrier (BBB) and blood-cerebrospinal fluid (blood-CSF) barrier are important CNS barriers that protect the brain from potentially harmful toxins, pathogens, and/or substances. The blood-CSF barrier is formed by tight junctions between epithelial cells in the choroid plexus, a small organ in the brain that serves to produce cerebrospinal fluid and remove metabolic wastes from the brain. We are interested in understanding how choroid plexus epithelial cells are assembled to establish the unique barrier integrity and properties, thereby regulating the CNS microenvironment and homeostasis. Developmental understanding of the blood-CSF barrier genesis will help to repair its barrier impairment in structure and function.