Cíntia Alves

A new multiplex for human identification using insertion/deletion polymorphisms.

Human identification is usually based on the study of STRs or SNPs depending on the particular characteristics of the investigation. However, other types of genetic variation such as insertion/deletion polymorphisms (indels) have considerable potential in the field of identification, since they can combine the desirable characteristics of both STRs and SNPs. In this study, a set of 38 non‐coding bi‐allelic autosomal indels reported to be polymorphic in African, European, and Asian populations were selected. We developed a sensitive genotyping assay, which is able to characterize all 38 bi‐allelic markers using a single multiplex PCR and detected with standard CE analyzers. Amplicon length was designed to be shorter than 160 bp. Complete profiles were obtained using 0.3 ng of DNA, and full genotyping of degraded samples was possible in cases where standard STR typing had partially failed. A total of 306 individuals from Angola, Mozambique, Portugal, Macau, and Taiwan were studied and population data are presented. All indels were polymorphic in the three population groups studied and the random match probabilities of the set ranged in orders of magnitude from 10−14 to 10−15. Therefore, the indel‐plex represents a valuable approach in human identification studies, especially in challenging DNA cases, as a more straightforward and efficient alternative to SNP typing.

New Microsatellite Multiplex PCR for Candida albicans Strain Typing Reveals Microevolutionary Changes

ABSTRACT Five new microsatellite loci were described and characterized for use as molecular markers for the identification and genetic differentiation of Candida albicans strains. Following the typing of 72 unrelated clinical isolates, the analysis revealed that they were all polymorphic, presenting from 5 to 30 alleles and 8 to 46 different genotypes. The discriminatory power obtained by combining the information generated by three microsatellites used in a multiplex PCR amplification strategy was 0.99, the highest ever reported. The multiplex PCR was later used to test a total of 114 C. albicans strains, including multiple isolates from the same patient collected from different body locations and along episodes of vulvovaginal infections. Three different scenarios for strain relatedness were identified: (i) different isolates that were revealed to be the same strain, (ii) isolates that were the same strain but that apparently underwent a process of microevolution, and (iii) isolates that corresponded to different strains. Analysis of the microevolutionary changes between isolates from recurrent infections indicated that the genotype alterations observed could be the result of events that lead to the loss of heterozygosity (LOH). In one case of recurrent infection, LOH was observed at the CAI locus, and this could have been related to exposure to fluconazole, since such strains were exposed to this antifungal during treatment. The analysis of microsatellites by a multiplex PCR strategy was found to be a highly efficient tool for the rapid and accurate differentiation of C. albicans strains and adequate for the identification of fine microevolutionary events that could be related to strain microevolution in response to environmental stress conditions.

A GEP-ISFG collaborative study on the optimization of an X-STR decaplex: data on 15 Iberian and Latin American populations

In a collaborative work carried out by the Spanish and Portuguese ISFG Working Group (GEP-ISFG), a polymerase chain reaction multiplex was optimized in order to type ten X-chromosome short tandem repeats (STRs) in a single reaction, including: DXS8378, DXS9902, DXS7132, DXS9898, DXS6809, DXS6789, DXS7133, GATA172D05, GATA31E08, and DXS7423. Using this X-decaplex, each 17 of the participating laboratories typed a population sample of approximately 200 unrelated individuals (100 males and 100 females). In this work, we report the allele frequencies for the ten X-STRs in 15 samples from Argentina (Buenos Aires, Córdoba, Río Negro, Entre Ríos, and Misiones), Brazil (São Paulo, Rio de Janeiro, Paraná, and Mato Grosso do Sul), Colombia (Antioquia), Costa Rica, Portugal (Northern and Central regions), and Spain (Galicia and Cantabria). Gene diversities were calculated for the ten markers in each population and all values were above 56%. The average diversity per locus varied between 66%, for DXS7133, and 82%, for DXS6809. For this set of STRs, a high discrimination power was obtained in all populations, both in males (≥1 in 5 × 105) and females (≥1 in 3 × 109), as well as high mean exclusion chance in father/daughter duos (≥99.953%) and in father/mother/daughter trios (≥99.999%). Genetic distance analysis showed no significant differences between northern and central Portugal or between the two Spanish samples from Galicia and Cantabria. Inside Brazil, significant differences were found between Rio de Janeiro and the other three populations, as well as between São Paulo and Paraná. For the five Argentinean samples, significant distances were only observed when comparing Misiones with Entre Ríos and with Río Negro, the only two samples that do not differ significantly from Costa Rica. Antioquia differed from all other samples, except the one from Río Negro.

Highly Polymorphic Microsatellite for Identification of Candida albicans Strains

ABSTRACT The polymorphism of a new microsatellite locus (CAI) was investigated in a total of 114 Candida albicans strains, including 73 independent clinical isolates, multiple isolates from the same patient, isolates from several episodes of recurrent vulvovaginal infections, and two reference strains. PCR genotyping was performed automatically, using a fluorescence-labeled primer, and in the 73 independent isolates, 26 alleles and 44 different genotypes were identified, resulting in a discriminatory power of 0.97. CAI was revealed to be species specific and showed a low mutation rate, since no amplification product was obtained when testing other pathogenic Candida species and no genotype differences were observed when testing over 300 generations. When applying this microsatellite to the identification of strains isolated from recurrent vulvovaginal infections in eight patients, it was found that 13 out of 15 episodes were due to the same strain. When multiple isolates, obtained from the same patient and plated simultaneously, were typed for CAI, the same genotype was found in each case, confirming that the infecting population was clonal. Moreover, the same genotype appeared in isolates from the rectum and the vagina, revealing that the former could be a reservoir of potentially pathogenic strains. This new microsatellite proves to be a valuable tool to differentiate C. albicans strains. Furthermore, when compared to other molecular genotyping techniques, CAI proved to be very simple, highly efficient, and reproducible, being suitable for low-quantity and very-degraded samples and for application in large-scale epidemiological studies.

Micro‐Phylogeographic and Demographic History of Portuguese Male Lineages

The clinal pattern observed for the distribution of Y‐chromosome lineages in Europe is not always reflected at a geographically smaller scale. Six hundred and sixty‐three male samples from the 18 administrative districts of Portugal were typed for 25 Y‐chromosome biallelic and 15 microsatellite markers, in order to assess the degree of substructuring of male lineage distribution. Haplogroup frequency distributions, Analysis of Molecular Variance (AMOVA) and genetic distance analyses at both Y‐SNP and Y‐STR levels revealed a general genetic homogeneity of Portuguese sub‐populations. The traditional division of the country in north, central and south, which is usually considered in studies addressing questions of the genetic variation distribution in Portugal, was not reflected in the Y‐haplotype distribution. Instead, just one sub–region (Alentejo) stood out due to the presence of high diversity levels and a higher number of different lineages, at higher frequencies than in other regions. These results are reconciled with the historical evidence available, assuming that from prehistorical times down to the end of the medieval period this region harboured the most diverse groups of people and, because of economic depression, remained relatively isolated from recent homogenisation movements. The finding of a broadly homogeneous background for the Portuguese population has vast repercussions in forensic, epidemiological and association studies.

Extending STR markers in Y chromosome haplotypes

Abstract. Two multiplex reactions were developed to amplify 16 Y-STRs (DYS19, DYS385, DYS389 I and II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438, DYS439, GATA A7.1, GATA A7.2, GATA A10, GATA C4, GATA H4). Here we extend previous population studies done in a sample from northern Portugal for the GATA A7.1, GATA A7.2, GATA C4 and GATA H4 loci. A total of 199 different haplotypes identified by the 16 Y-STR markers were observed in a sample of 208 male individuals, of which 190 were unique and 9 were found twice. The overall haplotype diversity was 0.9996. The haplotype diversity of the Y-STR set composed of the 8 new markers is higher than the Y-STR core set included in the Y-STR haplotype reference database. Sequence structure of new alleles for GATA C4 and GATA H4 is reported. The usefulness of the inclusion of this new set of Y-STRs in forensic casework was also assessed. The increase in haplotype diversity with the addition of any new Y-STR marker to the 8 Y-STR core set is dependent not only on the gene diversity (positively) but also (negatively) on the degree of gametic association between the markers and the haplotypes previously defined. For instance, in our sample the addition of the DYS437, DYS438 and GATA A7.2 to a 13-locus set increased haplotype diversity only by 0.0001.

Chimpanzee homologous of human Y specific STRs: A comparative study and a proposal for nomenclature

Eleven Y specific microsatellites, previously studied in humans, were typed for fragment length and sequenced in chimpanzees (Pan troglodytes). The primers described by Ayub et al. (Nucleic Acids Res. 28, 2000, 2) for amplifying DYS434, DYS435, DYS436, DYS437, DYS438, DYS439 and those described by White et al. (Genomics, 57, 1999, 433) for GATA A10, A7.1, A7.2, C4, and H4, were used to amplify DNA samples from chimpanzees. Primers described for Y GATA A4 were found to amplify the same region as reported for DYS439. Moreover, the GATA A4 forward primer only matches the repeat flanking region in 14 of the 28bp, being responsible for a very weak amplification. Therefore, this system was not included in this study. The analysis of the repeat and sequence structure observed in chimpanzee and human Y chromosomes allowed evolutionary comparisons as well as the basis for improving Y STR nomenclature and therefore, a unified nomenclature for these novel STRs is proposed to the scientific community following ISFG recommendations.

Bantu and European Y-lineages in Sub-Saharan Africa.

Ancient diversity in Sub-Saharan Africa is known to have been re-modulated to a large extent by Bantu migrations in the sub-Sahel region, in two southwards waves of advance through both the west and east coasts. Haplotype matching performed for Y-STR haplotypes in several sub-Saharan populations, both inside and outside the migration path, allowed the confirmation of a putative founder haplotype, and its one-step neighbours, of Bantu origin, and detected an increasing drift towards the south, with a stronger reduction of diversity along the western coast. A mixed frequency distribution for the Bantu haplotype core in South Africa, relative to the western and eastern pools, seems to provide evidence for the intermingling between both Bantu waves in that region. The proportion of male lineages considered as predating the Bantu expansion reached 8.8% in Mozambique. Further influence on sub-Saharan diversity may have occurred during the colonial period; in Mozambique, the European genetic impact in the male component was estimated to be around 5.9%, in significant contrast with the female counterpart where no European lineages were detected.

Reconstructing the Indian origin and dispersal of the European Roma: a maternal genetic perspective.

Previous genetic, anthropological and linguistic studies have shown that Roma (Gypsies) constitute a founder population dispersed throughout Europe whose origins might be traced to the Indian subcontinent. Linguistic and anthropological evidence point to Indo-Aryan ethnic groups from North-western India as the ancestral parental population of Roma. Recently, a strong genetic hint supporting this theory came from a study of a private mutation causing primary congenital glaucoma. In the present study, complete mitochondrial control sequences of Iberian Roma and previously published maternal lineages of other European Roma were analyzed in order to establish the genetic affinities among Roma groups, determine the degree of admixture with neighbouring populations, infer the migration routes followed since the first arrival to Europe, and survey the origin of Roma within the Indian subcontinent. Our results show that the maternal lineage composition in the Roma groups follows a pattern of different migration routes, with several founder effects, and low effective population sizes along their dispersal. Our data allowed the confirmation of a North/West migration route shared by Polish, Lithuanian and Iberian Roma. Additionally, eleven Roma founder lineages were identified and degrees of admixture with host populations were estimated. Finally, the comparison with an extensive database of Indian sequences allowed us to identify the Punjab state, in North-western India, as the putative ancestral homeland of the European Roma, in agreement with previous linguistic and anthropological studies.

A Perspective on the History of the Iberian Gypsies Provided by Phylogeographic Analysis of Y-Chromosome Lineages

The European Gypsies, commonly referred to as Roma, are represented by a vast number of groups spread across many countries. Although sharing a common origin, the Gypsy groups are highly heterogeneous as a consequence of genetic drift and different levels of admixture with surrounding populations. With this study we aimed at contributing to the knowledge of the Roma history by studying 17 Y‐STR and 34 Y‐SNP loci in a sample of 126 Portuguese Gypsies. Distinct genetic hallmarks of their past and migration route were detected, namely: an ancestral component, shared by all Roma groups, that reflects their origin in India (H1a‐M82; ∼17%); an influence from their long permanence in the Balkans/Middle‐East region (J2a1b‐M67, J2a1b1‐M92, I‐M170, Q‐M242; ∼31%); traces of contacts with European populations preceding the entrance in the Iberian Peninsula (R1b1c‐M269, J2b1a‐M241; ∼10%); and a high proportion of admixture with the non‐Gypsy population from Iberia (R1b1c‐M269, R1‐M173/del.M269, J2a‐M410, I1b1b‐M26, E3b1b‐M81; ∼37%). Among the Portuguese Gypsies the proportion of introgression from host populations is higher than observed in other groups, a fact which is somewhat unexpected since the arrival of the Roma to Portugal is documented to be more recent than in Central or East Europe.