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Transl Psychiatry. 2016 Jun 7;6(6):e831. doi: 10.1038/tp.2016.99.

CACNA1C hypermethylation is associated with bipolar disorder.

Author information

1
Department of Biomedicine, Aarhus University, Aarhus, Denmark.
2
The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Denmark.
3
Center for Integrative Sequencing, iSEQ, Aarhus University, Aarhus, Denmark.
4
Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark.
5
Molecular Psychiatry Laboratory, Division of Psychiatry, University College London, London, UK.
6
Research Department P, Aarhus University Hospital, Risskov, Denmark.

Abstract

The CACNA1C gene, encoding a subunit of the L-type voltage-gated calcium channel is one of the best-supported susceptibility genes for bipolar disorder (BD). Genome-wide association studies have identified a cluster of non-coding single-nucleotide polymorphisms (SNPs) in intron 3 to be highly associated with BD and schizophrenia. The mechanism by which these SNPs confer risk of BD appears to be through an altered regulation of CACNA1C expression. The role of CACNA1C DNA methylation in BD has not yet been addressed. The aim of this study was to investigate if CACNA1C DNA methylation is altered in BD. First, the methylation status of five CpG islands (CGIs) across CACNA1C in blood from BD subjects (n=40) and healthy controls (n=38) was determined. Four islands were almost completely methylated or completely unmethylated, while one island (CGI 3) in intron 3 displayed intermediate methylation levels. In the main analysis, the methylation status of CGI 3 was analyzed in a larger sample of BD subjects (n=582) and control individuals (n=319). Out of six CpG sites that were investigated, five sites showed significant hypermethylation in cases (lowest P=1.16 × 10(-7) for CpG35). Nearby SNPs were found to influence the methylation level, and we identified rs2238056 in intron 3 as the strongest methylation quantitative trait locus (P=2.6 × 10(-7)) for CpG35. In addition, we found an increased methylation in females, and no difference between bipolar I and II. In conclusion, we find that CACNA1C methylation is associated with BD and suggest that the regulatory effect of the non-coding risk variants involves a shift in DNA methylation.

PMID:
27271857
PMCID:
PMC4931616
DOI:
10.1038/tp.2016.99
[Indexed for MEDLINE]
Free PMC Article

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