Hyperactivity and attention deficits in mice with decreased levels of stress-inducible phosphoprotein 1 (STIP1)

Abstract

Stress-inducible phosphoprotein I (STIP1, STI1 or HOP) is a co-chaperone intermediating Hsp70/Hsp90 exchange of client proteins, but it can also be secreted to trigger prion protein-mediated neuronal signaling. Some mothers of children with autism spectrum disorders (ASD) present antibodies against certain brain proteins, including antibodies against STIP1. Maternal antibodies can cross the fetus blood-brain barrier during pregnancy, suggesting the possibility that they can interfere with STIP1 levels and, presumably, functions. However, it is currently unknown whether abnormal levels of STIP1 have any impact in ASD-related behavior. Here, we used mice with reduced (50%) or increased STIP1 levels (fivefold) to test for potential ASD-like phenotypes. We found that increased STIP1 regulates the abundance of Hsp70 and Hsp90, whereas reduced STIP1 does not affect Hsp70, Hsp90 or the prion protein. Interestingly, BAC transgenic mice presenting fivefold more STIP1 show no major phenotype when examined in a series of behavioral tasks, including locomotor activity, elevated plus maze, Morris water maze and five-choice serial reaction time task (5-CSRTT). In contrast, mice with reduced STIP1 levels are hyperactive and have attentional deficits on the 5-CSRTT, but exhibit normal performance for the other tasks. We conclude that reduced STIP1 levels can contribute to phenotypes related to ASD. However, future experiments are needed to define whether it is decreased chaperone capacity or impaired prion protein signaling that contributes to these phenotypes.

Keywords: ASD; Attention deficits; Autism; BAC; Mouse model; Stress-inducible phosphoprotein 1; Touchscreen.

Fig. 1.

Analyses of mRNA for STIP1 partners in STI1^+/+, STI1^−/+ and STI1^TGA mouse brains. (A) STIP1 mRNA expression (n=9 STI1^+/+, n=5 STI1^TGA and n=4 STI1^−/+). (B) PrP^C mRNA expression (n=8 STI1^+/+, n=4 STI1^TGA and n=7 STI1^−/+). (C) Hsp70 mRNA expression (n=8 STI1^+/+, n=4 STI1^TGA and n=7 STI1^−/+). (D) Hsp90 mRNA expression (n=3 STI1^+/+, n=4 STI1^TGA and n=4 STI1^−/+). Results are presented as means±s.e.m.; data were analyzed and compared by one-way ANOVA and Bonferroni multiple comparisons post-hoc test; **P<0.001 and ***P<0.0001 compared with control.

Fig. 2.

Analyses of protein levels for STIP1 partners in STI1^+/+, STI^−/+ and STI1^TGA mouse brains. (A,B) STIP1 expression in STI1^TGA (n=9 STI1^+/+ and n=8 STI1^TGA) and STI1^−/+ mice (n=8 STI1^+/+ and n=8 STI1^−/+). (C,D) PrP^C expression in STI1^TGA (n=6 STI1^+/+ and n=6 STI1^TGA) and STI1^−/+ mice (n=6 STI1^+/+ and n=9 STI1^−/+). (E,F) Hsp70 expression in STI1^TGA (n=5 STI1^+/+ and n=4 STI1^TGA) and STI1^−/+ mice (n=5 STI1^+/+ and n=4 STI1^−/+). (G,H) HSP90 expression in STI1^TGA (n=10 STI1^+/+ and n=14 STI1^TGA) and STI1^−/+ mice (n=6 STI1^+/+ and n=6 STI1^−/+). (I,J) Hsp90β (n=10 STI1^+/+ and n=8 STI1^TGA) and Hsp90α (n=5 STI1^+/+ and n=4 STI1^TGA) in STI1^TGA mice. Results are presented as means±s.e.m.; data were analyzed and compared by Student's t-test; *P<0.05 and ***P<0.0001 compared with control.

Fig. 3.

Locomotor activity in STI1^TGA and STI1^−/+mice and metabolic analyses in STI1^−/+mice. (A) Horizontal locomotor activity in an open-field for STI1^TGA (n=14) and STI^+/+ control mice (n=14). (B) Cumulative 1 h locomotion for STI1^TGA (n=14) and STI^+/+ control mice (n=14). (C) Time spent in the center of the locomotion boxes for STI1^TGA (n=14) and STI^+/+ control mice (n=14). (D) Horizontal locomotor activity in an open-field for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (E) Cumulative 1 h locomotion for STI1^−/+ (n=22) and STI^+/+ control mice (n=24). (F) Time spent in the center of the locomotion boxes for STI1^−/+ (n=22) and STI^+/+ control mice (n=24). (G) Total activity in metabolic cages for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (H) Ambulatory activity in metabolic cages for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (I) Sleep time for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (J) VO₂ for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (K) VCO₂ for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (L) Respiratory exchange ratio for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (M) Food consumption for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (N) Water consumption for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). (O) Energy expenditure for STI1^−/+ (n=8) and STI^+/+ control mice (n=8). Results are presented as means±s.e.m.; data were analyzed and compared by Student's t-test; *P<0.05 compared with control.

Fig. 4.

Anxiety-like behavior, depression-like behavior, social behavior and compulsivity in STI1^TGA and STI1^−/+ mice. (A) Percentage of time spent in the closed arm for STI1^TGA (n=17) and control mice (n=14). (B) Percentage of time spent in the open arm for STI1^TGA (n=17) and control mice (n=14). (C) Percentage of time spent in the closed arm for STI1^−/+ (n=13) and control mice (n=10). (D) Percentage of time spent in the open arm for STI1^−/+ (n=13) and control mice (n=10). (E) Immobility time in the forced-swimming test for STI1^TGA (n=17) and control mice (n=14). (F) Immobility time in the forced-swimming test for STI1^−/+ (n=6) and control mice (n=8). (G,H) Time spent grooming and number of grooming bouts for STI1^−/+ (n=11) and control mice (n=11). (I) Marbles buried by STI1^−/+ (n=12) and control mice (n=12).

Fig. 5.

Spatial memory in STI1^TGA and STI1^−/+ mice. For the tests, n=14 STI1^+/+ and 14 STI1^TGA mice were used to test spatial memory in STI1^TGA mice and n=11 STI1^+/+ and 11 STI1^−/+ for STI1^−/+ mice. (A) Latency to find the platform. (B) Distance traveled. (C) Speed for STI1^TGA mice. (D) Percentage time spent by STI1^TGA mice and controls in target quadrant (T) and in opposite (O), right (R) and left (L) quadrants was measured on day 5 in a 60 s probe trial with the platform removed. (E) Latency to find the platform. (F) Distance traveled. (G) Speed for STI1^−/+ mice. (H) Percentage time spent by STI1^−/+ mice and controls in each quadrant was measured on day 5 in a 60 s probe trial with the platform removed. Results are presented as means±s.e.m.; data were analyzed and compared by two-way ANOVA; ***P<0.001 and ****P<0.0001 compared with time spent in target quadrant.

Fig. 6.

Five-choice serial reaction time task used to measure attention in STI1^TGA and STI1^−/+. For the tests, n=10 STI1^+/+ and 10 STI1^TGA mice were used to test attention in STI1^TGA mice and n=13 STI1^+/+ and 13 STI1^−/+ for STI1^−/+ mice. (A) Accuracy during probe trial sessions. (B) Rate of omission. (C) Premature responses. (D) Response latency. (E) Reward collection latency. (F) Perseverative responses for STI1^TGA mice. (G) Accuracy during probe trial sessions. (H) Rate of omission. (I) Premature responses. (J) Response latency. (K) Reward collection latency. (L) Perseverative response for STI1^−/+ mice. Results are presented as means±s.e.m.; data were analyzed and compared by RM-ANOVA; *P<0.05, **P<0.001 compared with control.