CACNA1C polymorphism and brain cortical structure in bipolar disorder

Background: The CACNA1C gene encodes the 1C subunit of L-type voltage-gated calcium channels and has been associated with several psychiatric syndromes ­ including bipolar disorder ­ in several genome-wide association studies. Experimental and clinical studies have reported changes with respect to behaviour and biomarkers in risk allele carriers, corroborating the essential role of the CACNA1C gene in neurons, during development and in the mature brain. However, the association of this gene with regional cortical thickness has not been evaluated in patients with bipolar disorder. Methods: Using magnetic resonance imaging, we measured the average cortical thickness of 68 brain regions in 87 patients genotyped for the single-nucleotide polymorphism rs1006737 in CACNA1C. Results: We found associations with the mean thickness of several cortical areas: the left lateral orbitofrontal and rostral anterior cingulate cortices, as well as other parts of the frontal and parietal cortices. Limitations: This cross-sectional cohort study could not fully differentiate correlation from causation. Conclusion: The CACNA1C polymorphism rs1006737 is associated with the mean thickness of cortical brain areas that have been shown to be altered in bipolar disorder.