Ectopic white-matter bundles expressing myelin basic protein (MBP) immunoreactivity are present in the anterior cingulate cortex (ACC) of the BTBR mouse. Immunostaining of MBP in representative (A, C, E) BTBR and (B, D, F) B6 brains. (A, B) Absence of the corpus callosum was prominently seen at low magnification in BTBR. (C, D). At higher magnifications, small ectopic bundles of MBP-immunoreactive white-matter tracts were seen in the ACC of BTBR brain (arrows). (E, F) High magnification of MBP immunoreactivity in the cingulate cortex. Scale bars = (A, B) 500 μm, (C, D) 100 μm, (E, F) 50 μm.