HUWE1 mutation explains phenotypic severity in a case of familial idiopathic intellectual disability

The advent of next-generation sequencing has proven to be a key force in the identification of new genes associated with intellectual disability. In this study, high-throughput sequencing of the coding regions of the X-chromosome led to the identification of a missense variant in the HUWE1 gene. The same variant has been reported before by Froyen et al. (2008). We compare the phenotypes and demonstrate that, in the present family, the HUWE1 mutation segregates with the more severe ID phenotypes of two out of three brothers. The third brother has a milder form of ID and does not carry the mutation

Missense MED12 variants in 22 males with intellectual disability: From nonspecific symptoms to complete syndromes

Genotype; Intellectual disability; PhenotypeGenotipo; Discapacidad intelectual; FenotipoGenotip; Discapacitat intel·lectual; FenotipWe describe the phenotype of 22 male patients (20 probands) carrying a hemizygous missense variant in MED12. The phenotypic spectrum is very broad ranging from nonspecific intellectual disability (ID) to the three well-known syndromes: Opitz–Kaveggia syndrome, Lujan–Fryns syndrome, or Ohdo syndrome. The identified variants were randomly distributed throughout the gene (p = 0.993, χ2 test), but mostly outside the functional domains (p = 0.004; χ2 test). Statistical analyses did not show a correlation between the MED12-related phenotypes and the locations of the variants (p = 0.295; Pearson correlation), nor the protein domain involved (p = 0.422; Pearson correlation). In conclusion, establishing a genotype–phenotype correlation in MED12-related diseases remains challenging. Therefore, we think that patients with a causative MED12 variant are currently underdiagnosed due to the broad patients' clinical presentations.Foundation for Science and Technology (FCT), Grant/Award Number: UIDB/00215/2020 UIDP/00215/2020 LA/P/0064/2020; Broad Institute; National Eye Institute; National Heart, Lung and Blood Institute, Grant/Award Number: UM1 HG008900; National Human Genome Research Institute, Grant/Award Number: R01 HG009141

De novo SPAST mutations may cause a complex SPG4 phenotype

Item does not contain fulltex

Reduced MUNC18-1 Levels, Synaptic Proteome Changes, and Altered Network Activity in STXBP1-Related Disorder Patient Neurons

Background: STXBP1-related disorder (STXBP1-RD) is a neurodevelopmental disorder caused by pathogenic variants in the STXBP1 gene. Its gene product MUNC18-1 organizes synaptic vesicle exocytosis and is essential for synaptic transmission. Patients present with developmental delay, intellectual disability, and/or epileptic seizures, with high clinical heterogeneity. To date, the cellular deficits of neurons of patients with STXBP1-RD are unknown. Methods: We combined live-cell imaging, electrophysiology, confocal microscopy, and mass spectrometry proteomics to characterize cellular phenotypes of induced pluripotent stem cell–derived neurons from 6 patients with STXBP1-RD, capturing shared features as well as phenotypic diversity among patients. Results: Neurons from all patients showed normal in vitro development, morphology, and synapse formation, but reduced MUNC18-1 RNA and protein levels. In addition, a proteome-wide screen identified dysregulation of proteins related to synapse function and RNA processes. Neuronal networks showed shared as well as patient-specific phenotypes in activity frequency, network irregularity, and synchronicity, especially when networks were challenged by increasing excitability. No shared effects were observed in synapse physiology of single neurons except for a few patient-specific phenotypes. Similarities between functional and proteome phenotypes suggested 2 patient clusters, not explained by gene variant type. Conclusions: Together, these data show that decreased MUNC18-1 levels, dysregulation of synaptic proteins, and altered network activity are shared cellular phenotypes of STXBP1-RD. The 2 patient clusters suggest distinctive pathobiology among subgroups of patients, providing a plausible explanation for the clinical heterogeneity. This phenotypic spectrum provides a framework for future validation studies and therapy design for STXBP1-RD

Discovery of Novel Genes for Intellectual Disability and Multiple Congenital Anomalies in the Next Generation Sequencing Era

This study was aimed at exploring the utility of next-generation sequencing (NGS) in the discovery of novel genes causing intellectual disability (ID) and/or multiple congenital anomalies (MCA) (chapter 1 & 2). It was started in 2010, around the same time when NGS was initiated at the KU Leuven Center for Human Genetics. Our starting point were patients with either syndromic or non-syndromic forms of ID, including both sporadic and familial cases, without a molecular diagnosis. NGS was performed on the Illumina HiSeq 2000 platform (chapter 3), with exception of the family described in chapter 5.3. In order to investigate the benefit of NGS in sporadic ID, we collected DNA samples of patients sharing the same clinical phenotype of Circumferential skin creases Kunze type (CSC-KT), which thus far had an unknown genetic origin (chapter 4.1). After applying whole-exome sequencing (WES), we demonstrated the presence of causal MAPRE2 or TUBB mutations in the patient cohort, which was validated by Sanger sequencing and further confirmed in additional patients. Functional analysis of the mutations revealed their influence on microtubule dynamics. Therefore, CSC-KT can be categorized as a tubulinopathy. Pathogenicity of all mutations was further confirmed using a zebrafish model that showed perturbed craniofacial development. On the whole, the study highlighted the presence of multiple inheritance paradigms resulting in the same clinical phenotype. The role of NGS in familial ID was investigated in three families with separate entities. Family 1 (chapter 5.1) consisted of a consanguineous couple with six children, three of which had intellectual disability, seizures and behavioural problems. WES combined with linkage analysis on all family members, led to the identification of a homozygous missense variant in STYXL1 as the most likely candidate. We demonstrated a significant reduction of transcript levels of STYXL1 in the proband versus his carrier father, further supporting pathogenicity of the variant. A drawback of this study was the lack of additional cases with a mutation in STYXL1, which may be explained by the differing ethnicity and the extreme heterogeneity of the phenotype. The approach in family 2 (chapter 5.2) consisted of applying WES to two affected siblings, their unaffected parents as well as their unaffected sibling. Although it was the most likely inheritance pattern, we did not detect a causal recessive variant in the affected patients. Rather, we identified a heterozygous variant in the FHF1 gene, which turned out to be the result of germline mosaicism in either one of the parents. We established FHF1 as a novel gene associated with a severe phenotype of early-onset epileptic encephalopathy and cerebellar atrophy. Pathogenic effects of the mutation were further verified in a zebrafish model replicating epileptiform discharges through a gain-of-function mechanism. Finally, in family 3 we used an X-exome-based approach based on the pedigree (chapter 5.3). two out of three brothers had a severe ID and minor dysmorphic features. They carried a previously described pathogenic HUWE1 missense mutation. Through this additional family, we emphasize the importance of HUWE1 point mutations in cases with severe ID in males, variably associated with minor dysmorphism. In addition, we discuss the challenging interpretation of these findings in a familial setting, where other family members - including a sibling and their mother - also had some level of cognitive impairment. In conclusion, our study explored the application of NGS in the field of human genetics and ID (chapter 6). The value of NGS versus conventional techniques is illustrated by its benefit when it comes to a growing number of genetic heterogeneous disorders. Also, the constant drop in NGS costs makes it a more attractive choice when the clinical diagnosis is not very clear. On the other hand, clinical evaluation remains an indispensable part of a genetic workup and it's very important to remember the limitations of NGS techniques. Finally, we provide an overview of the challenges that emerge during diagnostic implementation of NGS and discuss some future perspectives on NGS.List of abbreviations Chapter 1: General introduction to rare diseases and next-generation sequencing Chapter 2: Research objectives Chapter 3: Materials and methods Chapter 4: Sporadic cases of syndromic intellectual disability Chapter 5: Familial cases of intellectual disability Chapter 6: General discussion, clinical implications and future perspectives Appendicesnrpages: 159status: publishe

Familial 16q24.3 microdeletion involving ANKRD11 causes a KBG-like syndrome

Haploinsufficiency of ANKRD11 encoding ankyrin repeat domain-containing protein 11 was recently reported as the cause of a syndrome due to microdeletion, characterized by intellectual disability with minor facial anomalies and short stature. Most recently, intragenic mutations of ANKRD11 were found in a cohort of patients with KBG syndrome. KBG is an autosomal dominant intellectual disability syndrome characterized by short stature, characteristic facial appearance, macrodontia, and skeletal anomalies. It remains unknown if deletion of the entire ANKRD11 causes KBG syndrome. We present a mother and child with a heterozygous 365 Kb deletion at 16q24.3 containing ANKRD11, ZNF778, and SPG7 genes. The child presented with developmental delay, facial anomalies, hand anomalies, and a congenital heart defect. The mother has short stature, facial anomalies, macrodontia, hand anomalies, and learning disability. Both individuals had many findings reported in KBG syndrome and the family met the suggested diagnostic criteria. However, typical macrodontia with fused incisors, costovertebral anomalies, and delayed bone age were not present. We conclude that microdeletions involving ANKRD11 result in a phenotype similar to that of KBG syndrome. © 2012 Wiley Periodicals, Inc

Measuring, logging, and visualizing pulsed Electromagnetic fields combined with GPS location information

Diode detectors and thermocouple detectors are the standard sensors for measuring electromagnetic fields. Thermocouple detectors are most suitable for detecting average values of pulsed signals. In case of peak detection of the field strength, the thermocouple detector is too slow and diode detectors have to be used. In case of a large crest factor, e.g. with a radar, a cascaded diode detector is needed, which is not available as a standard exposure electromagnetic field strength probe. Furthermore, a continuous registration of location while doing measurements is added. This paper describes a data acquisition (DAQ) system built in LabView(lv), which displays and logs the data of a cascaded diode-based wideband power sensor and a GPS sensor in a synchronized way. The LV program also displays the power sensor parameters and the associated GPS location in a heads up display (HUD) using the Microsoft HoloLens. This allows the user to walk and see the measured data in augmented reality without the need to look down on a laptop and missing the maximum measured electric field strength. This reduction in delay occurring from human reaction time allows to follow measurements more accurately in real time. The built system is convenient, compact and mobile in usage and can be used for compliance testing with the health and safety requirements for workers or the general public of radiated electrical fields in difficult to reach areas without compromising safety regulations

Partial Deletion of ANKRD11 Results in the KBG Phenotype Distinct from the 16q24.3 Microdeletion Syndrome

KBG syndrome (OMIM 148050) is a very rare genetic disorder characterized by macrodontia, distinctive craniofacial abnormalities, short stature, intellectual disability, skeletal, and neurologic involvement. Approximately 60 patients have been reported since it was first described in 1975. Recently mutations in ANKRD11 have been documented in patients with KBG syndrome, and it has been proposed that haploinsufficiency of ANKRD11 is the cause of this syndrome. In addition, copy number variation in the 16q24.3 region that includes ANKRD11 results in a variable phenotype that overlaps with KBG syndrome and also includes autism spectrum disorders and other dysmorphic facial features. In this report we present a 2½-year-old African American male with features highly suggestive of KBG syndrome. Genomic microarray identified an intragenic 154 kb deletion at 16q24.3 within ANKRD11. This child\u27s mother was mosaic for the same deletion (present in approximately 38% of cells) and exhibited a milder phenotype including macrodontia, short stature and brachydactyly. This family provides additional evidence that ANKRD11 causes KBG syndrome, and the mild phenotype in the mosaic form suggests that KBG phenotypes might be dose dependent, differentiating it from the more variable 16q24.3 microdeletion syndrome. This family has additional features that might expand the phenotype of KBG syndrome