Fig. 3: Knockdown of HTRA2 in hippocampal neurons of 7-month-old WT mice impairs synaptic and cognitive function.

A The scheme of AAV2/9 constructs expressing HTRA2 shRNA (AAV-shHTRA2) and scrambled negative control shRNA (AAV-shNC) injection in the hippocampal CA1 region and experimental procedures. B In the T maze test, the spontaneous alteration percentage of mice was studied for comparison. C In the novel object recognition test, the discrimination index of novel versus familiar objects was studied for comparison. In the Morris water maze test, the escape latency during a six-day training was recorded for comparison for every day (D). On the seventh day, the time spent for the first entry into the target quadrant (E) and the number of platform crossings (F) were recorded for comparison. AAV-shNC=11 mice, and AAV-shHTRA2 = 12 mice for all behavioral tests. LTP (G) and LTD (H) recordings in the hippocampal CA1 region and quantification of the mean fEPSP slope in the last 10 min of recordings (n = 8–10 slices from 5 mice per group). I Representative western blotting and quantification comparison of indicated proteins (shNC=8 mice, and shHTRA2 = 8 mice). J Representative images of the hippocampal region of WT mice injected with AAV-shNC or AAV-shHTRA2. Scale bar; 2000 μm. K Representative images of brain MRI scan and quantification comparison of the hippocampal region size (shNC = 5 mice, and shHTRA2 = 5 mice). Hippocampal regions were indicated with white dashed lines. A significant difference was determined using an unpaired t-test. Data represent means ± SEM. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; ns, not significant.