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Genomic Aberrations Associated with the Pathophysiological Mechanisms of Neurodevelopmental Disorders. Cells 2021; 10:cells10092317. [PMID: 34571966 PMCID: PMC8470284 DOI: 10.3390/cells10092317] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 08/30/2021] [Accepted: 09/03/2021] [Indexed: 12/27/2022] Open
Abstract
Genomic studies are increasingly revealing that neurodevelopmental disorders are caused by underlying genomic alterations. Chromosomal microarray testing has been used to reliably detect minute changes in genomic copy numbers. The genes located in the aberrated regions identified in patients with neurodevelopmental disorders may be associated with the phenotypic features. In such cases, haploinsufficiency is considered to be the mechanism, when the deletion of a gene is related to neurodevelopmental delay. The loss-of-function mutation in such genes may be evaluated using next-generation sequencing. On the other hand, the patients with increased copy numbers of the genes may exhibit different clinical symptoms compared to those with loss-of-function mutation in the genes. In such cases, the additional copies of the genes are considered to have a dominant negative effect, inducing cell stress. In other cases, not the copy number changes, but mutations of the genes are responsible for causing the clinical symptoms. This can be explained by the dominant negative effects of the gene mutations. Currently, the diagnostic yield of genomic alterations using comprehensive analysis is less than 50%, indicating the existence of more subtle alterations or genomic changes in the untranslated regions. Copy-neutral inversions and insertions may be related. Hence, better analytical algorithms specialized for the detection of such alterations are required for higher diagnostic yields.
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Yamamoto-Shimojima K, Imaizumi T, Akagawa H, Kanno H, Yamamoto T. Primrose syndrome associated with unclassified immunodeficiency and a novel ZBTB20 mutation. Am J Med Genet A 2019; 182:521-526. [PMID: 31821719 DOI: 10.1002/ajmg.a.61432] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 10/29/2019] [Accepted: 11/02/2019] [Indexed: 12/29/2022]
Abstract
Primrose syndrome is a congenital malformation syndrome characterized by intellectual disability, developmental delay, progressive muscle wasting, and ear lobe calcification. Mutations in the ZBTB20 gene have been established as being accountable for this syndrome. In this study, a novel de novo ZBTB20 mutation, NM_001164342.2:c.1945C>T (p.Leu649Phe), has been identified through whole exome sequencing (WES) in a female patient presenting a typical Primrose phenotype. Because the present patient exhibited recurrent otitis media, detailed immunological examinations were performed in this study and subnormal immunoglobulin levels were firstly identified in a Primrose patient. Anatomical anomaly of the inner ear has never been reported in this patient and WES data did not include any relevant variants causally linked with the immunologic defect. Thus, there is a possibility of a relation between an unclassified immunodeficiency with selective IgG2 deficiency and Primrose syndrome and this may be the reason of recurrent otitis media frequently observed in Primrose patients. Because subnormal levels of IgG2 in this patient might be caused by an unrelated and still uncharacterized genetic cause, further studies are required to prove the causal link between aberrant ZBTB20 function and immunodeficiency.
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Affiliation(s)
- Keiko Yamamoto-Shimojima
- Japan Society for the Promotion of Science (RPD), Tokyo, Japan.,Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan.,Tokyo Women's Medical University Institute for Integrated Medical Sciences, Tokyo, Japan
| | - Taichi Imaizumi
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan.,Department of Pediatrics, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Hiroyuki Akagawa
- Tokyo Women's Medical University Institute for Integrated Medical Sciences, Tokyo, Japan
| | - Hitoshi Kanno
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan.,Department of Transfusion Medicine and Cell Processing, Tokyo Women's Medical University, Tokyo, Japan
| | - Toshiyuki Yamamoto
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan.,Tokyo Women's Medical University Institute for Integrated Medical Sciences, Tokyo, Japan.,Department of Pediatrics, St. Marianna University School of Medicine, Kawasaki, Japan
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3
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Xie L, Luo X, Yang J, Wang J, Nie C, Wang Z. A Chinese patient with Toriello-Carey syndrome and an interstitial deletion of 3q. Am J Med Genet A 2016; 173:721-726. [PMID: 27748028 DOI: 10.1002/ajmg.a.38009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 09/21/2016] [Indexed: 01/13/2023]
Abstract
Toriello-Carey syndrome (T-CS), which was first described by Toriello and Carey, is a rare multiple congenital anomaly syndrome characterized by agenesis of the corpus callosum, Pierre Robin sequence, unusual facial appearance, and other anomalies. Tracheal or laryngeal anomalies are reported as a common manifestation of T-CS. These anomalies can lead to respiratory distress and respiratory tract infection. The cause of T-CS is unknown, although there have been reports of patients with a clinical diagnosis of T-CS and a chromosome anomaly. We describe another such patient who was found to have an interstitial deletion of 3q (3q12.1-q21.3). © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Lulu Xie
- NICU, Guangdong Women and Children Hospital of Guangzhou Medical University, Guangdong, China
| | - Xianqiong Luo
- NICU, Guangdong Women and Children Hospital of Guangzhou Medical University, Guangdong, China
| | - Jie Yang
- NICU, Guangdong Women and Children Hospital of Guangzhou Medical University, Guangdong, China
| | - Junping Wang
- NICU, Guangdong Women and Children Hospital of Guangzhou Medical University, Guangdong, China
| | - Chuan Nie
- NICU, Guangdong Women and Children Hospital of Guangzhou Medical University, Guangdong, China
| | - Zhu Wang
- NICU, Guangdong Women and Children Hospital of Guangzhou Medical University, Guangdong, China
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4
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Quintela I, Gomez-Guerrero L, Fernandez-Prieto M, Resches M, Barros F, Carracedo A. Female patient with autistic disorder, intellectual disability, and co-morbid anxiety disorder: Expanding the phenotype associated with the recurrent 3q13.2-q13.31 microdeletion. Am J Med Genet A 2015; 167A:3121-9. [PMID: 26332054 DOI: 10.1002/ajmg.a.37292] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 08/02/2015] [Indexed: 01/13/2023]
Abstract
In recent years, the advent of comparative genomic hybridization (CGH) and single nucleotide polymorphism (SNP) arrays and its use as a first genetic test for the diagnosis of patients with neurodevelopmental phenotypes has allowed the identification of novel submicroscopic chromosomal abnormalities (namely, copy number variants or CNVs), imperceptible by conventional cytogenetic techniques. The 3q13.31 microdeletion syndrome (OMIM #615433) has been defined as a genomic disorder mainly characterized by developmental delay, postnatal overgrowth, hypotonia, genital abnormalities in males, and characteristic craniofacial features. Although the 3q13.31 CNVs are variable in size, a 3.4 Mb recurrently altered region at 3q13.2-q13.31 has been recently described and non-allelic homologous recombination (NAHR) mediated by flanking human endogenous retrovirus (HERV-H) elements has been suggested as the mechanism of deletion formation. We expand the phenotypic spectrum associated with this recurrent deletion performing the clinical description of a 9-year-old female patient with autistic disorder, total absence of language, intellectual disability, anxiety disorder and disruptive, and compulsive eating behaviors. The array-based molecular karyotyping allowed the identification of a de novo recurrent 3q13.2-q13.31 deletion encompassing 25 genes. In addition, we compare her clinical phenotype with previous reports of patients with neurodevelopmental and behavioral disorders and proximal 3q microdeletions. Finally, we also review the candidate genes proposed so far for these phenotypes.
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Affiliation(s)
- Ines Quintela
- Grupo de Medicina Xenomica, Universidade de Santiago de Compostela, Centro Nacional de Genotipado-Plataforma de Recursos Biomoleculares y Bioinformaticos-Instituto de Salud Carlos III (CeGen-PRB2-ISCIII), Santiago de Compostela, Spain
| | - Lorena Gomez-Guerrero
- Grupo de Medicina Xenomica, CIBERER, Fundacion Publica Galega de Medicina Xenomica-SERGAS, Santiago de Compostela, Spain
| | - Montse Fernandez-Prieto
- Grupo de Medicina Xenomica, CIBERER, Fundacion Publica Galega de Medicina Xenomica-SERGAS, Santiago de Compostela, Spain
| | - Mariela Resches
- Departamento de Psicologia Evolutiva y de la Educacion, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Francisco Barros
- Grupo de Medicina Xenomica, CIBERER, Fundacion Publica Galega de Medicina Xenomica-SERGAS, Santiago de Compostela, Spain
| | - Angel Carracedo
- Grupo de Medicina Xenomica, Universidade de Santiago de Compostela, Centro Nacional de Genotipado-Plataforma de Recursos Biomoleculares y Bioinformaticos-Instituto de Salud Carlos III (CeGen-PRB2-ISCIII), Santiago de Compostela, Spain.,Grupo de Medicina Xenomica, CIBERER, Fundacion Publica Galega de Medicina Xenomica-SERGAS, Santiago de Compostela, Spain.,Center of Excellence in Genomic Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia
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Lowther C, Costain G, Melvin R, Stavropoulos DJ, Lionel AC, Marshall CR, Scherer SW, Bassett AS. Adult expression of a 3q13.31 microdeletion. Mol Cytogenet 2014; 7:23. [PMID: 24650298 PMCID: PMC4022390 DOI: 10.1186/1755-8166-7-23] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 03/11/2014] [Indexed: 11/30/2022] Open
Abstract
Background The emerging 3q13.31 microdeletion syndrome appears to encompass diverse neurodevelopmental conditions. However, the 3q13.31 deletion is rare and few adult cases have yet been reported. We examined a cohort with schizophrenia (n = 459) and adult control subjects (n = 26,826) using high-resolution microarray technology for deletions and duplications at the 3q13.31 locus. Results We report on the extended adult phenotype associated with a 3q13.31 microdeletion in a 41-year-old male proband with schizophrenia and a nonverbal learning disability. He was noted to have a speech impairment, delayed motor skills, and other features consistent with the 3q13.31 microdeletion syndrome. The 2.06 Mb deletion overlapped two microRNAs and seven RefSeq genes, including GAP43, LSAMP, DRD3, and ZBTB20. No overlapping 3q13.31 deletions or duplications were identified in control subjects. Conclusions Later-onset conditions like schizophrenia are increasingly associated with rare copy number variations and associated genomic disorders like the 3q13.31 microdeletion syndrome. Detailed phenotype information across the lifespan facilitates genotype-phenotype correlations, accurate genetic counselling, and anticipatory care.
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Affiliation(s)
| | | | | | | | | | | | | | - Anne S Bassett
- Clinical Genetics Research Program, Centre for Addiction and Mental Health, Toronto, ON, Canada.
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Karavitakis E, Kitsiou-Tzeli S, Xaidara A, Kosma K, Makrythanasis P, Apazidou E, Kanavakis E, Tzetis M. Microduplication 3q13.2q13.31 identified in a male with dysmorphic features and multiple congenital anomalies. Am J Med Genet A 2013; 164A:666-70. [DOI: 10.1002/ajmg.a.36346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Accepted: 10/06/2013] [Indexed: 11/10/2022]
Affiliation(s)
| | - Sofia Kitsiou-Tzeli
- Department of Medical Genetics; Medical School; University of Athens; Greece
| | - Athena Xaidara
- First Department of Pediatrics, Medical School; “Aghia Sophia” Children's Hospital, University of Athens; Athens Greece
| | - Konstantina Kosma
- Department of Medical Genetics; Medical School; University of Athens; Greece
| | - Periklis Makrythanasis
- Department of Medical Genetics; Medical School; University of Athens; Greece
- Department of Genetic Medicine and Development; University of Geneva; Geneva Switzerland
| | - Eleni Apazidou
- Neonatal Special Care Unit; General Hospital of Chania; Crete Greece
| | - Emmanuel Kanavakis
- Department of Medical Genetics; Medical School; University of Athens; Greece
- Research Institute for the Study of Genetic and Malignant Disorders in Childhood; “Aghia Sophia, Children's Hospital”; Athens Greece
| | - Maria Tzetis
- Department of Medical Genetics; Medical School; University of Athens; Greece
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Gimelli S, Leoni M, Di Rocco M, Caridi G, Porta S, Cuoco C, Gimelli G, Tassano E. A rare 3q13.31 microdeletion including GAP43 and LSAMP genes. Mol Cytogenet 2013; 6:52. [PMID: 24279697 PMCID: PMC3906914 DOI: 10.1186/1755-8166-6-52] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 10/28/2013] [Indexed: 11/26/2022] Open
Abstract
Background Interstitial deletions affecting the proximal long arm of chromosome 3 have been rarely reported in the literature. The deleted segments vary in localization and size with different breakpoints making genotype-phenotype correlation very difficult. Until now, a girl with a 1.9-Mb interstitial deletion of 3q13.2q13.31 and 14 novel patients with deletions in 3q11q23 have been reported. Results Here we report on a 7-year-old girl with neuropsychiatric disorders and renal, vascular and skeletal anomalies. Array-CGH analysis revealed a small rare inherited 3q13.31 deletion containing only two genes, GAP43 and LSAMP. The mutation analysis of the two genes was negative on the other non-deleted chromosome. GAP43 is considered a crucial component for an effective regenerative response in the nervous system and its mRNA is localized exclusively to nerve tissue where the protein is linked to the synaptosomal membrane. LSAMP is a 64- to 68-kD neuronal surface glycoprotein found in cortical and subcortical regions of the limbic system that acts as an adhesion molecule and guides the development of specific patterns of neuronal connection. The deleted region is adjacent to a “desert gene” region extending 2.099 Mb. Conclusions We discuss the effects of GAP43 and LSAMP haploinsufficiency, proposing that their deletion may be responsible for the main phenotype. Further cases with similar microdeletion are expected to be diagnosed and will help to better characterize the clinical spectrum of phenotypes associated with 3q13.31 microdeletion.
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Affiliation(s)
| | | | | | | | | | | | | | - Elisa Tassano
- Laboratorio di Citogenetica, Istituto G, Gaslini, Genoa, Italy.
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Vuillaume ML, Delrue MA, Naudion S, Toutain J, Fergelot P, Arveiler B, Lacombe D, Rooryck C. Expanding the clinical phenotype at the 3q13.31 locus with a new case of microdeletion and first characterization of the reciprocal duplication. Mol Genet Metab 2013; 110:90-7. [PMID: 23920044 DOI: 10.1016/j.ymgme.2013.07.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 07/11/2013] [Accepted: 07/11/2013] [Indexed: 11/30/2022]
Abstract
Congenital deletions at the 3q13.31 locus have been recently described as a novel microdeletion syndrome characterized by developmental delay, postnatal overgrowth, hypoplastic male genitalia and characteristic facial features. A common critical region of overlapping of 580kb was delineated including two strong candidate genes for developmental delay: DRD3 and ZBTB20. In this report, we describe a new case of 3q13.31 microdeletion identified by array-CGH in a 16year-old girl sharing clinical features commonly observed in the 3q13.31 microdeletion syndrome. This girl had a microdeletion of 7.39Mb spanning the common critical region of overlapping. More interestingly, we report for the first time the existence of a microduplication reciprocal to the microdeletion syndrome. This familial 2.76Mb microduplication identified by array-CGH was carried by two brothers and their father. The phenotype shared by the brothers resembled the phenotype related to the 3q13.31 microdeletion syndrome including especially severe intellectual disability, developmental delay, behavioral abnormalities and obesity. This microduplication involves three strong candidate genes for the developmental delay ZBTB20, LSAMP and GAP43. Further molecular characterization showed that DRD3, another strong candidate gene for developmental delay, was not included in the duplicated region. However, a dosage alteration of this gene cannot be completely excluded as the duplication was inverted at proximity of this gene, as revealed by FISH analysis. Finally, we hypothesized that the phenotype shared by the two brothers could be related to a gene dosage imbalance even if gene expression could not be measured in relevant tissues such as brain or adipocytes.
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Affiliation(s)
- Marie-Laure Vuillaume
- CHU Bordeaux, Service de Génétique Médicale, Place Amélie Raba Léon, Bordeaux, France.
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Shuvarikov A, Campbell IM, Dittwald P, Neill NJ, Bialer MG, Moore C, Wheeler PG, Wallace SE, Hannibal MC, Murray MF, Giovanni MA, Terespolsky D, Sodhi S, Cassina M, Viskochil D, Moghaddam B, Herman K, Brown CW, Beck CR, Gambin A, Cheung SW, Patel A, Lamb AN, Shaffer LG, Ellison JW, Ravnan JB, Stankiewicz P, Rosenfeld JA. Recurrent HERV-H-mediated 3q13.2-q13.31 deletions cause a syndrome of hypotonia and motor, language, and cognitive delays. Hum Mutat 2013; 34:1415-23. [PMID: 23878096 DOI: 10.1002/humu.22384] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 07/11/2013] [Indexed: 11/09/2022]
Abstract
We describe the molecular and clinical characterization of nine individuals with recurrent, 3.4-Mb, de novo deletions of 3q13.2-q13.31 detected by chromosomal microarray analysis. All individuals have hypotonia and language and motor delays; they variably express mild to moderate cognitive delays (8/9), abnormal behavior (7/9), and autism spectrum disorders (3/9). Common facial features include downslanting palpebral fissures with epicanthal folds, a slightly bulbous nose, and relative macrocephaly. Twenty-eight genes map to the deleted region, including four strong candidate genes, DRD3, ZBTB20, GAP43, and BOC, with important roles in neural and/or muscular development. Analysis of the breakpoint regions based on array data revealed directly oriented human endogenous retrovirus (HERV-H) elements of ~5 kb in size and of >95% DNA sequence identity flanking the deletion. Subsequent DNA sequencing revealed different deletion breakpoints and suggested nonallelic homologous recombination (NAHR) between HERV-H elements as a mechanism of deletion formation, analogous to HERV-I-flanked and NAHR-mediated AZFa deletions. We propose that similar HERV elements may also mediate other recurrent deletion and duplication events on a genome-wide scale. Observation of rare recurrent chromosomal events such as these deletions helps to further the understanding of mechanisms behind naturally occurring variation in the human genome and its contribution to genetic disease.
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Affiliation(s)
- Andrey Shuvarikov
- Signature Genomic Laboratories, PerkinElmer, Inc, Spokane, Washington
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Brett MS, Ng ISL, Lim ECP, Yong MH, Li Z, Lai A, Tan EC. De novo 3q22.1 q24 deletion associated with multiple congenital anomalies, growth retardation and intellectual disability. Gene 2013; 517:82-8. [PMID: 23313878 DOI: 10.1016/j.gene.2012.12.082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 11/15/2012] [Accepted: 12/19/2012] [Indexed: 10/27/2022]
Abstract
We describe a boy with a de novo deletion of 15.67 Mb spanning 3q22.1q24. He has bilateral micropthalmia, ptosis, cleft palate, global developmental delay and brain, skeletal and cardiac abnormalities. In addition, he has bilateral inguinal hernia and his right kidney is absent. We compare his phenotype with seven other patients with overlapping and molecularly defined interstitial 3q deletions. This patient has some phenotypic features that are not shared by the other patients. More cases with smaller deletions defined by high resolution aCGH will enable better genotype-phenotype correlations and prioritizing of candidate genes for the identification of pathways and disease mechanisms.
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Affiliation(s)
- Maggie S Brett
- KK Research Centre, KK Women's & Children's Hospital, Singapore
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Molin AM, Andrieux J, Koolen DA, Malan V, Carella M, Colleaux L, Cormier-Daire V, David A, de Leeuw N, Delobel B, Duban-Bedu B, Fischetto R, Flinter F, Kjaergaard S, Kok F, Krepischi AC, Le Caignec C, Ogilvie CM, Maia S, Mathieu-Dramard M, Munnich A, Palumbo O, Papadia F, Pfundt R, Reardon W, Receveur A, Rio M, Ronsbro Darling L, Rosenberg C, Sá J, Vallee L, Vincent-Delorme C, Zelante L, Bondeson ML, Annerén G. A novel microdeletion syndrome at 3q13.31 characterised by developmental delay, postnatal overgrowth, hypoplastic male genitals, and characteristic facial features. J Med Genet 2011; 49:104-9. [PMID: 22180640 PMCID: PMC3261728 DOI: 10.1136/jmedgenet-2011-100534] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Congenital deletions affecting 3q11q23 have rarely been reported and only five cases have been molecularly characterised. Genotype-phenotype correlation has been hampered by the variable sizes and breakpoints of the deletions. In this study, 14 novel patients with deletions in 3q11q23 were investigated and compared with 13 previously reported patients. METHODS Clinical data were collected from 14 novel patients that had been investigated by high resolution microarray techniques. Molecular investigation and updated clinical information of one cytogenetically previously reported patient were also included. RESULTS The molecular investigation identified deletions in the region 3q12.3q21.3 with different boundaries and variable sizes. The smallest studied deletion was 580 kb, located in 3q13.31. Genotype-phenotype comparison in 24 patients sharing this shortest region of overlapping deletion revealed several common major characteristics including significant developmental delay, muscular hypotonia, a high arched palate, and recognisable facial features including a short philtrum and protruding lips. Abnormal genitalia were found in the majority of males, several having micropenis. Finally, a postnatal growth pattern above the mean was apparent. The 580 kb deleted region includes five RefSeq genes and two of them are strong candidate genes for the developmental delay: DRD3 and ZBTB20. CONCLUSION A newly recognised 3q13.31 microdeletion syndrome is delineated which is of diagnostic and prognostic value. Furthermore, two genes are suggested to be responsible for the main phenotype.
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Affiliation(s)
- Anna-Maja Molin
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
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Abstract
AbstractWe present the case of a 20-year-old man referred to the clinical geneticist because of mental retardation and dysmorphic features because of concerns about hereditability when his older, healthy brother was expecting a child. Deletion of proximal 3q arm was found with standard G-banding, and array comparative genomic hybridisation (array-CGH) was used to further locate the breakpoints. A unique interstitial deletion del 3q13.11q13.33 was confirmed. The first clinical symptoms in the 20-year-old were described at the age of 4 months when the pediatrician reported muscle hypertonia of the lower limbs, which later evolved into hypotonia. Later clinical observations revealed that the patient’s psychomotor development was delayed: he exhibited craniofacial abnormalities, cryptorchidism, thoracic kyphosis, and tapering fingers. Interstitial deletions of the proximal long arm of chromosome 3 have rarely been reported:; there are only 12 previously reported cases. The breakpoints and sizes of described deletions vary greatly, which makes definite genotype-phenotype conclusions impossible at this time. Developmental delay is one of the common features described in the majority of reported cases. The BTB-zinc finger gene ZBTB20 might be a potential candidate gene: it was shown in the mouse hippocampus to be expressed during the important period of neurogenesis of pyramidal neurons. Also, four of patients reported to date had agenesis of the corpus callosum and one, holoprosencephaly. We suggest that the GAP43 gene is involved in the development of structural neurological abnormalities in patients with 3q deletion.
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