Supplementary Figure 15: Calretinin⁺ cells in the cortex are almost exclusively non-proliferative.

a) Human PCW12 frontal section stained for calretinin (CALB2), DLX2, and Ki67 to analyze the proliferative state of CALB2⁺ cells. While most were non-proliferative, DLX2⁺ CALB2⁺ cells in the CGE occasionally expressed the proliferation marker Ki67 (not shown). Many newborn/migrating neurons in the CGE and LGE expressed CALB2 (not shown). In the cortex, CALB2 labeled many interneuron precursors migrating in the germinal region or in the cortical plate, certain neurons of layer I, and thalamocortical fibers. Most CALB2⁺ cells in the cortex coexpressed DLX2 and COUP-TFII. Th, thalamus; dCx, dorsal cortex; vCx, ventral cortex. B-d) We searched cortical germinal regions for proliferating CALB2⁺ cells. Many examples of apparent overlap for CALB2 and Ki67 signals were observed, but upon closer examination it was clear that essentially all of these were false double positives from distinct cells lying one atop the other. Such an example is shown in c, with optical z sections showing the separate layering of Ki67 and CALB2/DLX2 signals (arrows). Only one out of 766 DLX2⁺ CALB2⁺ cells examined expressed Ki67 (arrowhead in d, single optical section). Similar to other isolated examples of DLX2⁺ Ki67⁺ cells that we observed in cortex, this cell was less than 0.5 mm outside the CGE, suggesting it was a CGE-derived interneuron precursor that proliferated after entering the cortex, and it also expressed COUP-TFII (not shown). We also examined cortical CALB2+ cells outside the germinal region, but did not find any that expressed Ki67. Panel e shows CALB2⁺ cells in cortical layer I, with the nearby neurovasculature containing two Ki67⁺ cells and three COUP-TFII⁺ pericytes.

Source data