Table 3.
Description and Function of Polymorphisms.
| Gene | Polymorphism (Alternative Name If Applicable) | Polymorphism Function |
|---|---|---|
| BDNF | rs6265 (val66met) | This missense variant results in an amino acid substitution (i.e., valine to methionine) at codon 66. This change impairs the secretion of BDNF in the nervous system (Chen et al., 2004; Egan et al., 2003). |
| COMT | rs4680 (val158met) | This missense variant results in an amino acid substitution (i.e., valine to methionine) at position 158 of COMT. This alters the structure of the COMT enzyme and reduces its activity, resulting in higher dopamine levels (Stein, Newman, Savitz, & Ramesar, 2006). |
| FKBP5 | rs3800373 | This variant is located in the 3 prime untranslated region and likely alters the stability and half-life of the mRNA and modulates glucocorticoid signaling and hypothalamic–pituitary–adrenal axis function. This variant has been associated with greater FKBP5 induction by cortisol and decreased glucocorticoid-receptor sensitivity (Fudalej et al., 2015; Tatro et al., 2009). |
| IL-6 | rs1800795 (-174 G/C) | This variant is located in the promoter region, which is a region essential for inducing transcription of IL-6. rs1800795 has been associated with differential gene expression and decreased plasma levels of IL-6 during immune activation (Bull et al., 2009; Paul-Samojedny et al., 2010). |
| NFKB2 | rs1056890 | This variant is located in the 3 prime untranslated region, which is a region known to bind miRNAs and regulate protein translation (Ma, Becker Buscaglia, Barker, & Li, 2011; Tian et al., 2018). |
| SLC6A4 | 5-HTTLPR + rs25531 | The HTTLPR variant is a 43-base-pair variable-number tandem repeat (VNTR) polymorphism, and rs25531 is a single nucleotide polymorphism (SNP) located in the promoter region of SLC6A4. The VNTR determines if the alleles are long or short, and the SNP further divides the long allele into La and Lg. The La allele produces significantly more 5-HTT mRNA and protein and results in increased expression and serotonin transporters in the cell membrane. The short allele results in lower levels of serotonin (Wendland, Martin, Kruse, Lesch, & Murphy, 2006). |
| TNFA | rs1799964 (-1031 T/C) | This variant is located in the promoter region and influences gene expression. The C allele is correlated with increased serum TNFA levels (Nourian et al., 2017; Sandoval-Pinto et al., 2016). |
| rs1800629 (-308 G/A) | This variant is located in the promoter region. The A allele has been associated with an increase in the binding of nuclear factors and heightened transcription of the gene (Kroeger, Carville, & Abraham, 1997; Wilson, Symons, McDowell, McDevitt, & Duff, 1997). |
Note. miRNAs = microRNAs; mRNA = messenger RNA.