<p>Supplemental Figure 1: Tracks of male Ackr1-/--, Ackr1+/-- and Ackr1+/+ mice on the elevated plus maze (5 min sessions). The left side shows the results of two experiments with non- littermates (different animals in exp. 1 and 2), the right side shows data from a littermate experiment. All analyses were performed with the Noldus Ethovision Software. In all images the horizontal arm represents the closed arm, while the vertical arm is the open compartment. The tracks are shown in red. Supplemental Figure 2: Characterization of learning and spatial orientation of male non- littermate Ackr1+/+ and Ackr1-/- mice in three independent water maze experiments. The first, second and third row contain the data from the first, second and third experiment, respectively. (A, E, I) Latency to find the platform; (B, F, J) swimming speed; (C, G, K) distance accumulated until platform is found and (D, H, L) thigmotaxis time (time spent close to the edge of the water maze). Day 0 indicates the habituation day, which is not included in the merged data shown in Figure 4. Supplemental Figure 3: Tracks of male (left side) and female (right side) irradiation bone marrow chimeras on the elevated plus maze (5 min sessions). The direction of bone marrow transfer is given on the left side of the figure (donor  recipient). All analyses were performed with the Noldus Ethovision Software. In all images, the horizontal arm represents the closed arm, while the vertical arm is the open compartment. The tracks are shown in red. Supplemental Figure 4: MRI analysis of Ackr1-/- and Ackr1+/+ mouse brain with focus on the dorsal part of the cerebellum (bregma -5.4 mm to -7.4 mm . (A) Example for the labeling of the dorsal cerebellar region in the MRI slices. The example represents an Ackr1-/- mouse brain. There were no visible morphological differences between MRI slices from Ackr1-/- and Ackr1+/+ mice. (B) Comparison of the volume of the dorsal part of the cerebellum of Ackr1+/+ and Ackr1-/- mice. (C) Areas of individual MRI slices; comparison of Ackr1+/+ and Ackr1-/- mice; n = 9 for each genotype, data are means ± SEM.</p>