Aberrant alpha-smooth muscle actin expression in the lateral ventricle of knockout rats.

() is a causative gene for genetic hydrocephalus found in hemorrhagic hydrocephalus () mice. The knockout (KO) rat has subcortical heterotopia with frequent brain hemorrhage as seen in mice. In this study, we report aberrant alpha-smooth muscle actin (α-SMA) expression in the wall of lateral ventricle of the KO rats. The α-SMA-positive cells were distributed at the dorsal, medial, and lateral regions of the lateral ventricle of KO rats. The expression of α-SMA was first observed on postnatal day 20 (P20) and became noticeably stronger at P26 when hydrocephalus was prominent. Double immunofluorescence showed co-expression of α-SMA with nestin, vimentin, and glial fibrillary acidic protein in the ventricular lining of KO rats. Therefore, we conclude that α-SMA-positive cells may represent an immature subpopulation of cells at adult age around the lateral ventricle of KO rats.