Replication Pauses of the Wild-Type and Mutant Mitochondrial DNA Polymerase Gamma: A Simulation Study

The activity of polymerase γ is complicated, involving both correct and incorrect DNA polymerization events, exonuclease activity, and the disassociation of the polymerase:DNA complex. Pausing of pol-γ might increase the chance of deletion and depletion of mitochondrial DNA. We have developed a stochastic simulation of pol-γ that models its activities on the level of individual nucleotides for the replication of mtDNA. This method gives us insights into the pausing of two pol-γ variants: the A467T substitution that causes PEO and Alpers syndrome, and the exonuclease deficient pol-γ (exo−) in premature aging mouse models. To measure the pausing, we analyzed simulation results for the longest time for the polymerase to move forward one nucleotide along the DNA strand. Our model of the exo− polymerase had extremely long pauses, with a 30 to 300-fold increase in the time required for the longest single forward step compared to the wild-type, while the naturally occurring A467T variant showed at most a doubling in the length of the pauses compared to the wild-type. We identified the cause of these differences in the polymerase pausing time to be the number of disassociations occurring in each forward step of the polymerase

Stochastic Drift in Mitochondrial DNA Point Mutations: A Novel Perspective Ex Silico

The mitochondrial free radical theory of aging (mFRTA) implicates Reactive Oxygen Species (ROS)-induced mutations of mitochondrial DNA (mtDNA) as a major cause of aging. However, fifty years after its inception, several of its premises are intensely debated. Much of this uncertainty is due to the large range of values in the reported experimental data, for example on oxidative damage and mutational burden in mtDNA. This is in part due to limitations with available measurement technologies. Here we show that sample preparations in some assays necessitating high dilution of DNA (single molecule level) may introduce significant statistical variability. Adding to this complexity is the intrinsically stochastic nature of cellular processes, which manifests in cells from the same tissue harboring varying mutation load. In conjunction, these random elements make the determination of the underlying mutation dynamics extremely challenging. Our in silico stochastic study reveals the effect of coupling the experimental variability and the intrinsic stochasticity of aging process in some of the reported experimental data. We also show that the stochastic nature of a de novo point mutation generated during embryonic development is a major contributor of different mutation burdens in the individuals of mouse population. Analysis of simulation results leads to several new insights on the relevance of mutation stochasticity in the context of dividing tissues and the plausibility of ROS ”vicious cycle” hypothesis

Patients’ experiences with pre-test genetic counseling provided by breast cancer healthcare professionals: Results from a large prospective multicenter study

Background: Pre-test genetic counseling of patients with breast cancer is increasingly being offered by non-genetic healthcare professionals. We aimed to evaluate the experiences of patients with breast cancer receiving pre-test genetic counseling from a non-genetic healthcare professional (i.e., surgeon or nurse). Methods: Patients who were diagnosed with breast cancer and received pre-test counseling from their surgeon or nurse (mainstream group), and patients who received pre-test counseling from a clinical geneticist (usual care group) were invited to participate in our multicenter study. Between September 2019 and December 2021, patients received a questionnaire after pre-test counseling (T0) and four weeks after receiving their test results (T1) to evaluate psychosocial outcomes, knowledge, discussed topics and satisfaction. Results: We included 191 patients in our mainstream and 183 patients in our usual care group and received, respectively 159 and 145 follow-up questionnaires. Levels of distress and decisional regret were comparable in both groups. Decisional conflict was higher in our mainstream group (p = 0.01), but only 7% had clinically relevant decisional conflict (vs 2% in usual care group). The possible implications of a genetic test on (secondary) breast or ovarian cancer risks were less frequently discussed in our mainstream group (p = 0.03 and p = 0.000, respectively). In both groups knowledge about genetics was comparable, satisfaction was high and the majority of patients in both groups preferred to give both verbal and written consent for genetic testing. Conclusion: Mainstreamed genetic care provides sufficient information for the majority of breast cancer patients to decide about genetic testing with minimal distress

Transcription errors induce proteotoxic stress and shorten cellular lifespan

Transcription errors occur in all living cells; however, it is unknown how these errors affect cellular health. To answer this question, we monitored yeast cells that were genetically engineered to display error-prone transcription. We discovered that these cells suffer from a profound loss in proteostasis, which sensitizes them to the expression of genes that are associated with protein-folding diseases in humans; thus, transcription errors represent a new molecular mechanism by which cells can acquire disease. We further found that the error rate of transcription increases as cells age, suggesting that transcription errors affect proteostasis particularly in aging cells. Accordingly, transcription errors accelerate the aggregation of a peptide that is implicated in Alzheimer’s disease, and shorten the lifespan of cells. These experiments reveal a novel, basic biological process that directly affects cellular health and aging

The New Anti-Dumping Methodology of the European Union – A Breach of WTO-Law?

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Ouder-kind relaties en sociaalemotionele problematiek in de volwassenheid

Contains fulltext : 56476.pdf (publisher's version ) (Open Access)16 p

The associations between structural treatment characteristics and post-treatment functioning in compulsory residential youth care

Contains fulltext : 102944.pdf (publisher's version ) (Open Access)In 2005 a new compulsory residential treatment program was developed for adolescents in need for protection against themselves or their environment. The aim of the present study was to examine the association of structural treatment characteristics of this new residential treatment program (i.e., duration of treatment, discharge status, and group composition in terms of sex) with post-treatment functioning. Additionally, the number of pre-treatment risk factors was included in the model. A total of 301 adolescents (174 boys, 127 girls), with a mean age at time of admittance of 15.50 (SD = 1.26) participated in this study. The number of risk factors was derived from treatment files of the adolescents at time of entrance. Six months after discharge, adolescents participated in a telephone interview to measure ten post-treatment variables indicating how well they were doing. The results showed that duration of treatment was related to post-treatment living situation, in that adolescents who were in treatment for shorter durations were more likely to live on their own after treatment. For discharge status, findings suggested that adolescents who were regularly discharged had more frequent contact with their family; however, they also showed higher alcohol consumption 6 months after treatment. Group composition was related to the girls' official offending, indicating that girls placed in mixed-sex groups showed significantly fewer official police contacts than did girls in girls-only treatment groups. Overall, structural treatment characteristics were hardly related to the adolescents' functioning after treatment. Suggestions for future research are discussed.20 p