[An internship rotation in a rural area: an unforgettably positive experience for medical students].
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Chile↗
Biomedical subjects
Hugo Henríquez
Publications and source records attributed to Hugo Henríquez.
Genotypic interaction between DRD4 and DAT1 loci is a high risk factor for attention-deficit/hyperactivity disorder in Chilean families.
Attention-deficit/hyperactivity disorder, ADHD [MIM 126452], is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness, and/or inattentiveness. As part of an ongoing study of ADHD, we carried out a family-based discordant sib-pair analysis to detect possible associations between dopamine receptor D4 (DRD4) and dopamine transporter 1 (DAT1) polymorphisms and ADHD in Chilean families. Both loci individually classified as homozygotes or heterozygotes for the DRD4 7-repeat and DAT1 10-repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings (Fisher's exact test P > 0.25 in both cases). However, the simultaneous presence of both DRD4 7-repeat heterozygosity and DAT1 10 allele homozygosity were significantly higher (34.6%) in cases (26), compared with their unaffected siblings (25) (4%; Fisher's exact test P = 0.0096; odds-ratio, OR = 12.71). Increased density of dopamine transporter 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 further incisive studies.
Adolescent↗
mtDNA microevolution in Southern Chile's archipelagos.
The genetic variability of four predominantly Indian populations of southern Chile's archipelagos was examined by determining the frequencies of four mitochondrial DNA haplogroups that characterize the American Indian populations. Over 90% of the individuals analyzed presented Native American mtDNA haplogroups. By means of an unweighted group pair method with arithmetic mean (UPGMA) dendrogram, a principal component analysis (PCA) derived from a distance matrix of mtDNA, and the exact test of population differentiation, we are able to prove the existence of a North-South cline. The populations in the northern part of the archipelagos are genetically similar to the Huilliche tribe, while the groups from the South are most closely related to the Fueguino tribe from the extreme South of Chile, and secondarily to the Pehuenche and Mapuche, who are found to the North and East of Chiloé archipelago. These results are consistent with a colonization of the southern archipelagos from Tierra del Fuego. We evaluate the evolutionary relationships of the population of the Chiloé area to groups from other geographic areas of Chile, using analysis of molecular variance (AMOVA). Three Amerindian clusters are identified: one formed by the Aymará and Atacameño, a second by the Huilliche, and a third including the Mapuche, Pehuenche, and Fueguino tribes, and the population inhabiting the South of the Chiloé arcipelago. These groups exhibit a North-South gradient in the frequency of haplogroup B, confirmed by F(ST) tests.
Chile↗
Brief communication: Molecular characterization of O alleles at the ABO locus in Chilean Aymara and Huilliche Indians.
A molecular characterization of alleles O1, O1variant (O1v), and the mutation G542A of the ABO blood group was performed in two Amerindian populations of Chile, the Aymara (n = 84) and the Huilliche (n = 75). In addition, a sample of 82 individuals of Santiago belonging to the mixed Chilean population was typed for comparative purposes. The polymorphisms which allow for molecular differentiation of different alleles of the O blood group were studied in genomic DNA. The mutations G188, G261-, G542A, T646A, and C771T, described for alleles O1, O1v, and G542A, were determined using the PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) technique. All individuals studied were group O homozygotes for the deletion G261-, which defines the O1 alleles. Results obtained indicate that allele O1v exhibits frequencies of 0.65, 0.81, and 0.60 in Aymara, Huilliche, and Santiago populations, respectively. The frequencies of allele O1(G542A) were 0.119, 0.113, and 0.079 in the same populations. Frequencies for alleles O1 and O1v obtained in the Chilean populations studied concur with the results obtained by other authors, respecting the greater frequency of allele O1v as well as with its heterogeneous distribution in aboriginal South American populations. In Chilean populations, Allele G542A exhibits lower frequencies than those described for indigenous populations from Brazil and may be used as an Amerind admixture marker.
ABO Blood-Group System↗
[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%), 19 had B haplogroup (47.5%), six had C haplogroup (15%) and 11 had D haplogrotup (27.5%). Three subjects (7.5%) 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.
ABO Blood-Group System↗
[Presence of DRD4/7R and DAT1/10R allele in Chilean family members with attention deficit hyperactivity disorder].
BACKGROUND: Genes for dopamine receptor DRD4 and dopamine transporter DAT1 have been implicated in attention deficit with hyperactivity disorder (ADHD). However, the findings are not conclusive. More studies in populations with different genetic backgrounds may contribute to solve the discrepancies observed. AIM: To test the hypothesis that affected members of Chilean families exhibit higher frequencies of the DRD4/7R and DAT1/10R alleles then their healthy sibs. MATERIAL AND METHODS: The parents of 51 children belonging to families of the Metropolitan Region of Chile, were approached to obtain clinical histories and blood samples, after the signature of a written informed consent. ADHD was diagnosed according to DSM-IV criteria, ancd intellectual coefficient was tested using the WISC-R test. Genomic DNA was extracted from lymphocytes and amplified by PCR. RESULTS: The 7R allele was identified in 13 out of 26 subjects diagnosed as ADHD and in 6 of 25 healthy sibs (p < 0.05). Parents with a history of ADHD, were conmpared with their healthy counterparts, exhibiting an identical tendency, that did not reach statistical significance. No significant differences in the frequencies of DAT1/10R alleles, were observed between cases and controls or their parents. CONCLUSIONS: Our results showed that ADHD in Chilean families is associated with the presence of DRD4/7R allele.
Adolescent↗
[Distribution of DRD4 and DAT1 alleles from dopaminergic system in a mixed Chilean population].
BACKGROUND: 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%, followed by DRD4.7, with a frequency of 15%. South American indigenous populations have higher frequencies for DRD4.7 (61%) than for DRD4.4 (29%). The ten repetition allele for DAT1 transporter has a high frequency among Europeans (72%) and Amerindians (100%). 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% and DRD4.7 a frequency of 27%. The allele DAT1*10 had a frequency of 74%, followed by DAT 1*9, with a frequency of 23%. DISCUSSION: In a Chilean population sample, the frequency of DRD4 and DAT1 alleles was very similar to that of European populations.
Alleles↗