Haplotype Analysis of the Melanopsin Gene in Seasonal Affective Disorder and Controls
Uniformed Services University Of The Health Sciences Bethesda United States
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Seasonal affective disorder SAD is characterized by winter depressive episodes and springtime remission. SAD may result from a genetically mediated abnormal response to low light availability during winter. One candidate gene for SAD is melanopsin, a non-visual photopigment. Variations in the gene for melanopsin may raise the threshold of light input needed for euthymic functioning such that low light levels fall below this threshold during winter in individuals with SAD. The present study investigated the haplotype structure of the melanopsin gene by genotyping loci throughout the gene as well as in up- and down-stream regions proximal to the gene. Genotyping was performed using two strategies, 5 exonuclease assays that employ strands of about 20 DNA base pairs complementary to variant sequences in the gene, and direct sequencing of certain segments of the gene. This study tested associations between both single-base variations and specific haplotypes in the melanopsin gene in SAD participants n 132 relative to low seasonality controls n 90 with no history of psychopathology.