DNA

The detection of genetic alterations in patients with acute leukemias is essential for the targeting of more specific and effective therapies. Therefore, the aim of this study was to compare the sensitivity of Nested-PCR and RT-qPCR techniques in the detection of genetic alterations in patients with acute leukemias. This study included samples from 117 patients treated at the Fortaleza General Hospital. All samples were submitted to analysis using the Nested-PCR and the RT-qPCR techniques. Acute Myeloid Leukemia (AML) patients’ samples were submitted to the analysis of the following alterations: FLT3-ITD, RUNX1::RUNX1T1, CBFB::MYH11 and PML::RARA; meanwhile, BCR::ABL1, TCF3::PBX1, KMT2A::AFF1, ETV6::RUNX1, and STIL::TAL1 fusions were investigated in the Acute Lymphoblastic Leukemia (ALL) patients’ samples. Throughout the study, 77 patients were diagnosed with AML and 40 with ALL. Among the 77 AML patients, FLT3-ITD, RUNX1::RUNX1T1, PML::RARA, and CBFB::MYH11 were detected in 4, 7, 10 and 8 patients, respectively. Among the 40 ALL patients, the presence of 23 patients with BCR::ABL1 translocation and 9 patients with TCF3::PBX1 translocation was observed through the RT-qPCR methodology. Overall, the present study demonstrated that the RT-qPCR technique presented a higher sensitivity when compared to the Nested-PCR technique at the time of diagnosis of the acute leukemia samples studied. Full article

The global prevalence of obesity among adults, adolescents, and children has increased to alarming levels, making this disease a serious public health problem. The etiology of obesity is complex and multifactorial. Currently, epigenetic alterations are being investigated to understand the mechanisms of interaction between genes and environmental and behavioral risk factors involved in the genesis of obesity. In this study, we examined the association of the DNA methyltransferase 3 (DNMT3B) gene-149 C>T variant (rs2424913) genotypes with global DNA methylation and the changes in anthropometric parameters in a cohort of 171 children followed from birth to 12 years old. Genotypes were obtained using real-time polymerase chain reaction, and global DNA methylation was measured in blood samples collected at 4 years old through enzyme-linked immunosorbent assays. Our results showed that the TT genotype is associated with an increase in global methylation levels at 4 years old and higher changes in body mass index, waist circumference, subscapular subcutaneous fat, body fat mass, body lean mass, and basal metabolic rate from 4 to 12 years. Our results suggest that this promoter DNMT3B gene variant and DNA methylation can be factors relevant to the increased risk of children developing obesity at an early age. Full article

The three 31 nucleotide minihelix tRNA evolution theorem describes the evolution of type I and type II tRNAs to the last nucleotide. In databases, type I and type II tRNA V loops (V for variable) were improperly aligned, but alignment based on the theorem is accurate. Type II tRNA V arms were a 3′-acceptor stem (initially CCGCCGC) ligated to a 5′-acceptor stem (initially GCGGCGG). The type II V arm evolved to form a stem–loop–stem. In Archaea, tRNA^Leu and tRNA^Ser are type II. In Bacteria, tRNA^Leu, tRNA^Ser, and tRNA^Tyr are type II. The trajectory of the type II V arm is determined by the number of unpaired bases just 5′ of the Levitt base (V_max). For Archaea, tRNA^Leu has two unpaired bases, and tRNA^Ser has one unpaired base. For Bacteria, tRNA^Tyr has two unpaired bases, tRNA^Leu has one unpaired base, and tRNA^Ser has zero unpaired bases. Thus, the number of synonymous type II tRNA sets is limited by the possible trajectory set points of the arm. From the analysis of aminoacyl-tRNA synthetase structures, contacts to type II V arms appear to adjust allosteric tension communicated primarily via tRNA to aminoacylating and editing active sites. To enhance allostery, it appears that type II V arm end loop contacts may tend to evolve to V arm stem contacts. Full article

This study begins by examining phenotypic variations in field growth among four parental Vietnamese rice lines, consisting of two Indica (PD211/GL37) and two Japonica (J23/SRA2-1) cultivars, which differ in life-cycle durations. Their phenotypic observations revealed both similarities and differences in growth patterns and field responses, setting the stage for further genomic investigation. We then focused on the sequencing and de novo genome assembly of these lines using high-coverage Illumina sequencing and achieving pseudochromosome assemblies ranging between 379 Mbp and 384 Mbp. The assemblies were further enhanced by annotation processes, designating between 44,427 and 48,704 gene models/genome. A comparative genomic analysis revealed that the Japonica varieties (J23/SRA2-1) exhibited more genetic similarity than the Indica varieties (PD211/GL37). From this, a phylogenetic analysis on the phytochrome C (phyC) gene distinctly positions the Indica and Japonica lines within their respective clades, affirming their genetic diversity and lineage accuracy. These genomic resources will pave the way for identifying quantitative trait loci (QTLs) critical for developing rice cultivars with shorter life cycles, thus enhancing resilience to adverse climatic impacts in Vietnam. This study provides a foundational step towards leveraging genomic data for rice breeding programs aimed at ensuring food security in the face of climate change. Full article

Oxidative stress-mediated biomolecular damage is a characteristic feature of ionizing radiation (IR) injury, leading to genomic instability and chronic health implications. Specifically, a dose- and linear energy transfer (LET)-dependent persistent increase in oxidative DNA damage has been reported in many tissues and biofluids months after IR exposure. Contrary to low-LET photon radiation, high-LET IR exposure is known to cause significantly higher accumulations of DNA damage, even at sublethal doses, compared to low-LET IR. High-LET IR is prevalent in the deep space environment (i.e., beyond Earth’s magnetosphere), and its exposure could potentially impair astronauts’ health. Therefore, the development of biomarkers to assess and monitor the levels of oxidative DNA damage can aid in the early detection of health risks and would also allow timely intervention. Among the recognized biomarkers of oxidative DNA damage, 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-OxodG) has emerged as a promising candidate, indicative of chronic oxidative stress. It has been reported to exhibit differing levels following equivalent doses of low- and high-LET IR. This review discusses 8-OxodG as a potential biomarker of high-LET radiation-induced chronic stress, with special emphasis on its potential sources, formation, repair mechanisms, and detection methods. Furthermore, this review addresses the pathobiological implications of high-LET IR exposure and its association with 8-OxodG. Understanding the association between high-LET IR exposure-induced chronic oxidative stress, systemic levels of 8-OxodG, and their potential health risks can provide a framework for developing a comprehensive health monitoring biomarker system to safeguard the well-being of astronauts during space missions and optimize long-term health outcomes. Full article

In forensic DNA laboratories, it is important to conduct internal validations of the commercially available kits of short tandem repeat (STR) loci and to investigate their individual and combined effectiveness. This study aims to report on a comparative investigation of the forensic kits used in our laboratory and their combinations in analysing low-copy-number (LCN) human DNA samples. We used five partly overlapping multiplex kits with different marker configurations from different manufacturers: the NGM Select^TM PCR Amplification Kit, NGM Detect^TM, the GlobalFiler^TM Amplification Kit (Applied Biosystem^TM, Foster City, CA, USA), the PowerPlex^® Fusion 6C System (Promega Co., Madison, WI, USA) and the Investigator^® 24plex QS Kit (Qiagen GmbH, Hilden, Germany). The efficacy of the kits was scrutinised by specific criteria, such as allelic dropout rate, the individually calculated Likelihood Ratio (LR) of consensus profiles and the LR value of the composite profile produced by the combined profiles of two kits. According to the results, the pairing of PowerPlex^® Fusion 6C System and Investigator^® 24plex QS produced the lowest, while the pairing of the NGM Detect^TM and GlobalFiler^TM kits provided the highest LR value. In summary, our study is meant to aid the selection of the optimal kit combination for samples of different qualities. Full article

Mammalian cell lines devoid of mitochondrial DNA (mtDNA) are indispensable in studies aimed at elucidating the contribution of mtDNA to various cellular processes or interactions between nuclear and mitochondrial genomes. However, the repertoire of tools for generating such cells (also known as rho-0 or ρ⁰ cells) remains limited, and approaches remain time- and labor-intensive, ultimately limiting their availability. Ethidium bromide (EtBr), which is most commonly used to induce mtDNA loss in mammalian cells, is cytostatic and mutagenic as it affects both nuclear and mitochondrial genomes. Therefore, there is growing interest in new tools for generating ρ⁰ cell lines. Here, we examined the utility of 2′,3′-dideoxycytidine (ddC, zalcitabine) alone or in combination with EtBr for generating ρ⁰ cell lines of mouse and human origin as well as inducing the ρ⁰ state in mouse/human somatic cell hybrids. We report that ddC is superior to EtBr in both immortalized mouse fibroblasts and human 143B cells. Also, unlike EtBr, ddC exhibits no cytostatic effects at the highest concentration tested (200 μM), making it more suitable for general use. We conclude that ddC is a promising new tool for generating mammalian ρ⁰ cell lines. Full article

Quantitative PCR is a molecular technique for DNA quantification that depends on reaction efficiency and the Ct value (“cycle threshold”). However, the results are dependent on laboratory conditions and mathematical approaches. Thus, the data of 16 genes from Pseudomonas aeruginosa strain AG1 were generated using qPCR to assess the effect of DNA concentration and three mathematical methods (a standard curve and two individual-curve-based approaches called exponential and sigmoidal models) on efficiency and DNA quantification. Differences in efficiency were revealed depending on the mathematical method used; the values were 100% in three out of the four standard curves, but estimations of the expected fold change in DNA serial dilutions were not achieved, indicating the possible overestimation of efficiency. Moreover, when efficiency was compared to DNA concentration, a decreasing trend in efficiency as DNA concentration increased in the reaction was observed in most cases, which is probably related to PCR inhibitors. For all 16 genes at a single DNA concentration, the efficiencies for the exponential model were found in the range of 1.5–2.79 (50–79%), and for the sigmoidal approach, the range was 1.52–1.75 (52–75%), with similar impact on normalized expression values, as indicated by the genes for standard curves. Jointly, DNA concentration and mathematical model choice were demonstrated to impact the estimation of reaction efficiency and, subsequently, DNA quantification when using qPCR. Full article

Children born from pregnancy complications are at higher risk of chronic diseases in adulthood. Identifying which children born from a complicated pregnancy are likely to suffer from later chronic disease is important in order to intervene to prevent or delay the onset of disease. This study examined the associations between the major pregnancy complications (gestational diabetes, high blood pressure, small- and large for gestational age, and preterm birth) and child telomere length, a biomarker of chronic disease risk. This was a population-based longitudinal analysis using data from the Longitudinal Study of Australian Children. The primary outcome is telomere length, measured in 11–12-year-old children. Multivariable linear regression was used to estimate the association between pregnancy complications and child telomere length, adjusting for a range of a priori confounders. Data from 841 families were used. One in four pregnancies (27.1%) featured a pregnancy complication. In the adjusted analysis, there was no association between pregnancy complications and child telomere length (high blood pressure: mean difference (95% CI): 0.00 (−0.12, 0.12); gestational diabetes (0.05 (−0.10, 0.19)); small for gestational age (0.07 (−0.04, 0.19)); large for gestational age (−0.06 (−0.15, 0.03)); and preterm birth (−0.10 (−0.21, 0.01)). Our results do not support the notion that telomere length is shorter in children born to mothers after a pregnancy complication. Methodological considerations should be rigorous to improve the reproducibility of findings. Full article

DNA knots are deleterious for living cells if not removed. Several theoretical and simulation approaches address the question of how topoisomerases select the intermolecular passages that preferentially lead to unknotting rather than to the knotting of randomly fluctuating DNA molecules, but the formation of knots in vivo remains poorly understood. DNA knots form in vivo in non-replicating and replicating molecules, and supercoiling as well as intertwining are thought to play a crucial role in both the formation and resolution of DNA knots by topoisomerase IV. To confirm this idea, we used two-dimensional agarose gel electrophoresis run with different concentrations of chloroquine to demonstrate that non-replicating pBR322 plasmids grown in a topoisomerase I-defective E. coli strain (RS2λ) were more negatively supercoiled than in a wild-type strain (W3110) and, concurrently, showed significantly fewer knots. In this way, using wild-type and E. coli mutant strains, we confirmed that one of the biological functions of DNA supercoiling is to reduce the formation of DNA knots. Full article

Ionizing radiation induces many different types of DNA lesions. But one of its characteristics is to produce complex DNA damage, of which tandem DNA damage has received much attention, owing to its promise of distinctive biological properties. Oxidative stresses in response to inflammation in tissues and metal-catalyzed reactions that result in generation of radicals also form these DNA lesions. In this minireview, we have summarized the formation of the tandem lesions as well as the replication and repair studies carried out on them after site-specific synthesis. Many of these lesions are resistant to the traditional base excision repair, so that they can only be repaired by the nucleotide excision repair pathway. They also block DNA replication and, when lesion bypass occurs, it may be significantly error-prone. Some of these tandem DNA lesions may contribute to ageing, neurological diseases, and cancer. Full article

Repetitive DNA sequences are abundant in the human genome and can adopt alternative (i.e., non-B) DNA structures. These sequences contribute to diverse biological functions, including genomic instability. Previously, we found that Z-DNA-, H-DNA- and cruciform DNA-forming sequences are mutagenic, implicating them in cancer etiology. These sequences can stimulate the formation of DNA double-strand breaks (DSBs), causing deletions via cleavage by the endonuclease ERCC1-XPF. Interestingly, the activity of ERCC1-XPF in H-DNA-induced mutagenesis is nucleotide excision repair (NER)-dependent, but its role in Z-DNA-induced mutagenesis is NER-independent. Instead, Z-DNA is processed by ERCC1-XPF in a mechanism dependent on the mismatch repair (MMR) complex, MSH2-MSH3. These observations indicate distinct mechanisms of non-B-induced genomic instability. However, the roles of NER and MMR proteins, as well as additional nucleases (CtIP and MRE11), in the processing of cruciform DNA remain unknown. Here, we present data on the processing of cruciform-forming short inverted repeats (IRs) by DNA repair proteins using mammalian cell-based systems. From this pilot study, we show that, in contrast to H-DNA and Z-DNA, short IRs are processed in a NER- and MMR-independent manner, and the nucleases CtIP and MRE11 suppress short IR-induced genomic instability in mammalian cells. Full article

Since the discovery of transposable elements (TEs) in maize in the 1940s by Barbara McClintock transposable elements have been described as junk, as selfish elements with no benefit to the host, and more recently as major determinants of genome structure and genome evolution. TEs are DNA sequences that are capable of moving to new sites in the genome and making additional copies of themselves while doing so. To limit the propagation of TEs, host silencing mechanisms are directed at transposon-encoded genes that are required for mobilization. The mutagenic properties of TEs, the potential of TEs to form new genes and affect gene expression, together with the host silencing mechanisms, shape eukaryotic genomes and drive genome evolution. While TEs constitute more than half of the genome in many higher eukaryotes, transposable elements in the nematode C. elegans form a relatively small proportion of the genome (approximately 15%). Genetic studies of transposon silencing, and the discovery of RNA interference (RNAi) in C. elegans, propelled Caenorhabditis elegans (C. elegans) to the forefront of studies of RNA-based mechanisms that silence TEs. Here, I will review the transposable elements that are present and active in the C. elegans genome, and the host defense mechanisms that silence these elements. Full article

Mosquitoes, like Drosophila, are dipterans, the order of “true flies” characterized by a single set of two wings. Drosophila are prime model organisms for biomedical research, while mosquito researchers struggle to establish robust molecular biology in these that are arguably the most dangerous vectors of human pathogens. Both insects utilize the RNA interference (RNAi) pathway to generate small RNAs to silence transposons and viruses, yet details are emerging that several RNAi features are unique to each insect family, such as how culicine mosquitoes have evolved extreme genomic feature differences connected to their unique RNAi features. A major technical difference in the molecular genetic studies of these insects is that generating stable transgenic animals are routine in Drosophila but still variable in stability in mosquitoes, despite genomic DNA-editing advances. By comparing and contrasting the differences in the RNAi pathways of Drosophila and mosquitoes, in this review we propose a hypothesis that transgene DNAs are possibly more intensely targeted by mosquito RNAi pathways and chromatin regulatory pathways than in Drosophila. We review the latest findings on mosquito RNAi pathways, which are still much less well understood than in Drosophila, and we speculate that deeper study into how mosquitoes modulate transposons and viruses with Piwi-interacting RNAs (piRNAs) will yield clues to improving transgene DNA expression stability in transgenic mosquitoes. Full article

Chromatin is the complex of DNA and associated proteins found in the nuclei of living organisms. How it is organized is a major research field as it has implications for replication, repair, and gene expression. This review summarizes the current state of the chromatin organization field, with a special focus on chromatin motor complexes cohesin and condensin. Containing the highly conserved SMC proteins, these complexes are responsible for organizing chromatin during cell division. Additionally, research has demonstrated that condensin and cohesin also have important functions during interphase to shape the organization of chromatin and regulate expression of genes. Using the model organism C. elegans, the authors review the current knowledge of how these complexes perform such diverse roles and what open questions still exist in the field. Full article

Embryogenesis is characterized by dynamic chromatin remodeling and broad changes in chromosome architecture. These changes in chromatin organization are accompanied by transcriptional changes, which are crucial for the proper development of the embryo. Several independent mechanisms regulate this process of chromatin reorganization, including the segregation of chromatin into heterochromatin and euchromatin, deposition of active and repressive histone modifications, and the formation of 3D chromatin domains such as TADs and LADs. These changes in chromatin structure are directly linked to developmental milestones such as the loss of developmental plasticity and acquisition of terminally differentiated cell identities. In this review, we summarize these processes that underlie this chromatin reorganization and their impact on embryogenesis in the nematode C. elegans. Full article

The PowerPlex Fusion 6C PCR™ amplification kit provides a strong discriminatory power for human identification. We have validated the kit with a reduced volume (12.5 µL) and as part of the validation we compared the efficiency of the polymerase chain reaction (PCR) prepared manually and on Hamilton Microlab^® Autolys STAR Biorobot. Three years of casework data has been also included in the validation. Optimisation was carried out on different types of samples (blood, saliva, semen) and DNA was extracted robotically. Tests were conducted at two different cycle numbers (30;32), followed by analysis on both the Applied Biosystems^TM 3500 and 3500 xL Genetic Analyzer instruments (Applied Biosystems®, Foster City, CA, USA). When the PCR was prepared manually, no allele dropout was observed over 0.15 ng input DNA. Whereas when the PCR was prepared robotically, dropout already appeared at the level of 0.15 ng input DNA. In cases when increased cycle number was utilised, an increasing number of dropouts started to arise from 0.075 ng total input DNA. Despite the fact that robotically prepared PCR produced more missing alleles than the manually prepared PCR, using the optimal 0.5 ng input DNA, both methods proved to be reliable. Based on the results, our half-volume protocol is robust, and after three years of application it has proven to be effective with respect to a large number of casework samples. Full article

Motivation: Clustered DNA-lesions are predominantly induced by ionizing radiation, particularly by high-LET particles, and considered as lethal damage. Quantification of this specific type of damage as a function of radiation parameters such as LET, dose rate, dose, and particle type can be informative for the prediction of biological outcome in radiobiological studies. This study investigated the induction and complexity of clustered DNA damage for three different types of particles at an LET range of 0.5–250 keV/µm. Methods: Nanometric volumes (36.0 nm³) of 15 base-pair DNA with its hydration shell was modeled. Electron, proton, and alpha particles at various energies were simulated to irradiate the nanometric volumes. The number of ionization events, low-energy electron spectra, and chemical yields for the formation of °OH, H°, ${\mathrm{e}}_{\mathrm{a}\mathrm{q}}^{-}$, and H₂O₂ were calculated for each particle as a function of LET. Single- and double-strand breaks (SSB and DSB), base release, and clustered DNA-lesions were computed from the Monte-Carlo based quantification of the reactive species and measured yields of the species responsible for the DNA lesion formation. Results: The total amount of DNA damage depends on particle type and LET. The number of ionization events underestimates the quantity of DNA damage at LETs higher than 10 keV/µm. Minimum LETs of 9.4 and 11.5 keV/µm are required to induce clustered damage by a single track of proton and alpha particles, respectively. For a given radiation dose, an increase in LET reduces the number of particle tracks, leading to more complex clustered DNA damage, but a smaller number of separated clustered damage sites. Conclusions: The dependency of the number and the complexity of clustered DNA damage on LET and fluence suggests that the quantification of this damage can be a useful method for the estimation of the biological effectiveness of radiation. These results also suggest that medium-LET particles are more appropriate for the treatment of bulk targets, whereas high-LET particles can be more effective for small targets. Full article

Zooplankton and ichthyoplankton community assessments depend on species diagnostics, yet morphological identifications are time-consuming, require taxonomic expertise, and are hampered by a lack of diagnostic characters, particularly for larval stages. Metabarcoding can identify multiple species in communities from short DNA sequences in comparison to reference databases. To evaluate species resolution across phylogenetic groups and food webs of zooplankton and ichthyoplankton, we compare five metabarcode mitochondrial (mt)DNA markers from gene regions of (a) cytochrome c oxidase subunit I, (b) cytochrome b, (c) 16S ribosomal RNA, and (d) 12S ribosomal RNA for DNA extracted from net tows in the Northeastern Pacific Ocean’s Salish Sea across seven sites and two seasons. Species resolved by metabarcoding are compared to invertebrate morphological identifications and biomass estimates. Results indicate that species resolution for different zooplankton and ichthyoplankton taxa can markedly vary among gene regions and markers in comparison to morphological identifications. Thus, researchers seeking “universal” metabarcoding should take caution that several markers and gene regions likely will be needed; all will miss some taxa and yield incomplete overlap. Species resolution requires careful attention to taxon marker selection and coverage in reference sequence repositories. In summary, combined multi-marker metabarcoding and morphological approaches improve broadscale zooplankton diagnostics. Full article