Author’s Accepted Manuscript Does COMT val158met polymorphism influence P50 sensory gating, eye tracking or saccadic inhibition dysfunctions in schizophrenia? Caroline Demily, Sandrine Louchart-de-laChapelle, Irène Nkam, Nicolas Ramoz, Pierre Denise, Alain Nicolas, Caroline Savalle, Florence. Thibaut
PII: DOI: Reference:
www.elsevier.com/locate/psychres
S0165-1781(16)30107-X http://dx.doi.org/10.1016/j.psychres.2016.07.066 PSY10054
To appear in: Psychiatry Research Received date: 19 January 2016 Revised date: 6 June 2016 Accepted date: 9 July 2016 Cite this article as: Caroline Demily, Sandrine Louchart-de-la-Chapelle, Irène Nkam, Nicolas Ramoz, Pierre Denise, Alain Nicolas, Caroline Savalle and Florence. Thibaut, Does COMT val158met polymorphism influence P50 sensory gating, eye tracking or saccadic inhibition dysfunctions in schizophrenia?, Psychiatry Research, http://dx.doi.org/10.1016/j.psychres.2016.07.066 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Does COMT val158met polymorphism influence P50 sensory gating, eye tracking or saccadic inhibition dysfunctions in schizophrenia? Caroline Demilya, Sandrine Louchart-de-la-Chapelleb, Irène Nkamc, Nicolas Ramozd, Pierre Denisee, Alain Nicolasf, Caroline Savalleg, Florence Thibauth* a
GénoPsy - Centre for the Detection and Management of Psychiatric Genetic Disorders Centre
Hospitalier le Vinatier, Bron , UMR 5229 (CNRS & Lyon 1 University), France b
Service de Gérontologie Clinique & Centre de la Mémoire, Centre de Gérontologie Clinique Rainier
III, Principauté de Monaco c
Secteur 92 G 01, Centre Hospitalier Roger Prévost, Moisselles, France
d
INSERM U 894, Centre Psychiatry and neurosciences, Paris, France
e
Groupe d'Imagerie Neurofonctionnelle, Centre Cycéron, CNRS/CEA/Université de Caen/Université
Paris V, UMR 6095, Bd H. Becquerel, Caen, France f
Unité Michel Jouvet, Centre Hospitalier le Vinatier, Bron, France
g
Service de Biostatistiques, CHU Charles Nicolle, Rouen, France
h
Dept of Psychiatry, University Hospital Cochin (Site Tarnier), University Sorbonne-Paris Cité (Faculty
of Medicine Paris Descartes), INSERM U 894, CPN, Paris France
[email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] *Corresponding author. Dept of Psychiatry, Hôpital Tarnier, 89 rue d’Assas 75006 Paris France. Tel: (33)158413304, Fax: (33)158413303.
Abstract Three electrophysiological endophenotypes are routinely studied in schizophrenia: smooth pursuit eye movement (SPEM) dysfunction, deficits in P50 auditory-evoked potential inhibition, and saccadic inhibition deficits. The current study aimed to investigate the relationship between the COMT val158met polymorphism and these three endophenotypes. One hundred four patients with schizophrenia (DSM-IV-R criteria) and 89 healthy controls were included in this study. P50 auditory1
evoked potential inhibition, antisaccade paradigm and SPEM were analyzed. All individuals were genotyped for the COMT val158met. Patients with schizophrenia showed a higher rate of deficits measured by the SPEM, antisaccade and P50 inhibition paradigms without association with COMT val158met. However, in our control group, we have found an association between the Val polymorphism and the smoking status. More importantly, we have found a higher accuracy of saccades during the predictive pursuit task associated to the Met polymorphism in controls but not in SCZ who were receiving antidopaminergic medications. This result is in line with the hypothesis of the relationship between the Met polymorphism of the COMT gene, a higher level of dopamine in the prefrontal cortex and the role of the fronto-cerebellar loop in smooth predictive pursuit. Keywords: COMT gene polymorphism; schizophrenia; association studies; electrophysiology; P50 auditory-evoked potential; endophenotypes; eye movements; smoking status.
1. Introduction Three electrophysiological endophenotypes are routinely studied in schizophrenia: smooth pursuit eye movement (SPEM) dysfunction, deficits in P50 auditory-evoked potential inhibition in a twoauditory-click conditioning test paradigm, and saccadic inhibition deficits. The genetic factors involved in these deficits remain poorly understood. Several studies have shown that SPEM dysfunction was present in a high percentage of drug naive patients with schizophrenia and their non-schizophrenic relatives (Holzman et al., 1974; Campion et al., 1992; Louchart-de la Chapelle et al., 2005). Nkam et al. (2010) have reported that poor pursuit performance during smooth pursuit was primarily a consequence of a predictive deficit in schizophrenia patients. Indeed, both frontal eye fields and supplementary eye fields make important contributions to predictive aspects of smooth pursuit, based on internal representation of a target motion (Leigh and Zee, 1999; Fukushima et al., 2005). Previous studies have also shown that patients with schizophrenia and their non-schizophrenic relatives have deficits in P50 inhibition, relative to
2
healthy subjects (Louchart-de la Chapelle et al., 2005; Adler et al., 2008). Using magnetoencephalography, the P50 was localized in the auditory cortex of the superior temporal gyrus but was also related to several sources in the frontal cortex (Garcia-Rill et al., 2008). Besides a cholinergic hippocampal pathway, P50 sensory gating studies suggested involvement of prefrontal cortex (PFC) and dopamine (Grunwald et al., 2003); amphetamine was associated to a disrupted suppression of the P50 in healthy controls; this effect was reversible when dopamine D2 receptor antagonists were administered (Light et al., 1999). Finally, patients with schizophrenia also demonstrate impaired ability to suppress a reflexive saccade to a peripheral visual stimulus when they are instructed to look as quickly as possible at the opposite location of the cue. This antisaccade task measures saccadic inhibition. Patients with schizophrenia and their non-schizophrenic first-degree relatives generate a higher proportion of errors (reflexive saccade to the stimulus) and higher antisaccade latencies, compared to controls (Fukushima et al., 1998; Crawford et al., 1998; Nkam et al., 2001; Louchart-de la Chapelle et al., 2005). Disinhibition on antisaccade tasks may reflect impairment in the dorsolateral prefrontal cortex and its associated circuitry (Pierrot-Deseilligny, 1994; McDowell et al., 2002). Interestingly, a previous study performed in 21 subjects with schizotypical personality showed that P50 inhibition and antisaccade deficits were present in 71% of subjects (Cadenhead et al., 2002). In summary, the frontal cortex may play a common role in all three paradigms. The catechol-O-methyl transferase (COMT) enzyme catabolizes dopamine and plays a major role in the regulation of dopamine levels in the PFC since other metabolizers such as the dopamine transporters are rare in this brain region. The COMT gene is located on chromosomal region 22q11.2 and is strongly expressed both in the hippocampus and PFC (Harrison and Weinberger, 2005). A val158met functional polymorphism located in exon 4 has been extensively studied in association with schizophrenia (Li et al., 2000; Shifman et al., 2002) with inconsistent results (Costas et al., 2011). In contrast, association studies between the COMT val/met and frontal lobe functions seem more consistent (Egan et al., 2011; Ira et al., 2013).
3
Based on the putative role of dopamine and frontal lobe dysfunction and the previous studies, the current study aimed to investigate the relationship between the COMT val158met polymorphism and these three endophenotypes. Several studies have previously reported either positive or negative associations between the COMT genotype and each of these three endophenotypes analyzed separately but no studies have analyzed concurrently the three paradigms in the same population.
2. Material and methods
2.1. Subjects: One hundred and four patients with schizophrenia (DSM-IV-R criteria) with a mean duration of the disease of 13 years, and 89 healthy controls were recruited for the study (see Table 1 for details). All schizophrenic patients were receiving antipsychotic treatment at inclusion (86 were receiving typicals and 15 atypicals) with a mean daily dosage in chlorpromazine equivalent (+ SD) of 430 + 241.5 mg. None of the patients were treated with clozapine, benzodiazepines, antidepressants or lithium at the time of the study in order to avoid any additional biases in the measurement of these endophenotypes (Becker et al., 2004; King et al., 1995; Jensen et al., 2008). Patients were in a clinically stable psychiatric condition at inclusion. In most cases their antipsychotic treatment was initiated some years ago without recent major change. All subjects were Caucasians of French origin and matched for geographic origin. The unrelated healthy comparison subjects, who had no personal or family history of neurological or psychiatric disease and were free of any psychotropic treatment, were recruited from the hospital staff. Subjects with neurological disease, intellectual deficiency, mood disorders or alcohol or substance abuse, at the time of the study, were excluded from the study. Visual acuity was corrected if necessary. Informed written consents were obtained from all participants. The study was approved by the Ethics Committee.
2.2. Oculomotor measures: 4
Horizontal eye movements were recorded with an infrared photoelectric limbus eye tracking device (IRIS eye tracker) (Skalar Medical, Delft, Netherlands). Subjects were tested in two paradigms (smooth pursuit and antisaccades) assigned in a random order (see Nkam et al., 2001 for methods). The pursuit gain was computed as the ratio of the amplitude of eye velocity to the amplitude of target velocity. Reflexive saccades in the wrong direction, i.e., toward the peripheral target, were considered as errors in the antisaccade paradigm; the latency of the antisaccades and the number of errors were measured.
2.3. P50 inhibition paradigm recording procedures: Auditory stimuli were delivered in a conditioning-testing paradigm consisting of click pairs (S1, conditioning click; S2, testing click; 500-msec inter-click interval; 10-second inter-pair interval) (see Louchart-de la Chapelle et al., 2005 for methods). Electroencephalographic activity was monitored on a Nihon-Kohden computer. Amplitude was measured as the difference between the peak of the P50 wave and the immediately preceding negative peak, in both the conditioning and test responses. Test/conditioning (T/C) ratios were calculated by dividing the test P50 amplitude by the conditioning P50 amplitude.
2.4. Genotyping: All individuals were genotyped for the COMT rs4680 polymorphism (G>A; val158met). The COMT genotypes were determined after polymerase chain reaction followed by fluorescent minisequencing reaction and electrophoresis on an ABI 3700 sequencer. The samples were processed as described by supplier (Applied Biosystems, Snapshot kit) using an ABI 3700 sequencer, then were analyzed with Genscan© and Genotyper© software (Applied Biosystems) for the size standard definition and the allele peaks recognition and calling.
2.5. Statistical analysis: 5
Means and standard deviations were reported for all data, and p values were two-tailed. Chi square tests and Kruskal-Wallis tests were used to compare respectively qualitative and quantitative variables in Table 1. Electrophysiological measurements were analyzed as quantitative variables and compared between healthy controls and SCZ patients using an ANOVA (Table 1bis). Then, the association between COMT genotypes and electrophysiological endophenotypes was tested by a one-way ANOVA in each group (controls and SCZ patients). The Levene’s test was carried out to test the homogeneity of the variances between groups. Each electrophysiological endophenotype was included as a dependent variable (Supplementary Table 1). Furthermore, to identify a significant association between electrophysiological endophenotypes and the COMT genotypes, SCZ and the interaction between genotypes and the disease, a two-way ANOVA, using the general linear model (GLM) in SPSS was carried out. In this model, age, gender, smoking status or antipsychotic treatment were defined as covariants due to their significant differences when healthy controls and SCZ patients were compared (Supplementary Tables 2, 3, 4, 5). Results obtained by each participant to the different electrophysiological tests were also categorized as normal or abnormal (by using specific cutoff values, for details of the method used, see Louchart et al., 2005), thus analyzed variables were considered as categorical variables. Participants were distributed into three age categories: ≥ 25, > 25 and < 45, ≥45. Univariate analyses were performed using a Chi square test and a non adjusted Odds Ratio (OR) has been calculated with a univariate logistic regression. In a second step, a multivariate analysis was performed using adjusted Odds Ratios (Table 2 and Supplementary Table 6). As analyses performed on two groups showed similar results as compared to analyses performed on three groups, we kept the three initial genotype groups (val/val, val/met and met/met).
3. Results
6
3.1. COMT genotype and clinical status: All subjects were genotyped for the COMT val158met polymorphism and divided into three groups according to their genotypes (val/val, val/met, and met/met). The genotype frequencies of onehundred-and-four patients with schizophrenia (SCZ) and 89 healthy controls were compared. The genotype frequencies of the control and patient groups were all consistent with Hardy Weinberg equilibrium. The respective frequencies of the three genotypes did not significantly differ between patients and controls (Chi square=1, df=2, p=0.82).
3.2. COMT genotype and electrophysiological paradigms: SPEM gain was measured in 58 comparison subjects and 79 patients with schizophrenia. The antisaccade paradigm (number of errors and antisaccade latency) was analyzed in 59 comparison subjects and 72 SCZ patients. The test/conditioning ratio of the P50 paradigm was measured in 78 comparison subjects and 90 SCZ patients. Data for all three paradigms—P50 suppression, smooth pursuit, and antisaccade—were available for 51 comparison subjects and 64 SCZ patients (Table 1bis).
3.2.1. Analysis of the electrophysiological endophenotypes as quantitative variables: Electrophysiological measurements showed significant impairments in SCZ patients as compared to healthy controls (Table 1bis). The analysis of the association between the COMT val158met genotypes and the electrophysiological endophenotypes was performed independently for the group of SCZ patients and the group of controls using an analysis of variance (Supplementary Table 1). Furthermore, to identify an association between the electrophysiological endophenotypes and the genetic variant of COMT independently of the schizophrenia status (or in interaction), we tested a mixed model. In this model, age, gender, smoking status or antipsychotic treatment, were defined as covariants due to their significant differences between SCZ patients and healthy controls which may have interfered (Supplementary Tables 2, 3, 4, and 5). In the group of SCZ patients, no significant 7
association between electrophysiological endophenotypes and COMT polymorphism was found. In contrast, in the group of controls, significant associations were observed between accuracy of saccades (right and left side) during the pursuit task and COMT genotype (a higher accuracy was observed in controls carrying the Met/Met genotype). Significant interaction of genetics by disorder found only for the accuracy of saccades during the pursuit task was due to the genetic associations reported in the control group. When age, gender, antipsychotic treatment and smoking status were defined as covariates and implemented in the mixed model, there was no impact of these covariates on the interaction between the genotype, the clinical status and the endophenotypes (Supplementary Tables 2, 3, 4, and 5 respectively). The C/T ratio was lower (higher sensory gating) in healthy controls carrying the Val/Val genotype but, in contrast, there was no significant interaction of genetics by disorder and, in addition, antipsychotic treatment may have interfered (Supplementary Tables 1 and 4). 3.2.2. Analysis of the electrophysiological endophenotypes as qualitative variables: Thus, for each paradigm, we have determined, in a previous study, two deficit cutoff scores (Louchart-de la Chapelle et al., (2005): a first cut off score was determined on the basis of the mean value for the comparison subjects plus or minus one standard deviation; a second cut off score was determined on the basis of the mean value for the comparison subjects that led to a specificity of 80% for the corresponding paradigm (receiver operating curve analysis). The cut off values were respectively: cutoff 1: 346 msec for the antisaccade latency; cutoff 1: >16 and cutoff 2: >14 for the number of antisaccade errors; and cutoff : >0.57 for the Test/Conditioning ratio. Performances on the P50 suppression, antisaccade, and smooth pursuit gain paradigms, categorized as normal or abnormal (by using the cutoff values), have been analyzed in association with the COMT val158met polymorphisms in patients with schizophrenia as compared to healthy controls. No significant associations were observed between SPEM gain, P50 ratio, the number of antisaccade errors and the genotypes taking into account clinical status, age and gender as potential confounding factors (Table 2). However 8
increased age was associated with increased antisaccade latencies in healthy controls as well as in schizophrenic patients; female gender was associated to increased number of errors in the antisaccade paradigm in both groups. When smoking status was taken into account, only the schizophrenic status played a role, there was no association between the genotype and smoking behavior in schizophrenic patients (multivariate analysis OR: 5.95 [3.09-11.46] p < 0.0001). Surprisingly, in healthy controls, when met/met was compared to val/met+val/val, there was an association between the genotype (carrying at least one Val allele) and the smoking status (multivariate analysis: OR: 3.92 [1.03-14.88], p < 0.04 in controls, as compared to OR: 0.64 [0.21-1.93], not significant in SCZ) (Supplementary Table 6).
4. Discussion Our study investigated for the first time the association between three electrophysiological paradigms (P50, SPEM and antisaccade paradigms) and COMT rs4680 polymorphisms in a large sample of patients with schizophrenia as compared to healthy controls. In a first step, as previously reported (Thaker et al., 2004; Haraldsson et al., 2009), we did not find any association between the COMT rs4680 (val158met) polymorphism and schizophrenia in our sample. Several meta-analyses have previously investigated the association between the COMT val158met polymorphism and schizophrenia: although the evidence is inconsistent (Williams et al 2005), the meta-analyses point to a very weak association between the COMT Val158Met polymorphism and schizophrenia (Glatt et al., 2003; Fan et al., 2005; Munafò et al., 2005; Allen et al., 2008). The val158met allele of rs4680 has yet physiological effects on prefrontal functions which are disturbed in schizophrenia. Interestingly, in our population, there was an association between the Val/Met polymorphism and smoking status in healthy controls but not in patients with schizophrenia, as previously reported by
9
Nedic et al. (2010) in healthy Caucasians. In our population of healthy controls, the risk of smoking was 4 times higher if the subject was carrying at least one Val allele.
In a second step, we have searched for an association between the COMT polymorphisms and each of the three electrophysiological paradigms studied in schizophrenic patients and healthy controls. The COMT gene has been considered as a candidate gene for several electrophysiological endophenotypes in schizophrenia because of its biological function, including degradation of catecholamines, especially in the prefrontal cortex (Cadenhead et al., 2002).
(1) Recently, Liu et al., (2013) showed a significant reduction in S2 (P50) amplitude between wildtype and mutation groups of the COMT rs4680. In contrast, our data do not support the hypothesis that P50 gating deficits are associated with COMT val158met polymorphisms.
In fact, considering the evidence accumulated over time, there is little support for any association between COMT val158met and P50 gating deficits in patients with schizophrenia. Actually, in a combined sample (42 patients with schizophrenia and 25 controls), the COMT polymorphism accounted for 10% of gating variance (p = .02), after variance due to diagnosis, smoking status, and antipsychotic treatment was removed. Val homozygous individuals exhibited the greatest gating deficit (Lu et al., 2007). Moreover, Shaikh et al., (2013) investigated the possible role of NRG1, COMT Val158Met and BDNF Val66Met gene polymorphisms on the P50 endophenotype in a large sample of psychotic patients, their unaffected relatives and unrelated healthy controls using linear regression analyses: there was no evidence for any association between NRG1, COMT Val158Met or BDNF Val66Met genotypes and the P50 endophenotype. These results are concordant with our study and previous results obtained in healthy populations (Majic et al., 2011). Olincy et al. (2010) have calculated a low residual heritability after adjustment for significant covariates (especially age and gender) for the P50 and antisaccade paradigms (0.20 and 0.36 respectively); finally, the Lod scores of the genome-wide single-nucleotide polymorphism linkage scan conducted in 296 nuclear families were < 1 in the 22q region for both the P50 and antisaccade paradigms. 10
In addition, antipsychotic treatments may interfere with sensory gating paradigm measurements. There is suggestive evidence that clozapine may normalize P50 T/C ratio. Taking this data into account, we decided to exclude patients receiving clozapine. Indeed, the effect of clozapine on P50 T/C ratio differs from the P50 T/C ratio effect of other agents that enhance cholinergic function. Clozapine appears to exert its effect through increased S1 amplitude, which suggests that clozapine is not
enhancing
sensory
gating,
but
is
exerting
an
effect
through
a
different
pharmacological/physiological mechanism (Becker et al., 2004). Boutros et al. (2005) found a significant increase in P50 amplitude in a medicated (conventional antispychotics) non-paranoid group. Previous studies have also described the effects of atypical antipsychotics on electrophysiological measures (Csomor et al. 2014). However, our team previously failed to find a relationship between conventional antipsychotic dosage and P50 ratio (Louchart-de-la-Chapelle et al., 2005). In the same way, the present study failed to find an impact of antipsychotic treatment or smoking status on the lack of association between the genotype and the electrophysiological measurements. This observation may be related to the clinical stability of our SCZ patients who were receiving moderate doses of (mainly conventional) antipsychotic treatment.
(2) In our study, patients with schizophrenia did not show any association between the COMT rs4680 polymorphisms and SPEM gain measurement deficits. In summary, most of the previously published observations were inconclusive regarding the small number of subjects or the weak role of the COMT gene. Park et al., (2009) have reported no association between SPEM quality using the natural logarithmic values of the signal-to-noise ratio and COMT rs6267 polymorphism (the gain was not measured). Yet, Haraldsson et al., (2009) reported that the val/val homozygotes SCZ patients (n=19) had lower pursuit gain (3-5%) than the met/met homozygotes SCZ patients (n=39) with a small effect size (d= 0.16-023). Rybakowski et al., (2002) have measured a lower mean intensity of saccades (frequency of catch-up, back-up, square wave jerks and intrusive saccades occurring during each task) in the met/met genotype in 24 male SCZ patients only as compared to the other genotypes ((all types of saccades were mixed up)). Thaker et al. (2004), using a different eye tracking paradigm, have 11
found that the predictive pursuit gain was significantly lower only in the met/met group of SCZ patients but there was a significant diagnosis by genotype effect (62 SCZ patients). The COMT genotype may have explained only about 10% of the variance in predictive pursuit performance in their study. Interestingly, in our study, we have found a higher accuracy of saccades during the predictive pursuit task associated to the Met polymorphism in controls but not in SCZ, which may support the hypothesis concerning the relation between COMT158Met polymorphism and dopamine in the prefrontal cortex. However, the majority of the patients included in our study were treated with predominantly anti-dopaminergic antipsychotic medication, which may have masked an association in SCZ patients. In positron emission tomography, pursuit was associated with greater activation of caudate than saccades, whereas saccades were associated with greater activation of cerebellum and frontal eye fields. A frontal-cerebellar loop may be important in coordinating the preparation and timing of saccades in predictive tracking (O'Driscoll et al., 2000). In the same way, in our study we have found a higher accuracy of saccades associated to the Met polymorphism in controls but not in SCZ, which is in line with the hypothesis of the relationship between the Met polymorphism of the COMT gene, a higher level of dopamine in the prefrontal cortex and the role of the fronto-cerebellar loop in smooth predictive pursuit. (3) Finally, in our study, no association was observed between the COMT genotypes and the number of errors or the latencies of antisaccades in the antisaccade paradigm. In the same way, Stefanis et al. (2004) have reported no association in men with schizotypal disorder (receiving no antipsychotic treatment). In contrast, Haraldsson et al. (2010) have shown that the antisaccade latency decreased with increasing number of val alleles in patients with schizophrenia and controls without group by genotype interaction. In contrast, there was no significant effect of the number of alleles on the percentage of reflexive errors. Interestingly, Ettinger et al. (2008) have reported that healthy controls with at least one val allele showed a lower blood oxygen level-dependent response in ventromedial and dorsomedial prefrontal cortex during antisaccades compared to val non-carriers using fMRI.
12
However, similarly to the SPEM paradigm, most of these observations were inconclusive regarding the small number of subjects.
5. Limitations of this study When schizophrenic patients and healthy controls were compared there was a significant difference concerning their mean age and sex ratio. There were more males and the patients were older in the SCZ group as compared to healthy controls. In our study, having less females in the SCZ group may have artificially improved the number of antisaccade errors in the SCZ group, while the fact that SCZ patients were older may have increased the antisaccade latencies in this group. This may have obscured a possible genotype effect of the COMT polymorphism. Gender is a possible modulator of COMT gene effects in major depressive disorders (Klein et al., 2016). In fact, in our study, age or gender may have played a role in the interaction between genetics and clinical status in the number of errors but not in the latencies in the antisaccade paradigm but none of these factors have had any significant confounding effect on the lack of association between the genotype and the number of errors (Supplementary Tables 2 and 3). In addition, neuroleptic treatment may also have played a role in the interaction between genetics and clinical status in the T/C ratio but we have not found any significant confounding effect of gender, age, antipsychotic treatment or smoking status on the lack of association between the genotype and the T/C ratio (Supplementary Table 4). In summary, in this study, differences in the measures in the SCZ patients compared to healthy controls, were mainly due to the schizophrenia status and not to the genetic status of the COMT without any additional effect of age, gender, antipsychotic treatment or smoking status. (Supplementary Tables 2, 3, 4 and 5).
6. Conclusion
13
Endophenotypes, particularly electrophysiological paradigms, may increase our understanding of the molecular mechanisms underlying schizophrenia risk and its clinical phenotype. Thus, investigating the link between electrophysiological impairments and the COMT gene, involved in the dopaminergic signaling in schizophrenia, may provide a better understanding of the pathophysiology of this disease. However, the COMT Val158Met polymorphism does not seem to be involved in these paradigms. On the basis of current empirical evidence, it appears that the historical candidate gene literature did not yield clear insights into the genetic basis of schizophrenia. A likely reason why historical candidate gene studies did not achieve their primary aims might be inadequate statistical power. However, the considerable efforts embodied in these early studies unquestionably set the stage for current successes in genomic approaches to schizophrenia. Further studies of the COMT gene or the locus remain justified given its important positional and functional relevance and the question of gender-specific modulation. A possible way to further dissect this topic is shifting the focus to gene-based or genome-wide analyses of intermediate phenotypes. Another main limitation of the COMT hypothesis is that schizophrenia is characterized by a complex genetic architecture, with an intricate interplay among several genes. In our population, we have found an association between the Val polymorphism and the smoking status in healthy controls as previously reported. More importantly, we have found a higher accuracy of saccades during the predictive pursuit task associated to the Met polymorphism in controls but not in SCZ, which is in line with the hypothesis of the relationship between the Met polymorphism of the COMT gene, a higher level of dopamine in the prefrontal cortex and the role of the frontocerebellar loop in smooth predictive pursuit. Conflicts of interest
none.
14
Acknowledgments
to all patients included in this study and to all clinicians who have included their patients in this study; Arnaud Leleu for his contribution to the statistical analysis; Emmanuelle Houy-Durand, Angélique Belmont, Daniel Levillain, Hélène Jacquet, Grégory Raux for their contribution to the electrophysiological and genetic analyses. The authors would like to thank the reviewers for their helpful comments.
References
Adler, L.E, Pachtman, E., Franks, R.D., Pecevich, M., Waldo, M.C., Freedman, R., 2008. Neurophysiological evidence for a defect in neuronal mechanisms involved in sensory gating in schizophrenia. Biol. Psychiatry 17 (6), 639–654. Allen, N.C., Bagade, S., McQueen, M.B., Ioannidis, J.P., Kavvoura, F.K., Khoury, M.J., Tanzi, R.E., Bertram, L., 2008. Systematic meta-analyses and field synopsis of genetic association studies in schizophrenia: the SzGene database. Nat. Genet. 40 (7), 827–34. Becker, J., Gomes, I., Ghisolfi, E.S., 2004. Clozapine, but not typical antipsychotics, correct P50 suppression deficits in patients with schizophrenia. Clin. Neurophysiol. 115, 396–401. Boutros, N.N., Trautner, P., Rosburg, T., Korzyukov, O., Grunwald, T., Schaller, C., Elger, C.E., Kurthen, M., 2005. Sensory gating in the human hippocampal and rhinal regions. Clin Neurophysiol. 116, 1967–1974. Cadenhead, K.S., Light, G.A., Geyer, M.A., McDowell, J.E., Braff, D.L., 2002. Neurobiological measures of schizotypal personality disorder: defining an inhibitory endophenotype? Am. J. Psychiatry 159 (5), 869–871. Campion, D., Thibaut, F., Denise, P., Courtin, P., Pottier, M., Levillain, D., 1992. SPEM impairment in drug-naive schizophrenic patients : evidence for a trait marker. Biol. Psychiatry 32 (10), 891-90. Costas, J., Sanjuán, J., Ramos-Ríos, R., Paz, E., Agra, S., Ivorra, J.L., Páramo, M., Brenlla, J., Arrojo, M., 2011. Heterozygosity at cathecol-O-methyltransferase Val158Met and schizophrenia : new data and 15
meta-analysis. J. Psychiatr. Res. 45 (1), 7-14.
Crawford, T.J., Sharma, T., Puri, B.K., Murray, R.M., Berridge, D.M., Lewis, S.W., 1998. Saccadic eye movements in families multiply affected with schizophrenia: the Maudsley Family Study. Am. J. Psychiatry 155 (12), 1703–1710.
Csomor, P.A., Preller, K.H., Geyer, M.A., Studerus, E., Huber, T., Vollenweider, F.X., 2014. Influence of aripiprazole, risperidone, and amisulpride on sensory and sensorimotor gating in healthy “low and high gating” humans and relation to psychometry. Neuropsychopharmacology 39(10), 2485-2496.
Egan, M.F., Goldberg, T.E., Kolachana, B.S., Callicott, J.H., Mazzanti, C.M., Straub, R.E., Goldman, D., Weinberger, D.R., 2001. Effect of COMT Val108/158 Met genotype on frontal lobe function and risk for schizophrenia. Proc. Natl. Acad. Sci. USA 98 (12), 6917-6922.
Ettinger U, Kumari V, Collier DA, Powell J, Luzi S, Michel TM, Zedomi O, Williams SC., 2008. CatecholO-methyltransferase (COMT) val158met genotype is associated with BOLD response as a function of task characteristic. Neuropsychopharmacology 33(13), 3046-3057.
Fan, J.B., Zhang, C.S., Gu, N.F, Li, X.W., Sun, W.W., Wang, H.Y., Feng, G.Y., St Clair, D., He, L., 2005. Catechol-O-methyltransferase gene Val/Met functional polymorphism and risk of schizophrenia: a large-scale association study plus meta-analysis. Biol. Psychiatry 57 (2), 139–144.
Fukushima, J., Fukushima, K., Chiba, T., Tanaka, S., Yamashita, I., Kato, M., 1998. Disturbances of voluntary control of saccadic eye movements in schizophrenia patients. Biol. Psychiatry 23 (7), 670– 677.
Fukushima, J., Tanaka, S., Williams, J.D., Fukushima, K., 2005. Voluntary control of saccadic and smooth-pursuit eye movements in children with learning disorders. Brain Dev. 27 (8), 579-588.
Garcia-Rill, E., Moran, K., Garcia, J., Findley, W.M., Walton, K., Strotman, B., Llinas, R.R., 2008. Magnetic sources of the M50 response are localized to frontal cortex. Clin. Neurophysiol. 119 (2), 388-398.
Glatt, S.J., Faraone, S.V., Tsuang, M.T., 2003. Association between a functional catechol Omethyltransferase gene polymorphism and schizophrenia: meta-analysis of case-control and family16
based studies. Am. J. Psychiatry 160 (3), 469–476.
Grunwald, T., Boutros, N.N., Pezer, N., von Oertzen, J., Fernández, G., Schaller, C., Elger, C.E., 2003. Neuronal substrates of sensory gating within the human brain. Biol. Psychiatry 15 (6), 511-519.
Haraldsson, H.M., Ettinger, U., Magnusdottir, B.B., Sigmundsson, T., Sigurdsson, E., Ingason, A., Petursson H., 2009. COMT val(158)met genotype and smooth pursuit eye movements in schizophrenia. Psychiatry Res. 169 (2), 173-175. Haraldsson, H.M., Ettinger, U., Magnusdottir, B.B., Sigmundsson, T., Sigurdsson, E., Ingason, A., Petursson, H., 2010. Cathecol-O-methyltransferase Val 158 Met polymorphism and antisaccade eye movements in schizophrenia. Schizophr. Bull. 36 (1), 157-164. Harrison, P.J., Weinberger, D.R., 2005. Schizophrenia gene, gene expression, and neuropathology: on the matter of their convergence. Mol. Psychiatry 10 (1), 40-68.
Holzman, P.S., Proctor, L.R., Levy, D.L., Yasillo, N.J., Meltzer, H.Y., Hurt, S.W., 1974. Eye-tracking dysfunctions in schizophrenic patients and their relatives. Arch. Gen. Psychiatry 31 (2), 143–151. Holzman, P.S., O'Brian, C., Waternaux, C., 1991. Effects of lithium treatment on eye movements. Biol Psychiatry 29(10), 1001-1015.
Ira, E., Zanoni, M., Ruggeri, M., Dazzan, P., Tosato, S., 2013. COMT, neuropsychological function and brain structure in schizophrenia: a systematic review and neurobiological interpretation. J. Psychiatry Neurosci. 38 (6), 366-380. Jensen, K.S., Oranje, B., Wienberg, M., Glenthøj, B.Y., 2008. The effects of increased serotonergic activity on human sensory gating and its neural generators. Psychopharmacology (Berl). 196(4), 631641.
King, D.J., Best, P., Lynch, G., Mannion, M.F., Montgomery, R.C., Tiplady, B., Yisak, W., 1995. The effects of remoxipride and chlorpromazine on eye movements and psychomotor performance in healthy volunteers. J Psychopharmacol. 9(2), 143-149.
17
Klein, M., Schmoeger, M., Kasper, S., Schosser, A., 2016. Meta-analysis of the COMT Val158Met polymorphism in major depressive disorder: the role of gender. World J. Biol. Psychiatry. 2016 17(2), 147-158. Leigh, R.J., Zee, D.S., 1999. The neurology of eye movements, 3rd ed. New York, Oxford University Press. Li, T., Ball, D., Zhao, J., Murray, R.M., Liu, X., Sham, P.C., Collier, D.A., 2000. Family-based linkage disequilibrium mapping using SNP marker haplotypes : application to a potential locus for schizophrenia at chromosome 22q11. Mol. Psychiatry 5 (5), 77-84. Light, G.A., Malaspina, D., Geyer, M.A., Luber, B.M., Coleman, E.A., Sackeim, H.A., Braff, D.L., 1999. Amphetamine disrupts P50 suppression in normal subjects. Biol. Psychiatry 46 (7), 990-996. Liu, X., Hong, X., Chan, R.C., Kong, F., Peng, Z., Wan, X., Wang, C., Cheng, L., 2013. Association study of polymorphisms in the alpha 7 nicotinic acetylcholine receptor subunit and cathecol-Omethyltransferase genes with sensory gating in first-episode schizophrenia. Psychiatry Res. 209 (6), 431-438. Louchart-de la Chapelle, S., Nkam, I., Houy, E., Belmont, A., Ménard, J.F., Rossignol, A.C., Siwek, O., Mezerai, M., Guillermou, M., Fouldrin, G., Levillain, D., Dollfus, S., Campion, D., Thibaut, F., 2005. A concordance study of three electrophysiological measures in schizophrenia. Am. J. Psychiatry 162 (3), 466-474. Lu, B.Y., Martin, K.E., Edgar, J.C., Smith, A.K., Lewis, S.F., Escamilla, M.A., Miller, G.A., Cañive, J.M., 2007. Effect of cathecol-O-methyltransferase val(158)met polymorphism on the P50 gating endophenotype in schizophrenia. Biol. Psychiatry 62 (7), 822-825. Majic, T., Rentzsch, J., Gudlowski, Y., Ehrlich, S., Juckel, G., Sander, T., Lang, U.E., Winterer, G., Gallinat, J., 2011. COMT val158met genotype modulates human sensory gating. Neuroimage 55 (2), 818-824. McDowell, J.E., Brown, G.G., Paulus, M., Martinez, A., Stewart, S.E., Dubowitz, D.J., Braff, D.L., 2002. Neural correlates of refixation saccades and antisaccades in normal and schizophrenia subjects. Biol. Psychiatry 51 (3), 216–223.
18
Munafò, M.R., Bowes, L., Clark, T.G., Flint, J., 2005. Lack of association of the COMT (Val158/108 Met) gene and schizophrenia: a meta-analysis of case-control studies. Mol. Psychiatry 10 (8), 765770. Nedic, G., Nikolac, M., Borovecki, F., Hajnsek, S., Muck-Seler, D., Pivac, N., 2010. Association study of a functional catechol-O-methyltransferase polymorphism and smoking in healthy Caucasian subjects. Neurosci Lett. 473 (3), 216-219.
Nkam, I., Thibaut, F., Denise, P., Van Der Elst, A., Ségard, L., Brazo, P., Ménard, J., Théry, S., Halbeck, I., Delamilleure, P., Vasse, T., Etard, O., Dollfus, S., Champion, D., Levillain, D., Petit, M., 2001. Saccadic and smooth-pursuit eye movements in deficit and non-deficit schizophrenia. Schizophr. Res. 48 (1), 145-153. Nkam, I., Bocca, M.L., Denise, P., Paoletti, X., Dollfus, S., Levillain, D., Thibaut, F., 2010. Impaired smooth pursuit in schizophrenia results from prediction impairment only. Biol. Psychiatry 67 (10), 992-997.
O'Driscoll GA, Wolff AL, Benkelfat C, Florencio PS, Lal S, Evans AC., 2000. Functional neuroanatomy of smooth pursuit and predictive saccades. Neuroreport 11(6), 1335-1340.
Olincy A, Braff DL, Adler LE, Cadenhead KS, Calkins ME, Dobie DJ, Green MF, Greenwood TA, Gur RE, Gur RC, Light GA, Mintz J, Nuechterlein KH, Radant AD, Schork NJ, Seidman LJ, Siever LJ, Silverman JM, Stone WS, Swerdlow NR, Tsuang DW, Tsuang MT, Turetsky BI, Wagner BD, Freedman R., 2010. Inhibition of the P50 cerebral evoked response to repeated auditory stimuli: results from the Consortium on Genetics of Schizophrenia. Schizophr. Res. 119(1-3), 175-182.
Park, B.L., Shin, H.D., Cheong, H.S., Park, C.S., Sohn, J.W., Kim, B.J., Seo, H.K., Kim, J.W., Kim, K.H., Shin, T.M., Choi, I.G., Kim, S.G., Woo, SI., 2009. Association analysis of COMT polymorphisms with schizophrenia and smooth pursuit eye movement abnormality. J. Hum. Genet. 54 (12), 709-712.
Pierrot-Deseilligny, C., 1994. Saccade and smooth-pursuit impairment after cerebral hemispheric lesions. Eur. Neurol. 34 (3), 121–134.
19
Rybakowski, J.K., Borkowska, A., Czerski, P.M., Hauser, J., 2002. Eye movement disturbances in schizophrenia and a polymorphism of cathecol-O-methyltransferase gene. Psychiatry Res. 113 (1-2), 49-57. Shaikh, M., Hall, M.H., Schulze, K., Dutt, A., Walshe, M., Williams, I., Constante, M., Picchioni, M., Tulopulou, T., Collier, D., Rijsdijk, F., Powell, J., Arranz, M., Murray, R.M., Bramon, E., 2011. Do COMT, BDNF and NRG1 polymorphismes influence P50 sensory gating in psychosis. Psychol. Med. 41 (2), 263-276. Shifman, S., Bronstein, M., Sternfeld, M., Pisanté-Shalom, A., Lev-Lehman, E., Weizman, A., Reznik, I., Spivak, B., Grisaru, N., Karp, L., Schiffer, R., Kotler. M., Strous, R.D., Swartz-Vanetik, M., Knobler, H.Y., Shinar, E., Beckmann, J.S., Yakir, B., Risch, N., Zak, N.B., Darvasi, A., 2002. A Highly significant association between a COMT haplotype and schizophrenia. Am. J. Med. Genet. 71 (6), 1296-1302. Stefanis NC, Van Os J, Avramopoulos D, Smyrnis N, Evdokimidis I, Hantoumi I, Stefanis CN., 2004. Variation in catechol-o-methyltransferase val158 met genotype associated with schizotypy but not cognition: a population study in 543 young men. Biol. Psychiatry 56(7), 510-515.
Thaker, G.K., Wonodi, I., Avila, M.T., Hong, L.E., Stine, O.C., 2004. Cathecol-O-methyltransferase polymorphism and eye tracking in schizophrenia: a preliminary report. Am. J. Psychiatry 161 (12), 2320-2322.
Williams, H.J., Glaser, B., Williams, N.M., Norton, N., Zammit, S., MacGregor, S., Kirov, G.K., Owen, M.J., O'Donovan, M.C., 2005. No association between schizophrenia and polymorphisms in COMT in two large samples. Am. J. Psychiatry 162 (9), 1736-1738.
20
Table 1: Socio-demographic and clinical data for patients and healthy controls. Frequency of the COMT genotypes in patients and healthy controls. Characteristics of the samples
Healthy controls
Patients with schizophrenia
89
104
Sex ratio (M/F)
44/45
71/33*
Mean age (+ SD)
30.7 + 6.7 years
36.3 + 8 years**
-
23.2 + 4.2 years
23/54 (30%)
71/28*** (72%)
12 + 4
18.5 + 6****
PANSS total mean score
-
68.1 + 12.6
Mean chlorpromazine equivalent (+ SD)
-
430 + 241.5 mg/day
Typicals/Atypicals
-
86/15
val/val genotype
25 (28%)
31 (30%)
val/met genotype
40 (45%)
49 (47%)
met/met genotype
24 (27%)
24 (23%)
N
Mean age of onset of SCZ (+ SD) Smoking/Nonsmoking Number of cigarettes/day (+ SD)
*Significant difference: Chi square=7.1, df=1, p
