Maternal choline availability alters the localization of p15Ink4B and p27Kip1 cyclin-dependent kinase inhibitors in the developing fetal rat brain hippocampus

Previously we have shown that changes in maternal dietary choline are assoc iated with permanent behavioral changes in offspring. Importantly, in adult male rats, feeding a choline-deficient diet increases the localization of cyclin-dependent kinase inhibitors (CDKIs) in the liver, whereas young adul t CDKI knockout mice (p15Ink4B or p27Kip1) exhibit behavioral abnormalities . Thus, maternal dietary choline-CDKI interactions could underlie the chang es we observe in fetal hippocampal development and cognitive function in of fspring. Here, timed-pregnant rats on embryonic day E12 were fed the AIN-76 diet with varying levels of dietary choline for 6 days, and, on E18, fetal brain sections were collected, and the localization of CDKI proteins was s tudied using immunohistochemistry and an unbiased image analysis method. In choline-supplemented animals compared to controls, the number of cells wit h nuclear immunoreactivity for p15Ink4b CDKI protein was decreased 2-to 3-f old in neuroepithelial ventricular zones and adjacent subventricular zones corresponding to the fimbria, primordial dentate gyrus and Ammon's horn reg ions in the fetal hippocampus. In contrast, maternal dietary choline defici ency significantly decreased nuclear p15Ink4b immunoreactivity in the neuro epithelial layer of the dentate gyrus. Unlike p15Ink4b, the CDKI protein p2 7Kip1 was observed almost exclusively in the cytoplasm, though the protein was distributed throughout the proliferating and postmitotic zones in the E 18 fetal hippocampus. Maternal dietary choline supplementation decreased th e cytoplasmic staining intensity for p27Kip1 throughout the fetal hippocamp us compared to control animals. Choline deficiency increased the staining i ntensity of p27Kip1 throughout the hippocampus in association with increase d expression of MAP-1 and vimentin proteins. These results link maternal di etary choline availability to CDKI protein immunoreactivity and commitment to differentiation during fetal hippocampal development. Copyright (C) 2001 S. Karger AG, Basel.