Publications by authors named "Marleen E H Simon"

20 Publications

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Rare deleterious mutations of HNRNP genes result in shared neurodevelopmental disorders.

Authors:
Madelyn A Gillentine Tianyun Wang Kendra Hoekzema Jill Rosenfeld Pengfei Liu Hui Guo Chang N Kim Bert B A De Vries Lisenka E L M Vissers Magnus Nordenskjold Malin Kvarnung Anna Lindstrand Ann Nordgren Jozef Gecz Maria Iascone Anna Cereda Agnese Scatigno Silvia Maitz Ginevra Zanni Enrico Bertini Christiane Zweier Sarah Schuhmann Antje Wiesener Micah Pepper Heena Panjwani Erin Torti Farida Abid Irina Anselm Siddharth Srivastava Paldeep Atwal Carlos A Bacino Gifty Bhat Katherine Cobian Lynne M Bird Jennifer Friedman Meredith S Wright Bert Callewaert Florence Petit Sophie Mathieu Alexandra Afenjar Celenie K Christensen Kerry M White Orly Elpeleg Itai Berger Edward J Espineli Christina Fagerberg Charlotte Brasch-Andersen Lars Kjærsgaard Hansen Timothy Feyma Susan Hughes Isabelle Thiffault Bonnie Sullivan Shuang Yan Kory Keller Boris Keren Cyril Mignot Frank Kooy Marije Meuwissen Alice Basinger Mary Kukolich Meredith Philips Lucia Ortega Margaret Drummond-Borg Mathilde Lauridsen Kristina Sorensen Anna Lehman Elena Lopez-Rangel Paul Levy Davor Lessel Timothy Lotze Suneeta Madan-Khetarpal Jessica Sebastian Jodie Vento Divya Vats L Manace Benman Shane Mckee Ghayda M Mirzaa Candace Muss John Pappas Hilde Peeters Corrado Romano Maurizio Elia Ornella Galesi Marleen E H Simon Koen L I van Gassen Kara Simpson Robert Stratton Sabeen Syed Julien Thevenon Irene Valenzuela Palafoll Antonio Vitobello Marie Bournez Laurence Faivre Kun Xia Rachel K Earl Tomasz Nowakowski Raphael A Bernier Evan E Eichler

Genome Med 2021 Apr 19;13(1):63. Epub 2021 Apr 19.

Department of Genome Sciences, University of Washington School of Medicine, 3720 15th Ave NE S413A, Box 355065, Seattle, WA, 981095-5065, USA.

Background: With the increasing number of genomic sequencing studies, hundreds of genes have been implicated in neurodevelopmental disorders (NDDs). The rate of gene discovery far outpaces our understanding of genotype-phenotype correlations, with clinical characterization remaining a bottleneck for understanding NDDs. Most disease-associated Mendelian genes are members of gene families, and we hypothesize that those with related molecular function share clinical presentations.

Methods: We tested our hypothesis by considering gene families that have multiple members with an enrichment of de novo variants among NDDs, as determined by previous meta-analyses. One of these gene families is the heterogeneous nuclear ribonucleoproteins (hnRNPs), which has 33 members, five of which have been recently identified as NDD genes (HNRNPK, HNRNPU, HNRNPH1, HNRNPH2, and HNRNPR) and two of which have significant enrichment in our previous meta-analysis of probands with NDDs (HNRNPU and SYNCRIP). Utilizing protein homology, mutation analyses, gene expression analyses, and phenotypic characterization, we provide evidence for variation in 12 HNRNP genes as candidates for NDDs. Seven are potentially novel while the remaining genes in the family likely do not significantly contribute to NDD risk.

Results: We report 119 new NDD cases (64 de novo variants) through sequencing and international collaborations and combined with published clinical case reports. We consider 235 cases with gene-disruptive single-nucleotide variants or indels and 15 cases with small copy number variants. Three hnRNP-encoding genes reach nominal or exome-wide significance for de novo variant enrichment, while nine are candidates for pathogenic mutations. Comparison of HNRNP gene expression shows a pattern consistent with a role in cerebral cortical development with enriched expression among radial glial progenitors. Clinical assessment of probands (n = 188-221) expands the phenotypes associated with HNRNP rare variants, and phenotypes associated with variation in the HNRNP genes distinguishes them as a subgroup of NDDs.

Conclusions: Overall, our novel approach of exploiting gene families in NDDs identifies new HNRNP-related disorders, expands the phenotypes of known HNRNP-related disorders, strongly implicates disruption of the hnRNPs as a whole in NDDs, and supports that NDD subtypes likely have shared molecular pathogenesis. To date, this is the first study to identify novel genetic disorders based on the presence of disorders in related genes. We also perform the first phenotypic analyses focusing on related genes. Finally, we show that radial glial expression of these genes is likely critical during neurodevelopment. This is important for diagnostics, as well as developing strategies to best study these genes for the development of therapeutics.
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http://dx.doi.org/10.1186/s13073-021-00870-6DOI Listing
April 2021

Disruption of RFX family transcription factors causes autism, attention-deficit/hyperactivity disorder, intellectual disability, and dysregulated behavior.

Genet Med 2021 Mar 3. Epub 2021 Mar 3.

Division of Genetics and Genomics, Department of Pediatrics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA.

Purpose: We describe a novel neurobehavioral phenotype of autism spectrum disorder (ASD), intellectual disability, and/or attention-deficit/hyperactivity disorder (ADHD) associated with de novo or inherited deleterious variants in members of the RFX family of genes. RFX genes are evolutionarily conserved transcription factors that act as master regulators of central nervous system development and ciliogenesis.

Methods: We assembled a cohort of 38 individuals (from 33 unrelated families) with de novo variants in RFX3, RFX4, and RFX7. We describe their common clinical phenotypes and present bioinformatic analyses of expression patterns and downstream targets of these genes as they relate to other neurodevelopmental risk genes.

Results: These individuals share neurobehavioral features including ASD, intellectual disability, and/or ADHD; other frequent features include hypersensitivity to sensory stimuli and sleep problems. RFX3, RFX4, and RFX7 are strongly expressed in developing and adult human brain, and X-box binding motifs as well as RFX ChIP-seq peaks are enriched in the cis-regulatory regions of known ASD risk genes.

Conclusion: These results establish a likely role of deleterious variation in RFX3, RFX4, and RFX7 in cases of monogenic intellectual disability, ADHD and ASD, and position these genes as potentially critical transcriptional regulators of neurobiological pathways associated with neurodevelopmental disease pathogenesis.
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http://dx.doi.org/10.1038/s41436-021-01114-zDOI Listing
March 2021

Syndromic disorders caused by gain-of-function variants in KCNH1, KCNK4, and KCNN3-a subgroup of K channelopathies.

Eur J Hum Genet 2021 Feb 16. Epub 2021 Feb 16.

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Decreased or increased activity of potassium channels caused by loss-of-function and gain-of-function (GOF) variants in the corresponding genes, respectively, underlies a broad spectrum of human disorders affecting the central nervous system, heart, kidney, and other organs. While the association of epilepsy and intellectual disability (ID) with variants affecting function in genes encoding potassium channels is well known, GOF missense variants in K channel encoding genes in individuals with syndromic developmental disorders have only recently been recognized. These syndromic phenotypes include Zimmermann-Laband and Temple-Baraitser syndromes, caused by dominant variants in KCNH1, FHEIG syndrome due to dominant variants in KCNK4, and the clinical picture associated with dominant variants in KCNN3. Here we review the presentation of these individuals, including five newly reported with variants in KCNH1 and three additional individuals with KCNN3 variants, all variants likely affecting function. There is notable overlap in the phenotypic findings of these syndromes associated with dominant KCNN3, KCNH1, and KCNK4 variants, sharing developmental delay and/or ID, coarse facial features, gingival enlargement, distal digital hypoplasia, and hypertrichosis. We suggest to combine the phenotypes and define a new subgroup of potassium channelopathies caused by increased K conductance, referred to as syndromic neurodevelopmental K channelopathies due to dominant variants in KCNH1, KCNK4, or KCNN3.
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http://dx.doi.org/10.1038/s41431-021-00818-9DOI Listing
February 2021

Collodion babies: A 15-year retrospective multicenter study in The Netherlands-Evaluation of severity scores to predict the underlying disease.

J Am Acad Dermatol 2021 Apr 12;84(4):1111-1113. Epub 2020 Jun 12.

Department of Dermatology, Erasmus MC Medical Center-Sophia Children's Hospital, Rotterdam, The Netherlands. Electronic address:

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http://dx.doi.org/10.1016/j.jaad.2020.06.021DOI Listing
April 2021

Characterization of SETD1A haploinsufficiency in humans and Drosophila defines a novel neurodevelopmental syndrome.

Mol Psychiatry 2020 Apr 28. Epub 2020 Apr 28.

Department of Human Genetics, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.

Defects in histone methyltransferases (HMTs) are major contributing factors in neurodevelopmental disorders (NDDs). Heterozygous variants of SETD1A involved in histone H3 lysine 4 (H3K4) methylation were previously identified in individuals with schizophrenia. Here, we define the clinical features of the Mendelian syndrome associated with haploinsufficiency of SETD1A by investigating 15 predominantly pediatric individuals who all have de novo SETD1A variants. These individuals present with a core set of symptoms comprising global developmental delay and/or intellectual disability, subtle facial dysmorphisms, behavioral and psychiatric problems. We examined cellular phenotypes in three patient-derived lymphoblastoid cell lines with three variants: p.Gly535Alafs*12, c.4582-2_4582delAG, and p.Tyr1499Asp. These patient cell lines displayed DNA damage repair defects that were comparable to previously observed RNAi-mediated depletion of SETD1A. This suggested that these variants, including the p.Tyr1499Asp in the catalytic SET domain, behave as loss-of-function (LoF) alleles. Previous studies demonstrated a role for SETD1A in cell cycle control and differentiation. However, individuals with SETD1A variants do not show major structural brain defects or severe microcephaly, suggesting that defective proliferation and differentiation of neural progenitors is unlikely the single underlying cause of the disorder. We show here that the Drosophila melanogaster SETD1A orthologue is required in postmitotic neurons of the fly brain for normal memory, suggesting a role in post development neuronal function. Together, this study defines a neurodevelopmental disorder caused by dominant de novo LoF variants in SETD1A and further supports a role for H3K4 methyltransferases in the regulation of neuronal processes underlying normal cognitive functioning.
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http://dx.doi.org/10.1038/s41380-020-0725-5DOI Listing
April 2020

De novo and inherited variants in ZNF292 underlie a neurodevelopmental disorder with features of autism spectrum disorder.

Genet Med 2020 03 14;22(3):538-546. Epub 2019 Nov 14.

Division of Genetic Medicine, Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, USA.

Purpose: Intellectual disability (ID) and autism spectrum disorder (ASD) are genetically heterogeneous neurodevelopmental disorders. We sought to delineate the clinical, molecular, and neuroimaging spectrum of a novel neurodevelopmental disorder caused by variants in the zinc finger protein 292 gene (ZNF292).

Methods: We ascertained a cohort of 28 families with ID due to putatively pathogenic ZNF292 variants that were identified via targeted and exome sequencing. Available data were analyzed to characterize the canonical phenotype and examine genotype-phenotype relationships.

Results: Probands presented with ID as well as a spectrum of neurodevelopmental features including ASD, among others. All ZNF292 variants were de novo, except in one family with dominant inheritance. ZNF292 encodes a highly conserved zinc finger protein that acts as a transcription factor and is highly expressed in the developing human brain supporting its critical role in neurodevelopment.

Conclusion: De novo and dominantly inherited variants in ZNF292 are associated with a range of neurodevelopmental features including ID and ASD. The clinical spectrum is broad, and most individuals present with mild to moderate ID with or without other syndromic features. Our results suggest that variants in ZNF292 are likely a recurrent cause of a neurodevelopmental disorder manifesting as ID with or without ASD.
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http://dx.doi.org/10.1038/s41436-019-0693-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7060121PMC
March 2020

Deficiency of the human cysteine protease inhibitor cystatin M/E causes hypotrichosis and dry skin.

Genet Med 2019 07 14;21(7):1559-1567. Epub 2018 Nov 14.

Department of Dermatology, Radboud Institute for Molecular Life Sciences (RIMLS), Radboud University Nijmegen Medical Center (Radboudumc), Nijmegen, The Netherlands.

Purpose: We aimed to assess the biological and clinical significance of the human cysteine protease inhibitor cystatin M/E, encoded by the CTS6 gene, in diseases of human hair and skin.

Methods: Exome and Sanger sequencing was performed to reveal the genetic cause in two related patients with hypotrichosis. Immunohistochemical, biophysical, and biochemical measurements were performed on patient skin and 3D-reconstructed skin from patient-derived keratinocytes.

Results: We identified a homozygous variant c.361C>T (p.Gln121*), resulting in a premature stop codon in exon 2 of CST6 associated with hypotrichosis, eczema, blepharitis, photophobia and impaired sweating. Enzyme assays using recombinant mutant cystatin M/E protein, generated by site-directed mutagenesis, revealed that this p.Gln121* variant was unable to inhibit any of its three target proteases (legumain and cathepsins L and V). Three-dimensional protein structure prediction confirmed the disturbance of the protease/inhibitor binding sites of legumain and cathepsins L and V in the p.Gln121* variant.

Conclusion: The herein characterized autosomal recessive hypotrichosis syndrome indicates an important role of human cystatin M/E in epidermal homeostasis and hair follicle morphogenesis.
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http://dx.doi.org/10.1038/s41436-018-0355-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752276PMC
July 2019

Correction: IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 Aug;21(8):1897-1898

INSERM, U 1127, CNRS UMR 7225, Sorbonne Universites, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle epiniere, ICM, Paris, France.

This Article was originally published under Nature Research's License to Publish, but has now been made available under a CC BY 4.0 license. The PDF and HTML versions of the Article have been modified accordingly.
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http://dx.doi.org/10.1038/s41436-018-0327-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608434PMC
August 2019

IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 04 12;21(4):837-849. Epub 2018 Sep 12.

INSERM, U 1127, CNRS UMR 7225, Sorbonne Universites, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle epiniere, ICM, Paris, France.

Purpose: Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences.

Methods: We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms.

Results: IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments.

Conclusion: This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.
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http://dx.doi.org/10.1038/s41436-018-0268-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752297PMC
April 2019

Integrating glycomics and genomics uncovers SLC10A7 as essential factor for bone mineralization by regulating post-Golgi protein transport and glycosylation.

Hum Mol Genet 2018 09;27(17):3029-3045

Department of Child Health, University Hospital of Wales, Cardiff, UK.

Genomics methodologies have significantly improved elucidation of Mendelian disorders. The combination with high-throughput functional-omics technologies potentiates the identification and confirmation of causative genetic variants, especially in singleton families of recessive inheritance. In a cohort of 99 individuals with abnormal Golgi glycosylation, 47 of which being unsolved, glycomics profiling was performed of total plasma glycoproteins. Combination with whole-exome sequencing in 31 cases revealed a known genetic defect in 15 individuals. To identify additional genetic factors, hierarchical clustering of the plasma glycomics data was done, which indicated a subgroup of four patients that shared a unique glycomics signature of hybrid type N-glycans. In two siblings, compound heterozygous mutations were found in SLC10A7, a gene of unknown function in human. These included a missense mutation that disrupted transmembrane domain 4 and a mutation in a splice acceptor site resulting in skipping of exon 9. The two other individuals showed a complete loss of SLC10A7 mRNA. The patients' phenotype consisted of amelogenesis imperfecta, skeletal dysplasia, and decreased bone mineral density compatible with osteoporosis. The patients' phenotype was mirrored in SLC10A7 deficient zebrafish. Furthermore, alizarin red staining of calcium deposits in zebrafish morphants showed a strong reduction in bone mineralization. Cell biology studies in fibroblasts of affected individuals showed intracellular mislocalization of glycoproteins and a defect in post-Golgi transport of glycoproteins to the cell membrane. In contrast to yeast, human SLC10A7 localized to the Golgi. Our combined data indicate an important role for SLC10A7 in bone mineralization and transport of glycoproteins to the extracellular matrix.
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http://dx.doi.org/10.1093/hmg/ddy213DOI Listing
September 2018

De novo mutations in MED13, a component of the Mediator complex, are associated with a novel neurodevelopmental disorder.

Hum Genet 2018 May 8;137(5):375-388. Epub 2018 May 8.

HudsonAlpha Institute for Biotechnology, 601 Genome Way, Huntsville, AL, 35806, USA.

Many genetic causes of developmental delay and/or intellectual disability (DD/ID) are extremely rare, and robust discovery of these requires both large-scale DNA sequencing and data sharing. Here we describe a GeneMatcher collaboration which led to a cohort of 13 affected individuals harboring protein-altering variants, 11 of which are de novo, in MED13; the only inherited variant was transmitted to an affected child from an affected mother. All patients had intellectual disability and/or developmental delays, including speech delays or disorders. Other features that were reported in two or more patients include autism spectrum disorder, attention deficit hyperactivity disorder, optic nerve abnormalities, Duane anomaly, hypotonia, mild congenital heart abnormalities, and dysmorphisms. Six affected individuals had mutations that are predicted to truncate the MED13 protein, six had missense mutations, and one had an in-frame-deletion of one amino acid. Out of the seven non-truncating mutations, six clustered in two specific locations of the MED13 protein: an N-terminal and C-terminal region. The four N-terminal clustering mutations affect two adjacent amino acids that are known to be involved in MED13 ubiquitination and degradation, p.Thr326 and p.Pro327. MED13 is a component of the CDK8-kinase module that can reversibly bind Mediator, a multi-protein complex that is required for Polymerase II transcription initiation. Mutations in several other genes encoding subunits of Mediator have been previously shown to associate with DD/ID, including MED13L, a paralog of MED13. Thus, our findings add MED13 to the group of CDK8-kinase module-associated disease genes.
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http://dx.doi.org/10.1007/s00439-018-1887-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5973976PMC
May 2018

De Novo Mutations in YWHAG Cause Early-Onset Epilepsy.

Am J Hum Genet 2017 Aug;101(2):300-310

Centre for Applied Neurogenetics, University of British Columbia, Vancouver, BC V5R 6H8, Canada. Electronic address:

Massively parallel sequencing has revealed many de novo mutations in the etiology of developmental and epileptic encephalopathies (EEs), highlighting their genetic heterogeneity. Additional candidate genes have been prioritized in silico by their co-expression in the brain. Here, we evaluate rare coding variability in 20 candidates nominated with the use of a reference gene set of 51 established EE-associated genes. Variants within the 20 candidate genes were extracted from exome-sequencing data of 42 subjects with EE and no previous genetic diagnosis. We identified 7 rare non-synonymous variants in 7 of 20 genes and performed Sanger sequence validation in affected probands and parental samples. De novo variants were found only in SLC1A2 (aka EAAT2 or GLT1) (c.244G>A [p.Gly82Arg]) and YWHAG (aka 14-3-3γ) (c.394C>T [p.Arg132Cys]), highlighting the potential cause of EE in 5% (2/42) of subjects. Seven additional subjects with de novo variants in SLC1A2 (n = 1) and YWHAG (n = 6) were subsequently identified through online tools. We identified a highly significant enrichment of de novo variants in YWHAG, establishing their role in early-onset epilepsy, and we provide additional support for the prior assignment of SLC1A2. Hence, in silico modeling of brain co-expression is an efficient method for nominating EE-associated genes to further elucidate the disorder's etiology and genotype-phenotype correlations.
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http://dx.doi.org/10.1016/j.ajhg.2017.07.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5544417PMC
August 2017

A study of the clinical and radiological features in a cohort of 93 patients with a COL2A1 mutation causing spondyloepiphyseal dysplasia congenita or a related phenotype.

Am J Med Genet A 2015 Mar 21;167A(3):461-75. Epub 2015 Jan 21.

Department of Medical Genetics, University Medical Centre Utrecht, Utrecht, The Netherlands.

Type 2 collagen disorders encompass a diverse group of skeletal dysplasias that are commonly associated with orthopedic, ocular, and hearing problems. However, the frequency of many clinical features has never been determined. We retrospectively investigated the clinical, radiological, and genotypic data in a group of 93 patients with molecularly confirmed SEDC or a related disorder. The majority of the patients (80/93) had short stature, with radiological features of SEDC (n = 64), others having SEMD (n = 5), Kniest dysplasia (n = 7), spondyloperipheral dysplasia (n = 2), or Torrance-like dysplasia (n = 2). The remaining 13 patients had normal stature with mild SED, Stickler-like syndrome or multiple epiphyseal dysplasia. Over 50% of the patients had undergone orthopedic surgery, usually for scoliosis, femoral osteotomy or hip replacement. Odontoid hypoplasia was present in 56% (95% CI 38-74) and a correlation between odontoid hypoplasia and short stature was observed. Atlanto-axial instability, was observed in 5 of the 18 patients (28%, 95% CI 10-54) in whom flexion-extension films of the cervical spine were available; however, it was rarely accompanied by myelopathy. Myopia was found in 45% (95% CI 35-56), and retinal detachment had occurred in 12% (95% CI 6-21; median age 14 years; youngest age 3.5 years). Thirty-two patients complained of hearing loss (37%, 95% CI 27-48) of whom 17 required hearing aids. The ophthalmological features and possibly also hearing loss are often relatively frequent and severe in patients with splicing mutations. Based on clinical findings, age at onset and genotype-phenotype correlations in this cohort, we propose guidelines for the management and follow-up in this group of disorders.
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http://dx.doi.org/10.1002/ajmg.a.36922DOI Listing
March 2015

Osteoporotic vertebral fractures during pregnancy: be aware of a potential underlying genetic cause.

J Clin Endocrinol Metab 2014 Apr 13;99(4):1107-11. Epub 2014 Jan 13.

Department of Internal Medicine (N.C.-O., L.O., M.C.Z.), Erasmus MC, 3015 CE Rotterdam, The Netherlands; Department of Human Genetics (L.H.H.), Radboud Medical Center, 6500 HC Nijmegen, The Netherlands; Department of Internal Medicine (R.M.K.), Albert Schweitzer Hospital, 3318 AT Dordrecht, The Netherlands; and Departments of Ophthalmology (C.C.W.K.) and Clinical Genetics (M.E.H.S.), Erasmus MC, 3015 CE Rotterdam, The Netherlands.

Context: Although the baby growing in its mother's womb needs calcium for skeletal development, osteoporosis and fractures very rarely occur during pregnancy.

Case Presentation: A 27-year-old woman in the seventh month of her first pregnancy contracted midthoracic back pain after lifting an object. The pain was attributed to her pregnancy, but it remained postpartum. Her past medical history was uneventful, except for severely reduced vision of her left eye since birth. Family history revealed that her maternal grandmother had postmenopausal osteoporosis and her half-brother had three fractures during childhood after minor trauma. Her height was 1.58 m; she had no blue sclerae or joint hyperlaxity. Laboratory examination including serum calcium, phosphate, alkaline phosphatase, creatinine, β-carboxyterminal cross-linking telopeptide of type I collagen, 25-hydroxyvitamin D, and TSH was normal. Multiple thoracic vertebral fractures were diagnosed on x-ray examination, and dual-energy x-ray absorptiometry scanning showed severe osteoporosis (Z-scores: L2-L4, -5.6 SD; femur neck, -3.9 SD). DNA analyses revealed two compound heterozygous missense mutations in LRP5. The patient's mother carried one of the LRP5 mutations and was diagnosed with osteoporosis. Her half-brother, treated with cabergoline for a microprolactinoma, also had osteoporosis of the lumbar spine on dual-energy x-ray absorptiometry and carried the same LRP5 mutation. The patient was treated with risedronate for 2.5 years. Bone mineral density and back pain improved. She stopped bisphosphonate use 6 months before planning a second pregnancy.

Conclusion: Our patient was diagnosed with osteoporosis pseudoglioma syndrome/familial exudative vitreoretinopathy. Potential underlying genetic causes should be considered in pregnancy-associated osteoporosis with implications for patients and relatives. More studies regarding osteoporosis treatment preceding conception are desirable.
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http://dx.doi.org/10.1210/jc.2013-3238DOI Listing
April 2014

PLS3 mutations in X-linked osteoporosis with fractures.

N Engl J Med 2013 Oct 2;369(16):1529-36. Epub 2013 Oct 2.

Department of Clinical Genetics, VU University Medical Center, Amsterdam, The Netherlands.

Plastin 3 (PLS3), a protein involved in the formation of filamentous actin (F-actin) bundles, appears to be important in human bone health, on the basis of pathogenic variants in PLS3 in five families with X-linked osteoporosis and osteoporotic fractures that we report here. The bone-regulatory properties of PLS3 were supported by in vivo analyses in zebrafish. Furthermore, in an additional five families (described in less detail) referred for diagnosis or ruling out of osteogenesis imperfecta type I, a rare variant (rs140121121) in PLS3 was found. This variant was also associated with a risk of fracture among elderly heterozygous women that was two times as high as that among noncarriers, which indicates that genetic variation in PLS3 is a novel etiologic factor involved in common, multi-factorial osteoporosis.
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http://dx.doi.org/10.1056/NEJMoa1308223DOI Listing
October 2013

The phenotype of Floating-Harbor syndrome: clinical characterization of 52 individuals with mutations in exon 34 of SRCAP.

Orphanet J Rare Dis 2013 Apr 27;8:63. Epub 2013 Apr 27.

Background: Floating-Harbor syndrome (FHS) is a rare condition characterized by short stature, delays in expressive language, and a distinctive facial appearance. Recently, heterozygous truncating mutations in SRCAP were determined to be disease-causing. With the availability of a DNA based confirmatory test, we set forth to define the clinical features of this syndrome.

Methods And Results: Clinical information on fifty-two individuals with SRCAP mutations was collected using standardized questionnaires. Twenty-four males and twenty-eight females were studied with ages ranging from 2 to 52 years. The facial phenotype and expressive language impairments were defining features within the group. Height measurements were typically between minus two and minus four standard deviations, with occipitofrontal circumferences usually within the average range. Thirty-three of the subjects (63%) had at least one major anomaly requiring medical intervention. We did not observe any specific phenotype-genotype correlations.

Conclusions: This large cohort of individuals with molecularly confirmed FHS has allowed us to better delineate the clinical features of this rare but classic genetic syndrome, thereby facilitating the development of management protocols.
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http://dx.doi.org/10.1186/1750-1172-8-63DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659005PMC
April 2013

Mutation-based growth charts for SEDC and other COL2A1 related dysplasias.

Am J Med Genet C Semin Med Genet 2012 Aug 12;160C(3):205-16. Epub 2012 Jul 12.

Department of Biomedical Genetics, University Medical Centre Utrecht, Utrecht, The Netherlands.

From data collected via a large international collaborative study, we have constructed a growth chart for patients with molecularly confirmed congenital spondylo-epiphyseal dysplasia (SEDC) and other COL2A1 related dysplasias. The growth chart is based on longitudinal height measurements of 79 patients with glycine substitutions in the triple-helical domain of COL2A1. In addition, measurements of 27 patients with other molecular defects, such as arginine to cysteine substitutions, splice mutations, and mutations in the C-terminal propeptide have been plotted on the chart. Height of the patients progressively deviate from that of normal children: compared to normal WHO charts, the mean length/height is -2.6 SD at birth, -4.2 SD at 5 years, and -5.8 SD in adulthood. The mean adult height (male and female combined) of patients with glycine substitutions in the triple-helical region is 138.2 cm but there is a large variation. Patients with glycine to cysteine substitutions tend to cluster within the upper part of the chart, while patients with glycine to serine or valine substitutions are situated between +1 SD and -1 SD. Patients with carboxy-terminal glycine substitutions tend to be shorter than patients with amino-terminal substitutions, while patients with splice mutations are relatively tall. However, there are exceptions and specific mutations can have a strong or a relatively mild negative effect on growth. The observation of significant difference in adult height between affected members of the same family indicates that height remains a multifactorial trait even in the presence of a mutation with a strong dominant effect.
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http://dx.doi.org/10.1002/ajmg.c.31332DOI Listing
August 2012

Abnormal facial appearance, body asymmetry, limb deformities, and internal malformations.

Am J Med Genet A 2012 Feb 2;158A(2):292-7. Epub 2011 Dec 2.

Department of Clinical Genetics, Erasmus Medical Center, University Medical Center, Rotterdam, The Netherlands.

We describe a newborn girl with multiple congenital anomalies and abnormal phenotype comprising underdeveloped corpus callosum with ventriculomegaly, chorioretinal atrophy, pulmonary arterial hypertension, annular pancreas, horseshoe kidney, asymmetric limb and chest anomalies, spinal segmentation defects, hypertrichosis, and unusual face with large anterior fontanel, high anterior hairline, broad forehead, mildly underdeveloped midface, hypertelorism, depressed nasal bridge, short and upturned nose, large mouth, retrognathia, and large and malformed ears. Work-up included cytogenetic studies of lymphocytes and skin fibroblasts, subtelomere Multiplex Ligation-dependent Probe Amplification (MLPA), whole-genome oligo-array, and molecular analysis of SETBP1 and NSDHL: no abnormalities were found. Mucopolysaccharide urinary excretion was elevated. Results of metabolic studies for sterol and peroxisomal abnormalities in fibroblasts were normal. Additional electronic microscopy studies in skin fibroblasts did not show evidence for storage in fibroblasts or lysosomal changes. Nosologic considerations allowed exclusion of Schinzel-Giedion and Urioste syndrome. This condition seems not to have been described before; a segregating Mendelian mutation is assumed.
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http://dx.doi.org/10.1002/ajmg.a.34396DOI Listing
February 2012

Deletions of the RUNX2 gene are present in about 10% of individuals with cleidocranial dysplasia.

Hum Mutat 2010 Aug;31(8):E1587-93

Institut für Medizinische Genetik, Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany.

Cleidocranial Dysplasia (CCD) is an autosomal dominant skeletal disorder characterized by hypoplastic or absent clavicles, increased head circumference, large fontanels, dental anomalies, and short stature. Hand malformations are also common. Mutations in RUNX2 cause CCD, but are not identified in all CCD patients. In this study we screened 135 unrelated patients with the clinical diagnosis of CCD for RUNX2 mutations by sequencing analysis and demonstrated 82 mutations 48 of which were novel. By quantitative PCR we screened the remaining 53 unrelated patients for copy number variations in the RUNX2 gene. Heterozygous deletions of different size were identified in 13 patients, and a duplication of the exons 1 to 4 of the RUNX2 gene in one patient. Thus, heterozygous deletions or duplications affecting the RUNX2 gene may be present in about 10% of all patients with a clinical diagnosis of CCD which corresponds to 26% of individuals with normal results on sequencing analysis. We therefore suggest that screening for intragenic deletions and duplications by qPCR or MLPA should be considered for patients with CCD phenotype in whom DNA sequencing does not reveal a causative RUNX2 mutation.
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http://dx.doi.org/10.1002/humu.21298DOI Listing
August 2010

The unfolding clinical spectrum of holoprosencephaly due to mutations in SHH, ZIC2, SIX3 and TGIF genes.

Eur J Hum Genet 2010 Sep 9;18(9):999-1005. Epub 2010 Jun 9.

Department of Clinical Genetics, School for Oncology & Developmental Biology (GROW), Maastricht UMC, The Netherlands.

Holoprosencephaly is a severe malformation of the brain characterized by abnormal formation and separation of the developing central nervous system. The prevalence is 1:250 during early embryogenesis, the live-born prevalence is 1:16 000. The etiology of HPE is extremely heterogeneous and can be teratogenic or genetic. We screened four known HPE genes in a Dutch cohort of 86 non-syndromic HPE index cases, including 53 family members. We detected 21 mutations (24.4%), 3 in SHH, 9 in ZIC2 and 9 in SIX3. Eight mutations involved amino-acid substitutions, 7 ins/del mutations, 1 frame-shift, 3 identical poly-alanine tract expansions and 2 gene deletions. Pathogenicity of mutations was presumed based on de novo character, predicted non-functionality of mutated proteins, segregation of mutations with affected family-members or combinations of these features. Two mutations were reported previously. SNP array confirmed detected deletions; one spanning the ZIC2/ZIC5 genes (approx. 100 kb) the other a 1.45 Mb deletion including SIX2/SIX3 genes. The mutation percentage (24%) is comparable with previous reports, but we detected significantly less mutations in SHH: 3.5 vs 10.7% (P=0.043) and significantly more in SIX3: 10.5 vs 4.3% (P=0.018). For TGIF1 and ZIC2 mutation the rate was in conformity with earlier reports. About half of the mutations were de novo, one was a germ line mosaic. The familial mutations displayed extensive heterogeneity in clinical manifestation. Of seven familial index patients only two parental carriers showed minor HPE signs, five were completely asymptomatic. Therefore, each novel mutation should be considered as a risk factor for clinically manifest HPE, with the caveat of reduced clinical penetrance.
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http://dx.doi.org/10.1038/ejhg.2010.70DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2987413PMC
September 2010