Why do some children easily find their way in social situations and are satisfied with their social lives, while others experience more difficulties? One key component that may explain this is... Show moreWhy do some children easily find their way in social situations and are satisfied with their social lives, while others experience more difficulties? One key component that may explain this is social competence: the ability to fulfill both own and other’s social goals. This thesis focused on individual differences in social competence from childhood to adolescence by examining contextual, developmental and neurobiological influences on aggressive and prosocial responses to social evaluation. Findings showed robust neural processes related to social feedback and subsequent aggression already in middle childhood. Additionally, this thesis revealed that the period between childhood and adolescence is important for the behavioral and neural development of inhibition of aggression following negative, neutral and positive social feedback. Aggression following social feedback decreased towards adolescence, but aggression following positive feedback decreased earlier in childhood than following negative feedback. Moreover, the involvement of the dorsolateral prefrontal cortex, known for its role in executive functioning, decreased over time. Finally, results indicated that the co-occurrence of aggression following rejection and prosocial behavior following observed rejection may possibly protect against externalizing behaviors and promote wellbeing. This thesis highlights the importance of examining the interplay of developmental processes across social contexts to understand mental health outcomes. Show less
The cellular response to transcription-blocking DNA lesions involves the stalling of elongating RNA Polymerase II (RNAPIIo) at the lesion as well as a global shutdown of transcription. The stalling... Show moreThe cellular response to transcription-blocking DNA lesions involves the stalling of elongating RNA Polymerase II (RNAPIIo) at the lesion as well as a global shutdown of transcription. The stalling of RNAPIIo at such lesions initiates the transcription-coupled nucleotide excision repair pathway (TCR) to efficiently remove the damage and restore transcription. The TCR proteins, CSB, CSA, and UVSSA, are essential for the repair of transcription-blocking DNA lesions, but how the interplay between these proteins targets the core repair machinery, including the TFIIH complex, to lesion stalled RNAPIIo remains largely unknown.Here, we demonstrate a sequential and highly cooperative assembly of TCR proteins and unveil the mechanism for TFIIH recruitment to DNA damage-stalled RNAPIIo. Importantly, we identified the previously uncharacterized ELOF1 gene as a core TCR factor with an additional role in preventing DNA damage during DNA replication. Show less
The research described in this thesis aimed focused on CHIKV replication and on the identification of much-needed inhibitors of CHIKV infection. Following the development of an in vitro assay to... Show moreThe research described in this thesis aimed focused on CHIKV replication and on the identification of much-needed inhibitors of CHIKV infection. Following the development of an in vitro assay to study CHIKV replication, this tool was used to characterize the mode of action (MoA) of antiviral compounds and suramin was identified as a potent inhibitor of viral RNA synthesis. However, we discovered that in cell culture, suramin’s antiviral activity was mainly due to inhibition of CHIKV binding/entry, and to a lesser extent of virus release. Suramin was also found to inhibit binding/entry and virion biogenesis of Zika virus (ZIKV), a recently emerged flavivirus. Due to its ability to form electrostatic interactions with positive charges on proteins, suramin may block the contact between virions and their (co)receptors, by interacting with either virus or receptor, or with both. Using radioactively-labelled suramin, it was clearly shown that the compound interacts with CHIKV particles, more specifically with their envelope proteins. Additionally, suramin could interfere with cell attachment and/or the structural changes required for fusion. Suramin-resistant CHIKV variants were selected, which contained mutations in the E2 envelope protein (involved in receptor interactions), supporting the idea that suramin blocks the early steps of the infectious cycle. Show less
We studied frontal asymmetry (FA) in relation to fearfulness, prosocial behavior and aggressive behavior in young twins. Based on the literature FA was a likely candidate to explain individual... Show moreWe studied frontal asymmetry (FA) in relation to fearfulness, prosocial behavior and aggressive behavior in young twins. Based on the literature FA was a likely candidate to explain individual differences in approach and withdrawal related behavior. However, our results showed no associations between fearfulness, prosocial behavior or aggressive behavior on the one hand and FA on the other in 4-6 year old children. We did show that genetic influences were involved in fearfulness, prosocial behavior and FA in young twins. Furthermore, we have developed two new, age appropriate, tasks: the Prosocial Owl Game (POG) and the Social Network Aggression Task – Early Childhood (SNAT-EC). In both tasks, young children show similar responses to social exclusion and social judgments as older children, adolescents and adults. The POG and SNAT-EC turned out to be reliable measures that can be used for long-term follow-up research. New insights in the role of FA may be revealed when the children grow older, increasing the value of the data in the coming years. Show less
In this thesis, I aimed at decoding the role of SUMO in the DNA damage repair pathway. The SUMO system is believed to be involved in this process at several levels. I focused on the most inevitable... Show moreIn this thesis, I aimed at decoding the role of SUMO in the DNA damage repair pathway. The SUMO system is believed to be involved in this process at several levels. I focused on the most inevitable DNA obstacle causing DNA replication stress, and the cellular roles of SUMOylation in repairing DNA replication stress caused DNA damage. Post-translational modifications are essential regulators of proteins. PTMs do not only play their roles solo but extensively interact with each other. Our knowledge about proteins modified by a combination of SUMO and ubiquitin, SUMO and phosphate and crosstalk between them is quite limited. This thesis also aimed at deciphering the crosstalk between SUMOylation and phosphorylation and ubiquitination during the DNA damage response and searching for indirect and direct targets for the human STUbL RNF4, which mediates the ubiquitination of SUMOylated target proteins. Lastly, we adopted the strategy described for SUMO and introduced His10-tagged UFM-1-K0 to identify UFM-1 acceptor lysines. We identified and confirmed RPL26 as a key UFM1 target and further confirmed that the UFMylated form of RPL26 can efficiently interact with the Signal Recognition Particle Receptor, implicating that UFMylation could regulate protein transfer to the Endoplasmic Reticulum. Show less
Background: Psychiatric disorders are highly heterogeneous, defined based on symptoms with little connection to potential underlying biological mechanisms. A possible approach to dissect biological... Show moreBackground: Psychiatric disorders are highly heterogeneous, defined based on symptoms with little connection to potential underlying biological mechanisms. A possible approach to dissect biological heterogeneity is to look for biologically meaningful subtypes. A recent study Drysdale et al. (2017) showed promising results along this line by simultaneously using resting state fMRI and clinical data and identified four distinct subtypes of depression with different clinical profiles and abnormal resting state fMRI connectivity. These subtypes were predictive of treatment response to transcranial magnetic stimulation therapy.Objective: Here, we attempted to replicate the procedure followed in the Drysdale a al. study and their findings in a different clinical population and a more heterogeneous sample of 187 participants with depression and anxiety. We aimed to answer the following questions: 1) Using the same procedure, can we find a statistically significant and reliable relationship between brain connectivity and clinical symptoms? 2) Is the observed relationship similar to the one found in the original study? 3) Can we identify distinct and reliable subtypes? 4) Do they have similar clinical profiles as the subtypes identified in the original study?Methods: We followed the original procedure as closely as possible, including a canonical correlation analysis to find a low dimensional representation of clinically relevant resting state fMRI features, followed by hierarchical clustering to identify subtypes. We extended the original procedure using additional statistical tests, to test the statistical significance of the relationship between resting state fMRI and clinical data, and the existence of distinct subtypes. Furthermore, we examined the stability of the whole procedure using resampling.Results and conclusion: As in the original study, we found extremely high canonical correlations between functional connectivity and clinical symptoms, and an optimal three-cluster solution. However, neither canonical correlations nor clusters were statistically significant. On the basis of our extensive evaluations of the analysis methodology used and within the limits of comparison of our sample relative to the sample used in Drysdale et al., we argue that the evidence for the existence of the distinct resting state connectivity-based subtypes of depression should be interpreted with caution. Show less
Results from this thesis have elucidated potential genetic markers, which were associated with treatment outcome to MTX and adalimumab. Furthermore, a model for predicting the efficacy of MTX in... Show moreResults from this thesis have elucidated potential genetic markers, which were associated with treatment outcome to MTX and adalimumab. Furthermore, a model for predicting the efficacy of MTX in patients with RA was validated in two cohorts indicating that predicting efficacy by a pharmacogenetic model is feasible in RA patients treated with MTX. Importantly, definitive conclusions about the role of genetic predictive factors in treatment outcome to DMARDS could not be drawn, since these results have to be further validated and replicated in future pharmacogenetic studies. Large randomized prospective studies should be planned to demonstrate its legitimate predictive and cost-effective value before a genetically individualized approach is applicable in daily clinical practice. The potential role of pharmacogenetics in the prediction of efficacy and adverse events in RA patients treated with DMARDs is presented in this thesis. Hereby, new knowledge is added to the relatively young research field of pharmacogenetics, which may hopefully lead to a better treatment strategy for RA patients Show less
Current generation adenoviral vectors (Ads) are not suitable for those gene therapy approaches that require long-term gene expression. This is due to their high immunogenicity and transient gene... Show moreCurrent generation adenoviral vectors (Ads) are not suitable for those gene therapy approaches that require long-term gene expression. This is due to their high immunogenicity and transient gene expression in fast dividing tissue. The development of gutless Ads, also known as helper-dependent Ads, is a major improvement in reducing the immunogenicity of the vector system. Gutless Ads lack virtually all viral protein-coding sequences, thus severely limiting the viral-antigen evoked cellular immune responses that may result in the elimination of the transduced cells. Safety wise, recombinant Ads are considered safe due to their inability to replicate autonomously. However, we show in this thesis that replication of recombinant Ads can be rescued by the co-infection of wild type (wt) Ads. In this thesis studies are described that aim at the development of a new system to prevent vector mobilization. Though at its present state not directly applicable, this system could also potentially be used for the production of gutless Ads devoid of helper Ad contamination. To improve efficacy of the Ad vector in dividing tissue we also studied two integration systems for their applicability in Ads. Overall, the experiments described in this thesis aim at generating safer vectors that should result in prolonged transgene expression due to lower immunogenicity and genomic integration. Show less
Viruses depend on their host cell for the production of their progeny. The genetic information that is required to regulate this process is contained in the viral genome. In the case of plus... Show moreViruses depend on their host cell for the production of their progeny. The genetic information that is required to regulate this process is contained in the viral genome. In the case of plus-stranded RNA viruses, like nidoviruses, the RNA genome is directly involved in translation (resulting in the synthesis of viral enzymes), replication, transcription and encapsidation into progeny virions. The multifunctional nature of these viral RNA genomes requires the tight control of all these processes for which they are equipped with RNA sequence motifs and higher order RNA structures. At 25-32 kilobases, nidoviruses possess the largest known RNA genomes. One characteristic of nidoviruses is that in infected cells they produce a nested set of subgenomic (sg) mRNAs. The sg mRNAs of two nidovirus families, arteri- and coronaviruses, consist of two RNA stretches that are noncontiguous in the genome. It was demonstrated that primary and higher order RNA structures play a crucial role during the synthesis of these special sg mRNAs. The obtained knowledge of arterivirus RNA synthesis, formed the basis for an virus inhibitor study in which regulatory RNA sequences were targeted in an attempt to block virus replication in cell culture using phosphorodiamidate morpholino oligomers (P-PMOs). Show less
