How do genes exert their role? Period 3 gene variants and possible influences on mood disorder phenotypes
Introduction
Recent genetic analyzes in psychiatric disturbances evidenced that gene variants are responsible for a number of phenotypical features. This is the case, for example, of a well known polymorphism (SERTPR) in the promoter region of serotonin transporter gene, which has been demonstrated to affect a very broad phenotypic, biological and anatomical facets, such as, periodicity (Cusin et al., 2001, Mundo et al., 2001, Smeraldi et al., 2002, Rousseva et al., 2003), treatment response (Serretti and Artioli, 2004), anxiety in normal subjects (Lesch et al., 1996, Schinka et al., 2004, Sen et al., 2004) and depressed patients (Serretti et al., 1999), mood disorders (Collier et al., 1996, Lotrich and Pollock, 2004), suicide (Anguelova et al., 2003), temperament (Szekely et al., 2004), hippocampal volume (Frodl et al., 2004), CSF 5-HIAA levels (Williams et al., 2003), tryptophan depletion effects (Neumeister et al., 2002), eating disorders (Matsushita et al., 2002), attention deficit hyperactivity disorder (Kent et al., 2002), reduced aggression in mice (Holmes et al., 2002), amygdala reaction to emotional stimuli (Hariri et al., 2002), smoking (Ishikawa et al., 1999), alcohol dependence (Hammoumi et al., 1999). This kind of studies suggests a new fashion to interpret the relationship between genes and phenotypic features in complex traits, both in healthy and affected status. On one hand, it is well known that a single complex trait is influenced by a large amount of genetic and environmental variables (Glazier et al., 2002); on the other hand, single genes (especially those influencing a complex trait) are probably unlike to outcome into a single trait. For example, single genes could influence traits that are someway linked, causing the contemporary transmission of features that, when inherited together, could give an evolutionary advantage. This is the case, for example, of the strong correlation between genes belonging to HLA complex and smell recognition, an essential component of mating behavior in animals. Thus HLA complex genes associated to smell recognition could have lead to the inheritance of an increased immune response to various pathogens (Nowak and Januszkiewicz-Lewandowska, 2001).
For the above-mentioned reasons, many analyses, focused on a specific feature, may lack of the necessary power to detect causative genes, not only because the genes are interconnected to each other and have reciprocal influences, but also for the cross-influences exerted on a huge number of features by each single gene.
Starting from this rationale, the search for biological features related to mood disorder recently focused on rhythm alterations. Human beings, such as most living organisms, exhibit a circadian rhythm of around 24 h, regulated by the environmental light–dark cycle, which influences many biological processes (sleep, hormone plasma levels and body core temperature) (Hastings, 1997).
From a clinical point of view, it is noteworthy that circadian rhythms are deeply compromised in mood disorders, showing sleep disturbances (Fahndrich, 1987, Reinink et al., 1993), together with a typical morning worsening and an evening improvement of symptoms (Fahndrich, 1987, Reinink et al., 1993). Finally, manipulations of the sleep–wake and of the dark–light rhythms can change the clinical status by triggering antidepressant response or reducing manic symptoms (Wirz-Justice et al., 2005).
The loop responsible for mammalian circadian rhythms consists of two Cryptochrome genes (Cry 1, Cry 2), Bmal1, Circadian Locomotor Output Cycles Kaput (clock), Casein kinase I epsilon genes and three Period genes (Per1, Per2, Per3), all expressed in the hypothalamic suprachiasmatic nuclei (SCN) (Dunlap, 1999, Lowrey and Takahashi, 2000). A T/C nucleotide substitution in position 3111 of the clock cDNA sequence has been found associated with morningness (Katzenberg et al., 1998). We previously observed an association between the same polymorphism and a significantly higher recurrence rate of illness episodes in bipolar patients homozygous for the C variant (Benedetti et al., 2003) and a strong association between the C variant and an increased lifetime sleep disturbances (initial and middle insomnia) in patients affected by mood disorders (Serretti et al., 2003). We also observed that clock variants were associated with the time course of insomnia symptomatology during SSRIs treatment, but not with the whole HAMD score (Serretti et al., 2005a). Similarly to SERTPR variants, clock 3111 C/C genotype was associated with a range of features, including sleep abnormalities related to a subsequent high rate of recurrence in bipolars (Benedetti et al., 2003, Serretti et al., 2003).
Such as clock gene, human per3 gene (hper3) is a relevant member of the circadian period gene family; it is located on the human chromosome 1 (1p36.22) (GenBank accession number Z98884) (Zylka et al., 1998) and is expressed in the hippocampus, piriform cortex, and cerebellum. A major point is that mper3 RNA levels exhibit a robust circadian variation in the SCN, similarly to mper1 and mper2. Differently from what happens for the former two, light pulses do not affect mper3 RNA levels during subjective night (Zylka et al., 1998). Ebisawa et al. (Ebisawa et al., 2001) identified six functional sequence variations; they predicted four haplotypes (H) for the hper3 gene and speculated that one out of the six polymorphisms may alter the phosphorylation and degradation of hper3, thus suggesting its possible implication in the pathogenesis of Delayed Sleep Phase Syndrome (DSPS).
This polymorphism consists of a T to G substitution at the position 1940 inside exon 15 and it causes a V647G amino-acidic substitution in the final protein (gene and protein are numbered according to the full length hper3 cDNA sequence: accession No. AB047686). Therefore the human hper3 was considered as a possible candidate for rhythm disorder susceptibility (Ebisawa et al., 2001).
Ebisawa et al. identified also other two polymorphisms, both located in exon 18.
The first is a domain composed by 4 or 5 tandem repeats of 54 bp. The four repeats allele, deriving from the loss of the third repeat, was more frequently expressed in DSPS subjects, and in those showing evening preference. Since this region contains potential CK I epsilon phosphorylation sites, the lack of the repeat in the four repeats variant could affect a property phosphorylation. Recently, this last polymorphism was found to be associated to DSPS and extreme diurnal preference (Archer et al., 2003). The second polymorphism is an SNP T3110C located in the fourth repeat, which caused an M1037T amino-acidic substitution (Ebisawa et al., 2001).
Given the observed role of per3 variants in the circadian system control and the multiple influences of the circadian system on personality (Caci et al., 2004), presentation and time course of mood illness (Goodwin and Jamison, 1990, Benedetti et al., 1996), short and long term treatment response (El-Mallakh, 1990, Goodwin and Jamison, 1990, El-Mallakh, 1996), we hypothesized that different per3 variants could identify different oscillation sensitive phenotypes in mood disorder patients.
Section snippets
Sample
The sample was composed by 519 Major Depressed and 512 Bipolar patients, consecutively admitted to the Mood Disorder Center, Department of Psychiatry, at the San Raffaele Institute (age = 49.91 ± 13.42 years; onset = 35.01 ± 13.02 years; female/male = 685/346). Lifetime diagnoses were assigned by trained psychiatrists and supervised by an independent senior psychiatrist, on the basis of unstructured clinical interviews and medical records, according to DSM-IV criteria (American Psychiatric Association,
DNA analysis
DNA was extracted from whole blood, using an Extragen 8C Automated DNA extractor (Talent s.r.l., Trieste, Italy). PCR was performed with the following primers: for Per3 ex15: 5′ CGTTGGGAATTTTTCTTTTCA 3′ and 5′-CAAAGTAAGAGGCGAGTGTGG-3′; for Per3 ex18 5′-TGTCTTTTCATGTGCCCTTACTT-3′ and 5′-TGTCTGGCATTGGAGTTTGA-3′; The PCR reaction was carried out in a 10 mcl volume containing 150 ng genomic DNA, 5 picoM of each primer, 200 mcM each dNTP, 1x PCR Gold Buffer (Applied Biosystems, Monza Italy), and
Statistical analysis
Seven HAM-D scores measurements (at baseline and 6 weeks) were analyzed. Repeated Measures Analysis of Variance (MANOVA) was used to examine the differences between genotypes on HAM-D scores. MANCOVA was used when including covariates. An “intent-to-treat” analysis was carried out for all patients who had a baseline assessment and at least one assessment after randomization, with a last observation carried forward (LOCF) approach. Student t-test and chi-square were used when appropriate. All p
Results
Our sample was in Hardy Weinberg equilibrium (HWE) for the hPer3 ex15 T1940G (Chi-sq. = 1.177; p = 0.27) and hPer3 ex 18 T3110C (Chi-sq. = 0.239; p = 0.62) loci, but it was not in HWE for hPer3 ex 18 ins/del locus (Chi-sq. = 5.421; p = 0.02).
A brief description of the sample is summarized in Table 1a, Table 1b. We observed that baseline clinical and demographic characteristics of subjects, grouped according to per3 variants, did not show any significant difference, except for age, in case of the hPer3 ex15
Discussion
We hypothesized that per3 variants could influence some oscillation-dependent depressive features. Indeed, our study evidenced how subjects carrying per3 mutated variants (Per3 ex15 GG, Per3 ex18 44, Per3 ex18 CC, respectively) show a range of features that could be dependent from their basic biologic rhythm. Mutated Per3 subjects are characterized by a tendency toward eveningness and delayed sleep syndrome (Ebisawa et al., 2001, Archer et al., 2003) and also by wider mood variations during the
Acknowledgement
This research was supported by Archimede's Prize fund (European Community): HPAW-CT-2002-80066.
References (69)
- et al.
Infradian mood fluctuations during a major depressive episode
J. Affect. Disord.
(1996) - et al.
Novelty seekers and impulsive subjects are low in morningness
Eur. Psychiatr.
(2004) - et al.
An analysis of the “eveningness–morningness” dimension in “depressive” college students
J. Affect. Disord.
(1999) - et al.
Distinctions between bipolar and unipolar depression
Clin. Psychol. Rev.
(2005) - et al.
Influence of 5-HTTLPR and TPH variants on illness time course in mood disorders
J. Psychiatr. Res.
(2001) Molecular bases for circadian clocks
Cell
(1999)- et al.
Does the short variant of the serotonin transporter linked polymorphic region constitute a marker of alcohol dependence?
Alcohol
(1999) Circadian clocks
Curr. Biol.
(1997)- et al.
Clinical and differential diagnostic aspects of treatment-resistant depression
J. Psychiatr. Res.
(1995) - et al.
Initial conditions of serotonin transporter kinetics and genotype: influence on SSRI treatment trial outcome
Biol. Psychiatry
(2002)
Prediction of the antidepressant response to total sleep deprivation of depressed patients: longitudinal versus single day assessment of diurnal mood variation
Biol. Psychiatry
Social adjustment could be associated with the serotonin transporter gene in remitted patients with mood disorders and healthy subjects
Psychiatry Res.
Serotonin transporter promoter genotype and illness recurrence in mood disorders
Eur. Neuropsychopharmacol.
Serotonergic autoreceptor blockade in the reduction of antidepressant latency: personality variables and response to paroxetine and pindolol
J. Affect. Disord.
Sleep deprivation and clomipramine in endogenous depression
Lancet
Three period homologs in mammals: differential light responses in the suprachiasmatic circadian clock and oscillating transcripts outside of brain
Neuron
Diagnostic and Statistical Manual of Mental Disorders
Fluoxetine and norfluoxetine plasma concentrations in major depression: a multicenter study
Am. J. Psychiatry
A systematic review of association studies investigating genes coding for serotonin receptors and the serotonin transporter: II. suicidal behavior
Mol. Psychiatry
A length polymorphism in the circadian clock gene Per3 is linked to delayed sleep phase syndrome and extreme diurnal preference
Sleep
Influence of CLOCK gene polymorphism on circadian mood fluctuation and illness recurrence in bipolar depression
Am. J. Med. Genet.
Lormetazepam in depressive insomnia: new evidence of phase-response effects of benzodiazepines
Int. Clin. Psychopharmacol.
The Temperament and Character Inventory (TCI): A Guide to its Development and Use
A novel functional polymorphism within the promoter of the serotonin transporter gene: possible role in susceptibility to affective disorders
Mol. Psychiatry
Association of structural polymorphisms in the human period 3 gene with delayed sleep phase syndrome
EMBO Rep.
Lithium
Conn. Med.
Litihum: Actions and Mechanisms
Biological predictors of success of antidepressant drug therapy
Psychiatr. Dev.
Reduced hippocampal volumes associated with the long variant of the serotonin transporter polymorphism in major depression
Arch. Gen. Psychiatry
Finding genes that underlie complex traits
Science
Manic-Depressive Illness
Development of a rating scale for primary depressive illness
Br. J. Soc. Clin. Psychol.
Serotonin transporter genetic variation and the response of the human amygdala
Science
Reduced aggression in mice lacking the serotonin transporter
Psychopharmacology (Berl)
Cited by (53)
Supersensitivity of Patients With Bipolar I Disorder to Light-Induced Phase Delay by Narrow Bandwidth Blue Light
2022, Biological Psychiatry Global Open ScienceProof-of-concept study of a multi-gene risk score in adolescent bipolar disorder
2020, Journal of Affective DisordersInsomnia and psychiatric disorders
2019, Sleep and HealthCircadian Rhythms and Addiction
2018, Neural Mechanisms of AddictionEmil Kraepelin's concepts of the phenomenology and physiology of sleep: The first systematic description of chronotypes
2016, Sleep Medicine ReviewsCitation Excerpt :While those results largely agree with Kraepelin's concepts, there are also some unsupportive results [88]. Molecular genetic studies indicate a functional connection between daytime preference, biological clock and mood for which various genes are considered to be responsible [75,89]. In line with those findings, Kraepelin had also already hypothesized that chronotypes are “an expression of disposition” [30].
The bipolarity of light and dark: A review on Bipolar Disorder and circadian cycles
2015, Journal of Affective DisordersCitation Excerpt :As for period genes, the most associated with BD is per3 (Mansour et al., 2006, 2009; Nievergelt et al., 2006). Mutations in this gene were related to the age of onset of the disease, response to treatment, circadian fluctuations of mood and temperament characteristics (Artioli et al., 2007, Rybakowski et al., 2014a, 2014b). Per2 has also been more recently related to the therapeutic effect of lithium (McCarthy et al., 2013) (detailed in Section 3.5.1).