Figure 9.

Differential loss of bipolar calretinin-expressing neurons in Dlx1/2–/– cortical cultures. A, Cultures of dissociates cortex from E18.5 wild-type embryos produce large numbers of calretinin-expressing cells, few of which colabel with reelin (B), a marker of Cajal-Retzius cells. C, Cultures from Dlx1/2 mutants show a large reduction of calretinin-labeled cells. D, Nearly all of the remaining calretinin+ cells from the mutant cultures strongly express reelin and have a large unipolar morphology that is suggestive of a Cajal-Retzius cell (Pappas and Parnavelas, 1998) (quantified in F; there were significantly lower percentages of bipolar and higher percentages of unipolar calretinin+ cells in the Dlx1/2–/–; p < 0.0001). This nearly complete loss of small bipolar reelin-negative calretinin-expressing cells stands in marked contrast to the more modest reductions of somatostatin- or NPY-expressing interneurons (quantified in E). Scale bar, 100 μm. *p < 0.05; paired t test.