Postnatal development of the wild-type and weaver cerebellum after embryonic administration of propylthiouracil (PTU).

In this study we used propylthiouracil (PTU), a thyroid hormone-inhibiting compound, to render +/+, wv/+, and wv/wv embryos hypothyroid in order to test if the appearance of external granule layer (EGL) cell death in the weaver cerebellum is affected by alteration of granule cell development. At birth, the number of EGL cells in the PTU-treated cerebellum was reduced, compared to control animals, by 50%. Also, the amount of cell death was reduced in the PTU-treated wv/wv cerebellum. As adults, no differences were seen between PTU-treated and untreated mutant or normal cerebella. If the hypothyroid treatment that results in a 50% decrease in EGL cell number is due to an extension of cell cycling time, then the expression of the weaver phenotype of cell death likely follows granule cell exit from the cell cycle.