Supplementary Material for: Differential Allelic Expression of HTR1B in Suicide Victims: Genetic and Epigenetic Effect of the Cis-Acting Variants

<p><b><i>Objectives:</i></b> In the present study, we tested the allelic imbalance of the C861G single nucleotide polymorphism (SNP) of HTR1B in the frontal cortex of suicide victims. <b><i>Methods:</i></b> The study was conducted using 3 sets of samples. First, C861G allele-specific mRNA levels in the frontal cortex were compared between suicide (<i>n</i> = 13) and nonsuicide controls (<i>n</i> = 13) from the Stanley Medical Research postmortem brain collection. Second, we tested common variants in the HTR1B promoter for linkage disequilibrium (LD) with the C861G variant in an unrelated sample of suicide attempters (SA; <i>n</i> = 38) and non-SA (NSA; <i>n</i> = 42). Finally, we performed a family-based association study of the C861G and promoter variants in 162 nuclear families using suicidal behavior severity scores as phenotype. <b><i>Results:</i></b> We observed no alterations in the C/G expression ratio in suicide victims compared to nonsuicide controls (<i>p</i> = 0.370). When comparing the LD between the C861G and <i>cis</i>-acting SNPs, we did not find any differences in SA and NSA. There was no association between preferential transmission of <i>cis</i>-acting SNPs and suicidal behavior severity scores in both maternal and paternal meiosis. <b><i>Conclusions:</i></b> We found several promoter variants in LD that may potentially influence the allelic imbalance in the C861G variant. However, no evidence of allelic imbalance nor parent-of-origin effects of the C861G variant was observed in suicidal behavior. Further research is required to assess this marker in larger cohorts.</p>