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. © 1995 Wiley-Liss, Inc.     

A genetic epidemiologic investigation of breast cancer in families with bilateral breast cancer. II. Linkage analysis

We conducted genetic linkage analyses of breast cancer in 20 pedigrees, each having at least one case of bilateral breast cancer diagnosed before 50 years of age. We tested for linkage using inheritance models from previous segregation analyses, incorporating differences in risk based on menopausal status into the analyses. We tested for heterogeneity by predividing the data set based on the interval between diagnoses of the proband's two primaries (less than 1 year (synchronous) versus at least 2 years (asynchronous], and on the histological types of breast cancer in the pedigrees. Very tight linkage could be excluded between breast cancer and ABO, GC, GPT, MNS, and PGM1 for some of the different linkage analyses. A maximum lod score of +1.01 (at theta = 0.001) between ACP1 and a breast cancer susceptibility locus was seen in the asynchronous all-cases subsample.     

Failure to find a chromosome 18 pericentric linkage in families with schizophrenia

A recent report of a possible linkage of bipolar affective disorder to a pericentric region of chromosome 18 initiated the present investigation to search for a similar linkage in 32 families with schizophrenia. The results of a study using 5 markers mapped to this region show negative lod scores and only weak evidence for any linkage by nonparametric analyses. If the previously reported finding is a true positive linkage for bipolar disorder, then either it is unlikely to be related to the genetics of schizophrenia, or the proportion of families linked to this region is small. © 1995 Wiley-Liss, Inc.     

Polymorphisms at the GLUT2 (β-cell/liver) glucose transporter gene and non-insulin-dependent diabetes mellitus (NIDDM): analysis in affected pedigree members

The precise genetic defects underlying the etiology of non-insulin-dependent diabetes mellitus (NIDDM) have yet to be identified. The beta-cell/liver glucose transporter gene GLUT2 represents a good candidate for the etiology of the disease, being involved in the glucose signalling for beta-cell insulin release. Population association studies of the GLUT2 gene in NIDDM have so far yielded controversial results. In order to determine the possible contribution of this gene to the inheritance of NIDDM, we have employed a new approach, where two polymorphic markers of the GLUT2 locus, detected with the restriction enzyme Taq-1, were examined for linkage with the disease in a group of 22 Italian pedigrees with affected members (n = 50). Departure from independent segregation between markers and disease was analyzed by the Affected-Pedigree-Members (APM) statistical method. Furthermore, association analysis between the Taq-1 RFLPs at the GLUT2 locus and NIDDM was performed in a group of diabetics with a strong family history, comprising the 22 probands and 23 other diabetics with an affected first-degree relative. The results indicate that there was no segregation distortion between the Taq-1 markers of the GLUT2 gene and the disease in the pedigrees examined. Also, no significant difference in genotype distribution, haplotype and allele frequencies was found between diabetics and controls for the two Taq-1 RFLPs. We conclude that genetic variation at the GLUT2 transporter gene is unlikely to contribute in a major way to the inheritance for NIDDM in this Italian population.     

Monoamine oxidases in age-associated diseases: New perspectives for old enzymes

Population aging is one of the most significant social changes of the twenty-first century. This increase in longevity is associated with a higher prevalence of chronic diseases, further rising healthcare costs. At the molecular level, cellular senescence has been identified as a major process in age-associated diseases, as accumulation of senescent cells with aging leads to progressive organ dysfunction. Of particular importance, mitochondrial oxidative stress and consequent organelle alterations have been pointed out as key players in the aging process, by both inducing and maintaining cellular senescence. Monoamine oxidases (MAOs), a class of enzymes that catalyze the degradation of catecholamines and biogenic amines, have been increasingly recognized as major producers of mitochondrial ROS. Although well-known in the brain, evidence showing that MAOs are also expressed in a variety of peripheral organs stimulated a growing interest in the extra-cerebral roles of these enzymes. Besides, the fact that MAO-A and/or MAO-B are frequently upregulated in aged or dysfunctional organs has uncovered new perspectives on their roles in pathological aging. In this review, we will give an overview of the major results on the regulation and function of MAOs in aging and age-related diseases, paying a special attention to the mechanisms linked to the increased degradation of MAO substrates or related to MAO-dependent ROS formation.     

Gender and Depression in Men

Four conceptual frameworks are presented for understanding the role of gender in the way men experience, express, and respond to depression. The sex differences framework is often limited by the absence of relevant theory to guide research. The masked depression framework assumes that depression in men can be hidden by substance abuse and other externalizing problems. The masculine depression framework assumes that gender norms affect the presentation of depression and create a phenotypic variant of the disorder. The gendered responding framework assumes that gender norms affect how different men respond to negative affect in general. Each framework is evaluated in light of relevant theory and empirical work, and recommendations are made for future research directions.     

Heritability of event-related brain potentials in families with a history of alcoholism.

Event-related brain potentials (ERPs) are altered in patients with a variety of psychiatric disorders and may represent quantitative correlates of disease liability that are more amenable to genetic analysis than disease status itself. Estimates of heritability are presented for amplitude and latency of the N1 and P3 components of the ERP measured at 19 scalp locations in response to visual and auditory stimuli for 604 individuals in 100 pedigrees ascertained as part of the Collaborative Study on the Genetics of Alcoholism. Significant heritabilities were found for visual P3 amplitude in response to all stimuli and for visual P3 latency in response to target and novel, but not non-target, stimuli. Heritability of visual N1 latencies was uniformly low, whereas heritability of visual N1 amplitude was significant for all electrodes in response to the non-target stimuli but only for posterior electrodes in the other two stimulus conditions. Heritabilities for auditory target P3 were similar to those of the visual stimuli, with auditory target P3 amplitudes and latencies both demonstrating significant heritability. For auditory P2 in response to non-target stimuli, peak amplitude was heritable, but latency was not. Auditory N1 amplitude and latency were significantly heritable for both target and non-target conditions and did not demonstrate the anterior/posterior patterning obtained for visual N1 amplitude. This study represents the first systematic assessment of heritability of these potential neurophysiological markers in families with a history of alcoholism and suggests that many of these ERP phenotypes have heritabilities strong enough to justify genomic screening for loci jointly influencing ERP abnormalities and liability to alcoholism.     

Linkage and association of a functional DRD2 variant [Ser311Cys] and DRD2 markers to alcoholism,substance abuse and schizophrenia in Southwestern American Indians

Alcoholism is one of a group of common psychiatric diseases which are well-defined clinically and strongly influenced genetically, but which are likely to be highly heterogeneous in causation, genetically and otherwise. Dopamine is a key neurotransmitter in drug-mediated reinforcement. Based on association studies with the Taq1A downstream marker, the D2 dopamine receptor has been proposed to be the “Reward Deficiency Syndrome Gene.” Ser311Cys, a naturally occurring variant which largely inactivates transduction after D2 receptor activation, was abundant (0.16) in a Southwestern American Indian population we studied. Therefore, we were able to provide a critical test of the D2 hypothesis of vulnerability to alcoholism by evaluating Ser311Cys and also the intron-2 STR and Taq1A markers at this locus in a total of 459 subjects, including 373 sib pairs, from large families. The result is that neither alcoholism, substance use disorders nor schizophrenia show a relationship to Ser311Cys genotype, even when the 15 Cys311/Cys311 homozygous individuals are compared to others. Furthermore, sib pair analysis incorporating information across all three sib pair categories: concordant affected, discordant and concordant unaffected revealed no effect of DRD2 genotype or haplotype on alcoholism or substance use disorder. Am. J. Med. Genet. 74:386–394, 1997. © 1997 Wiley-Liss, Inc.     

HLA and disease: haplotype sharing in multiplex families

Recently it has been argued that the distribution of shared haplotypes in multiplex sibships for HLA-associated diseases may be an indicator of the disorder's underlying mode of transmission. Specifically, it has been suggested that the presence of multiple disease susceptibility genes and/or loci may be inferred when an inverse relationship between the amount of haplotype sharing and the number of affected sibs is observed in families where neither parent is affected. This claim is evaluated using extensive computer simulations. It is shown that a variety of haplotype sharing patterns are possible, even for the simplest models, and that for a large segment of the parameter space the actual distribution of shared haplotypes is opposite to that predicted. Accordingly, the inference that more than one locus is involved in the etiology of an HLA-associated non-Mendelian disease, if based only on the distribution of shared haplotypes in multiplex sibships, is unjustified.     

Susceptibility loci for atopic dermatitis on chromosome 21 in a Swedish population

BACKGROUND: Atopic dermatitis (AD) is a hereditary, pruritic, chronic, relapsing, inflammatory skin disease resulting from multiplex interactions between genes and environmental factors. We have previously found several loci showing suggestive linkage on chromosomes 3q14, 13q14, 15q14-15 and 17q21, and weaker linkage to chromosomes 1p32, 4q24-26 and 21q21 in 109 Swedish families. METHODS: In order to confirm the linkage to chromosome 21, we carried out a replication linkage analysis with additional microsatellite markers on chromosome 21 in another set of 295 families. RESULTS: In the extended material, the Z-score was 2.40 (P < 7.4 x 10(-4)) in the region 21q21 for a semi-quantitative variable measurement; the severity of AD. When combining the two data sets into 404 families and stratifying according to asthma status, suggestive linkage was found only in the group of AD patients who also had asthma (Z-score 2.45, P < 7.4 x 10(-4) and 2.69, P < 7.4 x 10(-4)) in two different regions. CONCLUSIONS: Our results suggest that 21q21 could contain a susceptibility gene modulating the severity of AD especially in combination with asthma.     

酒依赖高发家系成员听觉P3的对照研究

为了验证事件相关电位Ｐ３波幅降低是酒依赖的遗传标志的假说，作者在５个酒依赖高发家系３２名１８周岁以上成员（其中有１４名酒依赖者）和８个无酒依赖的对照家系４５名１８周岁以上成员中采用Ｏｄｄｂａｌ方法测查了听觉Ｐ３，结果发现，高发家系中的酒依赖者、非酒依赖者与对照家系成员之间的Ｐ３波幅和潜伏期差异均无统计学显著性。作者探讨了假说未得到验证的原因。     

Sex linkage and race differences in spatial ability: A reply

Stevens and Hyde have questioned only the empirical evidence relevant to Jensen's formulation of a genetic hypothesis to explain race and sex differences in spatial visualization ability, rather than the formulation of the hypothesisper se, which at present remains the only non-ad hoc hypothesis concerning these phenomena, which are admittedly in need of further empirical investigation. The formulation of potentially falsifiable hypotheses derived from genetic theory is the surest means for advancing knowledge in behavioral genetics.     

Shyness and little boy blue: Iris pigmentation,gender, and social wariness in preschoolers

In recent years, researchers have uncovered a link between iris pigmentation and inhibition/social wariness among young children (e.g., Rosenberg & Kagan, 1987, 1989; Rubin & Both, 1989). In the present study, 152 Caucasian preschool-aged (M_age=54.09 months, SD=5.84) children (77 males) with either blue (n=84) or brown (n=68) eyes, were compared in terms of parental and teacher ratings of social wariness, social play, and aggression. A significant Eye Color×Gender Interaction was found in terms of indices of social wariness; blue-eyed males were rated as more socially wary than brown-eyed males, while blue- and brown-eyed females did not differ in this regard. These results supported the notion that eye color is a marker variable for social wariness in young children. © 1998 John Wiley & Sons, Inc. Dev Psychobiol 32: 37–44, 1998     

A comment on Jensen's note on sex linkage and race differences in spatial ability

Several criticisms of Jensen's hypothesis on sex linkage and race differences in spatial ability are raised. Data on whether blacks have a deficit in spatial ability are inconsistent. Whether there are X-linked influences on spatial ability has been questioned recently. Two studies provide data inconsistent with Jensen's hypothesis.     

Genetic heterogeneity in familial hypobetalipoproteinemia: Linkage and non-linkage to the apoB gene in caucasian families

Familial hypobetalipoproteinemia (FHBL) is an autosomal dominant disorder of lipid metabolism characterized by extremely low plasma levels of apolipoprotein B (apoB), and total-, and low-density lipoprotein (LDL) cholesterol. Various truncated forms of apoB have been found to cosegregate with the FHBL phenotype in more than 30 kindreds. By contrast, no truncated forms of apoB protein were detected with sensitive immunoblotting in the plasmas of any of the 6 kindreds reported here. Individuals with apoB levels in the 5th centile for their age and sex were considered as affected with FHBL. Linkage analysis was performed using 3 microsatellite markers flanking the apoB gene (D2S131, D2S149, and D2S144), a 3′ variable number of tandem repeats (VNTR) marker and one intragenic marker. Two-point linkage of FHBL was established to the 3′ VNTR marker with a combined maximum LOD score of 8.5 at θ = 0 for 5 of the 6 families. Maximum LOD scores for flanking microsatellite markers were 5.0, 2.4, 1.3, 1.2 and 2.1 for these kindreds (D, T, De, C and Z, respectively). A test of homogeneity differentiated the 6th family (F kindred) from the other five. LOD scores of −25.2 at the 3′ VNTR and −7.8 at the intragenic apoB/Xbal marker at θ = 0 excluded linkage to the apoB gene in the F kindred. These kindreds demonstrate the heterogeneity of FHBL and also offer the possibility to investigate as yet undescribed mutations of apoB, resulting in alterations of apoB metabolism. The F kindred may shed light on novel gene(s) contributing to the low apoB-phenotype. Am. J. Med. Genet. 76:79–86, 1998. © 1998 Wiley-Liss, Inc.