[Combination of DRD4 and DAT1 genotypes is an important risk factor for attention deficit disorder with hyperactivity families living in Santiago, Chile]. / Combinación de genotipos DRD4 y DAT1 constituye importante factor de riesgo en miembros de familias de Santiago de Chile con déficit atencional.

BACKGROUND: Attention deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness, and/or inattentiveness. AIM: To search for possible associations between dopamine receptor D4 (DRD4) and dopamine transponder 1 (DATl) polymorphisms and ADHD in Chilean families. MATERIAL AND METHODS: We extended a previous family-based discordant sib pair analysis that included 26 cases diagnosed according to DSM-IV criteria and 25 controls (healthy siblings of cases), adding 14 cases and 11 controls. RESULTS: Both loci, individually classified as homozygotes or heterozygotes for the DRD4 7-repeat and DATl 10-repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings. However, the simultaneous presence of both DRD4 7-repeat heterozygosity and DATl 10 allele homozygosity was significantly higher (22.5%) in cases (40), compared with (2.8%) unaffected siblings (36), with an odds-ratio of 10.16. CONCLUSIONS: The genotype combination DRD4/7 heterozygotes and DAT1/10 homozygotes is a high risk factors in Chilean families for ADHD. Increased density of dopamine transporters in ADHD brains, along with abundance of 7-repeat D4 receptors in prefrontal cortex, which is impaired in ADHD patients, make the observed gene-gene interaction worthy of studies to understand the functional basis of ADHD.

Combinación de genotipos DRD4 y DAT1 constituye importante factor de riesgo en miembros de familias de Santiago de Chile con déficit atencional / Combination of DRD4 and DAT1 genotypes is an important risk factor for attention déficit disorder with hyperactivity families living in Santiago, Chile

Background: Attention deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness, and/or inattentiveness. Aún: To search forpossible associations between dopamine receptor D4 (DRD4) and dopamine transponer 1 (DATl) polymorphisms and ADHD in Chilean families. Material and methods: We extended a previous family-based discordant sib pair analysis that included 26 cases diagnosed according to DSM-IV entena and 25 controls (healthy siblings of cases), adding 14 cases and 11 controls. Results: Both loci, individually classified as homozygotes or heterozygotes for the DRD4 7-repeat and DATl 10-repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings. However, the simultaneous presence of both DRD4 7-repeat heterozygosity and DATl 10 allele homozygosity was significantly higher (22.5 percent) in cases (40), compared with (2.8 percent) unaffected siblings (36), with an odds-ratio of 10.16. Conclusions: The genotype combination DRD4/7 heterozygotes and DAT1/10 homozygotes is a high risk factors in Chilean families for ADHD. Increased density of dopamine transporters in ADHD brains, along with abundance of 7-repeat D4 receptors in prefrontal cortex, which is impaired in ADHD patients, make the observed gene-gene interaction worthy of studies to understand the functional basis ofADHD.

[Molecular characterization of ABO*O alleles at the ABO group locus in three chilean populations]. / Caracterización molecular de alelos ABO*O del locus de grupo sanguíneo ABO en tres poblaciones chilenas.

BACKGROUND: Among the allelic variants of blood groups, the molecular characterization of ABO blood group has clinical and anthropological importance. AIM: To perform a characterization of the molecular variants of the allele ABO*O of the ABO blood group. MATERIAL AND METHODS: Eighty four subjects of Aymara origin, living in Northern Chile, 75 individuals of Huilliche origin, living in Southern Chile and 82 subjects living in Santiago (Central Chile), were studied. All individuals were of group O, homozygotes for G261- deletion, that defines O1 alleles. Mutations G188A, G261-, G542A, T646A and C771T, described for alleles O1, O1variant and G542A were determined by PCR-RFLP (polymerase chain reaction-restriction fragment lenght polymorphism). RESULTS: Allele O1variant has frequencies of 0.65, 0.81 and 0.6 in Aymara, Huilliche and Santiago subjects, respectively. The figures for allele O1 are 0.35, 0.19 and 0.4, respectively and those for the allele with G542A mutation are 0.119, 0.113 and 0.079, respectively. CONCLUSIONS: These results are concordant with the reported higher frequency of allele O1variant in South American aboriginal populations. The frequencies of G542A allele in these Chilean individuals are lower than those described for Amazon aborigines.

Caracterización molecular de alelos ABO*O del locus de grupo sanguíneo ABO en tres poblaciones chilenas / Molecular Characterization of ABO*O Alleles at the ABO Group Locus in Three Chilean Populations

Background: Among the allelic variants of blood groups, the molecular characterization of ABO blood group has clinical and anthropological importance. Aim: To perform a characterization of the molecular variants of the allele ABO*O of the ABO blood group. Material and methods: Eighty four subjects of Aymara origin, living in Northern Chile, 75 individuals of Huilliche origin, living in Southern Chile and 82 subjects living in Santiago (Central Chile), were studied. All individuals were of group O, homozygotes for G261- deletion, that defines O1 alleles. Mutations G188A, G261-, G542A, T646A and C771T, described for alleles O1, O1variant and G542A were determined by PCR-RFLP (polymerase chain reaction-restriction fragment lenght polymorphism). Results: Allele O1variant has frequencies of 0.65, 0.81 and 0.6 in Aymara, Huilliche and Santiago subjects, respectively. The figures for allele O1 are 0.35, 0.19 and 0.4, respectively and those for the allele with G542A mutation are 0.119, 0.113 and 0.079, respectively. Conclusions: These results are concordant with the reported higher frequency of allele O1variant in South American aboriginal populations. The frequencies of G542A allele in these Chilean individuals are lower than those described for Amazon aborigines.

Caracterización genético molecular de habitantes de Caleta Paposo, último reducto Chango en Chile / Molecular and genetic characterization of Changos descendants living in Paposo Cove

Background: There are geographic and ethno historic evidences that relate Paposo cove, located 150 km south of the city of Antofagasta, with old fishermen-collector populations known as Changos, that lived in that zone in the XVII and XVIII centuries. Aim: To perform a genetic and molecular characterization of current Paposo inhabitants, through mitochondrial DNA polymorphism analysis and molecular analysis of classical ABO and Duffy blood groups. Material and methods: Forty unrelated individuals were studied. The presence of restriction polymorphisms that define A, B, C, and D Amerindian founder mitochondrial haplogroups was studied and molecular determination of classical blood groups were done by PCR. Results: One individual had A haplogroup (2.5 percent), 19 had B haplogroup (47.5 percent), six had C haplogroup (15 percent) and 11 had D haplogroup (27.5 percent). Three subjects (7.5 percent) did not have any of these haplogroups. Among ABO blood groups, the frequency of O101 allele was 0.39, that of allele O201 was 0.53 and that of A allele was 0.08. Duffy blood group frequencies were 0.58 for FY*A and 0.42 for FY*B. FY null allele was not found. Conclusions: The frequency distribution of Amerindian mitochondrial haplogroups in Paposo inhabitants suggest that these individuals are related with Aymara and Atacameño Amerindians that can be considered culturally and geographically close populations. This proposal is supported by the results of the molecular determination of classical blood groups. Our findings in Paposo cove may represent the distribution of these markers in Chango Indians, of whom there is limited physical evidence and that became extinct near 1890 (Rev Méd Chile 2004; 132: 663-72).

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