The Csb-deficient rats (CsbR571X) demonstrated brain abnormalities such as cerebellar atrophy, thinning of the layers of the cerebellar cortex and degeneration of Purkinje neurons, which were features that have already been seen in some CS mouse models (such as Xpg -/-), but they also displayed reduced myelination in the cerebellum, the key aforementioned notable feature of the human CS neurologic disease, a characteristic not seen in CSB mice [72,73]. The gene discussed is ERCC6; the disease is Cowden syndrome 1.