Ectopic white-matter bundles in the anterior cingulate cortex (ACC) express 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) and lack synaptic antigens. Immunostaining of CNPase and synaptic markers in the ACC of representative (A, C, E, G) BTBR and (B, D, F, H) B6 brains. The images are nearly adjacent to those shown in Figure 3. (A) Focal white-matter bundles had strong immunoreactivity for CNPase, a marker of oligodendrocytes and myelinated fibers. An absence of markers of pre and postsynaptic antigens, as revealed by (C) drebrin (E) and vesicular glutamate transporter VGluT1 and (G) synaptophysin immunoreactivities, was seen in the anterior cingulate cortex of BTBR brain. (D, F, H) Staining with synaptic markers appeared to be uniform in the corresponding cortical region from B6 mice. Scale bar = 25 μm.