Distribución de alelos de los genes DRD4 y DAT1 del sistema dopaminérgico en la población mixta de Santiago de Chile / Distribution of alleles of DRD4 and DAT1 genes of the dopaminergic system in the mixed chilean population

Genes for dopamine receptor DRD4 and dopamine transporter DAT1 are highly polymorphic. Two alleles of these genes, namely the DRD4.7 and the DAT1*9 are frequently associated to the attention deficit disorder with hyperactivity. In Europe, the allele for DRD4 receptor with four repetitions (DRD4.4) has the highest frequency, with a median of 69 percent, followed by DRD4.7, with a frequency of 15 percent. South American indigenous populations have higher frequencies for DRD4.7 (61 percent) than for DRD4.4 (29 percent). The ten repetition allele for DAT1 transporter has a high frequency among Europeans (72 percent) and Amerindians (100 percent). The allele DAT1*9 is the second most frequent allele. Aim: To study the frequency of DRD4 and DAT1 alleles in a Chilean population sample. Material and methods: One hundred serum samples were obtained from blood donors in two public hospitals in Santiago. Polymorphic regions for DRD4 and DAT1 were amplified by polymerase chain reaction. Results: The allele DRD4.4 had a frequency of 59 percent and DRD4.7 a frequency of 27 percent. The allele DAT1*10 had a frequency of 74 percent, followed by DAT 1*9, with a frequency of 23 percent. Discussion: In a Chilean population sample, the frequency of DRD4 and DAT1 alleles was very similar to that of European populations

Composición genética de la población chilena: distribución de polimorfismos de DNA mitocondrial en grupos originarios y en la población mixta de Santiago / Genetic composition of the chilean population: analysis of mitochondrial DNA polymorphisms

Background: The analysis of mitochondrial DNA restriction site polymorphisms assigns most Latin American aborigines to four haplogroups. These are characterized by determined polymorphic restriction sites and a deletion of 9 base pairs in the intergenic region V. Aim: To study the distribution of mitochondrial DNA haplogroups in Chilean aboriginal groups, as well as in the mixed population of Santiago. Material and methods: One hundred twenty Aymara subjects and 23 Atacame-o subjects from the Northern part of Chile and 162 randomly chosen subjects residing in Santiago were studied. DNA was extracted from peripheral lymphocytes. Mitochondrial DNA was amplified by means of polymerase chain reaction. Results: The frequency of haplogroup B decreases from north to south. Aymaras in the north have the highest frequency (64 percent) and it is absent among the Yamanas (previously studied) in the extreme South. Haplogroups C and D show an inverse tendency. It is noteworthy that 84 percent of mitochondrial haplogroups of the mixed population of Santiago are of Amerindian origin whereas the Y-chromosomes are mainly European. Conclusions: The peculiar distribution of haplotypes indicate that the population of Santiago is the result of an asymmetric mating system in which the females ancestors were mainly Amerindian and the male ancestors mainly European

Genética de los desórdenes adictivos / Genetics of addictive disorders

Given the spectacular advances of genetics during the last five years, it seems appropriate to revisit the important subject of genetics of alcoholism and substance abuse. In recent studies alcohol abuse was shown to have an heredability of roughly 38 percent, whereas psychostimulant and opiate use exhibit heredabilities of 11 to 45 percent. The heredability of smoking was found to be around 50 percent. There is a strong comorbidity between alcoholism and smoking. More than 80 percent of alcoholics smoke cigarettes in the U.S.A.. Other genetic methods such as linkage analysis, allele sharing methods, association studies and analysis of inbred, transgenic and gene-knockout rodents, have partially agreed in showing that the 5HT-IB serotonin receptor and the DRDI, DRD2 and DRD4 dopamine receptors, as well as the dopamine transporter DAT, play an important role in behaviors related to alcoholism and substance abuse. Some neurochemical markers, as for example monoamine oxidase and adenylate cyclase have also been implicated in addictive disorders. The aldehyde dehydrogenase allele ALDH2*2 has a protective effect against alcoholism. Two whole genome linkage studies have shown linkage to chromosomal regions that are in the proximity of the DRD4 dopamine receptor, the GABA receptor gene cluster and the alcohol dehydrogenase gene cluster

Composición genética de la población chilena: las comunidades rurales de los valles de Elqui, Limarí y Choapa / Genetic composition of Chilean population: rural Chilean communities inhabiting Elqui, Limari and Choapa valleys

Background: The population that inhabits the semiarid Northern zone of Chile arose from ethnic admixture between aborigines, Spanish conquerors and the influx, during the XVII century, of foreign aboriginal workers and a minority of African slaves. Aim: To study the phenotypic frequencies of 15 genetic markers among populations inhabiting valleys in the Northern zone of Chile and to estimate the percentage of indigenous, African and Caucasian admixture in these populations. Material and methods: Throughout five different field works, blood samples were obtained from 120 individuals living in the Elqui valley, 120 individuals living in the Limari valley and 85 living in the Choapa valley. Blood groups, erythrocyte enzymes, plasma proteins and HLA markers were typified. Results: In the populations studied, the contribution of non indigenous genes was low in relation with the time elapsed since the Spanish invasion. The Hardy-Weinberg disequilibrium for MNS system would have microevolutive implications. The admixture percentages in these valleys confirm ethnic and historic information. The variation of the enzyme esterase D is identical to that of other Chilean populations. Conclusions: The phenotypic and genetic frequencies in the three populations studied and different admixture of indigenous genes is inversely proportional to the geographic distance from Santiago, in Central Chile

El sistema mayor de histocompatibilidad como factor de riesgo de la enfermedad hepática alcohólica / Major histocompatibility system as a risk factor of alcoholic hepatic disease

Several associations between alleles of the major histocompatibility system and alcoholic liver disease have been described. However, these are weak and changes from one population to another. The aim of this work was to search for a possible genetic risk factor for alcoholic liver disease among chilean alcoholics. We studied blood groups, serum proteins and HLA antigens in 39 alcoholic cirrhotics, 104 asymptomatic alcoholics and 44 non alcoholic controls. Asymptomatic alcoholics were also subjected to a percutaneous liver biopsy that showed moderate to severe histological liver damage in 46 subjects (44 percent). No differences in the studied genetic markers, were found among the four groups. It is concluded that this study does not confirm previously reported associations between genetic markers and alcoholic liver disease