This research focuses on creating composite biomarkers that can classify diagnoses, estimate symptom severity, and detect treatment effects using data from wearable sensors and smartphone... Show moreThis research focuses on creating composite biomarkers that can classify diagnoses, estimate symptom severity, and detect treatment effects using data from wearable sensors and smartphone applications. The thesis consists of an introduction to machine learning techniques and their use in developing biomarkers for the central nervous system; a narrative review of the relevant literature; and detailed studies on the application of these techniques in various health conditions. Specifically, the research includes observational and cross-sectional studies on facioscapulohumeral muscular dystrophy (FSHD) and major depressive disorder (MDD), demonstrating how smartphone and wearable sensor data can be used to monitor disease severity and progression. Additionally, the research identified the use of a tablet-based finger tapping task to monitor the real-time effects of antiparkinson's drugs on Parkinson's symptom severity. Key findings highlight the potential of mHealth biomarkers to provide continuous, real-time monitoring of patients, which can enhance the accuracy of clinical assessments and potentially reduce the burden on patients and healthcare systems. The thesis also addresses the challenges of variability in mHealth device data and emphasizes the need for robust validation and standardization to ensure the reliability of these biomarkers in clinical settings. Show less
Facioscapulohumeral muscular dystrophy (FSHD) is the second most common muscular dystrophy in adults, and it is associated with local D4Z4 chromatin relaxation, mostly via the contraction of the... Show moreFacioscapulohumeral muscular dystrophy (FSHD) is the second most common muscular dystrophy in adults, and it is associated with local D4Z4 chromatin relaxation, mostly via the contraction of the D4Z4 macrosatellite repeat array on chromosome 4q35. In this study, we aimed to investigate the use of Optical Genome Mapping (OGM) as a diagnostic tool for testing FSHD cases from the UK and India and to compare OGM performance with that of traditional techniques such as linear gel (LGE) and Pulsed-field gel electrophoresis (PFGE) Southern blotting (SB). A total of 6 confirmed and 19 suspected FSHD samples were processed with LGE and PFGE, respectively. The same samples were run using a Saphyr Genome-Imaging Instrument (1-color), and the data were analysed using custom EnFocus FSHD analysis. OGM was able to confirm the diagnosis of FSHD1 in all FSHD1 cases positive for SB (n = 17), and D4Z4 sizing highly correlated with PFGE-SB (p < 0.001). OGM correctly identified cases with mosaicism for the repeat array contraction (n = 2) and with a duplication of the D4Z4 repeat array. OGM is a promising new technology able to unravel structural variants in the genome and seems to be a valid tool for diagnosing FSHD1. Show less
Lemmers, R.J.L.F.; Butterfield, R.; Vliet, P.J. van der; Bleecker, J.L. de; Pol, L. van der; Dunn, D.M.; ... ; Maarel, S.M. van der 2023
Facioscapulohumeral dystrophy (FSHD) has a unique genetic aetiology resulting in partial chromatin relaxation of the D4Z4 macrosatellite repeat array on 4qter. This D4Z4 chromatin relaxation... Show moreFacioscapulohumeral dystrophy (FSHD) has a unique genetic aetiology resulting in partial chromatin relaxation of the D4Z4 macrosatellite repeat array on 4qter. This D4Z4 chromatin relaxation facilitates inappropriate expression of the transcription factor DUX4 in skeletal muscle. DUX4 is encoded by a retrogene that is embedded within the distal region of the D4Z4 repeat array. In the European population, the D4Z4 repeat array is usually organized in a single array that ranges between 8 and 100 units. D4Z4 chromatin relaxation and DUX4 derepression in FSHD is most often caused by repeat array contraction to 1-10 units (FSHD1) or by a digenic mechanism requiring pathogenic variants in a D4Z4 chromatin repressor like SMCHD1, combined with a repeat array between 8 and 20 units (FSHD2).With a prevalence of 1.5% in the European population, in cis duplications of the D4Z4 repeat array, where two adjacent D4Z4 arrays are interrupted by a spacer sequence, are relatively common but their relationship to FSHD is not well understood. In cis duplication alleles were shown to be pathogenic in FSHD2 patients; however, there is inconsistent evidence for the necessity of an SMCHD1 mutation for disease development.To explore the pathogenic nature of these alleles we compared in cis duplication alleles in FSHD patients with or without pathogenic SMCHD1 variant. For both groups we showed duplication-allele-specific DUX4 expression. We studied these alleles in detail using pulsed-field gel electrophoresis-based Southern blotting and molecular combing, emphasizing the challenges in the characterization of these rearrangements. Nanopore sequencing was instrumental to study the composition and methylation of the duplicated D4Z4 repeat arrays and to identify the breakpoints and the spacer sequence between the arrays. By comparing the composition of the D4Z4 repeat array of in cis duplication alleles in both groups, we found that specific combinations of proximal and distal repeat array sizes determine their pathogenicity. Supported by our algorithm to predict pathogenicity, diagnostic laboratories should now be furnished to accurately interpret these in cis D4Z4 repeat array duplications, alleles that can easily be missed in routine settings.Facioscapulohumeral muscular dystrophy (FSHD) is caused by shortening of the D4Z4 repeat array. Occasionally duplications of this array are found with unknown pathogenicity. Lemmers et al. have developed a formula to predict pathogenicity of these duplications and have unravelled the mechanism by which they cause FSHD. Show less
Background: Facioscapulohumeral muscular dystrophy (FSHD) is a progressive neuromuscular disease. Its slow and variable progression makes the development of new treatments highly dependent on... Show moreBackground: Facioscapulohumeral muscular dystrophy (FSHD) is a progressive neuromuscular disease. Its slow and variable progression makes the development of new treatments highly dependent on validated biomarkers that can quantify disease progression and response to drug interventions.Objective: We aimed to build a tool that estimates FSHD clinical severity based on behavioral features captured using smartphone and remote sensor data. The adoption of remote monitoring tools, such as smartphones and wearables, would provide a novel opportunity for continuous, passive, and objective monitoring of FSHD symptom severity outside the clinic.Methods: In total, 38 genetically confirmed patients with FSHD were enrolled. The FSHD Clinical Score and the Timed Up and Go (TUG) test were used to assess FSHD symptom severity at days 0 and 42. Remote sensor data were collected using an Android smartphone, Withings Steel HR+, Body+, and BPM Connect+ for 6 continuous weeks. We created 2 single-task regression models that estimated the FSHD Clinical Score and TUG separately. Further, we built 1 multitask regression model that estimated the 2 clinical assessments simultaneously. Further, we assessed how an increasingly incremental time window affected the model performance. To do so, we trained the models on an incrementally increasing time window (from day 1 until day 14) and evaluated the predictions of the clinical severity on the remaining 4 weeks of data.Results: The single-task regression models achieved an R2 of 0.57 and 0.59 and a root-mean-square error (RMSE) of 2.09 and 1.66 when estimating FSHD Clinical Score and TUG, respectively. Time spent at a health-related location (such as a gym or hospital) and call duration were features that were predictive of both clinical assessments. The multitask model achieved an R2 of 0.66 and 0.81 and an RMSE of 1.97 and 1.61 for the FSHD Clinical Score and TUG, respectively, and therefore outperformed the single-task models in estimating clinical severity. The 3 most important features selected by the multitask model were light sleep duration, total steps per day, and mean steps per minute. Using an increasing time window (starting from day 1 to day 14) for the FSHD Clinical Score, TUG, and multitask estimation yielded an average R2 of 0.65, 0.79, and 0.76 and an average RMSE of 3.37, 2.05, and 4.37, respectively. Conclusions: We demonstrated that smartphone and remote sensor data could be used to estimate FSHD clinical severity and therefore complement the assessment of FSHD outside the clinic. In addition, our results illustrated that training the models on the first week of data allows for consistent and stable prediction of FSHD symptom severity. Longitudinal follow-up studies should be conducted to further validate the reliability and validity of the multitask model as a tool to monitor disease progression over a longer period. Show less
Facioscapulohumeral muscular dystrophy (FSHD) is caused by incomplete epigenetic repression of the D4Z4 repeat resulting in misexpression of the repeat-encoded DUX4 gene in skeletal muscle. Two... Show moreFacioscapulohumeral muscular dystrophy (FSHD) is caused by incomplete epigenetic repression of the D4Z4 repeat resulting in misexpression of the repeat-encoded DUX4 gene in skeletal muscle. Two mechanisms are known to drive this D4Z4 epigenetic dysregulation: a contraction of the D4Z4 repeat or mutations in DNMT3B or SMCHD1, both epigenetic regulators of the repeat that are responsible for the establishment or maintenance of the repeat’s epigenetic repressive state in somatic cells. However, the aforementioned (epi)genetic changes lead to FSHD only if the individual also has a disease-permissive D4Z4 allele which allows for stable DUX4 expression in skeletal muscle. This disease permissivity of D4Z4 alleles has been attributed to the presence of a DUX4 polyadenylation signal adjacent to the D4Z4 repeat which is used for transcription termination. Despite knowing the root cause of FSHD, to date, there is no curative therapy available for FSHD and in some cases, the genetic etiology of the disease remains unknown. In this thesis, we identified a new FSHD disease gene called LRIF1 and performed its follow-up functional studies in human somatic cells and mouse embryonic stem cells. In addition, we also pursued a new targeted gene therapy for FSHD by employing CRISPR-based mutagenesis of the DUX4 polyadenylation signal. Show less
Maleki, G.; Zhuparris, A.; Koopmans, I.; Doll, R.J.; Voet, N.; Cohen, A.; ... ; Maeyer, J. de 2022
Background: Facioscapulohumeral dystrophy (FSHD) is a progressive muscle dystrophy disorder leading to significant disability. Currently, FSHD symptom severity is assessed by clinical assessments... Show moreBackground: Facioscapulohumeral dystrophy (FSHD) is a progressive muscle dystrophy disorder leading to significant disability. Currently, FSHD symptom severity is assessed by clinical assessments such as the FSHD clinical score and the Timed Up-and-Go test. These assessments are limited in their ability to capture changes continuously and the full impact of the disease on patients' quality of life. Real-world data related to physical activity, sleep, and social behavior could potentially provide additional insight into the impact of the disease and might be useful in assessing treatment effects on aspects that are important contributors to the functioning and well-being of patients with FSHD.Objective: This study investigated the feasibility of using smartphones and wearables to capture symptoms related to FSHD based on a continuous collection of multiple features, such as the number of steps, sleep, and app use. We also identified features that can be used to differentiate between patients with FSHD and non-FSHD controls.Methods: In this exploratory noninterventional study, 58 participants (n=38, 66%, patients with FSHD and n=20, 34%, non-FSHD controls) were monitored using a smartphone monitoring app for 6 weeks. On the first and last day of the study period, clinicians assessed the participants' FSHD clinical score and Timed Up-and-Go test time. Participants installed the app on their Android smartphones, were given a smartwatch, and were instructed to measure their weight and blood pressure on a weekly basis using a scale and blood pressure monitor. The user experience and perceived burden of the app on participants' smartphones were assessed at 6 weeks using a questionnaire. With the data collected, we sought to identify the behavioral features that were most salient in distinguishing the 2 groups (patients with FSHD and non-FSHD controls) and the optimal time window to perform the classification.Results: Overall, the participants stated that the app was well tolerated, but 67% (39/58) noticed a difference in battery life using all 6 weeks of data, we classified patients with FSHD and non-FSHD controls with 93% accuracy, 100% sensitivity, and 80% specificity. We found that the optimal time window for the classification is the first day of data collection and the first week of data collection, which yielded an accuracy, sensitivity, and specificity of 95.8%, 100%, and 94.4%, respectively. Features relating to smartphone acceleration, app use, location, physical activity, sleep, and call behavior were the most salient features for the classification.Conclusions: Remotely monitored data collection allowed for the collection of daily activity data in patients with FSHD and non-FSHD controls for 6 weeks. We demonstrated the initial ability to detect differences in features in patients with FSHD and non-FSHD controls using smartphones and wearables, mainly based on data related to physical and social activity. Show less
Voermans, N.C.; Bilt, R.C. van der; IJspeert, J.; Hogrel, J.Y.; Jeanpierre, M.; Behin, A.; ... ; Bassez, G. 2019
ObjectiveTo study scapular winging or other forms of scapular dyskinesis (condition of alteration of the normal position and motion of the scapula) in myotonic dystrophy type 1 (DM1), which is... Show moreObjectiveTo study scapular winging or other forms of scapular dyskinesis (condition of alteration of the normal position and motion of the scapula) in myotonic dystrophy type 1 (DM1), which is generally considered to be a distal myopathy, we performed an observational cohort study.MethodsWe performed a prospective cohort study on the clinical features and progression over time of 33 patients with DM1 and pronounced, mostly asymmetric scapular winging or other forms of scapular dyskinesis. We also explored if scapular dyskinesis in DM1 has the same genetic background as in facioscapulohumeral muscular dystrophy type 1 (FSHD1).ResultsThe cohort included patients with congenital (n=3), infantile (n=6) and adult-onset DM1 (n=24). Scapular girdle examination showed moderate shoulder girdle weakness (mean MRC 3) and atrophy of trapezius, infraspinatus, and rhomboid major, seemingly similar as in FSHD1. Shoulder abduction and forward flexion were limited (50-70 degrees). In five patients, scapular dyskinesis was the initial disease symptom; in the others it appeared 1-24 years after disease onset. Follow-up data were available in 29 patients (mean 8 years) and showed mild to severe increase of scapular dyskinesis over time. In only three patients, DM1 coexisted with a FSHD mutation. In all other patients, FSHD was genetically excluded. DM2 was genetically excluded in nine patients. The clinical features of the patients with both DM1 and FSHD1 mutations were similar to those with DM1 only.ConclusionScapular dyskinesis can be considered to be part of DM1 in a small proportion of patients. In spite of the clinical overlap, FSHD can explain scapular dyskinesis only in a small minority. This study is expected to improve the recognition of shoulder girdle involvement in DM1, which will contribute to the management of these patients. Show less
In this thesis two diseases that share a common feature of hypomethylation of repetitive DNA are studied: facioscapulohumeral muscular dystrophy (FSHD) and immunodeficiency, centromeric... Show moreIn this thesis two diseases that share a common feature of hypomethylation of repetitive DNA are studied: facioscapulohumeral muscular dystrophy (FSHD) and immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome. In FSHD there is hypomethylation of the macrosatellite repeat D4Z4 and the associated DUX4 gene, which is caused by a repeat contraction and/or variants in chromatin modifiers essential for a repressive D4Z4 chromatin structure in somatic cells. In ICF there is hypomethylation of centromeric repeats, which is caused by recessive variants in one of four ICF genes, of which two are established chromatin modifiers. In this thesis, the mutation spectrum of FSHD and ICF has been expanded. The SMCHD1 mutation spectrum in FSHD2 has been expanded with the discovery of exonic SMCHD1 variants, intronic SMCHD1 variants, and whole SMCHD1 gene deletions. In addition, we identified heterozygous variants in a new FSHD2 gene, DNMT3B, in two FSHD2 families. For ICF syndrome we expanded the mutation spectrum in the two most common ICF genes, DNMT3B and ZBTB24. Show less
A large part of the human genome consists of repetitive DNA. In this thesis two human diseases have been studied in which deregulation of repetitive DNA is a central feature: facioscapulohumeral... Show moreA large part of the human genome consists of repetitive DNA. In this thesis two human diseases have been studied in which deregulation of repetitive DNA is a central feature: facioscapulohumeral muscular dystrophy (FSHD) and immunodeficiency, centromere instability and facial anomalies (ICF) syndrome. FSHD is caused by the misexression of the transcription factor DUX4 in skeletal muscle. DUX4 is encoded in the D4Z4 repeat array and is silenced in healthy somatic tissues. In this thesis, several aspects of the epigenetic deregulation of DUX4 in FSHD are described. We have analysed possible correlations between disease severity and epigenetic organization of the D4Z4 repeat. Next we showed that cellular ageing results in deregulation of genomic regions like D4Z4. Moreover, we show that SMCHD1 is the main epigenetic repressor of DUX4 in somatic cells. We next showed that DUX4 misexpression results in the activation of an FSHD candidate gene, FRG2. Finally, we report the generation of a transgenic mouse model for FSHD. The disease mechanism of ICF syndrome remains to be elucidated. However, in this thesis we identify two new ICF disease genes. We highlight a role for all four known ICF genes in repressing repetitive DNA, suggesting functional convergence of these genes. Show less
Lemmers, R.J.L.F.; Boogaard, M.L. van den; Vliet, P.J. van der; Donlin-Smith, C.M.; Nations, S.P.; Ruivenkamp, C.A.L.; ... ; Maarel, S.M. van der 2015
Facioscapulohumeral muscular dystrophy is an autosomal dominant myopathy that is caused by a contraction of the D4Z4 repeat on the 4qA161 genetic variant of chromosome 4qter (FSHD1). FSHD1 patients... Show moreFacioscapulohumeral muscular dystrophy is an autosomal dominant myopathy that is caused by a contraction of the D4Z4 repeat on the 4qA161 genetic variant of chromosome 4qter (FSHD1). FSHD1 patients show loss of DNA methylation on the first D4Z4 repeat unit. Interestingly, a small group of patients with a myopathy clinically indistinguishable from FSHD1 but without a D4Z4 contraction (FSHD2) and patients suffering from the ICF (Immunodeficiency, Centromeric instability and Facial anomalies) syndrome also present with very low D4Z4 methylation. In this thesis studies are described that focused on the unraveling of the epigenetic disease mechanism responsible for FSHD development. These studies show that (1) the overlap between FSHD patients and ICF patients is restricted to low D4Z4 methylation levels, (2) FSHD1 and FSHD2 patients show loss of methyl groups on lysine 9 of histone protein H3 and a secondary loss of the proteins HP1? and cohesin at the D4Z4 repeat, (3) the combination of the 4qA161 genetic variant and low D4Z4 methylation is a necessary prerequisite for FSHD development and (4) supplementation with folic and methionine can raise the total amount of methyl groups present on the DNA but cannot restore D4Z4 methylation levels in FSHD1 and FSHD2 patients. Show less
Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscle diseases with an estimated frequency of 1 in 20000. The disease has an autosomal dominant inheritance... Show moreFacioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscle diseases with an estimated frequency of 1 in 20000. The disease has an autosomal dominant inheritance pattern and is characterised by a progressive and often asymmetric muscle weakness with an onset of disease in facial or shoulder girdle muscles. The major locus for FSHD is linked to 4q35, located in the subtelomere on the long arm of chromosome 4. This region harbours a highly polymorphic EcoRI fragment that contains a large polymorphic repeat structure, designated D4Z4, which consists of 3.3 kb tandemly arranged D4Z4 repeat units and is highly susceptible to rearrangement. In the majority of patients this repeat is contracted to an array of 1-10 repeat units. However, 5% of FSHD patients, termed phenotypic FSHD patients, do not manifest a contracted D4Z4 array on chromosome 4, but share all clinical characteristics. Complicating FSHD diagnosis, the subtelomere on the long arm of chromosome 10 (10q26) is highly similar to 4q35 and also contains a nearly identical polymorphic repeat array. However, size reductions of the chromosome 10 repeat array are non-pathogenic. Furthermore, exchanges between arrays on chromosomes 4 and 10 are frequently observed in patients and control individuals, but will only cause disease when a contracted array resides on chromosome 4. Finally, recent analysis of sequences distal to D4Z4 revealed two variants of the 4qter sequence, designated 4qA and 4qB. While both variants are almost equally present in the population, FSHD is uniquely associated with the 4qA variant. Although FSHD is associated with a repeat contraction on 4qA, the exact mechanism causing disease is still unknown. The work in this thesis focused on structure and behaviour of the 4q35 subtelomere, aiming at elucidating possible molecular mechanisms that may mediate or cause FSHD pathology. Subtelomeres are dynamic structures that are more often involved in recombination processes than other parts of the genome. Due to exchanges between subtelomeres of different chromosomes highly homologous DNA sequences can be dispersed throughout pericentromeric and subtelomeric domains in the genome. Since the repeat arrays located on the subtelomeres of the long arms of chromosomes 4 and 10 are highly homologous, we analysed these repeat array configurations in a healthy population, the results of which are presented in Chapters 2and 3. This revealed the existence of translocated repeat arrays in 20% of individuals. Besides the presence of homogeneous chromosome 4 repeat units on chromosome 10, and vice versa, we also detected hybrid arrays that contained repeat units derived from both chromosomes. With regard to repeat array size we observed that on average the arrays on chromosome 4 were longer than those on chromosome 10. This size difference was solely caused by alleles that carried the 4qA variant, as 4qB and 10q alleles did not differ in average length. Both repeat arrays of chromosomes 4 and 10 displayed a similar multimodal allele size distribution that possibly reflects a higher-order chromatin structure. This multimodal distribution on chromosome 4 furthermore indicated the presence of a premutation domain containing alleles shorter than approximately 100 kb. Alleles in this domain may be more prone to contraction to a disease allele than arrays located in the larger repeat size intervals and may thus be predisposing for FSHD development. In Chapters 3 and 4 we examined repeat array configurations in de novo FSHD families and observed somatic mosaicism in more than 40% of cases, in either an FSHD patient or an asymptomatic parent of a non-mosaic patient. This mosaicism for a contracted D4Z4 repeat was more often seen in male than in female patients. In addition, affected females showed a higher proportion of cells with the contracted 4q35 repeat array than males, indicating that females have a higher clinical tolerance for mosaic disease alleles. Consistent with this finding is that, on average, there are more females with mosaicism for the FSHD region among unaffected parents. Besides the observed mosaicism for a contracted FSHD allele generating two genetically distinct cell populations by gene conversion without crossover, we also identified FSHD patients with more complex rearrangements that resulted in three cell populations. This suggests that, alongside gene conversion without crossover, also gene conversion with crossover events that result in contraction and expansion of D4Z4 may contribute to the occurrence of mosaic D4Z4 alleles. Furthermore, whereas we did observe D4Z4 repeat units derived from chromosome 4 on chromosome 10 in mosaic individuals, the reverse configuration was never detected. The presence of such an extra chromosome 4 repeat array may facilitate gene conversion and may thus be a predisposing factor for contraction of the D4Z4 repeat array. Eukaryotic cells have the capacity to epigenetically modify their genomes with a biochemical mark to alter the phenotype without changing the genotype. Two major epigenetic processes that mark chromatin are DNA methylation and the modifications of histones, such as acetylation. Due to the repetitive nature and the location on the subtelomere of 4q35, D4Z4 has been proposed to have a heterochromatic character. Chapters 5, 6 and 7 present data on our studies on the chromatin structure of the D4Z4 repeat array, focussing on a possible change in structure of 4q35 in FSHD patients as a consequence of the chromosomal rearrangement. We demonstrated in Chapters 5 and 6 that the D4Z4 contraction is associated with a significant DNA hypomethylation of D4Z4 at the disease allele in FSHD patients. Furthermore, phenotypic FSHD patients that carry normal-sized 4q35 repeat arrays also showed a pronounced DNA hypomethylation of D4Z4 with levels even below those observed for FSHD patients with a contracted D4Z4 repeat array. While low DNA methylation values in FSHD patients linked to 4q35 are restricted to the disease allele, in phenotypic FSHD patients D4Z4 repeat arrays on both chromosomes 4 were found to be hypomethylated. These findings support an allelespecific chromatin change in FSHD patients with a D4Z4 contraction and strongly suggest that hypomethylation is a key event in the cascade of events causing the FSHD phenotype. Analysis of histone 4 acetylation levels in the 4q35 region, as described in Chapter 7, indicated that the chromatin structure close to D4Z4 resembled that of unexpressed euchromatin rather than constitutive heterochromatin. This suggests that D4Z4 and proximal sequences are not heterochromatic. Contrary to our data presented on D4Z4 methylation, no histone 4 acetylation differences were observed between control individuals and FSHD patients. However, it remains possible that other histone modifications may influence the chromatin conformation upon contraction of the D4Z4 array. The data presented in this thesis challenge the model suggesting the spreading of telomeric heterochromatin in a proximal direction upon contraction of the D4Z4 array, but fit in with other models that have been put forward to explain FSHD pathology. In addition to the repression model, suggesting that upon contraction a local reduction of a specific repressor complex bound to D4Z4 will cause inappropriate activation of 4q35 genes, our data also fit with the looping model, in which communication between a short D4Z4 repeat array and a target gene (or genes) occurs in cis by intrachromosomal looping. The model proposing a heterochromatic chromatin conformation as requirement for proper functioning of D4Z4 remains valid as well. Furthermore, as DUX4 located in D4Z4 encodes a putative homeoboxprotein, we cannot exclude whether expression of DUX4 in early development will be altered due to D4Z4 contraction and so contributes to or even initiates FSHD pathology. Probably the actual disease-causing process will be a combination of the proposed mechanisms in which also the unique perinuclear localisation of chromosome 4q also has to be taken into account. Besides providing new insights in the structure and complex behaviour of the chromosome 4q subtelomere associated with FSHD, this thesis also provides two observations relevant to the clinical practice. First, if mosaicism for D4Z4 is present in the germline, the percentage of these cells carrying the disease allele will determine the risk of having affected offspring, unlike in non-mosaic individuals carrying an FSHD-sized repeat array who have a 50% probability of transmitting the disease. More importantly, since mosaic females can carry a considerably higher percentage of cells with the disease fragment than male mosaics without manifesting FSHD, the disease may more easily go unnoticed in asymptomatic females than previously recognised. This indicates that there might be more apparently healthy women mosaic for a contracted FSHD allele who will have an increased risk of having a child that develops FSHD provided this mosaicism extends to the germline. It is therefore important to screen for mosaicism in de novo FSHD families to provide more accurate information on inheritance risks. Second, the methylation assay described in this thesis may have diagnostic and prognostic value, especially for phenotypic FSHD patients. Since we now know that the level of D4Z4 methylation in these individuals should be below the average methylation observed in FSHD patients with a 4q35 contraction, this can be used as a predictive molecular marker to confirm the status __phenotypic FSHD patient__. Hopefully, these two findings will become implemented in the molecular diagnosis of FSHD and contribute to improved genetic counselling. Show less
The purpose of this study is to discuss several aspects of facioscapulohumeral disease, also called "autosomal dominant facioscapulohumeral muscular dystrophy" or "Landouzy-Dejerine type of... Show moreThe purpose of this study is to discuss several aspects of facioscapulohumeral disease, also called "autosomal dominant facioscapulohumeral muscular dystrophy" or "Landouzy-Dejerine type of muscular dystrophy" or "Landouzy-Dejerine' s disease" . We consider this disorder well defined and recognizable, justifying the term facioscapulohumeral disease, abbreviated FSHD. Show less
