Fig. 2.

Midline brain defects in mutant mice and in Coffin–Siris syndrome (CSS) patients. a–d Hematoxylin–eosin-stained coronal sections of 3–4-week-old postnatal animals. One control animal (a) and three mutant animals with increasing phenotypic severity (b–d) are shown. Note the increased distance between the cerebral hemispheres (brackets) in mutant animals that is most severe in caudal sections at the level of the diencephalon. Black arrows point to a midline cleft between the two halves of the thalamus. ac anterior commissure, cc corpus callosum, cp choroid plexus, lv lateral ventricle, 3v third ventricle. Scale bars: 1 mm. e–j Magnetic resonance imaging scans of three CSS individuals with a germline mutation in SMARCE1 (patient 7, e, h), ARID1B (patient 4, f, i, j), and SMARCB1 (patient 1, g). Note the short and thin CC in e, hypoplastic septum pellucidum, small anterior and hippocampal commissures (h) and Dandy–Walker variant (asterisk in e) with a large posterior fossa, vermis hypoplasia, and cerebellar dysplasia in patient 7. Patient 4 lacks the CC, the anterior and hippocampal commissures, and the septum pellucidum (f, i). Moreover, a voluminous CP is present (arrowheads in j). A short and stubby CC is present in patient 1 (g)