Common and rare variation in CACNA1C gene expression has been consistently associated with neuropsychiatric disorders such as schizophrenia, bipolar disorder, and major depression. However, the underlying biological pathways that cause this association have yet to be fully determined. In this study, we present evidence that rats with a reduced gene dosage of Cacna1c have increased basal corticosterone levels in the periphery and reduced the expression of Nr3c1 encoding the glucocorticoid receptor in the hippocampus and hypothalamus. These results are consistent, with an effect of Cacna1c dosage on hypothalamus–pituitary–adrenal (HPA) axis function. Heterozygous Cacna1c rats had lower levels of the histone markers H3K4me3 and H3K27acat exon 1₇ of the Nr3c1 gene. These histone modifications are typically linked to increased gene expression, but here were not associated with changes in the expression of exon 1₇ variants under non-stress conditions. Heterozygous Cacna1c rats additionally show increased anxiety behaviours. These results support an association of Cacna1c heterozygosity with the altered activity of the HPA axis and function in the resting state, and this may be a predisposing mechanism that contributes to the increased risk of psychiatric disorders with stress.

Common and rare variation in CACNA1C gene expression has been consistently associated with neuropsychiatric disorders such as schizophrenia, bipolar disorder, and major depression, however the underlying biological pathways that cause this association have yet to be fully determined. In this study, we present evidence that rats with a reduced gene dosage of Cacna1c have increased basal corticosterone levels in the periphery and reduced Nr3c1 gene expression in the hippocampus and hypothalamus. These results are consistent with an effect of Cacna1c dosage on hypothalamus-pituitary-adrenal (HPA) axis function. We also show that the reduction of Nr3c1 in the hippocampus may be caused by epigenetic modification of exon 1 ₇ of Nr3c1 , including the reduced interaction with the histone modifying markers H3K4me3 and H3K27ac. Heterozygous Cacna1c rats additionally show increased anxiety behaviours. These results support an association of Cacna1c heterozygosity with the altered activity of the HPA axis and function in the resting state and this may be a predisposing mechanism that contributes to the increased risk of psychiatric disorders with stress.

The most recent Psychiatric Genomics Consortium (PGC) genome-wide association study of schizophrenia used the statistical fine-mapping tool FINEMAP to identify 70 genes that were likely to mediate common genetic variant associations with the disorder. Here, we extended that study by using two fine-mapping methods, SuSiE and FINEMAP, applying the methods to loci whose causal variant structure was considered too complex by the PGC, and optimising the proportion of posterior probability required by credible sets of causal SNPs for gene prioritisation. Prioritised gene sets were validated for schizophrenia relevance by testing for enrichment of loss-of-function mutation intolerance (LoFI), and for enrichment of rare deleterious coding variants associated with generalised cognition in UK Biobank, both known characteristics of schizophrenia associated genes. Concordance between FINEMAP and SuSiE was high, with most prioritised genes supported by both methods. Genes prioritised by both methods using a relaxed 80% posterior probability (PP) threshold for defining credible sets (N=98) were as enriched for LoFI and for rare deleterious missense variants associated with generalised cognition as genes prioritised using a more conservative 95% PP threshold (N=87). Loosening the credible set threshold combined with the joint application of SuSiE and FINEMAP increased the yield of prioritised genes by 40%, without reducing the orthogonal evidence for validity. Newly prioritised genes included calcium channel genes, CACNA1I and CACNB2 , a glutamate receptor gene, GRM3 , and TCF4 , which has been previously implicated in schizophrenia.

Latent inhibition (LI) refers to the reduced ability to learn or express learning about a stimulus following prior exposure to it without consequence. It has been extensively studied to investigate associative learning and memory as well as the aberrant attribution of salience to irrelevant stimuli in both humans and animals, a process which is thought to underpin hallucinations and delusions in psychosis. Despite sex differences observed in numerous aspects of psychosis, few studies have attempted to characterise sex differences in LI. This systematic review outlines the current evidence of sex differences in LI in both human and rodent studies, showing predominantly inconclusive and conflicting evidence for sex differences. However, the majority of cases in which sex differences were found were in studies that assessed the impact of additional factors on LI such as drug administration, juvenile handling, and oestrous phase, and demonstrated interactions between sex and these additional factors. Hence, there is stronger evidence for sex differences in vulnerability to perturbations in LI. Furthermore, we present data demonstrating sex differences in latent inhibition of contextual fear conditioning and associated gene expression in the hippocampus in rodents, suggesting sex differences in hippocampal processing underpinning latent inhibition at both the behavioural and neurobiological levels. Although there have been relatively few studies demonstrating sex differences in LI identified by the systematic review, the data suggest that in hippocampally dependent forms of LI, sex differences may be more apparent, which may be of relevance in relation to sex differences in the presentation of psychosis.