Chromosome 18p11.2 harbors susceptibility marker: D18S452, for bipolar affective disorder

The aim of our study was to investigate whether the tandem repeat polymorphism in D18S452 microsatellite marker at locus 18p11.2 is a risk factor of bipolar affective disorder (BPAD) in Kashmiri population.

The repeat polymorphism in D18S452 was evaluated by polymerase chain reaction (PCR) analysis of in 74 diagnosed BPAD patients and 74 controls subjects.

Tandem repeat (300 bp*) allele frequency was found to be 1.35% in controls and 8.108% in cases. The tandem repeat (250 bp*) allele frequency was found to be in 91.89% in cases and 98.65% in controls. The 252 bp/252 bp genotype was found to be present in 89.18% of cases and 98.64% of controls, the 300 bp/300 bp genotype in 5.40% of cases and 1.35% of controls and the 252 bp/300 bp variant in 5.40% of cases and none among the controls. Although the proportion of patients homozygous for tandem repeat (300 bp/300 bp) was higher in cases than in controls, the difference was not statistically significant when 252 bp/252 bp genotype was taken as reference (odds ratio [OR]=4.4242; 95% confidence interval [CI] 0.4822-40.5924); P=0.1529). However, when the frequency of heterozygous genotype (252 bp/300 bp) was compared with 252 bp/252 bp statistical significance was observed (OR=8.0603; 95% CI 1.1112-58.4646; P=0.0383).

This is the first study reporting a significant association between D18S452 maker with tandem repeat polymorphism in heterozygous condition (252 bp/300 bp) and the development of BPAD in Kashmiri population.