CLDN11 and nervous system disorder: Our findings of claudin-11 in the arachnoid blood-CSF barrier and EAAT1 and IL-13Rα2 in the outer CSF-brain barrier confirm their barrier properties and the spatiotemporal distribution of YKL-40/BLBP/SSEA-4 further establish the necessity of regarding these interfaces as separate entities, since they may play different roles in normal brain development and possibly in several neurological disorders.