Fig. 4: Tau-Cy5 impairs the connectivity of newborn granule neurons

(a) Representative images of 8-week-old RFP-labeled newborn granule neuron dendrites of PBS-Cy5- and Tau-Cy5-injected mice showing their dendritic spines. The distinct spine morphologies—stubby (orange triangles), thin (yellow triangles), and mushroom (green triangles)—are shown in high-power magnifications. (b–d) Quantification of the density of dendritic spines (b), spine head volume (c) and spine Max-DTS (d) of newborn granule neurons of PBS-Cy5- and Tau-Cy5-injected mice. Tau-Cy5 injection decreases the density of dendritic spines and alters their morphology. (e) Quantification of the percentages of stubby, thin and mushroom spines in newborn granule neurons of PBS-Cy5- and Tau-Cy5-injected mice. Tau-Cy5 injection altered the proportion of the different types of spines, decreasing that of mushroom spines and increasing that of stubby ones. (f–h) Quantification of the head diameter of stubby (f), thin (g) and mushroom (h) dendritic spines of newborn granule neurons of PBS-Cy5- and Tau-Cy5-injected mice. (i–k) Quantification of the Max-DTS of stubby (i), thin (j) and mushroom (k) dendritic spines of newborn granule neurons of PBS-Cy5- and Tau-Cy5-injected mice. Tau-Cy5 injection increased the head diameter of every type of spine and decreased the Max-DTS of thin and mushroom ones. (l,m) Representative images (l) and quantification (m) of the newborn neuron MFT area in the CA3 region of PBS-Cy5- and Tau-Cy5-injected mice. Tau-Cy5 injection reduced the area of newborn neuron MFTs. Graphs in (b–d, f–k, m) represent mean ± SEM; *0.05 > p ≥ 0.01, ***p < 0.001 (Mann–Whitney U test). Graph in (e) represent percentages. ***p < 0.001 (χ2 test). n = 4 mice per experimental condition. White scale bar: 3 µm. Red scale bar: 1 µm. Green scale bar: 20 µm