Silviene Fabiana de Oliveira

Major Gene and Multifactorial Inheritance of Mandibular Prognathism

Mandibular prognathism typically shows familial aggregation. Various genetic models have been described and it is assumed to be a multifactorial and polygenic trait, with a threshold for expression. Our goal was to examine specific genetic models of the familial transmission of this trait. The study sample comprised of 2,562 individuals from 55 families. Complete family histories for each proband were ascertained and the affection status of relatives were confirmed by lateral cephalograms, photographs, and dental models. Pedigrees were drawn using PELICAN and complex segregation analysis was performed using POINTER. Parts of some pedigrees were excluded to create one founder pedigrees, so the total N was 2,050. Analysis showed more affected females than males (P = 0.030). The majority of the pedigrees suggest autosomal dominant inheritance. Incomplete penetrance was demonstrated by the ratio of affected/unaffected parents and siblings. The heritability of mandibular prognathism was estimated to be 0.316. We conclude that there is a major gene that influences the expression of mandibular prognathism with clear signs of Mendelian inheritance and a multifactorial component.

Superoxide dismutase, catalase, glutathione peroxidase and gluthatione S-transferases M1 and T1 gene polymorphisms in three Brazilian population groups

Antioxidants such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX1) reduce the oxidation rates in the organism. Gluthatione S-transferases (GSTs) play a vital role in phase 2 of biotransformation of many substances. Variation in the expression of these enzymes suggests individual differences for the degree of antioxidant protection and geographical differences in the distribution of these variants. We described the distribution frequency of CAT (21A/T), SOD2 (Ala9Val), GPX1 (Pro198Leu), GSTM1 and GSTT1 polymorphisms in three Brazilian population groups: Kayabi Amerindians (n = 60), Kalunga Afro-descendants (n = 72), and an urban mixed population from Federal District (n = 162). Frequencies of the variants observed in Kalunga (18% to 58%) and Federal District (33% to 63%) were similar to those observed in Euro and Afro-descendants, while in Kayabi (3% to 68%), depending on the marker, frequencies were similar to the ones found in different ethnic groups. Except for SOD2 in all population groups studied here, and for GPX1 in Kalunga, the genotypic distributions were in accordance with Hardy-Weinberg Equilibrium. These data can clarify the contribution of different ethnicities in the formation of mixed populations, such as that of Brazil. Moreover, outcomes will be valuable resources for future functional studies and for genetic studies in specific populations. If these studies are designed to comprehensively explore the role of these genetic polymorphisms in the etiology of human diseases they may help to prevent inconsistent genotype-phenotype associations in pharmacogenetic studies.

Evaluation of coverage by a neonatal screening program for hemoglobinopathies in the Recôncavo region of Bahia, Brazil

In 2001, government ruling n. MS 822/01 by the Brazilian Ministry of Health made neonatal screening mandatory for hemoglobinopathies, with special focus on sickle cell disease, the most common hemoglobinopathy in Brazil. Bahia is the State of Brazil with the highest prevalence of this disease. The current paper reports on the prevalence of hemoglobin variants HbS and HbC, which cause sickle cell disease, in the cities of Cachoeira, Maragogipe, and São Félix, Bahia State. The overall proportion of carriers for the two forms of hemoglobin was 13%. From 2001 to 2003, the neonatal screening rate decreased from 82.6% to 46.4% in Cachoeira and increased from 37.0% to 56.2% in Maragogipe. Thus, only about one-half of children are being tested in these cities. The findings show that the public health care system in these cities is poorly prepared to screen for sickle cell disease in newborns and that there was a lack of health care personnel to follow up on newly diagnosed sickle cell patients or carriers of the sickle cell trait.

Exclusion of Class III Malocclusion Candidate Loci in Brazilian Families

The role played by genetic components in the etiology of the Class III phenotype, a class of dental malocclusion, is not yet understood. Regions that may be related to the development of Class III malocclusion have been suggested previously. The aim of this study was to search for genetic linkage with 6 microsatellite markers (D1S234, D4S3038, D6S1689, D7S503, D10S1483, and D19S566), near previously proposed candidate regions for Class III. We performed a two-point parametric linkage analysis for 42 affected individuals from 10 Brazilian families with a positive Class III malocclusion segregation. Analysis of our data indicated that there was no evidence for linkage of any of the 6 microsatellite markers to a Class III locus at θ = zero, with data supporting exclusion for 5 of the 6 markers evaluated. The present work reinforces that Class III is likely to demonstrate locus heterogeneity, and there is a dependency of the genetic background of the population in linkage studies.

Evidence for an association between haptoglobin and MnSOD (Val9Ala) gene polymorphisms in essential hypertension based on a Brazilian case-control study

Essential hypertension is a complex and multifactorial trait; genetic and environmental factors interact to produce the final phenotype. Studies have demonstrated association of hypertension with varied gene polymorphisms. However, demonstration of common genetic causes in the general population remains elusive. We investigated a possible association between hypertension and haptoglobin, angiotensin I-converting enzyme (ACE), glutathione S-transferases GSTM1 and GSTT1, MnSOD (Val9Ala), CAT (-21A/T), and GPX1 (Pro198Leu) gene polymorphisms in an urban Brazilian population group from Brasília. Although ACE has been reported to be one of the main polymorphisms associated with hypertension, we found no association with ACEs specific genotypes. However, a possible association with Hp1-1 and MnSOD Val/Ala genotypes suggests that, at least for the Brazilian population, polymorphisms related to oxidative stress should be more deeply investigated.

Who were the male founders of rural Brazilian Afro-derived communities? A proposal based on three populations

Background: Brazilian Quilombos are Afro-derived communities founded mainly by fugitive slaves between the 16th and 19th centuries; they can be recognized today by ancestral and cultural characteristics. Each of these remnant communities, however, has its own particular history, which includes the migration of non-African derived people. Methods: The present work presents a proposal for the origin of the male founder in Brazilian quilombos based on Y-haplogroup distribution. Y haplogroups, based on 16 binary markers (92R7, SRY2627, SRY4064, SRY10831.1 and .2, M2, M3, M09, M34, M60, M89, M213, M216, P2, P3 and YAP), were analysed for 98 DNA samples from genetically unrelated men from three rural Brazilian Afro-derived communities—Mocambo, Rio das Rãs and Kalunga—in order to estimate male geographic origin. Results: Data indicated significant differences among these communities. A high frequency of non-African haplogroups was observed in all communities. Conclusions: This observation suggested an admixture process that has occurred over generations and directional mating between European males and African female slaves that must have occurred on farms before the slaves escaped. This means that the admixture occurred before the slaves escaped and the foundation of the quilombo.

Afro-derived Brazilian populations: male genetic constitution estimated by Y-chromosomes STRs and AluYAP element polymorphisms.

The genetic constitution of Afro‐derived Brazilian populations is barely studied. To improve that knowledge, we investigated the AluYAP element and five Y‐chromosome STRs (DYS19, DYS390, DYS391, DYS392, and DYS393) to estimate ethnic male contribution in the constitution of four Brazilian quilombos remnants: Mocambo, Rio das Rãs, Kalunga, and Riacho de Sacutiaba. Results indicated significant differences among communities, corroborating historical information about the Brazilian settlement. We concluded that besides African contribution, there was a great European participation in the constitution of these four populations and that observed haplotype variability could be explained by gene flow to quilombos remnants and mutational events in microsatellites (STRs). Am. J. Hum. Biol., 2009.

Distribution of glutathione S-transferase GSTM1 and GSTT1 null phenotypes in Brazilian Amerindians

The distribution of glutathione S-transferase (GST) GSTM1 and GSTT1 null phenotype frequencies in two Brazilian Amerindian tribes, the Munduruku tribe from Missao Cururu village (79 individuals) and the Kayabi tribe (41 individuals), was analyzed by polymerase chain reaction (PCR) amplification. The GST null phenotype frequencies for the Munduruku sample were 0% for GSTM1 and 27% for GSTT1 while for the Kayabi sample the null phenotype frequencies were 27% for GSTM1 and 29% for GSTT1. This is the first report of the absence of the GSTM1 null phenotype in any ethnic group.

Heterogeneous Distribution of HbS and HbC Alleles in Afro-derived Brazilian Populations

Abstract Africans brought to Brazil as slaves established communities known as Quilombos. As a consequence of this migration, sickle cell diseases are currently the most frequent hemoglobinopathy in the country. We sampled and analyzed for the presence of HbS and HbC 1182 individuals belonging to 11 remnants of Quilombo communities, distributed over three administrative regions of Brazil. Our results were pooled with literature data, resulting in the analysis of 2601 individuals from 24 populations distributed over the five Brazilian administrative regions. There were differences among weighted averages frequencies for the five Brazilian regions, and there were remarkable heterogeneities among all populations and the ones located in the same region. Additionally, we evaluated the utilization of the test of solubility and its efficiency in the field in three communities, reinforcing the reliability of the test as a first screening of hemoglobinopathy. Frequencies of hemoglobin S allele ranged from 0 to 13% and HbC allele was absent in 18 out of the 24 communities. The distribution of HbS and HbC alleles in remnants of Quilombos are heterogeneous and independent of geographic location probably due to differences in their history of foundation and miscegenation.

Does celiac disease occur in Afro-derived Brazilian populations?

Celiac disease is an autoimmune disorder that occurs in genetically susceptible individuals in whom the ingestion of dietary gluten induces intestinal mucosa inflammation. Previous studies suggest that celiac disease may either be very rare or underdiagnosed in African and/or African‐derived population.