Prenatal interaction of mutant DISC1 and immune activation produces adult psychopathology

Abstract

Background: Gene-environment interactions (GEI) are involved in the pathogenesis of mental diseases. We evaluated interaction between mutant human disrupted-in-schizophrenia 1 (mhDISC1) and maternal immune activation implicated in schizophrenia and mood disorders.

Methods: Pregnant mice were treated with saline or polyinosinic:polycytidylic acid at gestation day 9. Levels of inflammatory cytokines were measured in fetal and adult brains; expression of mhDISC1, endogenous DISC1, lissencephaly type 1, nuclear distribution protein nudE-like 1, glycoprotein 130, growth factor receptor-bound protein 2, and glycogen synthase kinase-3beta were assessed in cortical samples of newborn mice. Tissue content of monoamines, volumetric brain abnormalities, dendritic spine density in the hippocampus, and various domains of the mouse behavior repertoire were evaluated in adult male mice.

Results: Prenatal interaction produced anxiety, depression-like responses, and altered social behavior that were accompanied by decreased reactivity of the hypothalamic-pituitary-adrenal axis, attenuated serotonin neurotransmission in the hippocampus, reduced enlargement of lateral ventricles, decreased volumes of amygdala and periaqueductal gray matter and density of spines on dendrites of granule cells of the hippocampus. Prenatal interaction modulated secretion of inflammatory cytokines in fetal brains, levels of mhDISC1, endogenous mouse DISC1, and glycogen synthase kinase-3beta. The behavioral effects of GEI were observed only if mhDISC1 was expressed throughout the life span.

Conclusions: Prenatal immune activation interacted with mhDISC1 to produce the neurobehavioral phenotypes that were not seen in untreated mhDISC1 mice and that resemble aspects of major mental illnesses. Our DISC1 mouse model is a valuable system to study GEI relevant to mental illnesses.

Figure 1

Secretion of cytokines in fetal brains (A) The levels of anti- and pro-inflammatory cytokines in fetal brains 6 hours after injection of Poly I:C, * denotes p<0.05 vs. the respective saline-treated group; # denotes p<0.05 vs. saline-treated control mice; (B) The fold changes in the levels of IL-6 and TNF-α as calculated in relation to the averaged value for control saline group; the bars correspond to the minus and plus range of the fold changes, n=5–10 mice per group.

Figure 2

The behavioral effects of interactions (A) Elevated peripheral activity in open field in mhDISC1 mice treated with Poly I:C, * denotes p<0.05 vs. the saline-treated mhDISC1 group; n=10–14 male mice per group; (B) Decreased time spent in open arms in mhDISC1 mice prenatally challenged with Poly I:C mice, * denotes p<0.05 vs. the saline-treated mhDISC1 group, n=10–14 male mice per group; (C) Time of immobility in forced swim test (FST). Note increased time of immobility in mhDISC1 mice treated with Poly I:C compared to the saline-treated mhDISC1 group, * denotes p<0.05 vs. the saline-treated group, n=10–14 male mice per group; (D) Sociability in mice in 3-chamber apparatus. The data reflect time of actively sniffing object or live mouse. Note an abnormal pattern of exploration in mhDISC1 given Poly I:C compared to all other groups, n=10–14 male mice per group, * denotes p<0.05 vs. object.

Figure 3

Attenuated reactivity of the HPA axis Quantitative analyses of levels of corticosterone (ng/ml) in blood sera in adult mice prenatally challenged with saline or Poly I:C; * denotes p<0.05 vs. stress; ** denotes p<0.05 vs. stress for saline-treated control mice only; # denotes p<0.05 vs. saline-treated control mice for stress conditions, n=5–7 in each group, line 1001B.

Figure 4

Brain effects of interaction (A–D) Representative MRI coronal images for control-saline (a), control-Poly I:C (b), mutant-saline (c) and mutant-Poly I:C (d) groups. The boundaries of the brain and the lateral ventricles are outlined; (E) Prenatal immune activation significantly increased volumes of the lateral ventricles in control mice and moderately decreased in mhDISC1 mice, n=3–5 mice per group, * denotes p<0.05 vs. saline-treated mhDISC1 mice; # denotes p<0.05 vs. saline-treated control mice; (F) Prenatal immune activation significantly decreased volumes of the amygdala, n=4 mice per group, * denotes p<0.05 vs. the respective saline-treated group; (G) Prenatal immune activation significantly decreased volumes of the periaqueductal gray matter (PAGM), n=4 mice per group, * denotes p<0.05 vs. the respective saline-treated group; (H) Quantitative analysis of the linear spine density on dendrites of granule cells of the dentate gyrus; * denotes p<0.05 vs. saline-treated mhDISC1 mice; n=10–20 neurons per mouse, 4 mice per group; (I) Representative images of dendritic spines from the groups of mice, scale bar - 20μm.

Figure 5

Molecular markers of interactions (A) Representative blots for mhDISC1, endogenous DISC1 (eDISC1) and GSK-3β from cortical samples collected at P2; (B) Prenatal immune activation significantly increased levels of mhDISC1, n=6–7 samples per group, * denotes p<0.05 vs. saline-treated mhDISC1 mice; (C) Prenatal immune activation significantly decreased levels of endogenous DISC1 in mhDISC1 mice, n=6–7 samples per group, # denotes p<0.05 vs. saline-treated mutant mice; (D) Prenatal stimulation significantly decreased levels of GSK-3β in control mice but not in mhDISC1 mice, n=6–7 samples per group, * denotes p<0.05 vs. saline-treated control mice.

Figure 6

Dependence of the behavioral effects on time of expression (A) Time of immobility in forced swim test (FST) in mice with expression of mhDISC1 on E0-P21. Note the lack of differences between control and mutant mice, n=10–21 mice per group; (B) Sociability in mice with expression of mhDISC1 on E0-P21. Note the lack of differences between control and mutant mice, n=10–21, * denotes p<0.05 vs. time spent in exploration of a live mouse; (C) Time of immobility in forced swim test (FST) in mice with expression of mhDISC1 on P21-adulthood. Note the absence of differences between control and mutant mice; n=10–14 mice per group; (D) Sociability in mice with expression of mhDISC1 on P21-adulthood. Note the lack of differences between control and mutant mice, * denotes p<0.05 vs. time spent in exploration of a live mouse; n=10–14 mice per group