Applicability of the SNPforID 52-plex panel for human identification and ancestry evaluation in a Brazilian population sample by next-generation sequencing.

SNP analysis is of paramount importance in forensic genetics. The development of new technologies in next-generation sequencing allowed processing a large number of markers in various samples simultaneously. Although SNPs are less informative than STRs, they present lower mutation rates and perform better when using degraded samples. Some SNP systems were developed for forensic usage, such as the SNPforID 52-plex, from the SNPforID Consortium, containing 52 bi-allelic SNPs for human identification. In this paper we evaluated the informativeness of this system in a Brazilian population sample (n = 340). DNA libraries were prepared using a customized HaloPlex Target Enrichment System kit (Agilent Technologies, Inc.) and sequenced in the MiSeq Personal Sequencer platform (Illumina Inc.). The methodology presented here allowed the analysis of 51 out of 52 SNPforID markers. Allele frequencies and forensic parameters were estimated, revealing high informativeness: the combined match probability and power of exclusion were 6.48 × 10-21 and 0.9997, respectively. Population admixture analysis indicates high European contribution (more than 70%) and low Amerindian contribution (less than 10%) in our population, while individual admixture analyses were consistent with the majority of individuals presenting high European contribution. This study demonstrates that the 52-plex kit is suitable for forensic cases in a Brazilian population, presenting results comparable with those obtained using a 16 STR panel.

Extended HLA-G genetic diversity and ancestry composition in a Brazilian admixed population sample: Implications for HLA-G transcriptional control and for case-control association studies.

Human leukocyte antigen-G (HLA-G) is a nonclassical Major Histocompatibility Complex (MHC) molecule with immunomodulatory function and restricted tissue expression. The genetic diversity of HLA-G has been extensively studied in several populations, however, the segment located upstream -1406 has not yet been evaluated. We characterized the nucleotide variation and haplotype structure of an extended distal region (-2635), all exons and the 3'UTR segment of HLA-G by next-generation sequencing (NGS) in a sample of 335 Brazilian individuals. We detected 29 variants at the HLA-G distal promoter region, arranged into 19 haplotypes, among which we identified sites that may influence transcription factor targeting. Although the variation pattern in the distal region resembled the one observed in the conventional promoter segment, molecular signature for balancing selection was observed in the promoter segment from -1406 to -1 (Tajima's D = 2.315, P = 0.017), but not in this distal segment (D = 1.049, P = 0.118). Furthermore, the ancestry composition of this Brazilian population sample was determined by the analysis of SNPforID 34-plex ancestry informative marker (AIM) SNP panel. The distribution of HLA-G haplotypes was ancestry-dependent, corroborating previous findings and emphasizing the importance of considering the ancestry information in association studies.

Haplotypes from the SLC45A2 gene are associated with the presence of freckles and eye, hair and skin pigmentation in Brazil.

The Solute Carrier Family 45, Member 2 (SLC45A2) gene encodes the Membrane-Associated Transporter Protein (MATP), which mediates melanin synthesis by tyrosinase trafficking and proton transportation to melanosomes. At least two SLC45A2 coding SNPs [E272K (rs26722) and L374F (rs16891982)] were reported influencing normal variation of human pigmentation. Here we aimed at evaluating the influence of haplotypes of 12 SNPs within SLC45A2 in the determination of eye, hair and skin pigmentation in a highly admixed population sample and comparing their frequencies with the ones found in data retrieved from the 1000 Genomes Project. To achieve this goal, 12 SLC45A2 SNPs were evaluated in 288 unrelated individuals from the Ribeirão Preto city area, Southeastern Brazil. SNPs were genotyped by PCR-RFLP or Allele-specific PCR, followed by polyacrylamide gel electrophoresis. Haplotypes of each individual were inferred by two independent computational methods, PHASE and Partition-Ligation-Expectation-Maximization (PL-EM) algorithms, and 34 different haplotypes were identified. The hp9 haplotype was the most frequent (58.3%) and was associated with the presence of blond/red hair, pale skin, blue eyes and freckles. All haplotypes significantly associated with dark or light pigmentation features harbor the 374L and 374F alleles, respectively. These results emphasize the role played by haplotypes at SLC45A2 in the determination of pigmentation aspects of human populations and reinforce the relevance of SNP L374F in human pigmentation.