Xeroderma pigmentosum variant: squamous cell carcinoma of the lower lip harboring exon 11 mutation of POLH.

Xeroderma pigmentosum (XP) is a rare inherited disease caused by deficiencies in DNA damage repair, which mainly results from the failure of nucleotide excision repair or defects in translesion DNA synthesis. The development of multiple malignancies is one of the most prominent features of this condition, which is clinically characterized by the occurrence of hyperpigmentation and lesions associated with sunlight exposure. Lip squamous cell carcinoma in patients with XP has rarely been reported, and information regarding the genetic analysis of these patients is limited. In this report, a case of a 20-year-old patient who developed squamous cell carcinoma in the lower lip is described. Although the tumor was surgically excised, the patient presented with recurrence a few months later. Targeted sequencing using a customized panel of DNA repair genes revealed a mutation in POLH, the gene encoding DNA polymerase eta. Therefore, molecular characterization is important to further improve the understanding of possible phenotype-genotype correlations and mechanisms involved in the pathogenesis of XP.

How natural selection shapes genetic differentiation in the MHC region: A case study with Native Americans.

The Human Leukocyte Antigen (HLA) loci are extremely well documented targets of balancing selection, yet few studies have explored how selection affects population differentiation at these loci. In the present study we investigate genetic differentiation at HLA genes by comparing differentiation at microsatellites distributed genomewide to those in the MHC region. Our study uses a sample of 494 individuals from 30 human populations, 28 of which are Native Americans, all of whom were typed for genomewide and MHC region microsatellites. We find greater differentiation in the MHC than in the remainder of the genome (FST-MHC = 0.130 and FST-Genomic = 0.087), and use a permutation approach to show that this difference is statistically significant, and not accounted for by confounding factors. This finding lies in the opposite direction to the expectation that balancing selection reduces population differentiation. We interpret our findings as evidence that selection favors different sets of alleles in distinct localities, leading to increased differentiation. Thus, balancing selection at HLA genes simultaneously increases intra-population polymorphism and inter-population differentiation in Native Americans.

A web resource for mining HLA associations with adverse drug reactions: HLA-ADR.

Human leukocyte antigens (HLA) are an important family of genes involved in the immune system. Their primary function is to allow the host immune system to be able to distinguish between self and non-self peptides-e.g. derived from invading pathogens. However, these genes have also been implicated in immune-mediated adverse drug reactions (ADRs), presenting a problem to patients, clinicians and pharmaceutical companies. We have previously developed the Allele Frequency Net Database (AFND) that captures the allelic and haplotype frequencies for these HLA genes across many healthy populations from around the world. Here, we report the development and release of the HLA-ADR database that captures data from publications where HLA alleles and haplotypes have been associated with ADRs (e.g. Stevens-Johnson Syndrome/toxic epidermal necrolysis and drug-induced liver injury). HLA-ADR was created by using data obtained through systematic review of the literature and semi-automated literature mining. The database also draws on data already present in AFND allowing users to compare and analyze allele frequencies in both ADR patients and healthy populations. The HLA-ADR database provides clinicians and researchers with a centralized resource from which to investigate immune-mediated ADRs.Database URL: http://www.allelefrequencies.net/hla-adr/.

Impact of population admixture on the distribution of immune response co-stimulatory genes polymorphisms in a Brazilian population.

Co-stimulatory molecules are essential in the orchestration of immune response and polymorphisms in their genes are associated with various diseases. However, in the case of variable allele frequencies among continental populations, this variation can lead to biases in genetic studies conducted in admixed populations such as those from Brazil. The aim of this study was to evaluate the influence of genomic ancestry on distributions of co-stimulatory genes polymorphisms in an admixed Brazilian population. A total of 273 individuals from the north of Brazil participated in this study. Nine single nucleotide polymorphisms in 7 genes (CD28, CTLA4, ICOS, CD86, CD40, CD40L and BLYS) were determined by polymerase chain reaction-restriction fragment length polymorphism. We also investigated 48 insertion/deletion ancestry markers to characterize individual African, European and Amerindian ancestry proportions in the samples. The analysis showed that the main contribution was European (43.9%) but also a significant contribution of African (31.6%) and Amerindian (24.5%) ancestry. ICOS, CD40L and CD86 polymorphisms were associated with genomic ancestry. However there were no significant differences in the proportions of ancestry for the other SNPs and haplotypes studied. Our findings reinforce the need to apply AIMs in genetic association studies involving these polymorphisms in the Brazilian population.

Allele frequency net 2015 update: new features for HLA epitopes, KIR and disease and HLA adverse drug reaction associations.

It has been 12 years since the Allele Frequency Net Database (AFND; http://www.allelefrequencies.net) was first launched, providing the scientific community with an online repository for the storage of immune gene frequencies in different populations across the world. There have been a significant number of improvements from the first version, making AFND a primary resource for many clinical and scientific areas including histocompatibility, immunogenetics, pharmacogenetics and anthropology studies, among many others. The most widely used part of AFND stores population frequency data (alleles, genes or haplotypes) related to human leukocyte antigens (HLA), killer-cell immunoglobulin-like receptors (KIR), major histocompatibility complex class I chain-related genes (MIC) and a number of cytokine gene polymorphisms. AFND now contains >1400 populations from more than 10 million healthy individuals. Here, we report how the main features of AFND have been updated to include a new section on 'HLA epitope' frequencies in populations, a new section capturing the results of studies identifying HLA associations with adverse drug reactions (ADRs) and one for the examination of infectious and autoimmune diseases associated with KIR polymorphisms-thus extending AFND to serve a new user base in these growing areas of research. New criteria on data quality have also been included.

Polymorphism of DC-SIGN (CD209) promoter in association with clinical symptoms of dengue fever.

C-type lectin DC-SIGN receptor, encoded by CD209, plays a key role in the infection of dendritic cells by dengue virus (DENV). Because the -336A/G SNP (rs4804803) polymorphism in the promoter of CD209 modulates DC-SIGN expression, we investigated the putative association of this polymorphism with DENV infection and its pathogenesis. A control sample of 72 individuals, rigorously selected through a clinical investigation for absence of past dengue fever (DF) was compared to a sample of 168 patients (156 classical DF; 12 dengue hemorrhagic fever), all residents from Pará, Brazil. However, the prevalence of symptoms showed a trend higher in the AA genotype (Wilcoxon test; Z=2.02; p=0.04). Hence, our findings indicate that the G allele downregulates the spectrum of symptoms during the early acute phase of DENV infection, putatively decreasing the viremia, as suggested in the literature.

Predisposition to idiopathic thrombocytopenic purpura maps close to the major histocompatibility complex class I chain-related gene A.

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune condition with poorly known etiology, characterized by platelet destruction. Genetic association studies of this disease are scarce, discrepant, and restricted to major histocompatibility complex (MHC) polymorphisms. Hence, a case-control study was conducted with an aim to map the MHC to IPT susceptibility using HLA-B and nine microsatellite loci encompassing MHC class I, II, and III regions. We compared the allelic frequencies in samples of unrelated healthy controls and ITP patients. After correction for multiple tests, only allele MICA*183, also known as A5.1, demonstrated an association, resulting in the identification of a major predisposing region close to STR-MICA. This result may highlight the putative functional role of MICA in the immune response to ITP.