Fig. 1: MCU expression is significantly reduced in CA2 neurons of cKO mice.

A. Representative images of MCU (yellow) and RGS14 (magenta) immunostaining in CTL (i) and cKO (ii) mice. Higher magnification images of CA2 neurons are shown to the right. Asterisks indicate RGS14-positive CA2 neurons.

B. Quantification of the number of RGS14+ CA2 neurons expressing MCU (CTL: 39.8 ± 2.6 neurons, N=7 mice, cKO: 4.3 ± 1.1 neurons, N=8 mice, two-tailed unpaired t-test, p<0.0001)

C. The total number of RGS14-positive CA2 neurons does not differ between CTL and cKO mice (CTL: 45.4 ± 2.6 neurons, cKO: 39.9 ± 3.1, two-tailed unpaired t-test, p= 0.2042)

D. Comparison of MCU fluorescence intensity in CTL and cKO mice in CA2, CA1, dentate gyrus (DG) and neighboring cortex (CTX). Data were normalized to the CTL average. (two-way ANOVA, overall effect of genotype F (1, 52) = 22.45, p<0.0001; overall effect of subregion F (3, 52) = 17.80, p<0.0001, interaction F (3, 52) = 12.74, p<0.0001; sidak’s post hoc test CTL v. cKO CA2 p< 0.0001).

E. Line plot analysis of MCU fluorescence intensity across CA2 layers in CTL and cKO mice. Data are normalized to the CA2 CTL average.

F. Representative super resolution image of MCU (yellow) in genetically labeled CA2 dendrites (magenta) using expansion microscopy. Scale = 200 μm and 25 μm (A) and 5 μm, ExM adjusted (F). ****p<0.0001