Calbindin Knockout Alters Sex-Specific Regulation of Behavior and Gene Expression in Amygdala and Prefrontal Cortex - PubMed (original) (raw)
Calbindin Knockout Alters Sex-Specific Regulation of Behavior and Gene Expression in Amygdala and Prefrontal Cortex
Erin P Harris et al. Endocrinology. 2016 May.
Abstract
Calbindin-D(28K) (Calb1), a high-affinity calcium buffer/sensor, shows abundant expression in neurons and has been associated with a number of neurobehavioral diseases, many of which are sexually dimorphic in incidence. Behavioral and physiological end points are affected by experimental manipulations of calbindin levels, including disruption of spatial learning, hippocampal long-term potentiation, and circadian rhythms. In this study, we investigated novel aspects of calbindin function on social behavior, anxiety-like behavior, and fear conditioning in adult mice of both sexes by comparing wild-type to littermate Calb1 KO mice. Because Calb1 mRNA and protein are sexually dimorphic in some areas of the brain, we hypothesized that sex differences in behavioral responses of these behaviors would be eliminated or revealed in Calb1 KO mice. We also examined gene expression in the amygdala and prefrontal cortex, two areas of the brain intimately connected with limbic system control of the behaviors tested, in response to sex and genotype. Our results demonstrate that fear memory and social behavior are altered in male knockout mice, and Calb1 KO mice of both sexes show less anxiety. Moreover, gene expression studies of the amygdala and prefrontal cortex revealed several significant genotype and sex effects in genes related to brain-derived neurotrophic factor signaling, hormone receptors, histone deacetylases, and γ-aminobutyric acid signaling. Our findings are the first to directly link calbindin with affective and social behaviors in rodents; moreover, the results suggest that sex differences in calbindin protein influence behavior.
Figures
Figure 1.
Impaired retention of cued fear memory in Calb1 KOs. Mean ± SEM percentage of time spent freezing for context-specific and cue-specific fear conditioning expressed as a percentage of baseline freezing: (context trial freezing − baseline trial freezing/total time) × 100% and (cue trial freezing − baseline trial freezing/total time) × 100%. *, Male WT significantly different from all other groups (P < .05).
Figure 2.
Decreased anxiety-like behavior in Calb1 KO mice on the elevated plus maze. Mean ± SEM time (seconds) spent in the open arms (A), in the closed arms (B), and turning around in the open arms (C) during the 10-minute (600 sec) test. Total crosses between open, closed, and center portions of the maze are represented in panel D. *, Significant main effect of genotype (P < .05); &, genotype trend (P = .06).
Figure 3.
Increased investigation during the social preference task by male KOs. Mean ± SEM time (seconds) spent investigating female stimulus mouse (A), male stimulus mouse (B), and total time with either stimulus (C) are shown. Total number of transitions between different compartments of the three-chambered box are represented in panel D. #, Significant main effect of sex (P < .05; *, significantly different from all other groups (P < .05).
Figure 4.
Sexually dimorphic expression of Esr1 and Gabrb1 in amygdala and PFC independent of genotype. Relative quantity (RQ) estrogen receptor (Esr1) (A) and GABA receptor subunit-β (Gabrb1) (B) mRNA in two brain areas: amygdala and PFC. WT and KO RQ values are combined by sex. Gray bars, Mean ± SEM WT male + KO male, white bars, Mean ± SEM WT female + KO female; #, significant main effect of sex within brain region (P < .05.).
Figure 5.
Elevated Bdnf expression in male Calb1 KO PFC but not amygdala. Mean ± SEM relative quantity (RQ) Bdnf (all exons) mRNA are expressed in the amygdala (A) and prefrontal cortex (C). RQ values of Bdnf exon IV mRNA in the amygdala (B) and prefrontal cortex (D) are shown. #, Significant main effect of sex (P < .05); *, significantly different from all other groups (P < .05).
Figure 6.
Genotype-dependent expression changes in amygdala and PFC. Mean ± SEM relative quantity (RQ) values for expression of histone deacetylase 3 (Hdac3) in the amygdala (A); histone deacetylase 4 (Hdac4) in the amygdala (B) and PFC (E); neurotrophic tyrosine kinase receptor 2 (Ntrk2) in the amygdala (C) and in PFC (F). &, Trend for a sex-by-genotype interaction: female knockout greater than female wild type (P = .06); §, significantly different from same-sex control group (P < .05); *, significantly different from all other groups (P < .05).
Figure 7.
Calb1 KO affects stress-related genes in the brain but not serum corticosterone levels in males. Mean ± SEM relative quantity (RQ) values of the CRH receptor 1 (Crhr1) in the amygdala (A) and glucocorticoid receptor (Nr3c1) in the prefrontal cortex (B). C, Serum corticosterone levels in WT and KO males at baseline (gray bars) and 15 minutes after a 15-minute restrain stressor (dark gray bars). §, Significantly different from WT male group (P < .05); #, significantly different from KO male group (P < .05); **, significant main effect of stress (P < .05).
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