Publications by authors named "Nicole De Leeuw"

Pathogenic SOX11 variants have been associated with intellectual developmental disorder with microcephaly, and with or without ocular malformations or hypogonadotropic hypogonadism (HH) (IDDMOH, OMIM # 615866). In this article, we report seven new patients with de novo SOX11 variants. Five of the variants are missense, one nonsense, and one whole-gene deletion, most of them are novel variants.

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Background: Current guidelines indicate that patients with extreme oligozoospermia or azoospermia should be tested for chromosomal imbalances, azoospermia factor (AZF) deletions and/or CFTR variants. For other sperm abnormalities, no genetic diagnostics are recommended.

Objectives: To determine whether exome sequencing (ES) with combined copy number variant (CNV) and single nucleotide variant (SNV) analysis is a reliable first-tier method to replace current methods (validation study), and to evaluate the diagnostic yield after 10 months of implementation (evaluation study).

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The shift to a genotype-first approach in genetic diagnostics has revolutionized our understanding of neurodevelopmental disorders, expanding both their molecular and phenotypic spectra. Kleefstra syndrome (KLEFS1) is caused by EHMT1 haploinsufficiency and exhibits broad clinical manifestations. EHMT1 encodes euchromatic histone methyltransferase-1-a pivotal component of the epigenetic machinery.

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Article Synopsis
  • The study highlights the lack of understanding regarding comorbidities in individuals with neurodevelopmental disorders (NDDs), which are crucial for accurate diagnosis and prognosis.
  • PhenomAD-NDD is a newly developed database that compiles comorbid phenotypic data from over 51,000 individuals with NDD, utilizing a standardized classification known as Human Phenotype Ontology (HPO).
  • The findings reveal that congenital anomalies are significantly more common in the NDD population compared to the general population, and highlight that many important phenotypes related to genetic NDDs are not currently documented in existing clinical resources like OMIM.
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  • 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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Fetal hydrops as detected by prenatal ultrasound usually carries a poor prognosis depending on the underlying aetiology. We describe the prenatal and postnatal clinical course of two unrelated female probands in whom heterozygous missense variants in the planar cell polarity gene were detected using exome sequencing. Using several in vitro assays, we show that the p.

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Article Synopsis
  • 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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Objective: The chromosome region 22q11.2 is highly susceptible to genomic rearrangements. It has become clear that genomic instability extends distally to the commonly deleted/duplicated region (Low Copy Repeats [LCR] A-D) and that a clear difference exists between the phenotypic presentation of patients with rearrangements in the common region versus that in the distal region (LCR D-H), particularly with respect to developmental and somatic issues.

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Article Synopsis
  • - PhenoScore is an open-source AI framework that combines facial recognition technology and Human Phenotype Ontology data to analyze and quantify phenotypic similarities in individuals.
  • - It successfully identifies distinct phenotypes for most of the 40 syndromes studied and proves to be more effective than previous methods in genotype-phenotype correlation investigations.
  • - PhenoScore also helps clarify roles of specific genetic variants by confirming known phenotypic subgroups in certain genes and providing clinical evidence for different ADNP-related phenotypes.
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Intellectual disability (ID) and multiple congenital anomalies (MCA) are major contributors to infant mortality, childhood morbidity, and long-term disability, with multifactorial aetiology including genetics. We aim to set a diagnostic approach for genetic evaluation of patients with ID and MCA, which can be applied efficiently with a good diagnostic rate in Indonesia or other low resources settings. Out of 131 ID cases, twenty-three individuals with ID/global developmental delay (GDD) and MCA were selected from two-steps of dysmorphology screening and evaluation.

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Split-hand/foot malformation (SHFM) is a congenital limb defect most typically presenting with median clefts in hands and/or feet, that can occur in a syndromic context as well as in isolated form. SHFM is caused by failure to maintain normal apical ectodermal ridge function during limb development. Although several genes and contiguous gene syndromes are implicated in the monogenic etiology of isolated SHFM, the disorder remains genetically unexplained for many families and associated genetic loci.

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  • The study investigates the role of the PRRX1 gene in craniosynostosis, focusing on how certain variants (missense and loss-of-function) affect craniofacial development, with previous research linking PRRX1 to preosteogenic cells in cranial sutures.
  • Researchers used sequencing methods to identify rare variants in PRRX1 among patients suffering from craniosynostosis, discovering a total of 18 individuals with potential pathogenic variants and noting abnormal behavior of mutant proteins through immunofluorescence analyses.
  • The findings highlight that PRRX1 plays a significant role in cranial suture development, and the presence of pathogenic variants is frequently inherited from non-affected relatives,
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Various groups of neurological disorders, including movement disorders and neuromuscular diseases, are clinically and genetically heterogeneous. Diagnostic panel-based exome sequencing is a routine test for these disorders. Despite the success rates of exome sequencing, it results in the detection of causative sequence variants in 'only' 25-30% of cases.

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Objective: We performed a 1-year evaluation of a novel strategy of simultaneously analyzing single nucleotide variants (SNVs), copy number variants (CNVs) and copy-number-neutral Absence-of-Heterozygosity from Whole Exome Sequencing (WES) data for prenatal diagnosis of fetuses with ultrasound (US) anomalies and a non-causative QF-PCR result.

Methods: After invasive diagnostics, whole exome parent-offspring trio-sequencing with exome-wide CNV analysis was performed in pregnancies with fetal US anomalies and a non-causative QF-PCR result (WES-CNV). On request, additional SNV-analysis, restricted to (the) requested gene panel(s) only (with the option of whole exome SNV-analysis afterward) was performed simultaneously (WES-CNV/SNV) or as rapid SNV-re-analysis, following a normal CNV analysis.

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The widespread use of whole exome sequencing (WES) resulted in the discovery of multilocus pathogenic variations (MPV), defined as two or more distinct or overlapping Mendelian disorders occurring in a patient, leading to a blended phenotype. In this study, we report on a child with autosomal recessive primary microcephaly-5 (MCPH5) and nephropathic cystinosis. The proband is the first child of consanguineous parents, presenting a complex phenotype including neurodevelopmental delay, microcephaly, growth restriction, significant delay of bone maturation, lissencephaly, and abnormality of neuronal migration, photophobia, and renal tubular acidosis.

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Genome sequencing (GS) can identify novel diagnoses for patients who remain undiagnosed after routine diagnostic procedures. We tested whether GS is a better first-tier genetic diagnostic test than current standard of care (SOC) by assessing the technical and clinical validity of GS for patients with neurodevelopmental disorders (NDD). We performed both GS and exome sequencing in 150 consecutive NDD patient-parent trios.

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Article Synopsis
  • The TBC1D2B gene has been identified as a cause of a specific neurodevelopmental disorder that includes symptoms like seizures and enlarged gums.
  • Two male siblings exhibited similar symptoms starting with gum overgrowth and soft tissue growth at age 3, later developing severe facial bone issues and neurological symptoms like mental decline and tremors.
  • Genetic testing revealed a new harmful variant of the TBC1D2B gene in both siblings, with parents carrying a single copy, further confirming the link between this gene and their rare condition.
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Introduction: The diagnosis of Ehlers-Danlos syndrome is usually based on well-defined diagnostic criteria and the result of DNA investigation. Classical (cEDS) and vascular type (vEDS) are the most prevalent subtypes and are caused by heterozygous pathogenic variants in COL5A1, COL5A2, COL1A1 or, respectively, in COL3A1. We describe 3 cases with contiguous deletions resulting in haploinsufficiency of both genes with relative mild features of connective tissue disease.

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Isolated aldosterone synthase deficiency is a rare autosomal recessive disorder caused by pathogenic variants in , resulting in impaired aldosterone synthesis. We report on a neonate with isolated aldosterone synthase deficiency caused by a novel homozygous variant Chr8:NM_000498.3:c.

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In 2016, guidelines for diagnostic Next Generation Sequencing (NGS) have been published by EuroGentest in order to assist laboratories in the implementation and accreditation of NGS in a diagnostic setting. These guidelines mainly focused on Whole Exome Sequencing (WES) and targeted (gene panels) sequencing detecting small germline variants (Single Nucleotide Variants (SNVs) and insertions/deletions (indels)). Since then, Whole Genome Sequencing (WGS) has been increasingly introduced in the diagnosis of rare diseases as WGS allows the simultaneous detection of SNVs, Structural Variants (SVs) and other types of variants such as repeat expansions.

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  • Intellectual Disability (ID) is a complex neurodevelopmental disorder affecting about 3% of children globally, with genetic causes being identified through advanced techniques like exome sequencing.
  • This study in Central Brazil analyzed 369 patients using karyotype, CMA, and exome sequencing to improve diagnosis rates for ID and related conditions, yielding a significant diagnostic success.
  • The combined methodologies allowed the researchers to determine genetic causes in 42.3% of patients, demonstrating that exome sequencing can effectively diagnose ID when used alongside other screening tests.
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  • LRFN5 is critical for synaptic development and is located in a unique genomic area linked to autism and developmental delay; its specific structural changes suggest a connection to autism susceptibility, especially in males.
  • Research indicates that a specific LRFN5 haplotype inherited from mothers is associated with autism in distant relatives, highlighting potential genetic factors contributing to this disorder.
  • An unexpected lower prevalence of a 60 kb deletion polymorphism in individuals with developmental delay suggests complex allelic interactions affecting LRFN5 regulation, which may be an epigenetic factor in the increased prevalence of autism in males.
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Purpose: Although the introduction of exome sequencing (ES) has led to the diagnosis of a significant portion of patients with neurodevelopmental disorders (NDDs), the diagnostic yield in actual clinical practice has remained stable at approximately 30%. We hypothesized that improving the selection of patients to test on the basis of their phenotypic presentation will increase diagnostic yield and therefore reduce unnecessary genetic testing.

Methods: We tested 4 machine learning methods and developed PredWES from these: a statistical model predicting the probability of a positive ES result solely on the basis of the phenotype of the patient.

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