Biology subjects

Hankeln, T.

Publications and source records attributed to Hankeln, T..

11 recordsLinked to original sources

bioRxiv2025

Repair of DNA double-strand breaks after low radiation doses in childhood cancer survivors and matched cancer-free individuals

DNA double-strand breaks (DSBs) which arise in G1- or G0-phase normal human cells are repaired by non-homologous end-joining (NHEJ), a pathway which is important for cell survival but can cause mutations at the break sites. DSB repair by NHEJ is very efficient at high damage levels of 1 or more DSBs per cell, much less efficient at lower damage levels and almost absent if only [~]0.05 DSBs per cell are induced. Repair at this low DSB level can be induced if cells are pre-treated prior to DSB induction with low concentrations of hydrogen peroxide, suggesting that the intracellular radical level modulates the efficiency of DSB repair at low damage levels. Here, we have investigated if the inefficiency of repair at low DSB levels contributes to the carcinogenic potential of DSBs or, counterintuitively, may serve as a mechanism to limit cancer development. We have analyzed the repair of high and low levels of radiation-induced DSBs in primary fibroblasts from 136 childhood cancer survivors, half of whom developed a second independent tumor later in life, and compared it to the response of primary fibroblasts from 68 individually matched cancer-free individuals. Although childhood cancer survivors and cancer-free individuals repaired DSBs at high damage levels equally efficiently, their response to low DSB levels differed drastically. While repair in cancer-free individuals was nearly absent at a level of [~]0.05 DSBs per cell, childhood cancer survivors repaired DSBs at this low damage level as efficiently as after high damage levels. These results suggest that most of the cancer survivors analyzed here carry a genetic predisposition that affects their response to low levels of DSBs. They also support the idea that the absence of repair observed in cancer-free individuals represents a mechanism limiting cancer formation.

cell biology↗

bioRxiv2025

Improved Metagenomic Analysis for All-Food-Sequencing with AFS-MetaCache2: Illumina vs. Nanopore

BackgroundAll-Food-Sequencing (AFS) is a method for untargeted metagenomic analysis that allows for the detection and quantification of food ingredients. While this approach avoids some of the shortcomings of targeted PCR-based methods, its performance depends on sequencing technologies, taxonomic classification tools, and genomic reference databases. ResultsAFS-MetaCache2 implements an improved reference database construction mechanism compared to prior approaches. To demonstrate the effectiveness to AFS, we sequenced sausages composed of mammalian and avian species using both short-read (Illumina) and long-read (Oxford Nanopore Technologies) platforms. While both approaches reliably detect the main components, our comparison shows that long-read sequencing is superior in terms of both quantification accuracy and false positive rates. The evaluation of representative metagenomic tools (Kraken2+Bracken, KrakenUniq, AFS-MetaCache1) demonstrates that AFS-MetaCache2 yields the best accuracy and fastest database build times, while reducing peak main memory consumption. It thus allows for efficient scaling to large reference genome sets. ConclusionOur study suggests that deep sequencing of total genomic DNA from samples with heterogeneous taxon composition, using 3rd generation sequencing technology followed by metagenomic analysis with AFS-MetaCache2, is a valuable approach for bio-surveillance of food ingredients. Our software is available at https://github.com/muellan/metacache.

bioinformatics↗

bioRxiv2023

Adaptation of the Spalax galili transcriptome to life under hypoxia may hold a key to a complex phenotype including longevity and cancer resistance

The muroid rodent Nannospalax galili (syn. Spalax) is adapted to life in underground burrows and tolerates acute exposure to severe hypoxia. Adaptation to hypoxia is correlated with delayed onset of ageing and resistance against tumour formation. Spalax becomes five to seven times older than its relatives, the mouse and rat, without displaying signs of ageing or developing ageing-related disorders like cancer. Investigating and understanding adapted genes and gene regulatory networks of Spalax might pinpoint novel strategies to maintain an extended healthy phenotype in humans. Here we analysed and compared RNA-Seq data of liver, kidney and spleen of Spalax and rat subjected to 6% O2 or normoxia. We identified differentially expressed genes and pathways common to multiple organs in Spalax and rat. Body-wide differences between Spalax and rat affected biological processes like cell death, defence against reactive oxygen species (ROS), DNA repair, energy metabolism, immune response and angiogenesis, which altogether might play a crucial role in Spalaxs adaptation to life under oxygen deprivation. In all organs, mRNA expression of genes associated with genome stability maintenance and DNA repair was elevated in Spalax compared to rat, accompanied by a lower gene expression of genes associated with aerobic energy metabolism and proinflammatory processes. These transcriptomic changes might be accountable for the extraordinary lifespan of Spalax and its cancer resistance. Our results reveal gene regulatory networks that become candidates for the investigation of the molecular bases that underlie the complex phenotype of Spalax.

evolutionary biology↗

bioRxiv2023

Nanopore adaptive sampling of a metagenomic sample derived from a human monkeypox case

In 2022, a series of human monkeypox cases in multiple countries led to the largest and most widespread outbreak outside the known endemic areas. Genomic surveillance is of utmost importance to control such outbreaks. To this end, we performed Nanopore Whole Genome Sequencing of a local monkeypox sample on a PromethION 24. Adaptive sampling was applied for in silico depletion of the human host genome, allowing for the enrichment of low abundance viral DNA without a priori knowledge of sample composition. Nanopore sequencing allowed for high viral genome coverage, tracking of sample composition during sequencing, strain determination, and preliminary assessment of mutational pattern. Nanopore sequencing is a highly versatile method to characterize a virus in real-time without pre-sequencing target enrichment.

microbiology↗

bioRxiv2022

Pro-apoptotic and anti-invasive properties underscore the tumor suppressing impact of myoglobin on subset of human breast cancer cells

Expression of myoglobin (MB), well known as the oxygen storage and transport protein of myocytes, is a novel hallmark of the luminal subtype in breast cancer patients and correlates with better prognosis. The mechanisms by which MB impacts mammary tumorigenesis are hitherto unclear. We aimed to unravel this role, by using CRISPR/Cas9 technology to generate MB-deficient clones of MCF7 and SKBR3 breast cancer cell lines and subsequently characterize them by transcriptomics plus molecular and functional analyses. As main findings, loss of MB, at normoxia, upregulated the expression of cell cyclins and increased cell survival while it prevented apoptosis in MCF7 cells. Also, MB-deficient cells were less sensitive to doxorubicin but not ionizing radiation. Under hypoxia, loss of MB enhanced partial epithelial to mesenchymal transition, thus augmenting the migratory and invasive cell behavior. Notably, in human invasive mammary ductal carcinoma tissues, MB and apoptotic marker levels were positively correlated. In addition, MB protein expression in invasive ductal carcinomas was associated with a positive prognostic value, independent of the known tumor suppressor p53. In conclusion, we provide multiple lines of evidence that endogenous MB in cancer cells by itself exerts novel tumor-suppressive roles through which it can reduce cancer malignancy.

cancer biology↗

bioRxiv2021

Androglobin, a chimeric mammalian globin, is required for male fertility

Spermatogenesis is a highly specialised process, involving multiple dedicated pathways and regulatory check-points. Defects ultimately lead to male sub-fertility or sterility, and numerous aspects of mammalian sperm formation remain unknown. The predominant expression of the latest globin family member, androglobin (Adgb) in mammalian testis tissue prompted us to assess its physiological function in spermatogenesis. Adgb knockout mice display male infertility, reduced testis weight, impaired maturation of elongating spermatids, abnormal sperm shape and ultrastructural defects in microtubule and mitochondrial organisation. Epididymal sperm from Adgb knockout animals display multiple flagellar malformations including coiled, bifide or shortened flagella, and erratic acrosomal development. Following immunoprecipitation and mass spectrometry, we could identify septin 10 (Sept10) as interactor of Adgb. The Sept10-Adgb interaction was confirmed both in vivo using testis lysates, and in vitro by reciprocal co-immunoprecipitation experiments. Furthermore, absence of Adgb leads to mislocalisation of Sept10 in sperm, indicating defective manchette and sperm annulus formation. Finally, in vitro data suggest that Adgb contributes to Sept10 proteolysis in a calmodulin (CaM)-dependent manner. Collectively, our results provide evidence that Adgb is essential for murine spermatogenesis and further suggest that interdependence between Adgb and Sept10 is required for sperm head shaping via the manchette and proper flagellum formation.

developmental biology↗

bioRxiv2019

What is in a lichen? A metagenomic approach to reconstruct the holo-genome of Umbilicaria pustulata

Lichens are valuable models in symbiosis research and promising sources of biosynthetic genes for biotechnological applications. Most lichenized fungi grow slowly, resist aposymbiotic cultivation, and are generally poor candidates for experimentation. Obtaining contiguous, high quality genomes for such symbiotic communities is technically challenging. Here we present the first assembly of a lichen holo-genome from metagenomic whole genome shotgun data comprising both PacBio long reads and Illumina short reads. The nuclear genomes of the two primary components of the lichen symbiosis - the fungus Umbilicaria pustulata (33 Mbp) and the green alga Trebouxia sp. (53 Mbp) - were assembled at contiguities comparable to single-species assemblies. The analysis of the read coverage pattern revealed a relative cellular abundance of approximately 20:1 (fungus:alga). Gap-free, circular sequences for all organellar genomes were obtained. The community of lichen-associated bacteria is dominated by Acidobacteriaceae, and the two largest bacterial contigs belong to the genus Acidobacterium. Gene set analyses showed no evidence of horizontal gene transfer from algae or bacteria into the fungal genome. Our data suggest a lineage-specific loss of a putative gibberellin-20-oxidase in the fungus, a gene fusion in the fungal mitochondrion, and a relocation of an algal chloroplast gene to the algal nucleus. Major technical obstacles during reconstruction of the holo-genome were coverage differences among individual genomes surpassing three orders of magnitude. Moreover, we show that G/C-rich inverted repeats paired with non-random sequencing error in PacBio data can result in missing gene predictions. This likely poses a general problem for genome assemblies based on long reads.

genomics↗

bioRxiv2019

Identification and quantification of meat product ingredients by whole-genome metagenomics (All-Food-Seq)

Complex food matrices bear the risk of intentional or accidental admixture of non-declared species. Moreover, declared components can be present in false proportions, since expensive taxa might be exchanged for cheaper ones. We have previously reported that PCR-free metagenomic sequencing of total DNA extracted from sausage samples combined with bioinformatic analysis (termed All-Food-Seq, AFS), can be a valuable screening tool to identify the taxon composition of food ingredients. Here we illustrate this principle by analysing regional Doner kebap samples, which revealed unexpected and unlabelled poultry and plant components in three of five cases. In addition, we systematically apply AFS to a broad set of reference meat material of known composition (i.e. reference sausages) to evaluate quantification accuracy and potential limitations. We include a detailed analysis of the effect of different food matrices and the possibility of false-positive sequence read assignment to closely related species, and we compare AFS quantification results to quantitative real-time PCR (qPCR) and droplet digital PCR (ddPCR). AFS emerges as a potent PCR-free screening tool, which can detect multiple target species of different kingdoms of life within a single assay. Mathematical calibration accounting for pronounced matrix effects can significantly improves AFS quantification accuracy. In comparison, AFS performs better than classical qPCR, and is on par with ddPCR.

genomics↗

bioRxiv2019

A high-quality genome assembly from short and long reads for the non-biting midge Chironomus riparius (Diptera)

BackgroundChironomus riparius is of great importance as a study species in various fields like ecotoxicology, molecular genetics, developmental biology and ecology. However, only a fragmented draft genome exists to date, hindering the recent rush of population genomic studies in this species.\n\nFindingsMaking use of 50 NGS datasets, we present a hybrid genome assembly from short and long sequence reads that make C. riparius genome one of the most contiguous Dipteran genomes published, the first complete mitochondrial genome of the species and the respective recombination rate as one of the first insect recombination rates at all.\n\nConclusionsThe genome and associated resources will be highly valuable to the broad community working with dipterans in general and chironomids in detail. The estimated recombination rate will help evolutionary biologist gain a better understanding of commonalities and differences of genomic patterns in insects.

genomics↗

bioRxiv2017

The genomic footprint of climate adaptation in Chironomus riparius

The gradual heterogeneity of climatic factors pose varying selection pressures across geographic distances that leave signatures of clinal variation in the genome. Separating signatures of clinal adaptation from signatures of other evolutionary forces, such as demographic processes, genetic drift, and adaptation to non-clinal conditions of the immediate local environment is a major challenge. Here, we examine climate adaptation in five natural populations of the harlequin fly Chironomus riparius sampled along a climatic gradient across Europe. Our study integrates experimental data, individual genome resequencing, Pool-Seq data, and population genetic modelling. Common-garden experiments revealed a positive correlation of population growth rates corresponding to the population origin along the climate gradient, suggesting thermal adaptation on the phenotypic level. Based on a population genomic analysis, we derived empirical estimates of historical demography and migration. We used an FST outlier approach to infer positive selection across the climate gradient, in combination with an environmental association analysis. In total we identified 162 candidate genes as genomic basis of climate adaptation. Enriched functions among these candidate genes involved the apoptotic process and molecular response to heat, as well as functions identified in other studies of climate adaptation in other insects. Our results show that local climate conditions impose strong selection pressures and lead to genomic adaptation despite strong gene flow. Moreover, these results imply that selection to different climatic conditions seems to converge on a functional level, at least between different insect species.

evolutionary biology↗

bioRxiv2016

Chironomus riparius (Diptera) genome sequencing reveals the impact of minisatellite transposable elements on population divergence

Active transposable elements (TEs) may result in divergent genomic insertion and abundance patterns among conspecific populations. Upon secondary contact, such divergent genetic backgrounds can theoretically give rise to classical Dobzhansky-Muller incompatibilities (DMI), a way how TEs can contribute to the evolution of endogenous genetic barriers and eventually population divergence. We investigated whether differential TE activity created endogenous selection pressures among conspecific populations of the non-biting midge Chironomus riparius, focussing on a Chironomus-specific TE, the minisatellite-like Cla-element, whose activity is associated with speciation in the genus. Using an improved and annotated draft genome for a genomic study with five natural C. riparius populations, we found highly population-specific TE insertion patterns with many private insertions. A highly significant correlation of pairwise population FST from genome-wide SNPs with the FST estimated from TEs suggests drift as the major force driving TE population differentiation. However, the significantly higher Cla-element FST level due to a high proportion of differentially fixed Cla-element insertions indicates that segregating, i.e. heterozygous insertions are selected against. With reciprocal crossing experiments and fluorescent in-situ hybridisation of Cla-elements to polytene chromosomes, we documented phenotypic effects on female fertility and chromosomal mispairings that might be linked to DMI in hybrids. We propose that the inferred negative selection on heterozygous Cla-element insertions causes endogenous genetic barriers and therefore acts as DMI among C. riparius populations. The intrinsic genomic turnover exerted by TEs, thus, may have a direct impact on population divergence that is operationally different from drift and local adaptation.

genomics↗