Haplotypes at the DRD2 locus and severe alcoholism.

Association studies of the minor TaqI A allele of the D(2) dopamine receptor (DRD2) gene with alcoholism have produced conflicting findings. Failure to assess alcoholics for severity of their disorder and to screen controls for substance use have been proposed as causes for the discrepant results. In the present study, five diallelic sites spanning the DRD2 gene were determined in combined Caucasian (non-Hispanic) studies of more severe alcoholics (n = 92) and controls screened for substance use (n = 85). The frequency of the minor alleles at the 3'-untranslated site (TaqI A) and two intronic sites (TaqI B and intron 6) of the DRD2 gene were each strongly associated with alcoholism. Moreover, the alcoholics compared with the controls at these three sites had a significantly higher frequency of the minor/major allele heterozygote haplotype combination (A1/A2 B1/B2 T/G) than the major allele homozygote haplotype combination (A2/A2 B2/B2 G/G). However, exon 7 and promoter alleles were not associated with alcoholism. In neither the alcoholics nor in the controls were there departures from Hardy-Weinberg equilibrium at any of the five sites examined. The most significant diallelic composite genotypic disequilibria were found when comparisons were made between TaqI A and TaqI B, TaqI A and intron 6, and TaqI B and intron 6 sites. Weaker but still significant disequilibria were observed when TaqI A and exon 7, TaqI B and exon 7, intron 6 and exon 7, and promoter and exon 7 sites were compared. However, no significant disequilibria were noted when TaqI A and promoter, TaqI B and promoter, and intron 6 and promoter sites were compared. In sum, the study found significant evidence for association of the minor alleles in the untranslated sites of the DRD2 gene and their haplotypes with the more severe alcoholic phenotype.

A new locus for autosomal dominant cataract on chromosome 12q13.

PURPOSE: To map the gene for autosomal dominant cataracts (ADC) in an American white family of European descent. METHODS: Ophthalmic examinations and linkage analyses using a variety of polymorphisms were performed; two-point lod scores calculated. RESULTS: Affected individuals (14 studied) exhibited variable expressivity of embryonal nuclear opacities based on morphology, location within the lens, and density. This ADC locus to 12q13 was mapped on the basis of statistically significantly positive lod scores and no recombinations (theta(m) = theta(f) = 0) with markers D12S368, D12S270, D12S96, D12S359, D12S1586, D12S312, D12S1632, D12S90, and D12S83; assuming full penetrance, a maximum lod score of 4.73 was calculated between the disease locus and D12S90. CONCLUSIONS: The disease in this family represents the first ADC locus on chromosome 12; major intrinsic protein of lens fiber (MIP) is a candidate gene.

Mapping and positional cloning of common idiopathic generalized epilepsies: juvenile myoclonus epilepsy and childhood absence epilepsy.

Among the 40 to 100 million persons with epilepsy worldwide and the 2 to 2.5 million persons with epilepsies in the United States, approximately 50% have generalized epilepsies. Among all epilepsies, the most common are juvenile myoclonus epilepsy (JME) with 10% to 30% of cases, childhood absence epilepsy (CAE) with 5% to 15% of cases, and pure grand mal on awakening with 22% to 37% of cases. In the last decade, six different chromosomal loci for common generalized epilepsies have been identified. These include two separate loci for JME in chromosomes 6p and 15q. The epilepsy locus in chromosome 6p expresses the phenotypes of classic JME, pure grand mal on awakening, and possibly JME mixed with absences. Two separate loci also are present for pyknoleptic CAE, namely, CAE that evolves to JME in chromosome 1p and CAE with grand mal in chromosome 8q24. Pandolfo et al. from the Italian League Against Epilepsy have reported two other putative susceptibility loci for idiopathic generalized epilepsies, namely, grand mal and generalized spike waves 35l in chromosome 3p and generalized epilepsies with febrile convulsions, grand mal, JME, absences, and electroencephalographic spike waves in 8q24. This chapter reports on the debate concerning whether there may be two separate epilepsy loci in chromosome 6p, one in the HLA region and one below HLA. The chapter then discusses the progress made in our laboratories as a result of the Genetic Epilepsy Studies (GENES) International Consortium. We discuss (a) the 2 to 6 cM critical region for classic JME located some 20 cM below HLA in chromosome 6p, (b) the 7-cM area for pyknoleptic CAE that evolves to JME in chromosome 1p, and (c) the 3.2 cM area for pyknoleptic CAE with grand mal and irregular 3 to 4 Hz spike waves in chromosome 8q24. We discusses efforts underway to refine the genetic map of JME in chromosome 6p11 and the advances in physical mapping and positioning of candidate genes, such as the gamma-aminobutyric acid receptor gene, the potassium channel gene of the long-QT family (KvLQT), named KCNQ3, and the human homologue of the mouse jerky gene for CAE in chromosome 8q24 and JME in chromosome 6p11.

Linkage analysis and loss of heterozygosity for chromosome arm 1p in familial breast cancer.

We conducted linkage analysis of 64 multiple-case families with early-onset bilateral breast cancer using DNA markers on chromosome band 1p36. Evidence against tight linkage was obtained using a dominant model for transmission (summary LOD scores at recombination fraction theta = 0.000001 were -4.71 for D1S160 and -2.70 for D1S170). Similar results were obtained after excluding 20 families that were potentially attributable to BRCA1 or BRCA2. We also investigated loss of heterozygosity for a panel of markers on chromosome arm 1p using breast tumors from affected family members. The most common regions of allele loss were 1p36 (32% for D1S160, 35% for D1S243) and 1p32 (51% for MYCL). The frequency and location of 1p allele loss did not differ substantially from previous studies of sporadic breast cancer. We conclude that 1p36 probably does not contain a locus of susceptibility for a large proportion of breast cancer families, but a variety of loci on 1p may contribute to progression of familial and sporadic disease. Genes Chromosomes Cancer 25:354-361, 1999.

D2 dopamine receptor and GABA(A) receptor beta3 subunit genes and alcoholism.

As the dopaminergic and GABAergic systems have been implicated in alcohol-related behaviors, variants of the D2 dopamine receptor (DRD2) and GABA(A) receptor beta3 subunit (GABRB3) genes were determined in a population-based association study of Caucasian non-alcoholic and alcoholic subjects. In severe alcoholics, compared to non-alcoholics, a significant increase was found in the prevalence (P = 1.7 x 10(-5)) and frequency (P = 1.6 x 10(-5)) of the DRD2 minor (A1) allele. Moreover, a significant progressive increase was observed in A1 allelic prevalence (P = 3.1 x 10(-6)) and frequency (P = 2.7 x 10(-6)) in the order of non-alcoholics, less severe and severe alcoholics. In severe alcoholics, compared to non-alcoholics, a significant decrease was found in the prevalence (P = 4.5 x 10(-3)) and frequency (P = 2.7 x 10(-2)) of the GABRB3 major (G1) allele. Furthermore, a significant progressive decrease was noted in G1 allelic prevalence (P = 2.4 x 10(-3)) and frequency (P = 1.9 x 10(-2)) in non-alcoholics, less severe and severe alcoholics, respectively. In sum, in the same population of non-alcoholics and alcoholics studied, variants of both the DRD2 and GABRB3 genes independently contribute to the risk for alcoholism, with the DRD2 variants revealing a stronger effect than the GABRB3 variants. However, when the DRD2 and the GABRB3 variants are combined, the risk for alcoholism is more robust than when these variants are considered separately.

D2 and D4 dopamine receptor polymorphisms and personality.

The relationship of various dimensions of temperament, measured by the Tridimensional Personality Questionnaire (TPQ), to polymorphisms of the D2 dopamine receptor (DRD2) and D4 dopamine receptor (DRD4) genes was determined in 119 healthy Caucasian boys who had not yet begun to consume alcohol and other drugs of abuse. Total Novelty Seeking score of the TPQ was significantly higher in boys having, in common, all three minor (A1, B1, and Intron 6 1) alleles of the DRD2 compared to boys without any of these alleles. Boys with the DRD4 7 repeat (7R) allele also had a significantly higher Novelty Seeking score than those without this allele. However, the greatest difference in Novelty Seeking score was found when boys having all three minor DRD2 alleles and the DRD4 7R allele were contrasted to those without any of these alleles. Neither the DRD2 nor the DRD4 polymorphisms differentiated total Harm Avoidance score. Whereas subjects having all three minor DRD2 alleles had a significantly higher Reward Dependence 2 (Persistence) score than subjects without any of these alleles, no significant difference in this personality score was found between subjects with and without the DRD4 7R allele. In conclusion, DRD2 and DRD4 polymorphisms individually associate with Novelty Seeking behavior. However, the combined DRD2 and DRD4 polymorphisms contribute more markedly to this behavior than when these two gene polymorphisms are individually considered.

Regional mapping of the human MP70 (Cx50; connexin 50) gene by fluorescence in situ hybridization to 1q21.1.

PURPOSE: Gap junctions play a critical role in the metabolic homeostasis and maintenance of transparency of fibers within the ocular lens. As part of a long-term effort to establish the relationship between lens gap junction proteins, normal lens development, and cataractogenesis, we report here the regional localization of the human MP70 (Connexin 50) gene. METHODS: Fluorescence in situ hybridization (FISH) was used to regionally map the human MP70 gene. The DNA probe contained the entire MP70 coding region within a clone isolated from a human genomic DNA library. RESULTS: The human gene encoding the lens intrinsic membrane protein MP70 was regionally mapped to q21.1 on the long arm of chromosome 1. CONCLUSIONS: This study confirms the previous provisional assignment of MP70 to human chromosome 1 and regionally localizes the gene to 1q21.1. When combined with previous mapping information, these data are consistent with the hypothesis that a genetic lesion in the gene encoding the lens intrinsic membrane protein MP70 may be the underlying molecular defect for zonular pulverulent (Coppock) cataract. Furthermore, these combined data support the hypothesis that other forms of human hereditary cataract may be the result of a mutation in one or more of the genes encoding gap junction proteins found in the ocular lens.

Juvenile myoclonic epilepsy in chromosome 6p12-p11: locus heterogeneity and recombinations.

We recently analyzed under homogeneity a large pedigree from Belize with classic juvenile myoclonic epilepsy (JME). After a genome wide search with 146 microsatellites, we obtained significant linkage between chromosome 6p markers, D6S257 and D6S272, and both convulsive and EEG traits of JME. Recombinations in two affected members defined a 40 cM JME region flanked by D6S313 and D6S258. In the present communication, we explored if the same chromosome 6p11 microsatellites also have a role in JME mixed with pyknoleptic absences. We allowed for heterogeneity during linkage analyses. We tested for heterogeneity by the admixture test and looked for more recombinations. D6S272, D6S466, D6S294, and D6S257 were significantly linked (Zmax > 3.5) to the clinical and EEG traits of 22 families, assuming autosomal dominant inheritance with 70% penetrance. Pairwise Zmax were 4.230 for D6S294 (theta m = f at 0.133) and 4.442 for D6S466 (theta m = f at 0.111). Admixture test (H2 vs. H1) was significant (P = 0.0234 for D6S294 and 0.0128 for D6S272) supporting the hypotheses of linkage with heterogeneity. Estimated proportion of linked families, alpha, was 0.50 (95% confidence interval 0.05-0.99) for D6S294 and D6S272. Multipoint analyses and recombinations in three new families narrowed the JME locus to a 7 cM interval flanked by D6S272 and D6S257.

Clinical and genetic analysis of a large pedigree with juvenile myoclonic epilepsy.

Juvenile myoclonic epilepsy is a common type of idiopathic generalized epilepsy characterized by myoclonic, generalized tonic-clonic, and in 30% of patients, absence seizures. We studied a three-generation pedigree of 33 members, 10 of whom were clinically affected with juvenile myoclonic epilepsy or presented with subclinical electroencephalographic (EEG) 3.5- to 6.0-Hz diffuse polyspike-wave or spike-wave complexes. Juvenile myoclonic epilepsy and the EEG trait segregated as an autosomal dominant trait with 70% penetrance. Linkage analysis using this model showed significant linkage to four microsatellite markers centromeric to human leukocyte antigen (HLA) in chromosome 6p. Maximum lod scores of 3.43 at theta(m=f)=0.00 for D6S272, D6S466, D6S257, and D6S402 were obtained. Recombinant events in 2 affected members defined the gene region to a 43-cM interval flanked by D6S258 (HLA region) and D6S313 (centromere). Our results in this large family provide evidence that a gene responsible for juvenile myoclonic epilepsy and the subclinical, 3.5- to 6.0-Hz, polyspike-wave or spike-wave EEG pattern is located in chromosome 6p.

Map refinement of locus RP13 to human chromosome 17p13.3 in a second family with autosomal dominant retinitis pigmentosa.

In order to elucidate the genetic basis of autosomal dominant retinitis pigmentosa (adRP) in a large eight-generation family (UCLA-RP09) of British descent, we assessed linkage between the UCLA-RP09 adRP gene and numerous genetic loci, including eight adRP candidate genes, five anonymous adRP-linked DNA loci, and 20 phenotypic markers. Linkage to the UCLA-RP09 disease gene was excluded for all eight candidate genes analyzed, including rhodopsin (RP4) and peripherin/RDS (RP7), for the four adRP loci RP1, RP9, RP10 and RP11, as well as for 17 phenotypic markers. The anonymous DNA marker locus D17S938, linked to adRP locus RP13 on chromosome 17p13.1, yielded a suggestive but not statistically significant positive lod score. Linkage was confirmed between the UCLA-RP09 adRP gene and markers distal to D17S938 in the chromosomal region 17p13.3. A reanalysis of the original RP13 data from a South African adRP family of British descent, in conjunction with our UCLA-RP09 data, suggests that only one adRP locus exists on 17p but that it maps to a more telomeric position, at band 17p13.3, than previously reported. Confirmation of the involvement of RP13 in two presumably unrelated adRP families, both of British descent, suggests that this locus is a distinct adRP gene in a proportion of British, and possibly other, adRP families.

The gene for progressive myoclonus epilepsy of the Lafora type maps to chromosome 6q.

Progressive myoclonus epilepsy of the Lafora type (Lafora's disease) is an autosomal recessive disease characterized by epilepsy, myoclonus, dementia, and periodic acid-Schiff-positive intracellular inclusion bodies. The inclusion deposits consist of branched polysaccharides (polyglucosans) but the responsible biochemical defect has not been identified. Onset is during late childhood or adolescence and the disease leads to a fatal outcome within a decade of first symptoms. We studied nine families in which Lafora's disease had been proven by biopsy in at least one member. In order to locate the responsible gene, we screened the human genome with microsatellite markers spaced an average of 13 cM. We used linkage analysis in all nine families and homozygosity mapping in four consanguineous families to define the Lafora's disease gene region. Two point linkage analysis resulted in a total peak lod score of 10.54 for marker D6S311. Six additional chromosome 6q23-25 microsatellites yielded lod scores ranging from 5.92 to 9.60 at theta m = f = 0. An extended pedigree with five affected members independently proved linkage with peak lod scores over 3.8 at theta m = f = 0 for D6S292, D6S403, and D6S311. The multipoint one-lod-unit support interval covered a 2.5 cM region surrounding D6S403. Homozygosity mapping defined a 17 cM region in chromosome 6q23-25 flanked by D6S292 and D6S420 that contains the Lafora's disease gene.

Polymorphic gene markers in Mexican-Americans residing in southern California.

The gene frequencies of nine different genetic polymorphic markers [ABO, MNS and P blood groups; haptoglobin, transferrin, Gc protein, complement (C3), properdin factor B and alpha 1-antitrypsin] were determined in 94 Mexican-Americans residing in the Los Angeles, California area. Comparisons with published data on Mexican-Americans living in other areas of the United States or in Mexico itself revealed no significant differences in the gene frequencies between this and previous studies. However, data from the current study demonstrated significant differences in ABO and haptoglobin allele frequencies compared to published non-Hispanic Caucasian data. These data suggest a large degree of genetic homogeneity in the Mexican-American population residing in the United States. Additional gene marker studies will be important to test this hypothesis and further define the degree of non-Hispanic Caucasian admixture in this population.

Chromosomal assignment of the human gene for the cancer-associated retinopathy protein (recoverin) to chromosome 17p13.1.

The gene for the mouse recoverin protein (23 kDa photoreceptor-specific protein, S-modulin, or the Cancer-Associated Retinopathy protein) was recently assigned to mouse chromosome 11, closely linked to trp53. In this paper, the human gene for recoverin was localized to human chromosome 17 by Southern analysis of restriction digests of the DNA from mouse/human somatic cell hybrids. Using a 7 kb subclone of the human recoverin gene, a positive fluorescence in situ hybridization signal was demonstrated near the terminus of the short arm of chromosome 17 at position p13.1. The mapping of recoverin to this region of human chromosome 17, which contains a number of cancer-related loci, suggests a possible mechanism by which cancer-associated retinopathy occurs in humans.

Localization of multiple human dihydrodiol dehydrogenase (DDH1 and DDH2) and chlordecone reductase (CHDR) genes in chromosome 10 by the polymerase chain reaction and fluorescence in situ hybridization.

Multiple human dihydrodiol dehydrogenases and human chlordecone reductase belong to the aldoketo reductase superfamily. These two enzymes are involved in the metabolism of xenobiotics, such as polycyclic aromatic hydrocarbons and pesticides. Recently we have isolated three closely related genes encoding two dihydrodiol dehydrogenases (DDH1 and DDH2) and the chlordecone reductase (CHDR). Mapping of the location of the genes was performed using the polymerase chain reaction using gene-specific primers to amplify gene sequences in human/hamster hybrid DNA. All three genes were found to be located on chromosome 10. In situ hybridization using a lambda clone as the probe further confirmed regional localization at 10p14-p15.

D2 dopamine receptor TaqI A alleles in medically ill alcoholic and nonalcoholic patients.

The prevalence of TaqI A alleles of the D2 dopamine receptor (DRD2) gene was examined in two subgroups of medically ill nonalcoholics (more prevalent and less prevalent substance users, MPSU and LPSU, respectively) and in two subgroups of medically ill alcoholics (more severe and less severe alcoholics, MSA and LSA, respectively). The prevalence of the A1 allele in the 80 nonalcoholic and 73 alcoholic patients was 30.0% and 52.1%, respectively (P = 0.009). In the four subgroups of these patients, the prevalence of this allele was: LPSU = 18.2%, MPSU = 34.5%, LSA = 44.4% and MSA = 58.3%. Linear trend analysis showed that as the use of substances and severity of alcoholism increase, so does A1 prevalence (P = 0.001). Specific, subgroup comparisons showed A1 prevalence in MSA to be about 3-fold (P = 0.007) and 1.5-fold (P = 0.04) higher than in LPSU and MPSU subgroups, respectively. Similarly, in a combined analysis of independent studies, A1 prevalence in MSA was higher when compared to LSA (P < 5 x 10(-3), MPSU (P < 10(-4) and LPSU (P < 10(-8) subgroups. There was virtually no difference in the prevalence of the A1 allele between LSA and MPSU subgroups. None of the specific medical or neuropsychiatric complications of alcoholism was associated with the A1 allele. In conclusion, the severity of alcohol dependence in alcoholics and of substance use behaviors in controls are important variables in DRD2 allelic association. The present report and converging lines of evidence suggest that the DRD2 locus could represent a prominent gene risk factor for susceptibility to severe alcoholism. However, other genes and environmental factors, when combined, still play the larger role.

Assignment of the zeta-crystallin gene (CRYZ) to human chromosome 1p22-p31 and identification of restriction fragment length polymorphisms.

zeta-Crystallin is a lens protein that has been associated with autosomal dominant congenital cataracts in guinea pigs and thus is a candidate for human congenital cataracts. We have assigned the zeta-crystallin gene (CRYZ) to human chromosome 1 using a Southern panel of 17 human-mouse somatic cell hybrids and regionally localized it to 1p22-p31 by fluorescence in situ hybridization. Five restriction fragment length polymorphisms were identified by analyzing the DNA from 10 unrelated, unaffected individuals. Our results will permit evaluation of its role in human cataractogenesis.

Molecular cloning of the human homeobox gene goosecoid (GSC) and mapping of the gene to human chromosome 14q32.1.

Goosecoid is a homeobox gene first isolated from a Xenopus dorsal lip cDNA library. Homologous genes have been isolated from mouse, zebrafish, and chick. In all species examined, the gene is expressed and plays an important role during the process of gastrulation in early embryonic development. We report here the cloning of the human goosecoid gene (GSC) from a genomic library and the sequence of its encoded protein. The genomic organization and protein sequence of the human gene are highly conserved with respect to those of its Xenopus and mouse counterparts: all three genes consist of three exons, with conserved exon-intron boundaries; the sequence of the homeodomain is 100% conserved in most vertebrates. Using somatic cell hybrid and chromosomal in situ hybridization, the gene was mapped to chromosome 14q32.1.