Figure 5.

Histopathologic analysis of a 27 week human fetus with MCSG. (a) H&E stained coronal section from the forebrain of a 27 week gestational age fetus with microcephaly with simplified gyri (LIS-2601). Section is at the rostral end of the caudate along the A–P axis. Locations of higher magnification views for additional panels are indicated. (b, c) H&E stained section demonstrating cortical layering. Compared to a (b) 24 week gestational age control fetus, (c) LIS-2601 exhibits an abnormally thin cortical plate (despite being three weeks older), suggestive of a proliferative defect and absence of normal appearing layer II/III cells underneath the molecular layer. The dimensions of the marginal zone are relatively preserved. (d) In addition to a smaller cortical plate, neurons in the cortical plate display abnormal persistence of a radial columnar pattern and disorganized clustering (Kluver-Barrera stain). (e) Occasionally, eruptions of neuroglial cells (arrows) through the pial surface into the subarachnoid space are seen, as are occasional (f) streaky heterotopia in the intermediate zone, and (g) clusters of small, darkly staining cells in the outer subventricular zone that resemble dividing cells. Abbreviations: IZ, intermediate zone; GE, ganglionic eminence; LV, lateral ventricle; bc, body of the caudate; cc, corpus callosum; ctx, cortex; LGE, lateral ganglionic eminence; MGE, medial ganglionic eminence; MZ, marginal zone; CP, cortical plate; SP, subplate; SVZ, subventricular zone; VZ, ventricular zone.