There are many different studies that contribute to the global picture of the ethnic heterogeneity in Brazilian populations. These studies use different types of genetic markers and are focused on the comparison of populations at different levels. In some of them, each geographical region is treated as a single homogeneous population, whereas other studies create different subdivisions: political (e.g., pooling populations by State), demographic (e.g., urban and rural), or ethnic (e.g., culture, self-declaration, or skin colour). In this study, we performed an enhanced reassessment of the genetic ancestry of ~ 1,300 Brazilians characterised for 46 autosomal Ancestry Informative Markers (AIMs). In addition, 798 individuals from twelve Brazilian populations representing the five geographical macro-regions of Brazil were newly genotyped, including a Native American community and a rural Amazonian community. Following an increasing North to South gradient, European ancestry was the most prevalent in all urban populations (with values up to 74%). The populations in the North consisted of a significant proportion of Native American ancestry that was about two times higher than the African contribution. Conversely, in the Northeast, Center-West and Southeast, African ancestry was the second most prevalent. At an intrapopulation level, all urban populations were highly admixed, and most of the variation in ancestry proportions was observed between individuals within each population rather than among population. Nevertheless, individuals with a high proportion of Native American ancestry are only found in the samples from Terena and Santa Isabel. Our results allowed us to further refine the genetic landscape of Brazilians while establishing the basis for the effective application of an autosomal AIM panel in forensic casework and clinical association studies within the highly admixed Brazilian populations.

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Pomeranian populations worldwide immigrated originally from the north of Europe, and because of their preferential marriage, religion, and cultural habits, they show little or no reproductive mixing with local populations. Methylenetetrahydrofolate reductase gene (MTHFR) C677T, Factor V Leiden, and Factor II G20210A polymorphisms are linked to augmented clotting and their frequencies may vary according to population ethnicity. We aimed to assess the frequencies of these thrombophilic alleles in the Pomeranian population residing in Espirito Santo and compare with the general population of the Espirito Santo state, Brazil. A total of 200 individuals were analyzed. The intrapopulation fixation index of the MTHFR C677T polymorphism was 0.03736. The observed heterozygosity was 0.44 and 0.4 for the general and Pomeranian populations, respectively. According to the chi-square test, both populations are in Hardy-Weinberg equilibrium. Four polymorphic alleles were detected for Factor II (2.02%) and 8 for Factor V (4.81%). Our results show that there is gene flow between the general and the Pomeranian population of Espirito Santo, which should no longer be considered an isolated population.

Breast cancer is a heterogeneous disease, previously associated with genomic instability. Our aim was to analyze microsatellite markers in order to determine patterns and levels of instability, as well as possible correlations with histopathological parameters. Polymerase chain reaction was used to characterize microsatellite instability (MSI) and loss of heterozygosity (LOH) in 107 breast carcinomas at twelve microsatellite loci. Some of the markers were selected because of their relation to steroid hormone metabolism, which seems to be related to sporadic breast cancer risk. D5S346 and D17S250 markers showed a statistically significant frequency of MSI. LOH in D3S1611, D17S250, AR and ER-β were associated with some parameters of worse prognosis. Marker group analysis showed that CYP19, AR and ER-β were related to histological grade III, ER-negative and PR-negative cases. Our results suggest that marker group analysis may be preferred to the single marker strategy, being predictive of worst prognosis when single markers are unable to provide such information. A further evaluation of steroid metabolism genes and their association with low penetrance genes in breast cancer may be useful.

Haemophilia A is an X-linked, recessively inherited bleeding disorder of varying severity, which results from the deficiency of procoagulant factor VIII f(8). Linkage diagnosis using polymorphic markers in the f8 gene is widely used to detect carriers. The objective of this study was to verify the informativeness of three polymorphic markers in the Brazilian population, to evaluate the usefulness of such markers in carrier detection procedures. Sixty-three unrelated healthy volunteers and 10 haemophilic families were studied. Two microsatellite repeats and one HindIII RFLP markers were used. Carrier and non-carrier status could be determined in 80% of females investigated. Intron 13 markers presented the highest heterozygosity rate (79%) followed by intron 22 (68%) and intron 19 (57%). When all three markers were used together, linkage analysis informativeness increased significantly. We conclude that these markers are suitable for carrier detection in the Brazilian population and we recommend their use in combination to maximize diagnostic efficiency.