Figure 4.

Molecular markers highlight layer-specific effects of tailless deletion. Panels show pairs of sagittal sections through parietal cortex of wild-type (+/+) and mutant (−/−) mice stained immunohistochemically for SMI-32 (left pair of panels) or for calbindin D-28k (right pair of panels). Large pyramidal cells immunoreactive for SMI-32 are present in deep layers (i.e. layer V) of both mouse strains (e.g. white arrows). Note also that these neurons support prominent apical dendrites (e.g. black arrowheads), exhibiting a relatively normal morphology in tlx−/− compared with wild-type cortex. Calbindin-D28k-immunoreactive neurons (right panels) are scattered diffusely throughout deep cortical layers. Their numbers are especially enriched, however, in a superficial stratum that coincides with cytoarchitectonically defined layers II/III. Note that calbindin-immunoreactive neurons in tlx−/− mice are distributed in a pattern resembling that observed in wild-type mice, except that the superficial stratum of these cells is abnormally thin. Cortical layers as deduced from nearby sections stained with thionin are indicated by Roman numerals. Bar = 300 µm for all panels.