PTPN20 and Hydrocephalus: In contrast, the expression of phosphorylated Na-K-Cl cotransporter 1 (pNKCC1) in the choroid plexus was significantly increased in mice with Ptpn20 gene deletion, suggesting that the overexpression of pNKCC1 on the epithelial cells of the cerebral choroid plexus, which results in excessive cerebrospinal fluid secretion, may be involved in hydrocephalus in HTX rats.