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. 2023 Oct 16;10(10):ENEURO.0054-23.2023. doi: 10.1523/ENEURO.0054-23.2023

Figure 4.

Figure 4.

The ΔNp73-Cre allele drives reporter expression in Cajal–Retzius cells and adult dentate gyrus granule neurons in different reporter lines. A, Left, Overview of ArchT-EGFP expression in the DG of 10-week-old ΔNp73-Cre; LSL-ArchT-EGFP mice. Note the extensive ArchT-EGFP fusion protein expression in the dendrites and axons of DG granule neurons. Scale bar, 200 μm. Right, Representative high-magnification images. ArchT-EGFP expression is found in the plasma membrane of TRP73+ CR cells (white arrows) and TRP73– DG granule neurons (yellow arrows). Scale bar, 50 μm. B, tdTomato reporter expression in the DG of 10-week-old (10W) ΔNp73-Cre; LSL-2XChETA-P2A-tdTomato mice. In these mice, ChETA and tdTomato are expressed separately and not as fusion proteins. tdTomato expression is found in the cytoplasm of TRP73+ CR cells (white arrows) and TRP73– DG granule neurons (yellow arrows). Scale bar, 50 μm. C, HA-hM3D reporter expression in the dentate gyrus of the ΔNp73-Cre; LSL-HA-hM3D mice. At P14, reporter expression is restricted to CR cells (white arrows). By 5 weeks of age, reporter expression is also observed in DG granule neurons (yellow arrows). Scale bar, 50 μm. Quantification of reporter-expressing granule neuron density is shown to the right. Cell densities were normalized to the length of the hippocampal fissure (HF) and the molecular layer of the DG infrapyramidal blade (loML). D, Quantification of reporter-expressing CR cell and granule neuron densities, as well as CR cell-targeting specificity in the three mouse lines. E, Representative confocal images of reporter expression in the two hemispheres of a ΔNp73-Cre; LSL-ArchT-EGFP mouse (top) and a ΔNp73-Cre; LSL-HA-hM3D mouse (bottom). Yellow arrows indicate reporter-expressing DG granule neurons. Scale bars, 200 μm. Quantification of variation indexes (the difference of cell densities between the two hemispheres divided by the sum of the cell densities) are shown to the right. V3, Third ventricle; SLM, stratum lacunosum-moleculare; GL, granular layer. Data are presented as scatter plots with all data points shown and error bars representing ±SD. Each data point is an individual animal, whereby three sections were measured for each animal. Statistical analyses were performed using nested t test or nested one-way ANOVA with Tukey’s post hoc test. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. The images that show the lack of reporter expression in the hippocampus of the LSL-tdTomato mice are provided in Extended Data Figure 4-1. The data that demonstrate reporter expression in the neocortex are shown in Extended Data Figure 4-2.