Agenesis of the corpus callosum in ddN strain mouse associated with unusual facial appearance (flat-face).

In the course of an experiment involving brother-sister matings between ddN strain mice, mice occurred with an unusual facial appearance (flat-face). Subsequently, 4 mice with flat-face were bred from the litters of the second birth (ca. 10% frequency). This flat-face was assumed to be the result of a malformed short nose, hypoplastic maxilla and mandible, and hypertelorism. These 4 flat-face mice exhibited no significant delays in growth, motor ability or the development of learning ability. Histologically, they were all characterized by an almost total absence of callosal fibers and the presence of abnormal longitudinal neuromatous bundles. Therefore, the flat-face mice may be useful as experimental animals for brain research, as one can easily judge that they lack the corpus callosum from the facial appearance.