Publications by authors named "Erik-Jan Kamsteeg"

Article Synopsis
  • The study assesses 24 patients with Nemaline myopathy type 6 (NEM6) in the Netherlands, focusing on detailed clinical characteristics and symptom reporting.
  • Key findings include reported symptoms of muscle weakness, slow movements, and difficulties with running, along with significantly reduced health-related quality of life and increased fatigue.
  • The research also highlights issues with balance and falls, as well as a slower muscle relaxation rate compared to normal standards.
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Tandem Repeats (TR) occupy a significant portion of the human genome and are the source of polymorphism due to variations in sizes and motif compositions. Some of these variations have been associated with various neuropathological disorders, highlighting the clinical importance of assessing the motif structure of TRs. Moreover, assessing the TR motif variation can offer valuable insights into evolutionary dynamics and population structure.

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Tandem repeats (TRs) play important roles in genomic variation and disease risk in humans. Long-read sequencing allows for the accurate characterization of TRs; however, the underlying bioinformatics perspectives remain challenging. We present and TREAT: is a fast targeted local assembler, cross-compatible across different sequencing platforms.

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Article Synopsis
  • Clinical exome sequencing (ES) aids in diagnosing rare genetic disorders by analyzing protein-coding sequences, but 40-60% of patients still lack a conclusive diagnosis, with some revealing monoallelic variants in recessive disorders.* -
  • The study explored short-read genome sequencing (GS) on 174 individuals with identified monoallelic variants, successfully uncovering additional pathogenic variants in five patients and rare non-coding variants in 24 others, with three variants confirmed to affect splicing.* -
  • Overall, GS increased the diagnostic yield, identifying a likely second pathogenic variant in 4.6% of the cohort and providing a possible diagnosis for 12.1%, suggesting it could be a valuable first-tier
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Background: Nemaline myopathy type 6 (NEM6) or KBTBD13-related congenital myopathy is the most prevalent type of nemaline myopathy in the Netherlands and is characterised by mild childhood-onset axial, proximal and distal muscle weakness with prominent neck flexor weakness combined with slowness of movements. The most prevalent variant in the Netherlands is the c.1222C > T p.

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  • AJAP1 is a protein linked to brain diseases and is found in neurons, specifically in dendrites, where it plays a role in recruiting GABA type B receptors (GBRs) to presynaptic sites.
  • Several genetic variants of AJAP1, including the p.(W183C), have been associated with epilepsy and neurodevelopmental disorders, particularly affecting its ability to bind GBRs.
  • Mice lacking functional AJAP1 showed decreased levels of presynaptic GBRs, leading to impaired synaptic inhibition and plasticity, highlighting the importance of AJAP1 in regulating neurotransmitter release.
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Background: Monoallelic, pathogenic STUB1 variants cause autosomal dominant cerebellar ataxia (ATX-STUB1/SCA48). Recently, a genetic interaction between STUB1 variants and intermediate or high-normal CAG/CAA repeats in TBP was suggested, indicating digenic inheritance or a disease-modifying role for TBP expansions.

Objective: To determine the presence and impact of intermediate or high-normal TBP expansions in ataxic patients with heterozygous STUB1 variants.

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Short tandem repeat (STR) expansions are associated with more than 60 genetic disorders. The size and stability of these expansions correlate with the severity and age of onset of the disease. Therefore, being able to accurately detect the absolute length of STRs is important.

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Intracellular trafficking involves an intricate machinery of motor complexes including the dynein complex to shuttle cargo for autophagolysosomal degradation. Deficiency in dynein axonemal chains as well as cytoplasmic light and intermediate chains have been linked with ciliary dyskinesia and skeletal dysplasia. The cytoplasmic dynein 1 heavy chain protein (DYNC1H1) serves as a core complex for retrograde trafficking in neuronal axons.

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Article Synopsis
  • Maternal cell contamination (MCC) can mislead prenatal genetic tests, and its impact is less recognized in tests using umbilical cord (CB) blood and samples.
  • A study analyzed samples from 1995 to 2021 and found a 4% MCC rate in umbilical CB samples while only one case was noted in cord samples, highlighting risks with sensitive tests that can yield false positives.
  • The research suggests that while umbilical samples can be safely used for genetic testing, routine MCC testing is crucial for both healthcare providers and genetic labs to avoid misdiagnosis.
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In digenic inheritance, pathogenic variants in two genes must be inherited together to cause disease. Only very few examples of digenic inheritance have been described in the neuromuscular disease field. Here we show that predicted deleterious variants in SRPK3, encoding the X-linked serine/argenine protein kinase 3, lead to a progressive early onset skeletal muscle myopathy only when in combination with heterozygous variants in the TTN gene.

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Brody disease is a rare autosomal recessive myopathy, caused by pathogenic variants in the gene. It is characterized by an exercise-induced delay in muscle relaxation, often reported as muscle stiffness. Children may manifest with an abnormal gait and difficulty running.

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Article Synopsis
  • Genetic laboratories currently use diverse workflows to diagnose hereditary and congenital diseases, and this study assesses the potential of genome sequencing (GS) to streamline these processes.
  • The researchers tested GS on 1,000 cases with known genetic variants to evaluate its effectiveness compared to existing methods, finding that GS detected 95% of variants across different categories.
  • The results suggest that adopting a GS-first approach could replace multiple workflows in around 85% of clinical cases, allowing for more efficient and comprehensive diagnostics for rare genetic diseases.
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  • Rapid exome sequencing (rES) is becoming the go-to genetic test for critically ill patients, especially neonates and young infants, helping quickly identify genetic causes of rare diseases to guide treatment.
  • A study evaluated rES on 575 patients over four years, revealing a significant increase in referrals and a decrease in turnaround time for results, with an overall diagnostic yield of 30.4%.
  • Even when no genetic diagnosis was found, rES still influenced clinical decision-making, highlighting its value for patients of all ages and various rare conditions.
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  • Short-read sequencing can struggle to analyze duplicated genomic regions, making it hard to identify many genetic variants in standard studies.
  • The new method, Chameleolyser, improves the identification of single nucleotide variants, small insertions/deletions, and other genetic events in these complex regions using whole-exome sequencing data.
  • In testing with 41,755 exome samples, the method discovered over 2.5 million rare variants and validated a significant percentage of them, providing molecular diagnoses for several previously undiagnosed patients.
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  • * The study evaluated six MEI detection tools (ERVcaller, MELT, Mobster, SCRAMble, TEMP2, and xTea) using both ES and genome sequencing (GS) data to assess their performance.
  • * MELT was the most effective tool for ES data, and when combined with SCRAMble, it significantly increased MEI detection, resulting in diagnoses for patients who had previously gone undiagnosed.
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Article Synopsis
  • - SELENON-related myopathy (SELENON-RM) is a rare genetic condition causing issues like muscle weakness, spinal stiffness, and respiratory problems, with no treatment options available yet, prompting ongoing research.
  • - An observational study in the Netherlands assessed 11 genetically confirmed SELENON-RM patients focusing on clinical symptoms, functional capabilities, and quality of life through various tests and questionnaires.
  • - Findings highlighted severe muscle weakness, impaired respiratory function, and complications like decreased bone density and cardiac strain, indicating significant health challenges for these patients.
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Background And Objectives: -related muscular dystrophy (-MD) is a rare neuromuscular disease characterized by proximal and axial muscle weakness, rigidity of the spine, scoliosis, and respiratory impairment. No curative treatment options exist, yet promising preclinical studies are ongoing. Currently, there is a paucity on natural history data, and appropriate clinical and functional outcome measures are needed.

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Ionic calcium (Ca) is a key messenger in signal transduction and its mitochondrial uptake plays an important role in cell physiology. This uptake is mediated by the mitochondrial Ca uniporter (MCU), which is regulated by EMRE (essential MCU regulator) encoded by the SMDT1 (single-pass membrane protein with aspartate rich tail 1) gene. This work presents the genetic, clinical and cellular characterization of two patients harbouring SMDT1 variants and presenting with muscle problems.

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A five-year-old girl presented with headache attacks, clumsiness, and a history of transient gait disturbances. She and her father, mother, twin sister, and brother underwent neurological evaluation, neuroimaging, and exome sequencing covering 357 genes associated with movement disorders. Sequencing revealed the new variant c.

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Centronuclear myopathy (CNM) is a heterogeneous group of muscle disorders primarily characterized by muscle weakness and variable degrees of respiratory dysfunction caused by mutations in MTM1, DNM2, RYR1, TTN and BIN1. X-linked myotubular myopathy has been the focus of recent natural history studies and clinical trials. Data on respiratory function for other genotypes is limited.

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