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Background: Oral squamous cell carcinoma (OSCC) is mainly caused by smoking and alcohol abuse and shows a five-year survival rate of ~50%. We aimed to explore the variation of somatic mitochondrial DNA (mtDNA) mutations in primary oral tumors, recurrences and metastases. Methods: We performed an in-depth validation of mtDNA next-generation sequencing (NGS) on an Illumina HiSeq 2500 platform for its application to cancer tissues, with the goal to detect low-level heteroplasmies and to avoid artifacts. Therefore we genotyped the mitochondrial genome (16.6 kb) from 85 tissue samples (tumors, recurrences, resection edges, metastases and blood) collected from 28 prospectively recruited OSCC patients applying both Sanger sequencing and high-coverage NGS (~35,000 reads per base). Results: We observed a strong correlation between Sanger sequencing and NGS in estimating the mixture ratio of heteroplasmies (r = 0.99; p<0.001). Non-synonymous heteroplasmic variants were enriched among cancerous tissues. The proportions of somatic and inherited variants in a given gene region were strongly correlated (r = 0.85; p<0.001). Half of the patients shared mutations between benign and cancerous tissue samples. Low level heteroplasmies (<10%) were more frequent in benign samples compared to tumor samples, where heteroplasmies >10% were predominant. Four out of six patients who developed a local tumor recurrence showed mutations in the recurrence that had also been observed in the primary tumor. Three out of five patients, who had tumor metastases in the lymph nodes of their necks, shared mtDNA mutations between primary tumors and lymph node metastases. The percentage of mutation heteroplasmy increased from the primary tumor to lymph node metastases. Conclusions: We conclude that Sanger sequencing is valid for heteroplasmy quantification for heteroplasmies ≥10% and that NGS is capable of reliably detecting and quantifying heteroplasmies down to the 1%-level. The finding of shared mutations between primary tumors, recurrences and metastasis indicates a clonal origin of malignant cells in oral cancer. [ABSTRACT FROM AUTHOR]

Background: Iron-refractory iron deficiency anaemia (IRIDA) is a rare disorder which was linked to mutations in two genes (SLC11A2 and TMPRSS6). Common polymorphisms within these genes were associated with serum iron levels. We identified a family of Serbian origin with asymptomatic non-consanguineous parents with three of four children presenting with IRIDA not responding to oral but to intravenous iron supplementation. After excluding all known causes responsible for iron deficiency anaemia we searched for mutations in SLC11A2 and TMPRSS6 that could explain the severe anaemia in these children. Methodology/Results: We sequenced the exons and exon-intron boundaries of SLC11A2 and TMPRSS6 in all six family members. Thereby, we found seven known and fairly common SNPs, but no new mutation. We then genotyped these seven SNPs in the population-based SAPHIR study (n = 1,726) and performed genetic association analysis on iron and ferritin levels. Only two SNPs, which were top-hits from recent GWAS on iron and ferritin, exhibited an effect on iron and ferritin levels in SAPHIR. Six SAPHIR participants carrying the same TMPRSS6 genotypes and haplotype-pairs as one anaemic son showed lower ferritin and iron levels than the average. One individual exhibiting the joint SLC11A2/TMPRSS6 profile of the anaemic son had iron and ferritin levels lying below the 5th percentile of the population's iron and ferritin level distribution. We then checked the genotype constellations in the Nijmegen Biomedical Study (n = 1,832), but the profile of the anaemic son did not occur in this population. Conclusions: We cannot exclude a gene-gene interaction between SLC11A2 and TMPRSS6, but we can also not confirm it. As in this case candidate gene sequencing did not reveal causative rare mutations, the samples will be subjected to whole exome sequencing. [ABSTRACT FROM AUTHOR]

Abstract: Genome-wide association studies (GWASs) led to impressive advances in the elucidation of genetic factors underlying complex phenotypes and diseases. However, the ability of GWAS to identify new susceptibility loci in a hypothesis-free approach requires tools to quickly retrieve comprehensive information about a genomic region and analyze the potential effects of coding and non-coding SNPs in a candidate gene region. Furthermore, once a candidate region is chosen for resequencing and fine-mapping studies, the identification of several rare mutations is likely and requires strong bioinformatic support to properly evaluate and prioritize the found mutations for further analysis. Due to the variety of regulatory layers that can be affected by a mutation, a comprehensive in-silico evaluation of candidate SNPs can be a demanding and very time-consuming task. Although many bioinformatic tools that significantly simplify this task were made available in the last years, their utility is often still unknown to researches not intensively involved in bioinformatics. We present a comprehensive guide of 64 tools and databases to bioinformatically analyze gene regions of interest to predict SNP effects. In addition, we discuss tools to perform data mining of large genetic regions, predict the presence of regulatory elements, make in-silico evaluations of SNPs effects and address issues ranging from interactome analysis to graphically annotated proteins sequences. Finally, we exemplify the use of these tools by applying them to hits of a recently performed GWAS. Taken together a combination of the discussed tools are summarized and constantly updated in the web-based “GenEpi Toolbox” (http://genepi_toolbox.i-med.ac.at) and can help to get a glimpse at the potential functional relevance of both large genetic regions and single nucleotide mutations which might help to prioritize the next steps. [Copyright &y& Elsevier]

Instances of point and length heteroplasmy in the mitochondrial DNA control region were compiled and analyzed from over 5,000 global human population samples. These data represent observations from a large and broad population sample, representing nearly 20 global populations. As expected, length heteroplasmy was frequently observed in the HVI, HVII and HVIII C-stretches. Length heteroplasmy was also observed in the AC dinucleotide repeat region, as well as other locations. Point heteroplasmy was detected in approximately 6% of all samples, and while the vast majority of heteroplasmic samples comprised two molecules differing at a single position, samples exhibiting two and three mixed positions were also observed in this data set. In general, the sites at which heteroplasmy was most commonly observed correlated with reported control region mutational hotspots. However, for some sites, observations of heteroplasmy did not mirror established mutation rate data, suggesting the action of other mechanisms, both selective and neutral. Interestingly, these data indicate that the frequency of heteroplasmy differs between particular populations, perhaps reflecting variable mutation rates among different mtDNA lineages and/or artifacts of particular population groups. The results presented here contribute to our general understanding of mitochondrial DNA control region heteroplasmy and provide additional empirical information on the mechanisms contributing to mtDNA control region mutation and evolution. [ABSTRACT FROM AUTHOR]

While a shift in energy metabolism is essential to cancers, the knowledge about the involvement of the mitochondrial genome in tumorigenesis and progression in oral squamous cell carcinoma (OSCC) is still very limited. In this study, we evaluated 37 OSCC tumors and the corresponding benign mucosa tissue pairs by deep sequencing of the complete mitochondrial DNA (mtDNA). After extensive quality control, we identified 287 variants, 137 in tumor and 150 in benign samples exceeding the 1% threshold. Variant heteroplasmy levels were significantly increased in cancer compared to benign tissues (p = 0.0002). Furthermore, pairwise high heteroplasmy frequency difference variants (∆HF% > 20) with potential functional impact were increased in the cancer tissues (p = 0.024). Fourteen mutations were identified in the protein-coding region, out of which thirteen were detected in cancer and only one in benign tissue. After eight years of follow-up, the risk of mortality was higher for patients who harbored at least one ∆HF% > 20 variant in mtDNA protein-coding regions relative to those with no mutations (HR = 4.6, (95%CI = 1.3–17); p = 0.019 in primary tumor carriers). Haplogroup affiliation showed an impact on survival time, which however needs confirmation in a larger study. In conclusion, we observed a significantly higher accumulation of somatic mutations in the cancer tissues associated with a worse prognosis. [ABSTRACT FROM AUTHOR]

DYS464 is a multi-copy STR system with four positions on the Y-chromosome (DYS464a, b, c, and d) which was recently identified and characterized [Forensic Sci. Int. 130 (2002) 97]. The aims of our study were to perform a population study, to estimate the mutation rate and an extensive sequence analysis in order to confirm the nomenclature. Fourteen different alleles were found in an Austrian population sample with an allele length varying from 9 to 19 repeats. All alleles were cloned and sequenced. Alleles 9–19 showed the general repeat structure (CCTT)n … (CCTT)2 … (CCTT)3 … (CCTT)4 … (CCTT)2 … (CCTT)2. The nomenclature is based on the number of repeated units of the variable (CCTT)n-stretch only. In 13% of the samples intermediate alleles, namely 14.3A, 14.3B and 15.3 were detected. In these alleles the variable repeat block is interrupted by a CTT motif (14.3A: (CCTT)3CTT(CCTT)11; 14.3B and 15.3: (CCTT)7CTT(CCTT)7/8). A comparison with GenBank entries revealed the existence of a length variant due to a deletion of one cytosine in the 5′ flanking region of the first repeat block. We designed an alternative forward primer to circumvent possible ambiguities in the allele designation. A total of 54 different genotypes were identified in 135 men corresponding to a discrimination capacity (DC) of 40% and a gene diversity (GD) of 0.97. These values are much higher than those of other Y-chromosomal short tandem repeats (Y-STRs). DYS464 has the same haplotype diversity (HD) as the combination of the five Y-STR loci with the lowest gene diversities of the Y-STR core set. On the other hand, a combination of the three most diverse loci (DYS464, DYS385 and DYS390) has the same capacity to distinguish between paternal lineages than the complete minimal haplotype (minHT) consisting of eight Y-STR loci. In our population sample the addition of DYS464 to the minHT increases the number of different haplotypes from 110 to 122. The mutation-rate estimate based on the 70 meioses analyzed amounts to 2.86×10−2 (95% confidence interval 3.5×10−3 to 9.95×10−2). This value is approximately 10 times higher than the average mutation-rate estimate for Y-STRs. [Copyright &y& Elsevier]

DYS464 is a multi-copy STR system with four positions on the Y chromosome (DYS464a, b, c, and d) which was recently identified and characterized. The aims of our study were to perform a population study, to estimate the mutation-rate and an extensive sequence analysis in order to confirm the nomenclature. Fourteen different alleles were found with allele lengths varying from 9 to 19 repeats. All alleles were cloned and sequenced. A total of 54 different genotypes were identified in 135 men corresponding to a gene diversity (GD) of 0.97. This value is much higher than those of other Y-STRs. DYS464 has the same discrimination capacity as the combination of the five Y-STR loci with the lowest gene diversity of the Y-STR core set. The mutation-rate estimate based on the 70 meioses analyzed amounts to 2.86×10−2. [Copyright &y& Elsevier]