Alcoholism and alleles of the human D2 dopamine receptor locus. Studies of association and linkage.

The association of the A1 allele of the D2 dopamine receptor gene with alcoholism was examined by comparing 32 unrelated white alcoholics with 25 unrelated white controls and by analysis of 17 nuclear families in multigenerational pedigrees of alcoholics in whom the A1 allele was segregating. All subjects had structured psychiatric interviews. Clinical assessment and genotyping were carried out independently. Thirteen (41%) of the 32 alcoholics carried the A1 allele compared with three (12%) of the 25 controls. The association with the A1 allele was significant when controls were compared with a subset of 10 alcoholics with severe medical problems (60% vs 12%), but not less severe cases. However, regardless of clinical severity or subtype, there was no evidence of linkage or cosegregation of the A1 allele and increased susceptibility to alcoholism in informative pedigrees. The possible association in the general population without linkage in families may be explained either by chance variation in our small samples or a modifying effect of the A1 allele that increases severity. Further study of the role of the D2 receptor gene in alcoholism is warranted.

A familial/genetic study of plasma serine and glycine concentrations.

Plasma serine and glycine concentrations were assayed in a sample of 28 nuclear families (n = 108). Complex segregation analysis of these familial data reveals significant genetic control of concentrations via a single major gene locus. The serine and glycine metabolizing enzyme serine hydroxymethyltransferase (SHMT) is suggested as the most likely candidate for this single major gene locus.

Use of high specific activity StarFire oligonucleotide probes to visualize low-abundance pre-mRNA splicing intermediates in S. pombe.

An oligonucleotide labeling system was developed that can produce radiolabeled hybridization probes with tenfold or more higher specific activity than is obtained by traditional 5'-end-labeling with polynucleotide kinase. Yet the system is as rapid and simple as kinase labeling. The reaction uses the Klenow fragment of E. coli DNA polymerase to add alpha-32P-dA residues to the 3'-end of an oligonucleotide in a primer-extension reaction. Unlike other methods of radioactive tailing (e.g., terminal transferase), a single species is produced of both known length and known specific activity. The reaction is efficient, and over 90% of probe molecules are routinely labeled. Using this method of labeling, an oligonucleotide was shown to be tenfold more sensitive in detecting target DNA sequences in a dot blot hybridization assay, compared to the same oligonucleotide labeled using polynucleotide kinase. Northern blots of Schizosaccharomyces pombe RNA were probed with an oligonucleotide specific for intron 1 of the tf2d gene, a TATA-box binding transcription factor. Kinase-labeled tf2d probe detected only unspliced RNA, while the same oligonucleotide labeled using the new method detected both unspliced tf2d RNA and rare pre-mRNA splicing intermediates.

Association of monoamine oxidase (MAO) activity with alcoholism and alcoholic subtypes.

A familial/genetic study of platelet monoamine oxidase (MAO) activity in alcoholics was carried out. MAO activities were determined using phenylethylamine (PEA) as substrate at Km concentration (1.2 microM) and at saturating concentration (12.0 microM). Complex segregation analysis of familial data indicated a single major gene mode of transmission of activity at both substrate concentrations. In addition, the present sample size (13 families, 108 members) proved sufficient to allow correlation analysis of enzyme activity with affection status and clinical subtypes of affecteds. MAO activity was significantly correlated with alcoholism at both Km and saturating substrate concentrations and a significant correlation between low MAO activity and Cloninger Type II alcoholism was seen at Km substrate concentration. These results confirm a hierarchical cosegregation of platelet MAO activity and alcoholism suggesting that MAO activity warrants continued status as a marker in alcoholism.

Serotonin transporter gene (5-HTT) polymorphisms and compulsive buying.

We examined a panel of 21 patients diagnosed with compulsive buying for two DNA sequence polymorphisms found in the gene that encodes the serotonin transport (5-HTT). One polymorphism, found in the promoter region of the 5-HTT gene, involves a 44-base pair (bp) deletion, and the other, found in the second intron, is due to variable numbers of a repeat sequence. We also typed a panel of 38 psychiatrically normal controls for both 5-HH markers. When compared to this control panel, no significant differences were seen for either 5-HTT marker among the compulsive buyers.

The Bal I and Msp I polymorphisms in the dopamine D3 receptor gene display, linkage disequilibrium with each other but no association with Tourette syndrome.

The D3-dopamine receptor gene, DRD3, has been considered as a candidate gene in several disorders in which the dopaminergic system has been implicated including Tourette syndrome and schizophrenia. The DRD3 studies to date have all used as the gene marker a Bal I polymerase chain reaction restriction fragment length polymorphism (PCR RFLP). There have been recent reports on a second marker, an Msp I PCR RFLP, that lies 40 kb downstream. We have typed a sample of 16 Tourette syndrome families with both markers and observed significant linkage disequilibrium between the two markers but no apparent association of either marker with Tourette syndrome.

Platelet MAO activity in type I and type II alcoholism.

Lowered activity of the enzyme MAOB in the platelets and other tissues of alcoholics than of nonalcoholics is the most replicated biological finding in genetic research in alcoholism. Data presented here and elsewhere also indicate that the relationship between MAOB activity and alcoholism extends to the clinical subtypes referred to as Type I and Type II alcoholism. A detailed examination of the relationship between in vitro platelet MAOB activity levels, alcoholic subtype, and general mental health status among the relatives of the probands suggests that low MAOB activity is a marker of increased risk overall and that the families of Type II alcoholics have a higher genetic risk loading than do the families of Type I alcoholics. This increased genetic loading is probably due to the classification of Type II alcoholics on the basis of features related to severity of illness and additional psychiatric features such as personality disorders. Although the families of alcoholics tend to have higher levels of psychiatric illness compared to the general population, the overall risk is compounded in the families of Type II alcoholics, and these differences in underlying risk are reflected in the observed differences in MAOB activities. Thus, MAOB is not a biological/genetic marker of alcoholism sensu stricto but is rather a biological/genetic marker of an underlying pathophysiologic process leading to alcoholism and other psychiatric illness. The task now before us is to understand this process and how the activity of MAOB is involved.

A developmental-genetic model of alcoholism: implications for genetic research.

The research for biological-genetic markers of alcoholism is discussed in the context of a multifactorial, heterogeneous, developmental model of the disease. It is suggested that the strategies used in both linkage and association studies require modification to accommodate this more complex model. It is also suggested that several extant associations of genetic markers with alcoholism represent true secondary interactive phenomena that alter the outcome of primary alcoholism genotypes at the phenotype level.

Biological relationship between Central and South American Chibchan speaking populations: evidence from mtDNA.

We examined mitochondrial DNA (mtDNA) haplogroup and haplotype diversity in 188 individuals from three Chibchan (Kogi, Arsario, and Ijka) populations and one Arawak (Wayuú) group from northeast Colombia to determine the biological relationship between lower Central American and northern South American Chibchan speakers. mtDNA haplogroups were obtained for all individuals and mtDNA HVS-I sequence data were obtained for 110 samples. Resulting sequence data were compared to 16 other Caribbean, South, and Central American populations using diversity measures, neutrality test statistics, sudden and spatial mismatch models, intermatch distributions, phylogenetic networks, and a multidimensional scaling plot. Our results demonstrate the existence of a shared maternal genetic structure between Central American Chibchan, Mayan populations and northern South American Chibchan-speakers. Additionally, these results suggest an expansion of Chibchan-speakers into South America associated with a shift in subsistence strategies because of changing ecological conditions that occurred in the region between 10,000-14,000 years before present.

Marital structure and genetic isolation in a rural Hispanic population in northern New Mexico.

An investigation of the mating structure of the rural Hispanic population of the village of abiquiu in northern New Mexico was carried out using village marriage registers. Marital movement and departure from random mating were analyzed by the distribution of birth places of marriage partners and by surname isonymy. The time periods studied were 1882 to 1910 and 1947 to 1977. The results of these analyses show marked marital isolation (median marital distances by birthplace of 11.5 and 20.0 miles, respectively) and a significant departure from random mating (F = 0.0556 and F = 0.0495, respectively). In each case the non-random component of the isonymy coeffient (Fn) greatly exceeds the random, or expected, component. Assortative mating for culture and proximity governed by the historical settlement pattern is indicated as the process producing these results. Isolation has begun to break down in recent years but as yet has had no great effect on the genetic structure of the Abiquiu population.

Why there is no gene for alcoholism.

The search for and recognition of biological and genetic markers of alcoholism are discussed in the context of a heuristic model of human alcoholism as a complex, multilocus, heterogeneous disorder. Implications of this model for the interpretation of results from both linkage and association studies are presented.

Molecular archeology of an SP100 splice variant revisited: dating the retrotranscription and Alu insertion events.

BACKGROUND: SP100 is a nuclear protein that displays a number of alternative splice variants. In Old World monkeys, apes and humans one of these variants is extended by a retroprocessed pseudogene, HMG1L3, whose antecedent gene is a member of the family of high-mobility-group proteins, HMG1. This is one of only a few documented cases of a retropseudogene being incorporated into another gene as a functional exon. In addition to the HMG1L3 insertion, Old World monkey genomes also contain an Alu sequence within the last SP100-HMG intron. PCR amplification of the 3' end of the SP100 gene using genomic DNAs from human and New World and Old World monkey species, followed by direct sequencing of the amplicons has made dating the HMG1L3 and Alu insertion events possible. RESULTS: PCR amplifications confirm that the HMG1L3 retrotransposition into the SP100 locus occurred after divergence of New World and Old World monkey lineages, some 35-40 million years ago. PCR amplification also shows that an upstream Alu sequence was inserted in the last SP100-HMG intron after divergence of the Old World monkey and ape lineages. Direct sequencing of the Alu in five Old World monkey species places the latter event at around 19 million years ago. Finally, ten single base mutations and one deletion in the Alu differentiate African from Asian Old World monkey species. CONCLUSIONS: PCR and DNA sequence analysis of 'genetic fossils' such as retropseudogenes and Alu elements in primates give details as to the timing of such events and can reveal sequence features useful for other molecular phylogenetic applications.

Genetic variation in transferrin alleles of rhesus macaques, Macaca mulatta.

The rhesus macaque displays an extensive polymorphism at the transferrin locus. A principal components analysis describes the variance and covariance of alleles at the transferrin locus in eight widely dispersed sample populations. Using an eigenvectorial representation of the covariance matrix and systematically approximated geographical locations the distribution of populations and transferrin alleles is compared. Alleles with high variance prove to be the determining factor in the placement of populations in a "genetic map" and provide a means for interpreting the low congruence of genetics and geography found.

Transmission of human craniofacial dimensions.

The transmissibilities of 11 human craniofacial dimensions are estimated by path analysis based upon familial correlations obtained in four different populations. Estimates from both the individual populations and from pooled correlations indicate that the observed variation in craniofacial dimensions is determined by genetic and nongenetic factors in roughly equal measure (.45 less than t 2 less than .60). These results implicate the possibility of complex gene-environment and gene-gene interactions in the development of the size and shape of the head and face and call for more detailed familial studies of these traits. This additional complexity further suggests the need for caution in interpreting such metrical variation, especially from a diagnostic or classificatory viewpoint.

Use of molecular beacons to verify that the serine hydroxymethyltransferase pseudogene SHMT-ps1 is unique to the order Primates.

BACKGROUND: The serine hydroxymethyltransferase processed pseudogene SHMT-ps1 has been suggested to be unique to the order Primates because of the failure to amplify this sequence by PCR from genomic DNAs of any non-primate mammal species. Here, 'molecular beacon' probes specific to SHMT-ps1 were used in an attempt to verify this suggestion. RESULTS: In a search for SHMT-ps1-specific sequences using molecular beacons across a range of mammalian species, SHMT-ps1 was only found in primates. The molecular beacon assays also showed that SHMT-ps1 is present in both Old World and New World species but not among prosimians. CONCLUSIONS: These results suggest that SHMT-ps1 originated close to the origin of the Anthropoidea, some 40 to 50 million years ago.

Untying the gordian knot: the genetics of Tourette syndrome.

A review of the current status of the genetics of Tourette syndrome is presented. Over the course of the 104 years since Gilles de la Tourette described the syndrome that bears his name, a body of carefully collected, described, and analyzed data has produced a model of the genetics that implicates a single dominant gene that is variably penetrant in males and females. Moreover, the locus of action of this gene is most likely in the dopaminergic system of the midbrain. A systematic search for this gene using recombinant DNA techniques is under way.

Complex segregation analysis of Gilles de la Tourette syndrome: further evidence for a major locus mode of transmission.

A sample of 35 published pedigrees of Gilles de la Tourette syndrome is studied using complex segregation analysis with pointers. Results indicate the presence of a rare, semidominant, incompletely penetrant allele leading to affection. This result is consistent with that previously reported by Comings et al. on a larger, independent sample.