CACNA1C gene linked to facial emotion recognition in bipolar patients
MedWire News: Patients with bipolar disorder (BD) who carry the Met allele of the α1-C subunit of the L-type voltage-gated calcium channel gene (CACNA1C) show impaired ability to recognize facial expressions of emotion, research suggests.
Genome-wide association studies have recently shown that the rs1006737 polymorphism of CACNA1C is significantly associated with an increased risk for BD, observe Márcio Gerhardt Soeiro-de-Souza (University of Sao Paulo, Brazil) and team.
Furthermore, they explain that "recent functional magnetic resonance imaging studies have revealed that the Met allele influences brain morphology and modulates activation in the limbic region during emotion processing tasks."
However, they add: "Despite this body of evidence linking CACNA1C to the limbic system and BD, no studies investigating the impact of this polymorphism on facial emotion recognition (FER) scores in BD have yet been conducted."
To address this, the team studied 39 euthymic BD patients and 40 mentally healthy controls. All of the participants were genotyped for CACNA1C and underwent the Ekman 60 Faces Test (EK) and the Emotion Hexagon Test (HX) to assess FER (happiness, sadness, disgust, fear, surprise, and anger).
Overall, the prevalence of Met/Met, Val/Met, and Val/Val genotypes was 8%, 44%, and 48%, respectively, with BD patients and controls showing a similar genotype frequency.
The researchers found that an effect of CACNA1C genotype on FER was only observed among BD patients.
Indeed, BD patients who were carriers of the Met/Met genotype had lower total HX and EK scores compared with carriers of the Val/Met or Val/Val genotypes, indicating a global dysfunction in FER among those homozygous for the CACNA1C Met allele.
Specifically, Met/Met carriers had poorer recognition of faces expressing disgust, sadness, happiness, surprise, and anger than BD patients with other genotypes.
CACNA1C genotype was not associated with amygdala or hippocampus volumes in either BD patients or controls, the researchers note.
Soeiro-de-Souza and colleagues conclude in the Journal of Affective Disorders: "The risk Met allele had a negative impact on FER scores in BD subjects only.
"Further studies exploring how this CACNA1C risk allele for BD impacts on the neurobiological basis of the illness associated with behavior and cognition may provide further insights into the role of this calcium channel mutation in the biobehavioral model of BD."
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By Mark Cowen