Herbert M. Lachman

Human catechol-O-methyltransferase pharmacogenetics: Description of a functional polymorphism and its potential application to neuropsychiatric disorders

Catechol-O-methyltransferase (COMT) inactivates catecholamines and catechol drugs such as L-DOPA. A common genetic polymorphism in humans is associated with a three-to-four-fold variation in COMT enzyme activity and is also associated with individual variation in COMT thermal instability. We now show that this is due to G-->A transition at codon 158 of the COMT gene that results in a valine to methionine substitution. The two alleles can be identified with a PCR-based restriction fragment length polymorphism analysis using the restriction enzyme Nla III. The identification of a gentic marker associated with significant alterations in enzyme activity will facilitate the analysis of a possible role for the COMT gene in neuropsychiatric conditions in which abnormalities in catecholamine neurotransmission are believed to occur, including mood disorders, schizophrenia, obsessive compulsive disorder, alcohol and substance abuse, and attention deficit hyperactivity disorder. In addition, this polymorphism may have pharmacogenetic significance in that it will help make it possible to identify patients who display altered metabolism of catechol drugs.

Association of codon 108/158 catechol‐O‐methyltransferase gene polymorphism with the psychiatric manifestations of velo‐cardio‐facial syndrome

Velo-cardio-facial-syndrome (VCFS) is a common congenital disorder associated with typical facial appearance, cleft palate, cardiac defects, and learning disabilities. The majority of patients have an interstitial deletion on chromosome 22q11. In addition to physical abnormalities, a variety of psychiatric illnesses have been reported in patients with VCFS, including schizophrenia, bipolar disorder, and attention deficit hyperactivity disorder. The psychiatric manifestations of VCFS could be due to haploin-sufficiency of a gene(s) within 22q11. One candidate that has been mapped to this region is catechol-O-methyltransferase (COMT). We recently identified a polymorphism in the COMT gene that leads to a valine-->methionine substitution at amino acid 158 of the membrane-bound form of the enzyme. Homozygosity for COMT158met leads to a 3-4-fold reduction in enzymatic activity, compared with homozygotes for COMT158val. We now report that in a population of patients with VCFS, there is an apparent association between the low-activity allele, COMT158met, and the development of bipolar spectrum disorder, and in particular, a rapid-cycling form.

Association between low activity serotonin transporter promoter genotype and early onset alcoholism with habitual impulsive violent behavior

A common 44-base pair insertion/deletion polymorphism in the promoter region of the human serotonin transporter (5-HTT) gene has been observed to be associated with affective illness and anxiety-related traits. This biallelic functional polymorphism, designated long (L) and short (S), affects 5-HTT gene expression since the S promoter is less active than the L promoter. Since there is strong evidence of a disturbance in brain serotonergic transmission among antisocial, impulsive, and violent type 2 alcoholic subjects, we decided to test the hypothesis that the frequency of the S allele, which is associated with reduced 5-HTT gene expression, is higher among habitually violent type 2 alcoholics when compared with race and gender-matched healthy controls and non-violent late-onset (type 1) alcoholics. The 5-HTT promoter genotype was determined by a PCR-based method in 114 late onset (type 1) non-violent alcoholics, 51 impulsive violent recidivistic offenders with early onset alcoholism (type 2), and 54 healthy controls. All index subjects and controls were white Caucasian males of Finnish origin. The S allele frequency was higher among type 2 alcoholics compared with type 1 alcoholics (χ2 = 4.86, P = 0.028) and healthy controls (χ2 = 8.24, P = 0.004). The odds ratio for SS genotype vs LL genotype was 3.90, 95% Cl 1.37–11.11, P = 0.011 when type 2 alcoholics were compared with healthy controls. The results suggest that the 5-HTT ‘S’ promoter polymorphism is associated with an increased risk for early onset alcoholism associated with antisocial personality disorder and impulsive, habitually violent behavior.

Analysis of a functional catechol-O-methyltransferase gene polymorphism in schizophrenia: evidence for association with aggressive and antisocial behavior.

We have recently characterized a functional polymorphism in the catechol-O-methyltransferase (COMT) gene that is responsible for substantial variability in COMT enzymatic activity found in humans. A common low-activity variant of the enzyme contains a methionine residue at amino acid 158 of membrane-bound COMT whereas the common high activity variant has a valine at this site. Considering the role of COMT in dopamine metabolism and the involvement of dopaminergic pathways in the pathogenesis of schizophrenia and violence, we screened 37 patients with schizophrenia to determine whether or not a behavioral association with the COMT polymorphism exists. Patients were assessed for dangerousness on the basis of a history of violent and threatening behavior, crime, cocaine and alcohol abuse, and other antisocial behaviors. We found that schizophrenic patients who were homozygous for the low activity allele were judged by their psychiatrists to be at higher risk for aggressive and dangerous behavior than those who were homozygous for the high activity allele (Kruskal-Wallis statistic = 10.43; P = 0.003).

Association between the functional variant of the catechol-O-methyltransferase (COMT) gene and type 1 alcoholism.

Catechol-O-methyltransferase (COMT) is an enzyme which has a crucial role in the metabolism of dopamine. It has been suggested that a common functional genetic polymorphism in the COMT gene, which results in 3 to 4-fold difference in COMT enzyme activity,1,2 may contribute to the etiology of mental disorders such as bipolar disorder and alcoholism.1 Since ethanol-induced euphoria is associated with the rapid release of dopamine in limbic areas, it is conceivable that subjects who inherit the allele encoding the low activity COMT variant would have a relatively low dopamine inactivation rate, and therefore would be more vulnerable to the development of ethanol dependence. The aim of this study was to test this hypothesis among type 1 (late-onset) alcoholics. The COMT polymorphism was determined in two independent male late onset (type 1) alcoholic populations in Turku (n = 67) and Kuopio (n = 56). The high (H) and low (L) activity COMT genotype and allele frequencies were compared with previously published data from 3140 Finnish blood donors (general population) and 267 race- and gender-matched controls. The frequency of low activity allele (L) was markedly higher among the patients both in Turku (P = 0.023) and in Kuopio (P = 0.005) when compared with the general population. When all patients were compared with the general population (blood donors), the difference was even more significant (P = 0.0004). When genotypes of all alcoholics (n = 123) were compared with genotypes of matched controls, the odds ratio (OR) for alcoholism for those subjects having the LL genotype vs those with HH genotype was 2.51, 95% CI 1.22–5.19, P = 0.006. Also, L allele frequency was significantly higher among alcoholics when compared with controls (P = 0.009). The estimate for population etiological (attributable) fraction for the LL genotype in alcoholism was 13.3% (95% CI 2.3–25.7%). The results indicate that the COMT polymorphism contributes significantly to the development of late-onset alcoholism.

High-Activity Catechol-O-Methyltransferase Allele is More Prevalent in Polysubstance Abusers

Allelic variants at the catechol-O-methyltransferase (COMT) locus are candidates to contribute to genetic components of interindividual differences in vulnerability to substance abuse. COMT plays a prominent role in dopaminergic circuits important for drug reward, and COMT alleles encode enzymes whose activities vary from three- to four-fold. We compared COMT allele frequencies in control research volunteers reporting insignificant lifetime use of addictive substances with those in volunteers reporting substantial polysubstance use. Homozygosity for the high-activity COMT allele was found in 18% of controls, 31% of volunteers with high lifetime substance use, and 39% meeting DSMIII-R substance abuse criteria [odds ratio (relative risks) 2.0 (control vs. use; 95% confidence interval 1.2-3.5; P < 0.013) and 2.8 (control vs. DSM; 1.3-6.1; P < 0.008)]. Individuals with the high-activity COMT variant may have greater genetic vulnerability to drug abuse.

Ultra-ultra rapid cycling bipolar disorder is associated with the low activity catecholamine-O- methyltransferase allele

Bipolar spectrum disorders are recurrent illnesses characterized by episodes of depression, hypomania, mania or the appearance of mixed states. Great variability is evident in the frequency of episode recurrence and duration.1–3 In addition to regular circannual episodes,4 a spectrum of cycle frequencies has been observed, from the classical rapid cycling (RC) pattern of four or more episodes per year,5,6 to those with distinct shifts of mood and activity occurring within a 24–48 h period, described as ultra-ultra rapid cycling (UURC) or ultradian cycling.7–10 RC has a female preponderance, and occurs with greater frequency premenstrually, at the puerperium and at menopause.11,12 Tricyclic antidepressants and MAOIs, both of which increase functional monoamines norepinephrine, dopamine and serotonin, are known to precipitate mania or rapid-cycling in an estimated 20–30% of affectively ill patients.13–15 We have recently reported a strong association between velo-cardio-facial syndrome (VCFS) patients diagnosed with rapid-cycling bipolar disorder, and an allele encoding the low enzyme activity catechol-O-methyltransferase variant (COMT L).16,17 Between 85–90% of VCFS patients are hemizygous for COMT.18 Homozygosity for the low activity allele (COMT LL) is associated with a 3–4 fold reduction of COMT enzyme activity compared with homozygotes for the high activity variant (COMT HH).19,20 There is nearly an equal distribution of L and H alleles in Caucasians.21 Individuals with COMT LL would be expected to have higher levels of transynaptic catecholamines due to a reduced COMT degradation of norepinephrine and dopamine. We therefore hypothesized that the frequency of COMT L would be greater in RC BPD ascertained from the general population. Significantly, we found that the frequency of COMT L was higher in the UURC variant of BPD than among all other groups studied (P = 0.002). These findings indicate that COMT L could represent a modifying gene that predisposes to ultra-ultra or ultradian cycling in patients with bipolar disorder.

Suicidal behavior in patients with schizophrenia is related to COMT polymorphism

&NA; A common functional polymorphism that results in a three‐ to four‐fold difference in catechol‐O‐methyltransferase (COMT) enzyme activity has been related to psychiatric disorders such as ultra‐ultra rapid cycling bipolar disorder, drug abuse and alcoholism (Lachman et al., 1996a; Karayiorgou et al., 1997; Vandenbergh et al., 1997; Papolos et al., 1998; Tiihonen et al., 1999). Several studies have also reported associations between the allele encoding the low enzyme activity COMT variant (L allele) and other‐directed aggression (Strous et al., 1997; Lachman et al., 1998; Kotler et al., 1999) in schizophrenic and schizoaffective patients. The current study investigated whether the COMT L allele is also associated with suicide attempts in schizophrenic and schizoaffective patients. COMT genotypes were determined and history of suicide attempts was retrospectively investigated in a Finnish sample (n = 94) and a US sample (n = 54). Significant associations were observed between COMT genotype and suicide; specifically, history of violent suicide attempts. The COMT L allele was more frequent in subjects who had attempted suicide by violent means. These associations were significant in males but not females. These findings support a common neurobiological substrate for self‐ and other‐directed aggression, and suggest that catecholaminergic alterations may contribute to these behaviors in schizophrenic and schizoaffective patients.

Aggressive behavior in schizophrenia is associated with the low enzyme activity COMT polymorphism: a replication study

We have previously reported that increased aggressive behavior in schizophrenic patients may be associated with a polymorphism at codon 158 of the catechol O‐methyltransferase (COMT) gene that encodes a low enzyme activity variant. The finding has been replicated by one group, but not others. The discordant findings could be due to statistical errors or methodological issues in the assessment of aggressive/violent behavior. Consequently, additional studies are needed. Patients with schizophrenia (SZ) were assessed for violent behavior using the Lifetime History of Aggression (LHA) scale, an 11‐item questionnaire that includes Aggression, Self‐Directed Aggression, and Consequences/Antisocial Behavior subscales. DNA was genotyped for the COMT 158 polymorphism, as well as a functional polymorphism in the monoamine oxidase A (MAOA) gene promoter. Similar to our previously reported findings, a statistically significant association was found between aggressive behavior in SZ and the COMT 158 polymorphism; mean LHA scores were higher in subjects homozygous for 158Met, the low enzyme activity COMT variant (F(2,105) = 5.616, P = 0.005). Analysis of the major LHA subscales revealed that the association with 158Met was due to high scores on the Aggression, and Self‐Directed Aggression subscales, but not the Consequences/Antisocial Behavior subscale. No significant association was detected for the MAOA gene alone. Our findings provide further support that COMT is a modifying gene that plays a role in determining interindividual variability in the proclivity for outward and self‐directed aggressive behavior found in some schizophrenic patients.

Linkage studies suggest a possible locus for bipolar disorder near the velo-cardio-facial syndrome region on chromosome 22

Velo-cardio-facial syndrome (VCFS) is a congenital anomaly characterized by multiple dysmorphisms, cleft palate, cardiac anomalies, and learning disabilities, that results from a microdeletion of chromosome 22q11. An increased prevalence of psychiatric illness has been observed, with both schizophrenia and bipolar disorder commonly being diagnosed. For these reasons, the VCFS region is an interesting candidate region for bipolar disorder. We examined this region in 17 bipolar families from three populations: 13 families from the general North American population (University of California, San Diego/University of British Columbia, UCSD/UBC), three larger families from New York, and a portion of Old Order Amish pedigree 110. Three microsatellite markers spanning 13 cM around the VCFS region were genotyped in all the families. A maximum lod score of 2.51 was obtained in the UCSD/UBC families under a dominant model at D22S303. In the combined family set, maximum lod scores of 1.68 and 1.28 were obtained at this marker under dominant and recessive models, respectively. Four additional markers were subsequently typed in selected positive families, and yielded positive lods at 6 of 7 markers spanning 18 cM in this region. Nonparametric, multipoint analyses using the affected pedigree member (APM) method also yielded suggestive evidence for linkage in both the UCSD/UBC family set (P = 0.0024) and in the combined families (P = 0.017). Affected sibpair analyses were similarly positive in the UCSD/UBC families (P = 0.017), and in the combined families (P = 0.004). These results are suggestive of a possible locus for bipolar disorder near the VCFS region on chromosome 22.