The circadian system has evolved to benefit the fitness of the organism. A properly functioning clock improves overall performance and promotes health. By gaining more knowledge about how the... Show moreThe circadian system has evolved to benefit the fitness of the organism. A properly functioning clock improves overall performance and promotes health. By gaining more knowledge about how the system works and responds to changes, therapies can be developed to promote the functioning of the circadian system. In this thesis, the response of the circadian system to changes in daylength (e.g. long summer days and short winter days was investigated. In addition the functioning of the circadian system with aging was investigated. This is relevant since aging is known to be accompanied by a weakening of the circadian system in humans, which has been associated with deterioration of a number of age-related conditions such as arteriosclerosis, type 2 diabetes and neurodegenerative diseases such as Parkinson's and Alzheimer's disease. In addition, a large proportion of the elderly will experience fragmentation of sleep, meaning that people have difficulty sleeping at night, while during the day they are very sleepy. Promoting the circadian rhythm with relatively simple interventions, such as correctly timed exposure to (day) light, physical activity and food intake can support the circadian system and promote general health. Show less
This dissertation showed that physicians must be aware of the constraints that allow them to identify or obviate (un)desirable effects most notably if they evaluate these effects in a blinded... Show moreThis dissertation showed that physicians must be aware of the constraints that allow them to identify or obviate (un)desirable effects most notably if they evaluate these effects in a blinded matter. Unblinding might partially mitigate the limitation, but current measurement methods have gaps that we should remain aware of. Detailed measurements of subintervals with characterization of ion channel profiles, concentration QTc modelling, or machine learning might help physicians in their decision making in the future. Show less
Background: Deep brain stimulation (DBS) is a highly efficient, evidence-based therapy to alleviate symptoms and improve quality of life in movement disorders such as Parkinson’s disease,... Show moreBackground: Deep brain stimulation (DBS) is a highly efficient, evidence-based therapy to alleviate symptoms and improve quality of life in movement disorders such as Parkinson’s disease, essential tremor, and dystonia, which is also being applied in several psychiatric disorders, such as obsessive-compulsive disorder and depression, when they are otherwise resistant to therapy. Summary: At present, DBS is clinically applied in the so-called open-loop approach, with fixed stimulation parameters, irrespective of the patients’ clinical state(s). This approach ignores the brain states or feedback from the central nervous system or peripheral recordings, thus potentially limiting its efficacy and inducing side effects by stimulation of the targeted networks below or above the therapeutic level. Key Messages: The currently emerging closed-loop (CL) approaches are designed to adapt stimulation parameters to the electrophysiological surrogates of disease symptoms and states. CL-DBS paves the way for adaptive personalized DBS protocols. This review elaborates on the perspectives of the CL technology and discusses its opportunities as well as its potential pitfalls for both clinical and research use in neuropsychiatric disorders. Show less
Complexity is not necessarily expected from monogenic diseases but for many cardiovascular diseases (CVD), simple genotype-phenotype relationship may be far from reality. As millions of people... Show moreComplexity is not necessarily expected from monogenic diseases but for many cardiovascular diseases (CVD), simple genotype-phenotype relationship may be far from reality. As millions of people globally die of CVD, it is important to find models to study CVD that recapitulate the conditions as manifest in humans, most importantly for these cases of unexpected complexity. For these, simple gene mutation or deletion in mice has often failed. Combining human induced pluripotent stem cell (hiPSC) with genetic editing technologies is providing new opportunities to bridge the gap, with many hPSC-CM models now showing promising results for testing drugs, discovering molecular pathways associated with disease and other types of (gene) therapies. The work in this thesis contributes to this area of research. Show less
Guimaraes, T.A.C. de; Georgiou, M.; Robson, A.G.; Fujinami, K.; Vincent, A.; Nasser, F.; ... ; Michaelides, M. 2023
Background/aims To investigate genotype-phenotype associations in patients with KCNV2 retinopathy.Methods Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants,... Show moreBackground/aims To investigate genotype-phenotype associations in patients with KCNV2 retinopathy.Methods Review of clinical notes, best-corrected visual acuity (BCVA), molecular variants, electroretinography (ERG) and retinal imaging. Subjects were grouped according to the combination of KCNV2 variants-two loss-of-function (TLOF), two missense (TM) or one of each (MLOF)-and parameters were compared.Results Ninety-two patients were included. The mean age of onset (mean +/- SD) in TLOF (n=55), TM (n=23) and MLOF (n=14) groups was 3.51 +/- 0.58, 4.07 +/- 2.76 and 5.54 +/- 3.38 years, respectively. The mean LogMAR BCVA ( +/- SD) at baseline in TLOF, TM and MLOF groups was 0.89 +/- 0.25, 0.67 +/- 0.38 and 0.81 +/- 0.35 for right, and 0.88 +/- 0.26, 0.69 +/- 0.33 and 0.78 +/- 0.33 for left eyes, respectively. The difference in BCVA between groups at baseline was significant in right (p=0.03) and left eyes (p=0.035). Mean outer nuclear layer thickness ( +/- SD) at baseline in TLOF, MLOF and TM groups was 37.07 +/- 15.20 mu m, 40.67 +/- 12.53 and 40.38 +/- 18.67, respectively, which was not significantly different (p=0.85). The mean ellipsoid zone width (EZW) loss ( +/- SD) was 2051 mu m ( +/- 1318) for patients in the TLOF, and 1314 mu m ( +/- 965) for MLOF. Only one patient in the TM group had EZW loss at presentation. There was considerable overlap in ERG findings, although the largest DA 10 ERG b-waves were associated with TLOF and the smallest with TM variants.Conclusions Patients with missense alterations had better BCVA and greater structural integrity. This is important for patient prognostication and counselling, as well as stratification for future gene therapy trials. Show less
This thesis aims to improve the understanding and identification of the ventricular tachycardia substrate in patients with right ventricular tachycardia. An isolated epicardial right ventricular... Show moreThis thesis aims to improve the understanding and identification of the ventricular tachycardia substrate in patients with right ventricular tachycardia. An isolated epicardial right ventricular outflow tract scar is described in high level endurance athletes. Novel parameters such as endocardial unipolar voltage, transmural activation time and CT heterogeneity may help to guide substrate mapping and ablation. Implementing these techniques in current clinical practice may improve the identification and treatment of ventricular tachycardia substrates in right ventricular cardiomyopathies. Show less
Background: Genomics enables individualized diagnosis and treatment, but large challenges remain to functionally interpret rare variants. To date, only one causative variant has been described for... Show moreBackground: Genomics enables individualized diagnosis and treatment, but large challenges remain to functionally interpret rare variants. To date, only one causative variant has been described for KCNK9 imprinting syndrome (KIS). The genotypic and phenotypic spectrum of KIS has yet to be described and the precise mechanism of disease fully understood. Methods: This study discovers mechanisms underlying KCNK9 imprinting syndrome (KIS) by describing 15 novel KCNK9 alterations from 47 KIS-affected individuals. We use clinical genetics and computer-assisted facial phenotyping to describe the phenotypic spectrum of KIS. We then interrogate the functional effects of the variants in the encoded TASK3 channel using sequence-based analysis, 3D molecular mechanic and dynamic protein modeling, and in vitro electrophysiological and functional methodologies. Results: We describe the broader genetic and phenotypic variability for KIS in a cohort of individuals identifying an additional mutational hotspot at p.Arg131 and demonstrating the common features of this neurodevelopmental disorder to include motor and speech delay, intellectual disability, early feeding difficulties, muscular hypotonia, behavioral abnormalities, and dysmorphic features. The computational protein modeling and in vitro electrophysiological studies discover variability of the impact of KCNK9 variants on TASK3 channel function identifying variants causing gain and others causing loss of conductance. The most consistent functional impact of KCNK9 genetic variants, however, was altered channel regulation. Conclusions: This study extends our understanding of KIS mechanisms demonstrating its complex etiology including gain and loss of channel function and consistent loss of channel regulation. These data are rapidly applicable to diagnostic strategies, as KIS is not identifiable from clinical features alone and thus should be molecularly diagnosed. Furthermore, our data suggests unique therapeutic strategies may be needed to address the specific functional consequences of KCNK9 variation on channel function and regulation. Show less
Hu, M.; Frega, M.; Tolner, E.A.; Maagdenberg, A.M.J.M. van den; Frimat, J.P.; Feber, J. le 2022
Functional assessment of in vitro neuronal networks-of relevance for disease modelling and drug testing-can be performed using multi-electrode array (MEA) technology. However, the handling and... Show moreFunctional assessment of in vitro neuronal networks-of relevance for disease modelling and drug testing-can be performed using multi-electrode array (MEA) technology. However, the handling and processing of the large amount of data typically generated in MEA experiments remains a huge hurdle for researchers. Various software packages have been developed to tackle this issue, but to date, most are either not accessible through the links provided by the authors or only tackle parts of the analysis. Here, we present ''MEA-ToolBox'', a free open-source general MEA analytical toolbox that uses a variety of literature-based algorithms to process the data, detect spikes from raw recordings, and extract information at both the single-channel and array-wide network level. MEA-ToolBox extracts information about spike trains, burst-related analysis and connectivity metrics without the need of manual intervention. MEA-ToolBox is tailored for comparing different sets of measurements and will analyze data from multiple recorded files placed in the same folder sequentially, thus considerably streamlining the analysis pipeline. MEA-ToolBox is available with a graphic user interface (GUI) thus eliminating the need for any coding expertise while offering functionality to inspect, explore and post-process the data. As proof-of-concept, MEA-ToolBox was tested on earlier-published MEA recordings from neuronal networks derived from human induced pluripotent stem cells (hiPSCs) obtained from healthy subjects and patients with neurodevelopmental disorders. Neuronal networks derived from patient's hiPSCs showed a clear phenotype compared to those from healthy subjects, demonstrating that the toolbox could extract useful parameters and assess differences between normal and diseased profiles. Show less
There is a lack of reliable, repeatable, and non-invasive clinical endpoints when investigating treatments for intellectual disability (ID). The aim of this study is to explore a novel approach... Show moreThere is a lack of reliable, repeatable, and non-invasive clinical endpoints when investigating treatments for intellectual disability (ID). The aim of this study is to explore a novel approach towards developing new endpoints for neurodevelopmental disorders, in this case for ARID1B-related ID. In this study, twelve subjects with ARID1B-related ID and twelve age-matched controls were included in this observational case-control study. Subjects performed a battery of non-invasive neurobehavioral and neurophysiological assessments on two study days. Test domains included cognition, executive functioning, and eye tracking. Furthermore, several electrophysiological assessments were performed. Subjects wore a smartwatch (Withings (R) Steel HR) for 6 days. Tests were systematically assessed regarding tolerability, variability, repeatability, difference with control group, and correlation with traditional endpoints. Animal fluency, adaptive tracking, body sway, and smooth pursuit eye movements were assessed as fit-for-purpose regarding all criteria, while physical activity, heart rate, and sleep parameters show promise as well. The event-related potential waveform of the passive oddball and visual evoked potential tasks showed discriminatory ability, but EEG assessments were perceived as extremely burdensome. This approach successfully identified fit-for-purpose candidate endpoints for ARID1B-related ID and possibly for other neurodevelopmental disorders. Next, results could be replicated in different ID populations or the assessments could be included as exploratory endpoint in interventional trials in ARID1B-related ID. Show less
Atrial fibrillation (AF) is the clinically most prevalent rhythm disorder with large impact on quality of life and increased risk for hospitalizations and mortality in both men and women. In recent... Show moreAtrial fibrillation (AF) is the clinically most prevalent rhythm disorder with large impact on quality of life and increased risk for hospitalizations and mortality in both men and women. In recent years, knowledge regarding epidemiology, risk factors, and patho-physiological mechanisms of AF has greatly increased. Sex differences have been identified in the prevalence, clinical presentation, associated comorbidities, and therapy outcomes of AF. Although it is known that age-related prevalence of AF is lower in women than in men, women have worse and often atypical symptoms and worse quality of life as well as a higher risk for adverse events such as stroke and death associated with AF. In this review, we evaluate what is known about sex differences in AF mechanisms-covering structural, electrophysiological, and hormonal factors-and underscore areas of knowledge gaps for future studies. Increasing our understanding of mechanisms accounting for these sex differences in AF is important both for prognostic purposes and the optimization of (targeted, mechanism-based, and sex-specific) therapeutic approaches. Show less
The suprachiasmatic nucleus (SCN) functions as a circadian clock that drives 24-hour rhythms in physiology and behavior. The SCN neurons function as cell-autonomous oscillators, and the... Show more The suprachiasmatic nucleus (SCN) functions as a circadian clock that drives 24-hour rhythms in physiology and behavior. The SCN neurons function as cell-autonomous oscillators, and the production of a coherent SCN rhythm is dependent upon synchronization among single cells. We investigated how changes in phase-synchronization between individual cells effect the ability of the SCN to phase-shift its rhythm. Empirical and modelling studies revealed larger phase-shifts in synchronized SCN than in desynchronized SCN. The major external stimulus affecting the SCN is light. We explored the ability of melanopsin and rod- and cone photoreceptors to mediate the effects of light on SCN discharge, and found that melanopsin and cones are able to mediate light responses of the SCN. Studies performed in nocturnal species have indicated that the SCN’s rhythmicity is also influenced by the animal’s own behavioral activity. We assessed the effect behavioral activity on the amplitude of the circadian rhythm in SCN electrical discharge rate in the day-active Arvicanthis ansorgei. The results showed acute enhancements of SCN discharge during episodes of behavioral activity. The studies described in this thesis indicate that the SCN is part of a brain network that includes the retina and areas involved in behavioral activity and sleep. Show less
Almer, J.; Jennings, R.B.; Maan, A.C.; Ringborn, M.; Maynard, C.; Pahlm, O.; ... ; Engblom, H. 2016
De draaiing van de aarde zorgt voor dagelijkse veranderingen in licht en donker. Om op deze dagelijkse veranderingen te kunnen anticiperen hebben alle organismen een ingebouwd mechanisme, namelijk... Show moreDe draaiing van de aarde zorgt voor dagelijkse veranderingen in licht en donker. Om op deze dagelijkse veranderingen te kunnen anticiperen hebben alle organismen een ingebouwd mechanisme, namelijk de biologische klok. De biologische klok bevindt zich in de suprachiasmatische nucleus (SCN) en bestaat uit ongeveer 20 000 neuronen. De SCN ontvangt lichtinformatie uit de omgeving via lichtgevoelige cellen in het netvlies van het oog. Deze cellen geven de informatie door aan de SCN. In het netvlies zijn drie typen lichtgevoelige cellen aanwezig, de staafjes, de kegeltjes en retinale ganglion cellen met melanopsine. In dit proefschrift is de relatieve bijdrage van de verschillende lichtgevoelige cellen op de verwerking van lichtinformatie door de SCN onderzocht. Het onderzoek heeft zich met name gericht op de specifieke bijdragen van de kegeltjes. Ook is onderzocht welke neurotransmitters van invloed zijn op de lichtgevoeligheid van de SCN. Samenvattend laten de resultaten zien dat de hoeveelheid lichtinformatie die de SCN bereikt kan worden bepaald door zowel staafjes, kegeltjes als melanopsine en dat dit afhankelijk is van golflengte, duur en intensiteit van het licht. Daarnaast kan de hoeveelheid lichtinformatie die de SCN bereikt ook afhankelijk zijn van de neurotransmitters adenosine en VIP. Show less
Plomp, J.J.; Morsch, M.; Phillips, W.D.; Verschuuren, J.J.G.M. 2015
Het dagelijkse ritme van slapen en waken wordt gereguleerd door de suprachiasmatische nuclei, twee kleine kernen die diep in de hersenen liggen en functioneren als een interne biologische klok.... Show moreHet dagelijkse ritme van slapen en waken wordt gereguleerd door de suprachiasmatische nuclei, twee kleine kernen die diep in de hersenen liggen en functioneren als een interne biologische klok. Dankzij de werking van deze kernen vertonen allerlei hersenstructuren en fysiologische processen 24 uurs ritmen die het lichaam in staat stellen zich optimaal aan te passen aan het dagelijks ritme van dag en nacht. Het onderzoek in dit proefschrift bestaat uit twee experimentele delen. In het eerste deel worden de mechanismes onderzocht waarmee de suprachiasmatische nuclei de timing van gedragsactiviteit en rust reguleren. In het tweede deel is onderzocht hoe verstoringen van de biologische klok samenhangen met ziekteontwikkeling in de context van psychiatrische aandoeningen, metabole stoornissen en chronisch nierfalen. Show less
Piers, S.R.; Tao, Q.; Taxis, C.F.V. van; Schalij, M.; Geest, R.J. van der; Zeppenfeld, K. 2012
While the embryonic heart is developing and maturing towards its four-chambered form, the cardiac conduction system (CCS) is developing as well. The CCS will provide the heart with the required... Show moreWhile the embryonic heart is developing and maturing towards its four-chambered form, the cardiac conduction system (CCS) is developing as well. The CCS will provide the heart with the required wiring system to ensure the properly orchestrated contraction of the myocardial chambers. In both the young and adult population rhythm disturbances or cardiac arrhythmias can occur. Electrophysiological studies have shown that these events do not occur randomly in the heart but rather at anatomical predilection sites. This thesis presents our results on the morphological as well as electrophysiological changes that occur during heart development, specifically in the developing sinoatrial and atrioventricular node. By studying the developmental changes we aim to increase our knowledge on the mechanism underlying arrhythmias. Show less
This thesis is separated in two parts (Part I and Part II) in which normal and abnormal heart development are studied and related to congenital heart disease, in particular to the etiology of... Show moreThis thesis is separated in two parts (Part I and Part II) in which normal and abnormal heart development are studied and related to congenital heart disease, in particular to the etiology of supraventricular arrhythmias in fetuses and neonates. Part I describes the development of the posterior heart field derived venous pole of the heart specifically in correlation to the role of Shox2 and podoplanin in that particular area. Furthermore, the developmental processes in this region seem to have an important role in the anlage of the cardiac conduction system and epicardial lineage development of the heart. In the second part of this thesis (Part II) the aetiology of a specific subtype of supraventricular tachycardias i.e. atrioventricular reentry tachycardias (AVRTs) are related to normal heart development in human and mouse. AVRTs are one of the most common types of tachyarrhythmias at the perinatal period of development. We demonstrate that perinatal AVRTs might be related to incomplete formation of the isolating annulus fibrosus resulting in the temporary persistence of accessory myocardial connections between the atria and ventricles. We furthermore, demonstrate the late outcome of fetal brady- and tachyarrhythmia cases. Show less
