A functional polymorphism within the serotonin transporter gene (5-HTTLPR) has been reported to modulate emotionality and risk for affective disorders.
Exposure to maternal mood disorder in utero may program infant neurobehavior via DNA methylation of the glucocorticoid receptor (NR3C1) and 11β-hydroxysteroid dehydrogenase type 2 ( 11β-HSD-2), two placental genes that have been implicated in perturbations of the hypothalamic pituitary adrenocortical (HPA) axis.
Serotonin transporter gene (SLC6A4) has been shown to play an important role in the pathophysiology of mood disorders including poststroke depression (PSD).
It is not known how 5-HTTLPR genotype x childhood adversity (CA) interactions that are associated with an increased risk for affective disorders in population studies operate at the neural systems level.
This study contributes to the growing evidence for a role of the glucocorticoid receptor gene (NR3C1) in vulnerability to mood disorders, and BPD in particular, and warrants further in vitro investigation of the at-risk haplotypes with respect to disease etiology.
The serotonin transporter (5HTT) plays an important role in the pathophysiology of mood disorders and may also be involved in suicidal behaviour since 5HTT binding is decreased in the brain of suicide completers.
SLC6A4 expression was significantly increased in placentas from women with untreated mood disorders and from women treated with SSRIs, compared to controls.
Given that the 5-HTTLPR polymorphism has been associated with mood disorders, it is plausible that the abnormal pattern of regional brain activity detected here, in children carrying the S allele, increases susceptibility to emotional dysregulation and depressive symptoms.
In particular, the presence of one or two copies of the short (s) allele of the 5-HTTLPR polymorphism has been associated with reduced serotonin transporter expression and function, and vulnerability to affective disorders.
To investigate whether the distribution of the alleles of the 5-HTTLPR is associated with a genetic predisposition to affective disorder and whether these variations interact with life events in relation to depressive symptoms, neuroticism and salivary cortisol.
The main conclusions of the review are: i) there is an association between TPH2 and genetically defined behavioral variations, ii) the haplotypes, including some human TPH2 gene SNPs, can predict the risk of affective disorders and the sensitivity to antidepressant therapeutics, iii) mutations decreasing TPH2 activity produce negative effects on behavior and, possibly, on survival, iv) the effect of dietary tryptophan manipulations on human mood and behavior is modest compared with that of inhibitors of 5-HT transporter and monoamine oxidase.
Moreover, BDNF gene expression is also significantly reduced in leukocytes from healthy subjects carrying the S allele of the 5-HTTLPR, suggesting that the changes observed in SERT mutant rats may also be present in humans and may confer enhanced vulnerability to mood disorders.
5-HTT CpG methylation may be an important regulator of 5-HTT expression early in development and may contribute to the risk for mood disorders observed in 'high-risk'5-HTTLPR carriers.
Three genes contributed exclusively to mood disorders, one through a main effect (HTR5A (rs1657268)) and two through gene-environment interactions with CPA (HTR1A (rs878567) and SLC6A4 (rs3794808)).
In this overview, currently known clinically relevant GR and MR polymorphisms are discussed in relation to mood disorders (both unipolar depression and bipolar disorder) and cognitive function.
Subtle changes in glucocorticoid receptor (GR) functioning caused by polymorphisms of the GR gene (NR3C1) may be at the base of the altered reaction of the HPA axis to stress and subsequently related to the development and course of affective disorders.