Publications by authors named "Kosuke Izumi"

68 Publications

Expanding the genotypic and phenotypic spectrum in a diverse cohort of 104 individuals with Wiedemann-Steiner syndrome.

Authors:
Sarah E Sheppard Ian M Campbell Margaret H Harr Nina Gold Dong Li Hans T Bjornsson Julie S Cohen Jill A Fahrner Ali Fatemi Jacqueline R Harris Catherine Nowak Cathy A Stevens Katheryn Grand Margaret Au John M Graham Pedro A Sanchez-Lara Miguel Del Campo Marilyn C Jones Omar Abdul-Rahman Fowzan S Alkuraya Jennifer A Bassetti Katherine Bergstrom Elizabeth Bhoj Sarah Dugan Julie D Kaplan Nada Derar Karen W Gripp Natalie Hauser A Micheil Innes Beth Keena Neslida Kodra Rebecca Miller Beverly Nelson Malgorzata J Nowaczyk Zuhair Rahbeeni Shay Ben-Shachar Joseph T Shieh Anne Slavotinek Andrew K Sobering Mary-Alice Abbott Dawn C Allain Louise Amlie-Wolf Ping Yee Billie Au Emma Bedoukian Geoffrey Beek James Barry Janet Berg Jonathan A Bernstein Cheryl Cytrynbaum Brian Hon-Yin Chung Sarah Donoghue Naghmeh Dorrani Alison Eaton Josue A Flores-Daboub Holly Dubbs Carolyn A Felix Chin-To Fong Jasmine Lee Fong Fung Balram Gangaram Amy Goldstein Rotem Greenberg Thoa K Ha Joseph Hersh Kosuke Izumi Staci Kallish Elijah Kravets Pui-Yan Kwok Rebekah K Jobling Amy E Knight Johnson Jessica Kushner Bo Hoon Lee Brooke Levin Kristin Lindstrom Kandamurugu Manickam Rebecca Mardach Elizabeth McCormick D Ross McLeod Frank D Mentch Kelly Minks Colleen Muraresku Stanley F Nelson Patrizia Porazzi Pavel N Pichurin Nina N Powell-Hamilton Zoe Powis Alyssa Ritter Caleb Rogers Luis Rohena Carey Ronspies Audrey Schroeder Zornitza Stark Lois Starr Joan Stoler Pim Suwannarat Milen Velinov Rosanna Weksberg Yael Wilnai Neda Zadeh Dina J Zand Marni J Falk Hakon Hakonarson Elaine H Zackai Fabiola Quintero-Rivera

Am J Med Genet A 2021 Mar 30. Epub 2021 Mar 30.

Department of Paediatrics and Adolescent Medicine, Hong Kong Children's Hospital, The University of Hong Kong, Pok Fu Lam, Hong Kong SAR.

Wiedemann-Steiner syndrome (WSS) is an autosomal dominant disorder caused by monoallelic variants in KMT2A and characterized by intellectual disability and hypertrichosis. We performed a retrospective, multicenter, observational study of 104 individuals with WSS from five continents to characterize the clinical and molecular spectrum of WSS in diverse populations, to identify physical features that may be more prevalent in White versus Black Indigenous People of Color individuals, to delineate genotype-phenotype correlations, to define developmental milestones, to describe the syndrome through adulthood, and to examine clinicians' differential diagnoses. Sixty-nine of the 82 variants (84%) observed in the study were not previously reported in the literature. Common clinical features identified in the cohort included: developmental delay or intellectual disability (97%), constipation (63.8%), failure to thrive (67.7%), feeding difficulties (66.3%), hypertrichosis cubiti (57%), short stature (57.8%), and vertebral anomalies (46.9%). The median ages at walking and first words were 20 months and 18 months, respectively. Hypotonia was associated with loss of function (LoF) variants, and seizures were associated with non-LoF variants. This study identifies genotype-phenotype correlations as well as race-facial feature associations in an ethnically diverse cohort, and accurately defines developmental trajectories, medical comorbidities, and long-term outcomes in individuals with WSS.
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http://dx.doi.org/10.1002/ajmg.a.62124DOI Listing
March 2021

Variants in NAA15 cause pediatric hypertrophic cardiomyopathy.

Am J Med Genet A 2021 01 26;185(1):228-233. Epub 2020 Oct 26.

Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.

The NatA N-acetyltransferase complex is important for cotranslational protein modification and regulation of multiple cellular processes. The NatA complex includes the core components of NAA10, the catalytic subunit, and NAA15, the auxiliary component. Both NAA10 and NAA15 have been associated with neurodevelopmental disorders with overlapping clinical features, including variable intellectual disability, dysmorphic facial features, and, less commonly, congenital anomalies such as cleft lip or palate. Cardiac arrhythmias, including long QT syndrome, ventricular tachycardia, and ventricular fibrillation were among the first reported cardiac manifestations in patients with NAA10-related syndrome. Recently, three individuals with NAA10-related syndrome have been reported to also have hypertrophic cardiomyopathy (HCM). The general and cardiac phenotypes of NAA15-related syndrome are not as well described as NAA10-related syndrome. Congenital heart disease, including ventricular septal defects, and arrhythmias, such as ectopic atrial tachycardia, have been reported in a small proportion of patients with NAA15-related syndrome. Given the relationship between NAA10 and NAA15, we propose that HCM is also likely to occur in NAA15-related disorder. We present two patients with pediatric HCM found to have NAA15-related disorder via exome sequencing, providing the first evidence that variants in NAA15 can cause HCM.
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http://dx.doi.org/10.1002/ajmg.a.61928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8007079PMC
January 2021

JARID2 haploinsufficiency is associated with a clinically distinct neurodevelopmental syndrome.

Genet Med 2021 Feb 20;23(2):374-383. Epub 2020 Oct 20.

Department of Pediatrics, University of Montreal, Montreal, QC, Canada.

Purpose: JARID2, located on chromosome 6p22.3, is a regulator of histone methyltransferase complexes that is expressed in human neurons. So far, 13 individuals sharing clinical features including intellectual disability (ID) were reported with de novo heterozygous deletions in 6p22-p24 encompassing the full length JARID2 gene (OMIM 601594). However, all published individuals to date have a deletion of at least one other adjoining gene, making it difficult to determine if JARID2 is the critical gene responsible for the shared features. We aim to confirm JARID2 as a human disease gene and further elucidate the associated clinical phenotype.

Methods: Chromosome microarray analysis, exome sequencing, and an online matching platform (GeneMatcher) were used to identify individuals with single-nucleotide variants or deletions involving JARID2.

Results: We report 16 individuals in 15 families with a deletion or single-nucleotide variant in JARID2. Several of these variants are likely to result in haploinsufficiency due to nonsense-mediated messenger RNA (mRNA) decay. All individuals have developmental delay and/or ID and share some overlapping clinical characteristics such as facial features with those who have larger deletions involving JARID2.

Conclusion: We report that JARID2 haploinsufficiency leads to a clinically distinct neurodevelopmental syndrome, thus establishing gene-disease validity for the purpose of diagnostic reporting.
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http://dx.doi.org/10.1038/s41436-020-00992-zDOI Listing
February 2021

EP300-related Rubinstein-Taybi syndrome: Highlighted rare phenotypic findings and a genotype-phenotype meta-analysis of 74 patients.

Am J Med Genet A 2020 12 11;182(12):2926-2938. Epub 2020 Oct 11.

Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA.

Pathogenic variants in the homologous and highly conserved genes-CREBBP and EP300-are causal for Rubinstein-Taybi syndrome (RSTS). CREBBP and EP300 encode histone acetyltransferases (HAT) that act as transcriptional co-activators, and their haploinsufficiency causes the pathology characteristic of RSTS by interfering with global transcriptional regulation. Though generally a well-characterized syndrome, there is a clear phenotypic spectrum; rare associations have emerged with increasing diagnosis that is critical for comprehensive understanding of this rare syndrome. We present 12 unreported patients with RSTS found to have EP300 variants discovered through gene sequencing and chromosomal microarray. Our cohort highlights rare phenotypic features associated with EP300 variants, including imperforate anus, retained fetal finger pads, and spina bifida occulta. Our findings support the previously noted prevalence of pregnancy-related hypertension/preeclampsia seen with this disease. We additionally performed a meta-analysis on our newly reported 12 patients and 62 of the 90 previously reported patients. We demonstrated no statistically significant correlation between phenotype severity (within the domains of intellectual disability and major organ involvement, as defined in our Methods section) and variant location and type; this is in contrast to the conclusions of some smaller studies and highlights the importance of large patient cohorts in characterization of this rare disease.
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http://dx.doi.org/10.1002/ajmg.a.61883DOI Listing
December 2020

Further delineation of the clinical spectrum of KAT6B disorders and allelic series of pathogenic variants.

Genet Med 2020 08 19;22(8):1338-1347. Epub 2020 May 19.

Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine, University of Montreal, Montreal, QC, Canada.

Purpose: Genitopatellar syndrome and Say-Barber-Biesecker-Young-Simpson syndrome are caused by variants in the KAT6B gene and are part of a broad clinical spectrum called KAT6B disorders, whose variable expressivity is increasingly being recognized.

Methods: We herein present the phenotypes of 32 previously unreported individuals with a molecularly confirmed diagnosis of a KAT6B disorder, report 24 new pathogenic KAT6B variants, and review phenotypic information available on all published individuals with this condition. We also suggest a classification of clinical subtypes within the KAT6B disorder spectrum.

Results: We demonstrate that cerebral anomalies, optic nerve hypoplasia, neurobehavioral difficulties, and distal limb anomalies other than long thumbs and great toes, such as polydactyly, are more frequently observed than initially reported. Intestinal malrotation and its serious consequences can be present in affected individuals. Additionally, we identified four children with Pierre Robin sequence, four individuals who had increased nuchal translucency/cystic hygroma prenatally, and two fetuses with severe renal anomalies leading to renal failure. We also report an individual in which a pathogenic variant was inherited from a mildly affected parent.

Conclusion: Our work provides a comprehensive review and expansion of the genotypic and phenotypic spectrum of KAT6B disorders that will assist clinicians in the assessment, counseling, and management of affected individuals.
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http://dx.doi.org/10.1038/s41436-020-0811-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7737399PMC
August 2020

A Centralized Approach for Practicing Genomic Medicine.

Pediatrics 2020 03 26;145(3). Epub 2020 Feb 26.

Roberts Individualized Medical Genetics Center, Division of Human Genetics.

Next-generation sequencing has revolutionized the diagnostic process, making broadscale testing affordable and applicable to almost all specialties; however, there remain several challenges in its widespread implementation. Barriers such as lack of infrastructure or expertise within local health systems and complex result interpretation or counseling make it harder for frontline clinicians to incorporate genomic testing in their existing workflow. The general population is more informed and interested in pursuing genetic testing, and this has been coupled with the increasing accessibility of direct-to-consumer testing. As a result of these changes, primary care physicians and nongenetics specialty providers find themselves seeing patients for whom genetic testing would be beneficial but managing genetic test results that are out of their scope of practice. In this report, we present a practical and centralized approach to providing genomic services through an independent, enterprise-wide clinical service model. We present 4 years of clinical experience, with >3400 referrals, toward designing and implementing the clinical service, maximizing resources, identifying barriers, and improving patient care. We provide a framework that can be implemented at other institutions to support and integrate genomic services across the enterprise.
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http://dx.doi.org/10.1542/peds.2019-0855DOI Listing
March 2020

Interstitial 4q Deletion Syndrome Including Causing Pseudohypoaldosteronism.

Mol Syndromol 2020 Jan 21;10(6):327-331. Epub 2019 Dec 21.

Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.

Interstitial and terminal deletions of chromosome 4q have been described for many years and have variable phenotypes depending on the size of the deletion present. Clinical features can include developmental delay, growth difficulty, digital differences, dysmorphic features, and cardiac anomalies. Here, we present an infant with pseudohypoaldosteronism found to have a deletion of 4q31.21q31.23, including Heterozygous mutations in have been reported to cause autosomal dominant pseudohypoaldosteronism type 1 (PHA1A). This represents a rare case of PHA1A due to a contiguous interstitial deletion and highlights the importance of evaluating patients with overlapping deletions for PHA1A.
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http://dx.doi.org/10.1159/000505279DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6995944PMC
January 2020

Missense Mutations in NKAP Cause a Disorder of Transcriptional Regulation Characterized by Marfanoid Habitus and Cognitive Impairment.

Am J Hum Genet 2019 11 3;105(5):987-995. Epub 2019 Oct 3.

Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA; Division of Genomic Diagnostics, Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Laboratory of Rare Disease Research, Institute for Quantitative Biosciences, The University of Tokyo, Tokyo 113-8657, Japan. Electronic address:

NKAP is a ubiquitously expressed nucleoplasmic protein that is currently known as a transcriptional regulatory molecule via its interaction with HDAC3 and spliceosomal proteins. Here, we report a disorder of transcriptional regulation due to missense mutations in the X chromosome gene, NKAP. These mutations are clustered in the C-terminal region of NKAP where NKAP interacts with HDAC3 and post-catalytic spliceosomal complex proteins. Consistent with a role for the C-terminal region of NKAP in embryogenesis, nkap mutant zebrafish with a C-terminally truncated NKAP demonstrate severe developmental defects. The clinical features of affected individuals are highly conserved and include developmental delay, hypotonia, joint contractures, behavioral abnormalities, Marfanoid habitus, and scoliosis. In affected cases, transcriptome analysis revealed the presence of a unique transcriptome signature, which is characterized by the downregulation of long genes with higher exon numbers. These observations indicate the critical role of NKAP in transcriptional regulation and demonstrate that perturbations of the C-terminal region lead to developmental defects in both humans and zebrafish.
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http://dx.doi.org/10.1016/j.ajhg.2019.09.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6848994PMC
November 2019

Clinical utility of exome sequencing in infantile heart failure.

Genet Med 2020 02 17;22(2):423-426. Epub 2019 Sep 17.

Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA.

Purpose: Pediatric cardiomyopathy is rare, has a broad differential diagnosis, results in high morbidity and mortality, and has suboptimal diagnostic yield using next-generation sequencing panels. Exome sequencing has reported diagnostic yields ranging from 30% to 57% for neonates in intensive care units. We aimed to characterize the clinical utility of exome sequencing in infantile heart failure.

Methods: Infants diagnosed with acute heart failure prior to 1 year old over a period of 34 months at a large tertiary children's hospital were recruited. Demographic and diagnostic information was obtained from medical records. Fifteen eligible patients were enrolled.

Results: Dilated cardiomyopathy was the predominant cardiac diagnosis, seen in 60% of patients. A molecular diagnosis was identified in 66.7% of patients (10/15). Of those diagnoses, 70% would not have been detected using multigene next-generation sequencing panels focused on cardiomyopathy or arrhythmia disease genes. Genetic testing changed medical decision-making in 53% of all cases and 80% of positive cases, and was especially beneficial when testing was expedited.

Conclusion: Given the broad differential diagnosis and critical status of infants with heart failure, rapid exome sequencing provides timely diagnoses, changes medical management, and should be the first-tier molecular test.
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http://dx.doi.org/10.1038/s41436-019-0654-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7339672PMC
February 2020

De Novo Variants Disturbing the Transactivation Capacity of POU3F3 Cause a Characteristic Neurodevelopmental Disorder.

Am J Hum Genet 2019 08 11;105(2):403-412. Epub 2019 Jul 11.

Language and Genetics Department, Max Planck Institute for Psycholinguistics, PO Box 310, 6500AH Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, PO Box 9104, 6500HE Nijmegen, the Netherlands. Electronic address:

POU3F3, also referred to as Brain-1, is a well-known transcription factor involved in the development of the central nervous system, but it has not previously been associated with a neurodevelopmental disorder. Here, we report the identification of 19 individuals with heterozygous POU3F3 disruptions, most of which are de novo variants. All individuals had developmental delays and/or intellectual disability and impairments in speech and language skills. Thirteen individuals had characteristic low-set, prominent, and/or cupped ears. Brain abnormalities were observed in seven of eleven MRI reports. POU3F3 is an intronless gene, insensitive to nonsense-mediated decay, and 13 individuals carried protein-truncating variants. All truncating variants that we tested in cellular models led to aberrant subcellular localization of the encoded protein. Luciferase assays demonstrated negative effects of these alleles on transcriptional activation of a reporter with a FOXP2-derived binding motif. In addition to the loss-of-function variants, five individuals had missense variants that clustered at specific positions within the functional domains, and one small in-frame deletion was identified. Two missense variants showed reduced transactivation capacity in our assays, whereas one variant displayed gain-of-function effects, suggesting a distinct pathophysiological mechanism. In bioluminescence resonance energy transfer (BRET) interaction assays, all the truncated POU3F3 versions that we tested had significantly impaired dimerization capacities, whereas all missense variants showed unaffected dimerization with wild-type POU3F3. Taken together, our identification and functional cell-based analyses of pathogenic variants in POU3F3, coupled with a clinical characterization, implicate disruptions of this gene in a characteristic neurodevelopmental disorder.
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http://dx.doi.org/10.1016/j.ajhg.2019.06.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6698880PMC
August 2019

Clinical and molecular spectrum of CHOPS syndrome.

Am J Med Genet A 2019 07 6;179(7):1126-1138. Epub 2019 May 6.

Division of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.

CHOPS syndrome is a multisystem disorder caused by missense mutations in AFF4. Previously, we reported three individuals whose primary phenotype included cognitive impairment and coarse facies, heart defects, obesity, pulmonary involvement, and short stature. This syndrome overlaps phenotypically with Cornelia de Lange syndrome, but presents distinct differences including facial features, pulmonary involvement, and obesity. Here, we provide clinical descriptions of an additional eight individuals with CHOPS syndrome, as well as neurocognitive analysis of three individuals. All 11 individuals presented with features reminiscent of Cornelia de Lange syndrome such as synophrys, upturned nasal tip, arched eyebrows, and long eyelashes. All 11 individuals had short stature and obesity. Congenital heart disease and pulmonary involvement were common, and those were seen in about 70% of individuals with CHOPS syndrome. Skeletal abnormalities are also common, and those include abnormal shape of vertebral bodies, hypoplastic long bones, and low bone mineral density. Our observation indicates that obesity, pulmonary involvement, skeletal findings are the most notable features distinguishing CHOPS syndrome from Cornelia de Lange syndrome. In fact, two out of eight of our newly identified patients were found to have AFF4 mutations by targeted AFF4 mutational analysis rather than exome sequencing. These phenotypic findings establish CHOPS syndrome as a distinct, clinically recognizable disorder. Additionally, we report three novel missense mutations causative for CHOPS syndrome that lie within the highly conserved, 14 amino acid sequence of the ALF homology domain of the AFF4 gene, emphasizing the critical functional role of this region in human development.
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http://dx.doi.org/10.1002/ajmg.a.61174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7473581PMC
July 2019

A Syndromic Neurodevelopmental Disorder Caused by Mutations in SMARCD1, a Core SWI/SNF Subunit Needed for Context-Dependent Neuronal Gene Regulation in Flies.

Am J Hum Genet 2019 04 14;104(4):596-610. Epub 2019 Mar 14.

Centre Hospitalier Universitaire Sainte-Justine Research Center, University of Montreal, Montreal, QC H3T 1C5, Canada; Department of Pediatrics, University of Montreal, Montreal, QC H4A 3J1, Canada. Electronic address:

Mutations in several genes encoding components of the SWI/SNF chromatin remodeling complex cause neurodevelopmental disorders (NDDs). Here, we report on five individuals with mutations in SMARCD1; the individuals present with developmental delay, intellectual disability, hypotonia, feeding difficulties, and small hands and feet. Trio exome sequencing proved the mutations to be de novo in four of the five individuals. Mutations in other SWI/SNF components cause Coffin-Siris syndrome, Nicolaides-Baraitser syndrome, or other syndromic and non-syndromic NDDs. Although the individuals presented here have dysmorphisms and some clinical overlap with these syndromes, they lack their typical facial dysmorphisms. To gain insight into the function of SMARCD1 in neurons, we investigated the Drosophila ortholog Bap60 in postmitotic memory-forming neurons of the adult Drosophila mushroom body (MB). Targeted knockdown of Bap60 in the MB of adult flies causes defects in long-term memory. Mushroom-body-specific transcriptome analysis revealed that Bap60 is required for context-dependent expression of genes involved in neuron function and development in juvenile flies when synaptic connections are actively being formed in response to experience. Taken together, we identify an NDD caused by SMARCD1 mutations and establish a role for the SMARCD1 ortholog Bap60 in the regulation of neurodevelopmental genes during a critical time window of juvenile adult brain development when neuronal circuits that are required for learning and memory are formed.
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http://dx.doi.org/10.1016/j.ajhg.2019.02.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451697PMC
April 2019

Cathepsin L-deficiency enhances liver regeneration after partial hepatectomy.

Life Sci 2019 Mar 20;221:293-300. Epub 2019 Feb 20.

Department of Gastroenterology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan.

Aim: Cathepsin L (Ctsl) plays a pivotal role in lysosomal and autophagic proteolysis. Previous investigations revealed that partial hepatectomy (PH) decreases biosynthesis of cathepsins in liver, followed by suppression of lysosomal and autophagic proteolysis during liver regeneration. Conversely, it was reported that autophagy-deficiency suppressed liver regeneration. Thus, the purpose of this study is to determine if Ctsl deficiency affects liver regeneration after PH.

Methods: 70% of PH was performed in male Ctsl-deficient mice (Ctsl-/-) and wild-type littermates (Ctsl +/+) after PH. Mice were sacrificed and wet weight of the whole remaining liver was measured. Bromodeoxyuridine (BrdU)-immunostaining of liver sections was performed. Expression of cyclin D1, p62, LC-3, Nrf2, cleaved-Notch1, Hes1 was evaluated by western blot analysis. NQO1 mRNA expression was measured by realtime-PCR.

Results: After a 70% of PH, the liver mass was significantly restored within 5 days in Ctsl-/- mice compared to wild-type. Ctsl-deficiency enhanced the increases in both the rate of BrdU-positive cells and cyclin D1 expression after PH more than wild-type mice. On the other hand, Ctsl-deficiency upregulated p62, cleaved-Notch1 and Hes1 expression after PH. Moreover, the protein level of Nrf2 in the nucleus and mRNA expression of NQO1 in the liver after PH was also up-regulated in Ctsl-/- mice.

Conclusions: These findings suggest that accumulation of p62 due to loss of Ctsl plays an important role in liver regeneration through activation of Nrf2-Notch1 signaling. Taken together, Ctsl might be a new therapeutic target on disorder of liver regeneration.
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http://dx.doi.org/10.1016/j.lfs.2019.02.040DOI Listing
March 2019

Increased Clinical Sensitivity and Specificity of Plasma Protein -Glycan Profiling for Diagnosing Congenital Disorders of Glycosylation by Use of Flow Injection-Electrospray Ionization-Quadrupole Time-of-Flight Mass Spectrometry.

Clin Chem 2019 05 15;65(5):653-663. Epub 2019 Feb 15.

Division of Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA;

Background: Congenital disorders of glycosylation (CDG) represent 1 of the largest groups of metabolic disorders with >130 subtypes identified to date. The majority of CDG subtypes are disorders of -linked glycosylation, in which carbohydrate residues, namely, -glycans, are posttranslationally linked to asparagine molecules in peptides. To improve the diagnostic capability for CDG, we developed and validated a plasma -glycan assay using flow injection-electrospray ionization-quadrupole time-of-flight mass spectrometry.

Methods: After PNGase F digestion of plasma glycoproteins, -glycans were linked to a quinolone using a transient amine group at the reducing end, isolated by a hydrophilic interaction chromatography column, and then identified by accurate mass and quantified using a stable isotope-labeled glycopeptide as the internal standard.

Results: This assay differed from other -glycan profiling methods because it was free of any contamination from circulating free glycans and was semiquantitative. The low end of the detection range tested was at 63 nmol/L for disialo-biantennary -glycan. The majority of -glycans in normal plasma had <1% abundance. Abnormal -glycan profiles from 19 patients with known diagnoses of 11 different CDG subtypes were generated, some of which had previously been reported to have normal -linked protein glycosylation by carbohydrate-deficient transferrin analysis.

Conclusions: The clinical specificity and sensitivity of -glycan analysis was much improved with this method. Additional CDGs can be diagnosed that would be missed by carbohydrate-deficient transferrin analysis. The assay provides novel biomarkers with diagnostic and potentially therapeutic significance.
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http://dx.doi.org/10.1373/clinchem.2018.296780DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6886244PMC
May 2019

NFIB Haploinsufficiency Is Associated with Intellectual Disability and Macrocephaly.

Am J Hum Genet 2018 11;103(5):752-768

Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia; School of Biomedical Sciences, The Faculty of Medicine Brisbane, The University of Queensland, Brisbane, QLD 4072, Australia.

The nuclear factor I (NFI) family of transcription factors play an important role in normal development of multiple organs. Three NFI family members are highly expressed in the brain, and deletions or sequence variants in two of these, NFIA and NFIX, have been associated with intellectual disability (ID) and brain malformations. NFIB, however, has not previously been implicated in human disease. Here, we present a cohort of 18 individuals with mild ID and behavioral issues who are haploinsufficient for NFIB. Ten individuals harbored overlapping microdeletions of the chromosomal 9p23-p22.2 region, ranging in size from 225 kb to 4.3 Mb. Five additional subjects had point sequence variations creating a premature termination codon, and three subjects harbored single-nucleotide variations resulting in an inactive protein as determined using an in vitro reporter assay. All individuals presented with additional variable neurodevelopmental phenotypes, including muscular hypotonia, motor and speech delay, attention deficit disorder, autism spectrum disorder, and behavioral abnormalities. While structural brain anomalies, including dysgenesis of corpus callosum, were variable, individuals most frequently presented with macrocephaly. To determine whether macrocephaly could be a functional consequence of NFIB disruption, we analyzed a cortex-specific Nfib conditional knockout mouse model, which is postnatally viable. Utilizing magnetic resonance imaging and histology, we demonstrate that Nfib conditional knockout mice have enlargement of the cerebral cortex but preservation of overall brain structure and interhemispheric connectivity. Based on our findings, we propose that haploinsufficiency of NFIB causes ID with macrocephaly.
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http://dx.doi.org/10.1016/j.ajhg.2018.10.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6218805PMC
November 2018

Variable Clinical Manifestations of Xia-Gibbs syndrome: Findings of Consecutively Identified Cases at a Single Children's Hospital.

Am J Med Genet A 2018 09 27;176(9):1890-1896. Epub 2018 Aug 27.

Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia, Pennsylvania, Philadelphia, USA.

Xia-Gibbs syndrome (XGS) is a recently described neurodevelopmental disorder due to heterozygous loss-of-function AHDC1 mutations. XGS is characterized by global developmental delay, intellectual disability, hypotonia, and sleep abnormalities. Here we report the clinical phenotype of five of six individuals with XGS identified prospectively at the Children's Hospital of Philadelphia, a tertiary children's hospital in the USA. Although all five patients demonstrated common clinical features characterized by developmental delay and characteristic facial features, each of our patients showed unique clinical manifestations. Patient one had craniosynostosis; patient two had sensorineural hearing loss and bicuspid aortic valve; patient three had cutis aplasia; patient four had soft, loose skin; and patient five had a lipoma. Differential diagnoses considered for each patient were quite broad, and included craniosynostosis syndromes, connective tissue disorders, and mitochondrial disorders. Exome sequencing identified a heterozygous, de novo AHDC1 loss-of-function mutation in four of five patients; the remaining patient has a 357kb interstitial deletion of 1p36.11p35.3 including AHDC1. Although it remains unknown whether these unique clinical manifestations are rare symptoms of XGS, our findings indicate that the diagnosis of XGS should be considered even in individuals with additional non-neurological symptoms, as the clinical spectrum of XGS may involve such non-neurological manifestations. Adding to the growing literature on XGS, continued cohort studies are warranted in order to both characterize the clinical spectrum of XGS as well as determine standard of care for patients with this diagnosis.
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http://dx.doi.org/10.1002/ajmg.a.40380DOI Listing
September 2018

Cardiac Fibroma with Ventricular Tachycardia: An Unusual Clinical Presentation of Nevoid Basal Cell Carcinoma Syndrome.

Mol Syndromol 2018 Jul 19;9(4):219-223. Epub 2018 May 19.

Division of Human Genetics.

Pediatric cardiac tumors are rare and often benign with an incidence of approximately 0.03-0.32% and can be associated with genetic conditions. For example, approximately 3% of individuals with nevoid basal cell carcinoma syndrome (NBCCS), also known as Gorlin syndrome, have a cardiac fibroma. NBCCS is also characterized by lamellar or early calcification of the falx, jaw keratocysts, palmar and/or plantar pits, and a predisposition for basal cell carcinomas. Given the management implications of NBCCS, including appropriate cancer screenings and precautions, prompt identification of affected individuals is critical. We report a case of a 6-year-old female presenting with ventricular tachycardia secondary to cardiac fibroma. After diagnosis of recurrent jaw keratocysts, she was clinically and molecularly diagnosed with NBCCS. Identification of a cardiac fibroma should prompt careful assessment of past medical and family history with consideration of a diagnosis of NBCCS.
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http://dx.doi.org/10.1159/000489056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6103330PMC
July 2018

PCDH19-related epilepsy in a male with Klinefelter syndrome: Additional evidence supporting PCDH19 cellular interference disease mechanism.

Epilepsy Res 2018 09 18;145:89-92. Epub 2018 Jun 18.

Division of Genomic Diagnostics, Children's Hospital of Philadelphia, Philadelphia, PA, United States; Department of Pathology & Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, United States. Electronic address:

Heterozygous de novo or inherited pathogenic variants in the PCDH19 gene cause a spectrum of neurodevelopmental features including developmental delay and seizures. PCDH19 epilepsy was previously known as "epilepsy and mental retardation limited to females", since the condition almost exclusively affects females. It is hypothesized that the co-existence of two populations of neurons, some with and some without PCDH19 protein expression, results in pathologically abnormal interactions between these neurons, a mechanism also referred to as cellular interference. Consequently, PCDH19-related epilepsies are inherited in an atypical X-linked pattern, such that hemizygous, non-mosaic, 46,XY males are typically unaffected, while individuals with a disease-causing PCDH19 variant, mainly heterozygous females and mosaic males, are affected. As a corollary to this hypothesis, an individual with Klinefelter syndrome (KS) (47,XXY) who has a heterozygous disease-causing PCDH19 variant should develop PCDH19-related epilepsy. Here, we report such evidence: - a male child with KS and PCDH19-related epilepsy - supporting the PCDH19 cellular interference disease hypothesis.
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http://dx.doi.org/10.1016/j.eplepsyres.2018.06.008DOI Listing
September 2018

De novo variants in Myelin regulatory factor (MYRF) as candidates of a new syndrome of cardiac and urogenital anomalies.

Am J Med Genet A 2018 04 15;176(4):969-972. Epub 2018 Feb 15.

Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.

Myelin Regulatory Factor (MYRF) is a transcription factor that has previously been associated with the control of the expression of myelin-related genes. However, it is highly expressed in human tissues and mouse embryonic tissues outside the nervous system such as the stomach, lung, and small intestine. It has not previously been reported as a cause of any Mendelian disease. We report here two males with Scimitar syndrome [MIM 106700], and other features including penoscrotal hypospadias, cryptorchidism, pulmonary hypoplasia, tracheal anomalies, congenital diaphragmatic hernia, cleft spleen, thymic involution, and thyroid fibrosis. Gross neurologic functioning appears to be within normal limits. In both individuals a de novo variant in MYRF was identified using exome sequencing. Neither variant is found in gnomAD. Heterozygous variants in MYRF should be considered in patients with variants of Scimitar syndrome and urogenital anomalies.
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http://dx.doi.org/10.1002/ajmg.a.38620DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5867271PMC
April 2018

DOCK3-related neurodevelopmental syndrome: Biallelic intragenic deletion of DOCK3 in a boy with developmental delay and hypotonia.

Am J Med Genet A 2018 01 12;176(1):241-245. Epub 2017 Nov 12.

Division of Human Genetics, Department of Pediatrics, The Children's Hospital, Pennsylvania, Philadelphia.

Dedicator of cytokinesis (DOCK) family are evolutionary conserved guanine nucleotide exchange factors (GEFs) for the Rho GTPases, Rac, and Cdc42. DOCK3 functions as a GEF for Rac1, and plays an important role in promoting neurite and axonal growth by stimulating actin dynamics and microtubule assembly pathways in the central nervous system. Here we report a boy with developmental delay, hypotonia, and ataxia due to biallelic DOCK3 deletion. Chromosomal single nucleotide polymorphism (SNP) microarray analysis detected a 170 kb homozygous deletion including exons 6-12 of the DOCK3 gene at 3p21.2. Symptoms of our proband resembles a phenotype of Dock3 knockout mice exhibiting sensorimotor impairments. Furthermore, our proband has clinical similarities with two siblings with compound heterozygous loss-of-function mutations of DOCK3 reported in [Helbig, Mroske, Moorthy, Sajan, and Velinov (); https://doi.org/10.1111/cge.12995]. Biallelic DOCK3 mutations cause a neurodevelopmental disorder characterized by unsteady gait, hypotonia, and developmental delay.
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http://dx.doi.org/10.1002/ajmg.a.38517DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726891PMC
January 2018

Disorders of Transcriptional Regulation: An Emerging Category of Multiple Malformation Syndromes.

Authors:
Kosuke Izumi

Mol Syndromol 2016 Oct 2;7(5):262-273. Epub 2016 Sep 2.

Division of Human Genetics, The Children's Hospital of Philadelphia, Philadelphia, Pa., USA.

Some genetic disorders caused by mutations in genes encoding components of the transcriptional machinery as well as proteins involved in epigenetic modification of the genome share many overlapping features, such as facial dysmorphisms, growth problems and developmental delay/intellectual disability. As a basis for some shared phenotypic characteristics in these syndromes, a similar transcriptome disturbance, characterized by global transcriptional dysregulation, is believed to play a major role. In this review article, a general overview of gene transcription is provided, and the current knowledge of the mechanisms underlying some disorders of transcriptional regulation, such as Rubinstein- Taybi, Coffin-Siris, Cornelia de Lange, and CHOPS syndromes, are discussed.
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http://dx.doi.org/10.1159/000448747DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5109993PMC
October 2016

Exome sequencing-based identification of mutations in non-syndromic genes among individuals with apparently syndromic features.

Am J Med Genet A 2016 11 26;170(11):2889-2894. Epub 2016 Aug 26.

Division of Medical Genetics, Nagano Children's Hospital, Azumino, Japan.

In a clinical setting, the number of organ systems involved is crucial for the differential diagnosis of congenital genetic disorders. When more than one organ system is involved, a syndromic diagnosis is suspected. In this report, we describe three patients with apparently syndromic features. Exome sequencing identified non-syndromic gene mutations as a potential cause of part of their phenotype. The first patient (Patient 1) is a girl with cleft lip/palate, meningoencephalocele, tetralogy of Fallot, and developmental delay. The second and third patients (Patients 2 and 3) are brothers with developmental delay, deafness, and low bone mineral density. Exome sequencing revealed the presence of a CDH1 mutation in Patient 1 and a PLS3 mutation in Patients 2 and 3. CDH1 mutations are known to be associated with non-syndromic cleft lip/palate, while PLS3 mutations are associated with osteoporosis. Thus, these variants may explain a part of the complex phenotype of the patients, although the effects of these missense variants need to be evaluated by functional assays in order to prove pathogenicity. On the basis of these findings, we emphasize the importance of scrutinizing non-syndromic gene mutations even in individuals with apparently syndromic features. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37826DOI Listing
November 2016

ARCN1 Mutations Cause a Recognizable Craniofacial Syndrome Due to COPI-Mediated Transport Defects.

Am J Hum Genet 2016 Aug 28;99(2):451-9. Epub 2016 Jul 28.

Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan; CREST, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan.

Cellular homeostasis is maintained by the highly organized cooperation of intracellular trafficking systems, including COPI, COPII, and clathrin complexes. COPI is a coatomer protein complex responsible for intracellular protein transport between the endoplasmic reticulum and the Golgi apparatus. The importance of such intracellular transport mechanisms is underscored by the various disorders, including skeletal disorders such as cranio-lenticulo-sutural dysplasia and osteogenesis imperfect, caused by mutations in the COPII coatomer complex. In this article, we report a clinically recognizable craniofacial disorder characterized by facial dysmorphisms, severe micrognathia, rhizomelic shortening, microcephalic dwarfism, and mild developmental delay due to loss-of-function heterozygous mutations in ARCN1, which encodes the coatomer subunit delta of COPI. ARCN1 mutant cell lines were revealed to have endoplasmic reticulum stress, suggesting the involvement of ER stress response in the pathogenesis of this disorder. Given that ARCN1 deficiency causes defective type I collagen transport, reduction of collagen secretion represents the likely mechanism underlying the skeletal phenotype that characterizes this condition. Our findings demonstrate the importance of COPI-mediated transport in human development, including skeletogenesis and brain growth.
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http://dx.doi.org/10.1016/j.ajhg.2016.06.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4974084PMC
August 2016

Mosaic ratio quantification of isochromosome 12p in Pallister-Killian syndrome using droplet digital PCR.

Mol Genet Genomic Med 2016 May 20;4(3):257-61. Epub 2016 Jan 20.

Research Center for Epigenetic Disease, Institute for Molecular and Cellular Biosciences The University of Tokyo Tokyo Japan.

Background: Pallister-Killian syndrome (PKS) is a prototypic mosaic aneuploidy syndrome caused by mosaic supernumerary marker isochromosome 12p. Cells possessing the isochromosome 12p rapidly diminish after birth in the peripheral blood, often necessitating a skin biopsy for diagnosis. Therefore, a genomic testing that is capable of detecting low percent mosaic isochromosome 12p is preferred for the diagnosis of PKS.

Methods: The utility of the droplet digital PCR system in quantifying the mosaic ratio of isochromosome 12p in PKS was evaluated.

Results: Droplet digital PCR was able to precisely quantify isochromosome 12p mosaic ratio, and copy number measured by droplet digital PCR was correlated well with that of fluorescence in situ hybridization analysis.

Conclusion: Droplet digital PCR should be considered as an effective tool for both clinical and research analytics to precisely quantify mosaic genomic copy number alterations or mosaic mutations.
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http://dx.doi.org/10.1002/mgg3.200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4867559PMC
May 2016

Discordant clinical phenotype in monozygotic twins with Alagille syndrome: Possible influence of non-genetic factors.

Am J Med Genet A 2016 Feb 13;170A(2):471-475. Epub 2015 Oct 13.

Department of Pathology and Laboratory Medicine, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.

Alagille syndrome is a multisystem developmental disorder characterized by bile duct paucity, congenital heart disease, vertebral anomalies, posterior embryotoxon, and characteristic facial features. Alagille syndrome is typically the result of germline mutations in JAG1 or NOTCH2 and is one of several human diseases caused by Notch signaling abnormalities. A wide phenotypic spectrum has been well documented in Alagille syndrome. Therefore, monozygotic twins with Alagille syndrome provide a unique opportunity to evaluate potential phenotypic modifiers such as environmental factors or stochastic effects of gene expression. In this report, we describe an Alagille syndrome monozygotic twin pair with discordant placental and clinical findings. We propose that environmental factors such as prenatal hypoxia may have played a role in determining the phenotypic severity.
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http://dx.doi.org/10.1002/ajmg.a.37429DOI Listing
February 2016

Exome Sequencing Identification of EP300 Mutation in a Proband with Coloboma and Imperforate Anus: Possible Expansion of the Phenotypic Spectrum of Rubinstein-Taybi Syndrome.

Mol Syndromol 2015 Jul 3;6(2):99-103. Epub 2015 Mar 3.

Institute for Molecular and Cellular Biosciences, Research Center for Epigenetic Disease, The University of Tokyo, Tokyo, Japan ; Division of Medical Genetics, Nagano Children's Hospital, Azumino, Japan.

Rubinstein-Taybi syndrome (RSTS) is a multisystem developmental disorder characterized by facial dysmorphisms, broad thumbs and halluces, growth retardation, and intellectual disability. In about 8% of RSTS cases, mutations are found in EP300. Previously, the EP300 mutation has been shown to cause the highly variable RSTS phenotype. Using exome sequencing, we identified a de novo EP300 frameshift mutation in a proband with coloboma, facial asymmetry and imperforate anus with minimal RSTS features. Previous molecular studies have demonstrated the importance of EP300 in oculogenesis, supporting the possibility that EP300 mutation may cause ocular coloboma. Since a wide phenotypic spectrum is well known in EP300-associated RSTS cases, the atypical phenotype identified in our proband may be an example of rare manifestations of RSTS.
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http://dx.doi.org/10.1159/000375542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4521068PMC
July 2015

The Deubiquitinating Enzyme USP7 Regulates Androgen Receptor Activity by Modulating Its Binding to Chromatin.

J Biol Chem 2015 Aug 14;290(35):21713-23. Epub 2015 Jul 14.

From the Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032 and

The androgen receptor (AR), a nuclear receptor superfamily transcription factor, plays a key role in prostate cancer. AR signaling is the principal target for prostate cancer treatment, but current androgen-deprivation therapies cannot completely abolish AR signaling because of the heterogeneity of prostate cancers. Therefore, unraveling the mechanism of AR reactivation in androgen-depleted conditions can identify effective prostate cancer therapeutic targets. Increasing evidence indicates that AR activity is mediated by the interplay of modifying/demodifying enzymatic co-regulators. To better understand the mechanism of AR transcriptional activity regulation, we used antibodies against AR for affinity purification and identified the deubiquitinating enzyme ubiquitin-specific protease 7, USP7 as a novel AR co-regulator in prostate cancer cells. We showed that USP7 associates with AR in an androgen-dependent manner and mediates AR deubiquitination. Sequential ChIP assays indicated that USP7 forms a complex with AR on androgen-responsive elements of target genes upon stimulation with the androgen 5α-dihydrotestosterone. Further investigation indicated that USP7 is necessary to facilitate androgen-activated AR binding to chromatin. Transcriptome profile analysis of USP7-knockdown LNCaP cells also revealed the essential role of USP7 in the expression of a subset of androgen-responsive genes. Hence, inhibition of USP7 represents a compelling therapeutic strategy for the treatment of prostate cancer.
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http://dx.doi.org/10.1074/jbc.M114.628255DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4571893PMC
August 2015

Fetal akinesia deformation sequence due to a congenital disorder of glycosylation.

Am J Med Genet A 2015 Oct 31;167A(10):2411-7. Epub 2015 May 31.

Genetics Program, Children's Regional Hospital, Cooper University Health Care.

Congenital disorders of Glycosylation (CDG) are increasingly emerging as a major underlying etiology for patients with complex neurogenetic malformations and dysmorphic features. We describe a newborn female with arthrogryposis multiplex due to fetal akinesia secondary to CDG-DPAGT1. Pregnancy was complicated by reduced fetal movements. At birth, the patient was evaluated for intrauterine growth restriction, bilateral cataracts, and multiple joint contractures. She had markedly reduced spontaneous movements, hypotonia, weak cry, and poor suck. She had ventilator-dependent central respiratory depression. Brain MRI showed delayed myelination and an incomplete cerebellar vermis. Transferrin isoelectric focusing was suggestive of a type I congenital disorder of glycosylation. Sequencing revealed a homozygous missense mutation in dolichyl-phosphate N-acetylglucosaminephosphotransferase (DPAGT1), exon 3, p.Leu118Val, consistent with DPAGT1-CDG. There have been seventeen previously reported cases of DPAGT1-CDG, including two similar cases with multiple contractures. This case highlights the importance of considering congenital disorders of glycosylation in the differential diagnosis for arthrogryposis.
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http://dx.doi.org/10.1002/ajmg.a.37184DOI Listing
October 2015

Elevation of insulin-like growth factor binding protein-2 level in Pallister-Killian syndrome: implications for the postnatal growth retardation phenotype.

Am J Med Genet A 2015 Jun 21;167(6):1268-74. Epub 2015 Apr 21.

Divisionof Human Genetics, The Children Hospital of Philadelphia, Philadelphia, Pennsylvania.

Pallister-Killian syndrome (PKS) is a multi-system developmental disorder caused by tetrasomy 12p that exhibits tissue-limited mosaicism. Probands with PKS often demonstrate a unique growth profile consisting of macrosomia at birth with deceleration of growth postnatally. We have previously demonstrated that cultured skin fibroblasts from PKS probands have significantly elevated expression of insulin-like growth factor binding protein-2 (IGFBP2). To further evaluate the role of IGFBP2 in PKS, the amount of IGFBP2 secreted from cultured skin fibroblast cell lines and serum IGFBP2 levels were measured in probands with PKS. Approximately 60% of PKS fibroblast cell lines secreted higher levels of IGFBP2 compared to control fibroblasts, although the remaining 40% of PKS samples produced comparable level of IGFBP2 to that of control fibroblasts. Serum IGFBP2 levels were also measured in PKS probands and were elevated in 40% of PKS probands. PKS probands with elevated IGFBP2 manifested with severe postnatal growth retardation. IGFBPs are the family of related proteins that bind IGFs with high affinity and are typically thought to attenuate IGF action. We suggest that elevated IGFBP2 levels might play a role in the growth retardation phenotype of PKS.
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http://dx.doi.org/10.1002/ajmg.a.36976DOI Listing
June 2015

Dissecting the phenotype of supernumerary marker chromosome 20 in a patient with syndromic Pierre Robin sequence: combinatorial effect of gene dosage and uniparental disomy.

Am J Med Genet A 2015 Jun 2;167(6):1289-93. Epub 2015 Apr 2.

Department of Laboratory Medicine, Nagano Children's Hospital, Azumino, Japan.

Clinical phenotypes in individuals with a supernumerary marker chromosome (SMC) are mainly caused by gene dosage effects due to the genes located on the SMC. An additional effect may result from uniparental disomy (UPD). Consequently, the occurrence of UPD may be a confounding factor in identifying genotype-phenotype correlations in SMC syndromes. Here, we report on a patient that illustrates this problem; the phenotype of this patient was a consequence of a combined effect of gene dosage and UPD. The proband showed facial dysmorphisms, growth retardation and developmental delay. G-band karyotype of the proband's peripheral blood showed the presence of mosaic SMC. A SNP array analysis documented maternal UPD20 and 20p duplication. It is known that maternal UPD20 causes prenatal onset growth retardation and feeding difficulties. By contrast, duplication of 20p causes facial dysmorphisms, micrognathia, cleft palate, developmental delay and vertebral anomalies. Our classification of the proband's phenotype showed a mixture of these two effects. Therefore, we suggest the routine use of genome-wide SNP array towards the detailed genotype-phenotype correlations for SMC syndromes.
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http://dx.doi.org/10.1002/ajmg.a.36921DOI Listing
June 2015