Figure 5. Miro1 knock-out results in altered hippocampal network activity and anxiety-related behavior.

(A) Miro1 KO PV+ interneurons received increased glutamateric input. Representative electrophysiological traces from WT (black) and Miro1 KO (red) cells. (B) Quantification for the mean inter event interval (IEI). (C) Quantification for the median amplitude (n_WT = seven recordings, two animals and n_KO = 10 recordings, two animals). (D) Loss of Miro1 increases the frequency of γ-oscillations. Representative local field potential recordings from the stratum pyramidale of the CA3 hippocampal area in acute brain slices from WT, ΗΕT, and Miro1 KO mice. (E) Representative auto-correlogram of γ-oscillations from WT, ΗΕT, and Miro1 KO animals. (F) Quantification of the peak frequency. (G) Quantification of the normalized peak power. (H) Quantification of the normalized power area. (I) Quantification of the 50% width dispersion of the FFT distribution (n_WT = 12 slices, two animals, n_ΗΕT = 23 slices, six animals, and n_KO = 20 slices, six animals). (J) Assessment of anxiety-related behavior using the elevated plus maze (EPM). Schematic diagram of the EPM and representative ToxTrac trajectories (green) from WT and Miro1 KO animals. (K) Boxplot for the quantification of the percentage of time that WT and Miro1 KO animals spent in the closed, open arms and center of the EPM (n_WT = nine animals, n_KO = eight animals).

Figure 5—figure supplement 1. Loss of Miro1 is accompanied by a general increase in excitatory drive in the hippocampus without altering the total levels of excitatory pre- and post- synaptic markers in the hippocampus.

(A) Representative confocal images of the hippocampal pyramidal and dendritic cell layers that were immuno-stained for the presynaptic marker Bassoon, and the postsynaptic marker Homer. Scale bar = 10 μm. The quantification shows the total immunostained area occupied by the markers and their extent of overlap (colocalization). (Pyramidal Cell Layer: n_WT = 23 hippocampal strata, 10 slices, three animals, n_KO = 23 hippocampal strata, 10 slices, three animals, Dendritic (oriens/radiatum) Cell Layers: n_WT = 37 hippocampal strata, 10 slices, three animals, n_KO = 36 hippocampal strata, 11 slices, three animals). (B) Input–output relationship for WT and Miro1 KO slope of fEPSP against increasing stimulus intensity. Bar chart shows the slope of fEPSPs at low (25–50 μA) and high (50–75 μA) stimulations (n_WT = 7 slices, three animals, n_KO = 7 slices, three animals).

Figure 5—figure supplement 2. Loss of Miro1 does not affect husbandry behavior, motor coordination, short-term memory, and spatial exploration.

(A) Assessment of husbandry behavior based on the amount of shredded and unshredded Nestlet between WT and Miro1 KO animals. Bar chart shows the quantification of the percentage of unshredded Nestlet. Blue points represent values from male mice and pink points represent values from female mice (n_WT = nine animals, n_KO = eight animals). (B) Assessment of motor coordination using the rotarod. The animal is placed on the revolving rot until it falls and the speed at which it falls is registered to calculate the revolutions per minute (RPM) indicated by the box plot (n_WT = five animals, n_KO = five animals). (C) Assessment of short-term memory using the spontaneous alternation T-maze behavioral paradigm. The animal starts every trial at position marked as start, the animal is allowed to make a decision at the end of the maze and is kept in that arm for 30 s. A correct entry is considered when the animal makes the opposite decision from the previous trial. A wrong entry is when the animals makes the same decision as in the previous trial. Box plot shows the quantification of the percentage of correct entries. (n_WT = eight animals, n_KO = seven animals). (D) Assessment of general exploration in an open field. Example trajectories (green) of WT and Miro1 KO animals. (E) Box plot for the quantification of the average velocity. (F) Box plot for the quantification of the distance traveled. (G) Quantification of the percentage time spent at distances away from the centre of the box (n_WT = nine animals, n_KO = nine animals).