SPINT1 Expressed in Epithelial Cells of Choroid Plexus in Human and Mouse Brains

The functional significance of the choroid plexus (CP), such as in the control of circadian rhythm as well as production of cerebrospinal fluid, is attracting attention. Transepithelial and junctional transport between epithelial cells of CP plays an important role in its function. Recently, an epithelial cadherin, E-cadherin, as well as non-epithelial cadherins were confirmed to be expressed in CP epithelial cells. The serine protease inhibitor Kunitz type 1 (SPINT1) is expressed in many kinds of epithelial cells and affects epithelial developmental function by controlling E-cadherin expression. However, it has not been confirmed whether SPINT1 is expressed in epithelial cells of CP. Thus, in this study, we examined whether SPINT1 is expressed in CP epithelial cells by immunohistochemistry and RT-PCR. Immunohistochemical expression of SPINT1 was noted in the cytoplasm of epithelial cells of humans and mice, and mRNA of SPINT1 was expressed in samples derived from the CP of mice. SPINT1 was typically expressed in CP epithelial cells with E-cadherin and Smad-interacting protein (SIP1), an E-cadherin transcriptional repressor. Some enlarged epithelial cells showed strong SPINT1 signals. These findings indicate that SPINT1 is expressed in epithelial cells of CP in relation to E-cadherin expression.