Abnormal behavior associated with a point mutation in the structural gene for monoamine oxidase A

Screening the monoamine oxidase B gene in 100 male patients with schizophrenia: a cluster of polymorphisms in African-Americans but lack of functionally significant sequence changes

The monoamine oxidase B (MAO-B) gene was examined in 100 alleles derived from 80 Caucasian, 10 African-American, 5 Asian, and 5 Native American male patients with schizophrenia to identify sequence changes that might be associated with the disease. Approximately 235 kb of genomic sequence, primarily in coding regions, were screened by dideoxy fingerprinting, a modification of single-strand conformational polymorphism (SSCP) analysis that detects virtually 100% of sequence changes [Sarkar et al. (1992): Genomics 13:441-443; Liu and Sommer (1994): PCR Methods Appl 4:97-108]. No sequence changes of likely functional significance were identified, suggesting that mutations affecting the structure of the MAO-B protein are uncommon in the general population and are unlikely to contribute significantly to the genetic predisposition to schizophrenia. Eight polymorphisms were identified in African-Americans and Native Americans, but none were identified among Caucasians. Of the eight observed polymorphisms, a set of five transitions and one microdeletion was identified within approximately 17 kb of genomic sequence in the same 3 African-American individuals, while the remaining 7 African-Americans had a sequence identical to that in Caucasians. The presence of two such haplotypes, without intermediates, is compatible with the hypothesis that germline mutations can occur in clusters, as also suggested by other recent findings.

Human hair follicles as a peripheral source of tyrosine hydroxylase and aromatic L-amino acid decarboxylase mRNA

Total RNA from human hair follicles was reverse transcribed and amplified using primers specific for aromatic L-amino acid decarboxylase (AADC) and tyrosine hydroxylase (TH). Agarose electrophoresis of the amplified products showed reverse transcription polymerase chain reaction (RT-PCR) products of the expected size for both TH and AADC. Sequencing showed that the amplified products matched the known sequences of TH and AADC. This study identifies hair follicles as a convenient, uninvasive, source of the mRNA for TH and AADC. Analysis of these mRNA's may be useful in the diagnosis and investigation of conditions resulting from qualitative changes in the genes that code for these enzymes.

Relationship between imidazoline/guanidinium receptive sites and monoamine oxidase A and B

Imidazoline binding sites or imidazoline/guanidinium receptive sites (IGRS) recognize bioactive endogenous substances and a variety of pharmacologically active compounds containing imidazoline or guanidinium moieties. The family of imidazoline binding proteins consists of multiple membrane-associated proteins that differ in their tissue/subcellular localization, M(r) and ligand recognition properties. Two of the imidazoline binding proteins are identical to the mitochondrial enzyme monoamine oxidase (MAO) A and B isoforms, which contain imidazoline binding domains distinct from the enzyme active site. The relationship between the imidazoline binding proteins and monoamine oxidases was further characterized in the present report using a covalent probe (2-[3-azido-4[125I]iodophenoxy] methyl imidazoline, [125I]-AZIPI) to label the imidazoline binding proteins in different species and following transient expression of MAO- A and -B in COS 7 cells. Species homologues of MAO-A and -B in rat and human differ in their apparent molecular weight by approximately 2000 Da. In rat and human liver [125I]-AZIPI identified peptides with apparent molecular weights similar to those of the species homologues of MAO. Peptides of M(r) approximately 63,000 (MAO-A) and approximately 59,000 (MAO-B) were also photolabeled in membranes prepared from COS-7 cells transfected with human cDNA clones encoding MAO-A or -B. Additional experiments indicate that the imidazoline binding domains on MAO-A and -B exhibit different ligand recognition properties. The covalent labeling of human liver MAO-B was more sensitive than that of placenta MAO-A to inhibition by the imidazoline 2-(4,5-dihydroimidaz-2-yl)-quinoline (BU224). These data indicate that the A and B isoforms of MAO possess imidazoline binding domains that differ in their ligand recognition properties. Allosteric regulation of the activity of MAO via the imidazoline binding domains may be of significance in various disease states associated with elevated enzyme expression or in which the enzyme is a therapeutic target.

Mean genes and the biology of aggression: a critical review of recent animal and human research

Recent genetic work has suggested that abnormalities in serotonin biochemistry are directly causally linked to aggressive behavior, and there appears to be a consensus in the psychiatric literature that low levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid are specifically associated with impulsive violent behavior. We review the limitations of the genetic studies and conduct a meta-analysis of 39 studies linking 5-HIAA to aggression in humans. No differences in mean 5-HIAA levels were found between groups of violent impulsive psychiatric patients and groups of subjects diagnosed with other psychiatric or medical conditions not considered to involve violence once these levels had been corrected for three nonpsychiatric sources of variation (age, sex and height). However, mean 5-HIAA levels in both of these groups were lower than the mean corrected level in groups of normal healthy volunteers. The results confirm an association between low 5-HIAA levels and psychiatric disorders, but fail to support any specific relationship between low 5-HIAA levels and impulsive aggression or criminality. It is premature and misleading to speak of "mean genes" (Hen 1996) or a specific neurochemistry of aggressive behavior.

Power and gender: violence and affection experienced by children in Barbados, West Indies

Discourses on violence conceptualize the phenomenon as a property of (1) individuals, (2) social circumstances, and (3) social relationships. Rigorous comparative tests fail to support the first and second hypotheses. Survey data collected in 1990 from a national random sample of 407 men and women aged twenty to forty-five from the West Indian island of Barbados indicate that one of four experienced physical and emotional violence as children. Boys and girls were equally likely to be abused by both mothers (or other female caregivers) and fathers (or other male caregivers); stepparents were no more likely to treat children violently than were biological parents. However, the presence of a stepfather increased the likelihood that women battered their daughters and decreased the likelihood that women battered their sons. In general, powerful women protected their children from violence, treated them affectionately, and elicited affection for them from their men. The probability that a son experienced an affectionate relationship with a biological father rose with the length of time the two lived together, but only for sons with powerful mothers. By contrast, men battered powerless women and the children of powerless women. Powerless women battered their own children.

Monoamine oxidase B isolated from bovine liver exists as large oligomeric complexes in vitro

The quaternary structure and subunit composition of bovine liver monoamine oxidase B (MAO B) was investigated using size-exclusion chromatography, sucrose gradient centrifugation and electron microscopy. Purified enzyme was subjected to Superdex gel filtration column chromatography in the presence of the non-ionic detergents, n-octyl beta-D-glucopyranoside (octyl glucoside) and Triton X-100R-PC (Triton). The specific activity and elution profiles indicate that the enzyme exists as a dimer and preferentially functions as larger oligomeric complexes. Distribution of the oligomeric forms of MAO B was found to be dependent upon protein concentration. Dilution of the enzyme, however, had little or no effect upon the specific activity profiles. In Triton and octyl glucoside, plots of specific activity versus molecular mass displayed a sigmoidal shape. The chromatographic data suggest that detergent-solubilized bovine liver MAO B exists as cooperative oligomeric enzyme complexes. Similarly, sucrose density gradient centrifugation of purified MAO B exhibited a direct correlation between enzyme activity and molecular mass of the MAO complexes. MAO B activity was found to be widely distributed throughout the sucrose gradient and the highest enzyme activity was contained in the high-density sucrose layers. MAO B specific activity is dependent upon the size of the protein complexes and, therefore, oligomerization of the enzyme may play a role in the regulation of MAO B. Transmission electron microscopy of purified MAO B was performed using protein prepared by octyl glucoside extraction. Purified enzyme was applied to Formvar-coated copper grids and negatively stained with methylamine tungstate. MAO-B-specific monoclonal antibody (MAO B-1C2) conjugated to colloidal gold was used as a probe. Contrast enhancement of the electron microscopy data showed that detergent-depleted enzyme tends to aggregate in a linear arrangement of oligomeric complexes. Our data suggest that the MAO B oligomeric complexes are hexamers which contain threefold rotational symmetry. The individual complexes have globular morphology and the hexamers appear to be composed of a trimer of MAO B homodimers.

Transgenic and null mutant animals for psychosomatic research

OBJECTIVE

Progress in the use of genetically altered animals for psychosomatic research is reviewed.

METHOD

Analysis of the strengths and weaknesses of these models, particularly from a developmental and behavioral prospective is used to assess the validity of these models.

RESULTS

Genetically altered animals can be used to create models of the estimated 5000 human diseases in which genetic predispositions play a role, as well as models for diseases that do not involve gene defects, such as human immunodeficiency virus (HIV) infection. In addition, these models have already contributed immensely to our understanding of basic biology and the biology of behavior. Replication of human gene defects in mice has provided direct models of human disease, but there are various factors that sometimes prevent the gene defect from producing the human disease in mice. However, even in this case, the models can contribute to understanding the basic biology of the disease.

CONCLUSIONS

While genetically altered animals have revolutionized the understanding of single gene disorders, their promise has not yet been fulfilled for multigenic behavioral disorders. Newer techniques to allow control of the tissue and stage of development at which a gene is expressed are likely to enhance the usefulness of these models for psychosomatic research. New models of disease for testing psychological impacts on illness and specific ways altering neurotransmitter function will be discovered. While these models will be extremely useful to psychosomatic medicine, the nature of this discipline of necessity involves emphasis on individual experience, and thus will never be amenable to exclusively genetic analysis.

Developmental factors influencing aggression. Animal models and clinical correlates

Clearly, models of developmentally induced aggression in animals can give us important insights into the factors inducing aggression in children. Several such models have been produced, and the neurochemical substrates eliciting the aggressive behavior have been identified. In many cases, the serotonergic system is involved. In the future, these animal models may also prove useful in identifying appropriate treatments.

Association of monoamine oxidase A alleles with alcoholism among male Chinese in Taiwan

OBJECTIVE

The role of monoamine oxidase (MAO) in alcoholism was assessed by genetic association studies separately in five ethnic groups in Taiwan.

METHOD

Restriction fragment length polymorphisms (RFLP) and dinucleotide repeat polymorphisms (DNRP) were used to determine MAOA and MAOB alleles in male alcoholic patients and nonalcoholic comparison subjects among Han Chinese and four aboriginal groups.

RESULTS

Significant associations of alcohol dependence with MAOA alleles (RFLP and DNRP) were found among the Han Chinese, but not among the aboriginal groups. No significant association with MAOB DNRP alleles was found in any group.

CONCLUSIONS

Genetic heterogeneity may underlie alcoholism among different ethnic groups in Taiwan, and MAOA mutations may play a role in susceptibility to alcoholism among Han Chinese.

X-linked mental retardation with neonatal hypotonia in a French family (MRX15): gene assignment to Xp11.22-Xp21.1

Linkage analysis was performed in a family with non-specific X-linked mental retardation (MRX 15). Hypotonia in infancy was the most remarkable physical manifestation. The severity of mental deficiency was variable among the patients, but all of them had poor or absent speech. Significant lod scores at a recombination fraction of zero were detected with the marker loci DXS1126, DXS255, and DXS573 (Zmax = 2.01) and recombination was observed with the two flanking loci DXS164 (Xp21.1) and DXS988 (Xp11.22), identifying a 17 cM interval. This result suggests a new gene localization in the proximal Xp region. In numerous families with non-specific X-linked mental retardation (MRX), the corresponding gene has been localized to the paracentromeric region in which a low recombination rate impairs the precision of mapping.

Association study between schizophrenia and monoamine oxidase A and B DNA polymorphisms

Monoamine oxidases (MAO) A and B, which are encoded by two distinct genes located on the human X chromosome, are both involved in the oxidative metabolism of dopamine. Decreased levels of platelet MAO-B activity has been reported in patients with schizophrenia and genetic variation in MAO activity had been proposed as a significant factor in the etiology of this disease. We carried out an association study using two intragenic polymorphisms within the MAO-A and MAO-B genes in 110 schizophrenic patients and 87 control subjects. For each polymorphic marker, no significant difference in allelic frequencies was observed between patients and controls. Nevertheless, a trend toward an association between allele 1 of the MAO-B gene and paranoid schizophrenia was found. Our results do not support the hypothesis that inherited variants of MAO genes might play a major role in a genetic predisposition to schizophrenia. Since several previous reports found a low MAO-B platelet activity in patients with paranoid schizophrenia, the identification of polymorphisms related to enzyme activity would be useful.

Annotation: behavioural phenotypes: a window onto the biology of behaviour

Characteristic behavioural patterns (including cognitive processes and social interactions) have been reported in a number of syndromes arising from genetic or chromosomal abnormalities, suggesting that molecular analysis of the underlying defect could reveal the biological basis of the behavioural phenotype. Because of the rarity of many of the syndromes, and the complexity of their genetic basis, there are great difficulties in establishing the validity of the association between syndrome and behavioural phenotype. Nevertheless, evidence from animal studies with relevance to human behavioural phenotypes shows that the pathway from genotype to phenotype may be accessible by careful delineation of behavioural phenotypes.

No evidence of linkage between schizophrenia and D2 dopamine receptor gene locus in Italian pedigrees

Our purpose was to test the dopamine D2 receptor gene (DRD2), the tyrosine hydroxylase (TH) gene and the monoamino oxydase A (MAO-A) gene for linkage to schizophrenia and bipolar disorders. We have analyzed seven Italian families with schizophrenia and four families with bipolar disorders for a total of 68 individuals; 32 individuals were affected. Diagnoses were made using the structured clinical interview Schedule for Affective Disorders and Schizophrenia, Lifetime version (SADS-L). The results of our study provide no evidence of linkage between alleles at D2 dopamine receptor loci and schizophrenia or bipolar disorders. The markers TH gene and MAO-A gene give slightly positive or negative results suggesting the utility of further analysis on more informative families.

Genes and aggressiveness. Behavioral genetics

Four strains of 'knockout' mice, each with a different gene inactivated, have been found to show increased aggressive behavior. The generation of such knockout strains and quantitative trait locus analysis will help identify the genetic determinants of this complex trait.

Mutational analysis of the human MAOA gene

The monoamine oxidases (MAO-A and MAO-B) are the enzymes primarily responsible for the degradation of amine neurotransmitters, such as dopamine, norepinephrine, and serotonin. Wide variations in activity of these isozymes have been reported in control humans. The MAOA and MAOB genes are located next to each other in the p11.3-11.4 region of the human X chromosome. Our recent documentation of an MAO-A-deficiency state, apparently associated with impulsive aggressive behavior in males, has focused attention of genetic variations in the MAOA gene. In the present study variations in the coding sequence of the MAOA gene were evaluated by RT-PCR, SSCP, and sequencing a mRNA or genomic DNA in 40 control males with > 100-fold variations of MAO-A activity, as measured in cultured skin fibroblasts. Remarkable conservation of the coding sequence was found with only 5 polymorphisms observed. All but one of these were in the third codon position and thus did not alter the deduced amino acid sequence. The one amino acid alteration observed, lys --> arg, was neutral and should not affect the structure of the protein. This study demonstrates high conservation of coding sequence in the human MAOA gene in control males, and provides primer sets which can be used to search genomic DNA for mutations in this gene in males with neuropsychiatric conditions.

Specific genetic deficiencies of the A and B isoenzymes of monoamine oxidase are characterized by distinct neurochemical and clinical phenotypes

Monoamine oxidase (MAO) exists as two isoenzymes and plays a central role in the metabolism of monoamine neurotransmitters. In this study we compared the neurochemical phenotypes of previously described subjects with genetically determined selective lack of MAO-A or a lack of both MAO-A and MAO-B with those of two subjects with a previously described X chromosome microdeletion in whom we now demonstrate selective MAO-B deficiency. Mapping of the distal deletion breakpoint demonstrates its location in intron 5 of the MAO-B gene, with the deletion extending proximally into the Norrie disease gene. In contrast to the borderline mental retardation and abnormal behavioral phenotype in subjects with selective MAO-A deficiency and the severe mental retardation in patients with combined MAO-A/MAO-B deficiency and Norrie disease, the MAO-B-deficient subjects exhibit neither abnormal behavior nor mental retardation. Distinct neurochemical profiles characterize the three groups of MAO-deficient patients. In MAO-A-deficient subjects, there is a marked decrease in deaminated catecholamine metabolites and a concomitant marked elevation of O-methylated amine metabolites. These neurochemical changes are only slightly exaggerated in patients with combined lack of MAO-A and MAO-B. In contrast, the only biochemical abnormalities detected in subjects with the MAO-B gene deletion are a complete absence of platelet MAO-B activity and an increased urinary excretion of phenylethylamine. The differences in neurochemical profiles indicate that, under normal conditions, MAO-A is considerably more important than MAO-B in the metabolism of biogenic amines, a factor likely to contribute to the different clinical phenotypes.

Lack of barrels in the somatosensory cortex of monoamine oxidase A-deficient mice: role of a serotonin excess during the critical period

In a transgenic mouse line (Tg8) deficient for the gene encoding monoamine oxidase A (MAOA), we show that the primary somatosensory cortex (S1) lacks the characteristic barrel-like clustering of layer IV neurons, whereas normal pattern formation exists in the thalamus and the trigeminal nuclei. No barrel-like patterns were visible with tenascin or serotonin immunostaining or with labeling of thalamocortical axons. An excess of brain serotonin during the critical period of barrel formation appears to have a causal role in these cortical abnormalities, since early administration of parachlorophenylalanine, an inhibitor of serotonin synthesis, in Tg8 pups restored the formation of barrels in S1, whereas inhibition of catecholamine synthesis did not. Transient inactivation of MAOA in normal newborns reproduced a barrelless phenotype in parts of S1.

Legal implications of genetics and crime research

Two controversial topics dominate discussions of the legal implications of genetics and crime research; (1) the viability and politics of such research, which has sparked fervent debate in the USA; and (2) the current status of new or atypical criminal law defences, which would include a genetic-defect defence to criminal behaviour. This chapter begins by examining the scientifically discredited XYY chromosome syndrome defence, the major genetic-defect defence that defendants have attempted, albeit unsuccessfully. It then focuses on attorneys' efforts to test for evidence of genetic abnormality in the recent and highly publicized case involving convicted murderer Stephen Mobley, whose family history reveals four generations of violent, aggressive and behaviourally disordered men and women. Mobley is currently appealing his death sentence before the Georgia Supreme Court on the basis that the trial court denied his request both to have genetic testing performed and to have such testing allowed as evidence into court. This chapter concludes by emphasizing that the question is not whether genetic evidence will ever be admitted into court, but when and under what kinds of circumstances. No doubt, genetic evidence, and comparable kinds of biological evidence, will have a major impact on juries when such evidence is more fully accepted by the legal and scientific communities.

Identification of a region important for human monoamine oxidase B substrate and inhibitor selectivity

Monoamine oxidase (MAO) A and B are flavoenzymes that catalyze the oxidative deamination of biogenic and xenobiotic amines. To search for domains that confer substrate and inhibitor selectivities, two chimeric proteins were constructed and expressed in yeast. The kinetic constants and IC50 values were determined for these chimeric enzymes using MAO-A/B selective substrates and inhibitors. Replacement of MAO-A amino acids 161-375 with the corresponding region of MAO-B, termed AB(161-375)A, converted MAO-A catalytic properties to MAO-B like ones. The specificity constants (k(cat)/K(m))for the oxidation of beta-phenylethylamine (PEA) (1.6 x 10(5) s-1 M-1) and benzylamine (2.4 x 10(4) s-1 M-1) by AB (161-375)A were similar to wild-type MAO-B (PEA, 8 x 10(5)s(-1) M(-1); benzylamine, 4.9 x 10(4) s(-1) M(-1). Serotonin (5-HT), a preferred substrate for MAO-A, was not oxidized by AB(161-375)A or wild-type MAO-B. Furthermore, (AB161-375)A was more sensitive to the MAO-B specific inhibitor deprenyl (IC50 2.7 +/- 0.4 x 10(-8) M) than to the MAO-A specific inhibitor clorgyline (IC50 5.4 +/- 0.8 x 10(-7) M). However, the reciprocal chimera in which a MAO-B segment was replaced with the corresponding region of MAO-A, termed ++(+BA152-366B), lacked catalytic activity. The lack of catalytic activity was not due to aberrant expression but rather an inactive protein as demonstrated by Western blot analysis. These results demonstrate that MAO-B amino acids 152-366 contain a domain(s) that confers substrate and inhibitor selectivity.

Executive functions and developmental psychopathology

In this paper, we consider the domain of executive functions (EFs) and their possible role in developmental psychopathologies. We first consider general theoretical and measurement issues involved in studying EFs and then review studies of EFs in four developmental psychopathologies: attention deficit hyperactivity disorder (ADHD), conduct disorder (CD), autism, and Tourette syndrome (TS). Our review reveals that EF deficits are consistently found in both ADHD and autism but not in CD (without ADHD) or in TS. Moreover, both the severity and profile of EF deficits appears to differ across ADHD and autism. Molar EF deficits are more severe in the latter than the former. In the few studies of more specific EF tasks, there are impairments in motor inhibition in ADHD but not in autism, whereas there are impairments in verbal working memory in autism but not ADHD. We close with a discussion of implications for future research.

Cellular expression of mRNAs encoding monoamine oxidases A and B in the rat central nervous system

Monoamine oxidases A and B (MAO-A and MAO-B) oxidatively deaminate neurotransmitter and xenobiotic amines. The cellular localization of these isoenzymes in the central nervous system (CNS) differs markedly and only partly reflects the distribution of their presumed natural substrates. In the present study, by using in situ hybridization with 35S-labelled oligonucleotide probes, we examined the distribution of mRNAs encoding MAO-A and MAO-B in the rat CNS. Probes for tyrosine hydroxylase, histidine decarboxylase, and tryptophan hydroxylase mRNAs were used to demonstrate the catecholaminergic, histaminergic, or serotoninergic nature of some cell populations in adjacent sections. The radioligands [3H]-Ro 41-1049 and [3H]lazabemide (reversible and selective inhibitors of MAO-A and MAO-B, respectively) were used to reveal the protein distribution by enzyme radioautography. The distribution and abundance of transcripts for both isoenzymes in the tissues investigated differed markedly but, in general, correlated with the protein distribution. MAO-A mRNA and protein were most abundant in noradrenergic neurons. However, moderate levels of transcript expression and protein were also detected in the serotoninergic neurons, and low but significant levels were detected in the dopaminergic neurons. An unexpectedly remarkable degree of hybridization signal was apparent in nonaminergic cell populations, e.g., in the cerebral cortices, the hippocampal formation (CA1-3, dentate gyrus), the cerebellar granule cell layer, and the spinal cord motoneurons. In contrast, MAO-B mRNA and protein were most abundant in serotoninergic and histaminergic neurons, Bergmann glial cells, and circumventricular organs, including the ependyma. MAO-B transcripts were also weakly expressed in nonaminergic cells, e.g., in the hippocampal formation (CA1-2). A further nonneuronal localization of MAO-B transcripts was also resolved, e.g., in the glia limitans, the olfactory nerve layer, and the cerebellar peduncle. These findings reveal further the potential of various cell populations to synthesize the isoenzymes, and homologous (aminergic) and heterologous (nonaminergic) patterns of expression as well as coexpression of MAO mRNAs are described.

Monoamine oxidase A and B activities in heavy smokers

There is a strong association between depression and smoking. Because monoamine oxidase (MAO) inhibition leads to antidepressant effect and in vitro studies have shown that cigarette smoke inhibits MAO activity, it is conceivable that smoking may have an antidepressant effect, if smokers have reduced MAO activity. Therefore, we assessed platelet MAO-B activity and plasma concentration of catecholamine metabolites reflecting MAO-A activity in heavy dependent smokers and nonsmokers matched for sociodemographic characteristics. Platelet MAO-B activity, plasma 3,4-dihydroxyphenylglycol, plasma 3,4-dihydroxyphenylacetic acid, and plasma 3,4-dihydroxyphenylalanine concentrations were significantly lower in smokers than in nonsmokers, whereas plasma norepinephrine did not differ. Significantly more smokers reported previous history of depression, manic episode, panic attack, agoraphobia, and simple phobia. Smokers had higher scores (p < 0.001) on the Montgomery-Asberg Depression Rating Scale (MADRS) and the Hamilton Anxiety Scales. It is concluded that the activities of both forms of the MAO are reduced in heavy dependent smokers.

A dinucleotide repeat polymorphism at the gene for monoamine oxidase A and measures of aggressiveness

The relationship between measures of aggressiveness (personality questionnaire scales, conduct disorder diagnosis, and symptom count) and a recently discovered dinucleotide repeat length polymorphism at the monoamine oxidase type A (MAOA) gene (MAOCA-1) as a candidate locus was examined in adolescents using polymerase chain reaction. No significant correlation between aggression scales and repeat length at the MAOCA-1 marker was found, whereas the categorical diagnosis of conduct disorder showed a nonsignificant trend for an association with the marker. Alternative explanations of this trend are discussed. The data obtained suggest that the polymorphism studied is not associated with the variation in aggressiveness.

Behavioural abnormalities in male mice lacking neuronal nitric oxide synthase

In addition to its role in blood vessel and macrophage function, nitric oxide (NO) is a neurotransmitter found in high densities in emotion-regulating brain regions. Mice with targeted disruption of neuronal NO synthase (nNOS) display grossly normal appearance, locomotor activity, breeding, long-term potentiation and long-term depression. The nNOS- mice are resistant to neural stroke damage following middle cerebral artery ligation. Although CO2-induced cerebral vasodilatation in wild-type mice is NO-dependent, in nNOS- mice this vasodilation is unaffected by NOS inhibitors. Establishing a behavioural role for NO has, until now, not been feasible, as NOS inhibitor drugs can only be administered acutely and because their pronounced effects on blood pressure and other body functions obfuscate behavioural interpretations. We now report a large increase in aggressive behaviour and excess, inappropriate sexual behaviour in nNOS- mice.

How is the Human Genome Project doing, and what have we learned so far?

In this paper, we describe the accomplishments of the initial phase of the Human Genome Project, with particular attention to the progress made toward achieving the defined goals for constructing genetic and physical maps of the human genome and determining the sequence of human DNA, identifying the complete set of human genes, and analyzing the need for adequate policies for using the information about human genetics in ways that maximize the benefits for individuals and society.

Monoamine oxidases and alcoholism. I. Studies in unrelated alcoholics and normal controls

Low platelet MAO activity has been associated with alcoholism. In order to evaluate the role of MAO genes in susceptibility to alcoholism, we have taken a biochemical and molecular genetic approach. The sample consisted of 133 alcoholic probands who were classified by subtypes of alcoholism and 92 normal controls. For those subjects typed for platelet MAO activity, alcoholics (N = 74) were found not to differ from the non-alcoholics controls (N = 34). Neither was there a significant difference between type I and type II alcoholics or between either subtype and normal controls. However, we do find significant differences between male and female alcoholics, but not between male and female controls. The allele frequency distribution for the MAO-A and MAO-B dinucleotide repeats is different between the alcoholic sample (N = 133) and the normal control sample (N = 92). In a two-way analysis of variance of MAO-B activity as a function of the allelic variation of each marker locus and diagnosis, there is no evidence for mean differences in activity levels for the different alleles. Our findings do not rule out a role for the MAO-B gene in controlling the enzyme activity because the dinucleotide repeats are located in introns.

Estrogenic control of monoamine oxidase A activity in human neuroblastoma cells expressing physiological concentrations of estrogen receptor

Several lines of evidence support the hypothesis of a role played by estrogens in the manifestation of affective disorders in women. The analysis of the mechanism of action of a number of antidepressant drugs clearly demonstrated the involvement of the catecholaminergic system in the etiology of these complex behavioral pathologies. The present in vitro study was therefore undertaken to investigate the presence of a functional link between estrogen and catecholamine metabolism in cells of neural origin. The model system utilized was a human neuroblastoma cell line which was obtained by stable transfection of the estrogen receptor cDNA (SK-ER3). The present study shows that in SK-ER3 activation of the estrogen receptor correlates with a marked decrease in monoamine oxidase A activity. This effect is observed following treatment with a physiological concentration of 17 beta-estradiol and can be blocked by the specific antagonist of the steroid receptor, ICI 182,780. Dibutyryl cyclic AMP acting, like estrogens, on the state of differentiation of SK-ER3 cells did not affect monoamine oxidase A activity. The present study provides strong evidence of a strict relationship between estrogen receptor and monoamine oxidase A activity in human cells of neural origin, thus favoring the hypothesis of an antidepressive effect of estrogens exerted via inhibition of the monoamine oxidative pathway.

Fatherless rearing leads to sociopathy

Endorsing Mealey's analysis, it is pointed out that increasing rates of crime and violence are due to increasing proportions of children being reared in circumstances radically different from the extendedfamily environment to which we are evolntionarily adapted, that is, they are reared without fathers.

Sociopathy and sociobiology: Biological units and behavioral units

Behavioral biologists have long sought to link behavioral units (e.g., aggression, depression, sociopathy) with biological units (e.g., genes, neurotransmitters, hormones, neuroanatomical loci). These units, originally contrived for descriptive purposes, often lead to misunderstandings when they are reified for purposes of causal analysis. This genetic and biochemical explanation for sociopathy reflects such problems.

Is sociopathy a type or not? Will the “real” sociopathy please stand up?

The validity of the classification of “primary sociopaths” as a qualitatively distinct group in the general population is questioned. Cenetic variation in the experience and expression of emotions may play a role in the development of antisocial behavior. However, research clearly documents that socialization environments powerfully modify the expression of genetic biases in a manner that increases or decreases the risk for “sociopathy.”

Sociobiology, sociopathy, and social policy

Evolutionary analysis suggests that policies based on deterrence may cope effectively with primary sociopathy if the threat of punishment fits the crime in the cost/benefit calculus of the sociopath, not that of the public. On the other hand, policies designed to offset serious disadvantage in social competition may help inhibit the development of secondary sociopathy, rather than deter its expression.

Implications of an evolutionary biopsychosocial model

Mealey's work has several interesting implications: It refutes the charge that sociobiology paints a cynical portrait of human nature and adopts a one-sided reductionism; it exemplifies a general theoretical scheme for constructing evolutionary biopsychosocial models of human behavior; and it has the practical effect of promoting and informing early intervention in children at risk for psychopathic disorder.

The role of attachment in the development and prevention of sociopathy

Mealey's sociobiological model of sociopathy could profit from attachment theory, in particular, the theory and research on the basis of the Adult Attachment Interview (Main & Goldwyn 1985–1993). Findings of an adult attachment study in a forensic psychiatric setting are summarized. Three attachment-oriented strategies for families, schools, and forensic settings are proposed to help reduce or prevent secondary sociopathy and criminal recidivism.

The role of emotion in sociopathy: Contradictions and unanswered questions

Emotion is critical in Mealey's conceptual arguments. However, several of her assertions about the role of emotion in sociopathy are problematic. Questions are raised regarding the link between lack of anxiety and low levels of secondary emotions such as love and sympathy, the argument that sociopaths are low in anxiety but high in neuroticism, and the designation of anxiety as a secondary emotion.

Psychopathy and violence: Arousal, temperament, birth complications, maternal rejection, and prefrontal dysfunction

The key questions arising from Mealey's analysis are: Do environmental factors such as early maternal rejection also contribute to the emotional deficits observed in psychopaths? Are there psychophysiological protective factors for antisocial behavior that have clinical implications? Does a disinhibited temperament and low arousal predispose to primary psychopathy? Would primary or secondary psychopaths be most characterized by prefrontal dysfunction?

Cheaters never prosper, sometimes

In the Frank (1988) model, a small increase in the number of cheaters will soon be reversed. It is not clear that this prediction holds for sociopathy. There are also many attractive evolutionary models that do not admit a small, stable proportion of cheaters. Hence, without definitive evidence about the character of early human society, we cannot conclude that sociopathy has an evolutionary origin.

Sociopathy, evolution, and the brain

We propose that Mealey's model is limited in its description of sociopathy because it does not provide an adequate role for the main organ mediating genes and behavior, namely, the brain. Further, on the basis of our research, we question the view of sociopaths as a homogeneous group.