RFX4 and Hydrocephalus: Using an antibody specific to Reissner's fibers, we detected SCOs (Fig 2B) that were approximately 300 μm long on average (as seen in coronal serial sections) in the control mice, but they were only approximately 75 μm long on average in the Rfx4+/- mice with hydrocephalus (Fig 2C) (P< 0.01, n = 3).