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Ahmed MR, Sethna S, Krueger LA, Yang MB, Hufnagel RB. Variable Anterior Segment Dysgenesis and Cardiac Anomalies Caused by a Novel Truncating Variant of FOXC1. Genes (Basel) 2022; 13:genes13030411. [PMID: 35327965 PMCID: PMC8949076 DOI: 10.3390/genes13030411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 02/15/2022] [Accepted: 02/18/2022] [Indexed: 02/04/2023] Open
Abstract
Anterior segment dysgenesis (ASD) encompasses a wide spectrum of developmental abnormalities of the anterior ocular segment, including congenital cataract, iris hypoplasia, aniridia, iridocorneal synechiae, as well as Peters, Axenfeld, and Rieger anomalies. Here, we report a large five-generation Caucasian family exhibiting atypical syndromic ASD segregating with a novel truncating variant of FOXC1. The family history is consistent with highly variable autosomal dominant symptoms including isolated glaucoma, iris hypoplasia, aniridia, cataract, hypothyroidism, and congenital heart anomalies. Whole-exome sequencing revealed a novel variant [c.313_314insA; p.(Tyr105*)] in FOXC1 that disrupts the α-helical region of the DNA-binding forkhead box domain. In vitro studies using a heterologous cell system revealed aberrant cytoplasmic localization of FOXC1 harboring the Tyr105* variant, likely precluding downstream transcription function. Meta-analysis of the literature highlighted the intrafamilial variability related to FOXC1 truncating alleles. This study highlights the clinical variability in ASD and signifies the importance of combining both clinical and molecular analysis approaches to establish a complete diagnosis.
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Affiliation(s)
- Mariya R. Ahmed
- Medical Genetics and Ophthalmic Genomics Unit, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA;
- Department of Otorhinolaryngology—Head & Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
| | - Saumil Sethna
- Department of Otorhinolaryngology—Head & Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
| | - Laura A. Krueger
- Department of Ophthalmology, Division of Pediatric Ophthalmology, Abrahamson Pediatric Eye Institute, University of Cincinnati College of Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA; (L.A.K.); (M.B.Y.)
| | - Michael B. Yang
- Department of Ophthalmology, Division of Pediatric Ophthalmology, Abrahamson Pediatric Eye Institute, University of Cincinnati College of Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA; (L.A.K.); (M.B.Y.)
| | - Robert B. Hufnagel
- Medical Genetics and Ophthalmic Genomics Unit, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA;
- Correspondence:
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Multiple Dental Inclusion in Monozygotic Twins with Congenital Visual Impairment. Case Rep Dent 2020; 2020:8856206. [PMID: 32832166 PMCID: PMC7428941 DOI: 10.1155/2020/8856206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 07/13/2020] [Accepted: 07/24/2020] [Indexed: 11/18/2022] Open
Abstract
The study presents two monozygotic twins (MZ) with multiple impacted teeth, affecting the upper canines and lower second molars, as well as congenital aniridia. The clinical aspect of the upper canines is peculiar because of the different positions—palatal in one and buccal in the other twin. Studies reporting different scenarios of impaction in monozygotic twins can contribute more data to the debate on tooth eruption aetiology and more so in this case because of the association with a genetic panocular disease. Patients' Concerns. The patients were referred by a general dentist, who diagnosed the presence of multiple inclusions. Diagnostic Study. Both patients showed severe malocclusion, classified as grade 5 of the Index of Orthodontic Treatment Need (IOTN). The MZ showed class I malocclusion, upper and lower crowding, and impacted lower right and left second molars. A Dentascan was prescribed for the canine impaction. The impaction of the upper canine was palatal of 2.3 in one of the MZ and buccal of 1.3 in the other one. The same altered pattern of eruption of the lower second molars was identified in both twins. The proposed treatment plan contemplated orthodontic surgical recovery of the impacted elements, followed by orthodontic treatment with multibracket appliance after the extraction of the first four premolars, given the crowding entity. The use of a retraction spring action was chosen for the recovery of the lower second molars. Many aspects of the possible genetic aetiology of tooth impaction are still under discussion. The study of diseases in twins offers decisive information. Finally, the possibility that alterations in the eruptive pattern of the dental elements may be associated with other congenital problems broadens the range of investigations related to the possible aetiological causes of the inclusions in humans.
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Abstract
The development of the anterior pituitary gland occurs in distinct sequential developmental steps, leading to the formation of a complex organ containing five different cell types secreting six different hormones. During this process, the temporal and spatial expression of a cascade of signaling molecules and transcription factors plays a crucial role in organ commitment, cell proliferation, patterning, and terminal differentiation. The morphogenesis of the gland and the emergence of distinct cell types from a common primordium are governed by complex regulatory networks involving transcription factors and signaling molecules that may be either intrinsic to the developing pituitary or extrinsic, originating from the ventral diencephalon, the oral ectoderm, and the surrounding mesenchyme. Endocrine cells of the pituitary gland are organized into structural and functional networks that contribute to the coordinated response of endocrine cells to stimuli; these cellular networks are formed during embryonic development and are maintained or may be modified in adulthood, contributing to the plasticity of the gland. Abnormalities in any of the steps of pituitary development may lead to congenital hypopituitarism that includes a spectrum of disorders from isolated to combined hormone deficiencies including syndromic disorders such as septo-optic dysplasia. Over the past decade, the acceleration of next-generation sequencing has allowed for rapid analysis of the patient genome to identify novel mutations and novel candidate genes associated with hypothalmo-pituitary development. Subsequent functional analysis using patient fibroblast cells, and the generation of stem cells derived from patient cells, is fast replacing the need for animal models while providing a more physiologically relevant characterization of novel mutations. Furthermore, CRISPR-Cas9 as the method for gene editing is replacing previous laborious and time-consuming gene editing methods that were commonly used, thus yielding knockout cell lines in a fraction of the time. © 2020 American Physiological Society. Compr Physiol 10:389-413, 2020.
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Affiliation(s)
- Kyriaki S Alatzoglou
- Genetics and Genomic Medicine Programme, UCL Great Ormond Street Institute of Child Health, University College London (UCL), London, UK
| | - Louise C Gregory
- Genetics and Genomic Medicine Programme, UCL Great Ormond Street Institute of Child Health, University College London (UCL), London, UK
| | - Mehul T Dattani
- Genetics and Genomic Medicine Programme, UCL Great Ormond Street Institute of Child Health, University College London (UCL), London, UK
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Fan Z, Sun S, Liu H, Yu M, Liu Z, Wong SW, Liu Y, Han D, Feng H. Novel PITX2 mutations identified in Axenfeld-Rieger syndrome and the pattern of PITX2-related tooth agenesis. Oral Dis 2019; 25:2010-2019. [PMID: 31529555 DOI: 10.1111/odi.13196] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/25/2019] [Accepted: 09/07/2019] [Indexed: 12/27/2022]
Abstract
OBJECTIVES To investigate the mutations in patients with Axenfeld-Rieger syndrome (ARS) and the pattern of PITX2-related tooth agenesis. METHODS Whole-exome sequencing (WES) and copy number variation (CNV) array were used to screen the mutations in four ARS probands. After Sanger sequencing and quantitative polymerase chain reaction (qPCR) validation, secondary structure prediction and dual-luciferase assay were employed to investigate the functional impact. Eighteen PITX2-mutated patients with definite dental records were retrieved from our database and literatures, and the pattern of PITX2-related tooth agenesis was analyzed. RESULTS A novel de novo segmental deletion of chromosome 4q25 (GRCh37/hg19 chr4:111, 320, 052-111, 754, 236) encompassing PITX2 and three novel PITX2 mutations c.148C > T, c.257G > A, and c.630insCG were identified. Preliminary functional studies indicated the transactivation capacity of mutant PITX2 on Distal-less homeobox 2 (DLX2) promoter was compromised. The maxillary teeth showed significantly higher rate of agenesis (57.94%) than the mandibular teeth (44.05%). The most often missing teeth were upper lateral incisors (83.33%) and upper second premolars (69.44%). Teeth with the least agenesis rate were the lower second molars (19.44%) and lower first molars (8.33%). CONCLUSIONS We identified a novel 4q25 microdeletion including PITX2 and three novel PITX2 mutations, and statistically analyzed the PITX2-related tooth agenesis pattern.
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Affiliation(s)
- Zhuangzhuang Fan
- Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China
- National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, National Clinical Research Center for Oral Diseases, Beijing, China
- Peking University School and Hospital of Stomatology, Beijing, China
| | - Shichen Sun
- Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China
- National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, National Clinical Research Center for Oral Diseases, Beijing, China
- Peking University School and Hospital of Stomatology, Beijing, China
| | - Haochen Liu
- Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China
- National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, National Clinical Research Center for Oral Diseases, Beijing, China
- Peking University School and Hospital of Stomatology, Beijing, China
| | - Miao Yu
- Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China
- National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, National Clinical Research Center for Oral Diseases, Beijing, China
- Peking University School and Hospital of Stomatology, Beijing, China
| | - Ziyuan Liu
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China
| | - Sing-Wai Wong
- Division of Comprehensive Oral Health, Adams School of Dentistry, University of North Carolina at Chapel Hill, NC, USA
| | - Yang Liu
- Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China
- National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, National Clinical Research Center for Oral Diseases, Beijing, China
- Peking University School and Hospital of Stomatology, Beijing, China
| | - Dong Han
- Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China
- National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, National Clinical Research Center for Oral Diseases, Beijing, China
- Peking University School and Hospital of Stomatology, Beijing, China
| | - Hailan Feng
- Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, China
- National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, National Clinical Research Center for Oral Diseases, Beijing, China
- Peking University School and Hospital of Stomatology, Beijing, China
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Seifi M, Footz T, Taylor SAM, Elhady GM, Abdalla EM, Walter MA. Novel PITX2 gene mutations in patients with Axenfeld-Rieger syndrome. Acta Ophthalmol 2016; 94:e571-e579. [PMID: 27009473 DOI: 10.1111/aos.13030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 01/23/2016] [Indexed: 02/06/2023]
Abstract
PURPOSE Mutations in the bicoid-like transcription factor PITX2 gene often result in Axenfeld-Rieger syndrome (ARS), an autosomal-dominant inherited disorder. We report here the discovery and characterization of novel PITX2 deletions in a small kindred with ARS. METHODS Two familial patients (father and son) from a consanguineous family were examined in the present study. Patient DNA samples were screened for PITX2 mutations by DNA sequencing and for copy number variation by SYBR Green quantitative polymerase chain reaction (PCR) analysis. RESULTS We report a novel deletion involving the coding region of PITX2 in both patients. The minimum size of the deletion is 1 421 914 bp that spans one upstream regulatory element (CE4), PITX2 and a minimum of 13 neighbouring genes. The maximum size of the deletion is 3 789 983 bp. The proband (son) additionally possesses a novel 2-bp deletion in a non-coding exon of the remaining PITX2 allele predicted to alter correct splicing. CONCLUSION Our findings implicate a novel deletion of the PITX2 gene in the pathogenesis of ARS in the affected family. This ARS family presented with an atypical and extremely severe phenotype that resulted in four miscarriages and the death at 10 months of age of a sib of the proband. As the phenotypic manifestations in the proband are more severe than that of the father, we hypothesize that the deletion of the entire PITX2 allele plus a novel 2-bp deletion (observed in the proband) within the remaining PITX2 allele together contributed to the atypical ARS presentation in this family. This is the first study reporting on bi-allelic changes of PITX2 potentially contributing to a more severe ARS phenotype.
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Affiliation(s)
- Morteza Seifi
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Tim Footz
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Sherry A M Taylor
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Ghada M Elhady
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Ebtesam M Abdalla
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Michael A Walter
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
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Tooth agenesis and orofacial clefting: genetic brothers in arms? Hum Genet 2016; 135:1299-1327. [PMID: 27699475 PMCID: PMC5065589 DOI: 10.1007/s00439-016-1733-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 09/21/2016] [Indexed: 12/16/2022]
Abstract
Tooth agenesis and orofacial clefts represent the most common developmental anomalies and their co-occurrence is often reported in patients as well in animal models. The aim of the present systematic review is to thoroughly investigate the current literature (PubMed, EMBASE) to identify the genes and genomic loci contributing to syndromic or non-syndromic co-occurrence of tooth agenesis and orofacial clefts, to gain insight into the molecular mechanisms underlying their dual involvement in the development of teeth and facial primordia. Altogether, 84 articles including phenotype and genotype description provided 9 genomic loci and 26 gene candidates underlying the co-occurrence of the two congenital defects: MSX1, PAX9, IRF6, TP63, KMT2D, KDM6A, SATB2, TBX22, TGFα, TGFβ3, TGFβR1, TGFβR2, FGF8, FGFR1, KISS1R, WNT3, WNT5A, CDH1, CHD7, AXIN2, TWIST1, BCOR, OFD1, PTCH1, PITX2, and PVRL1. The molecular pathways, cellular functions, tissue-specific expression and disease association were investigated using publicly accessible databases (EntrezGene, UniProt, OMIM). The Gene Ontology terms of the biological processes mediated by the candidate genes were used to cluster them using the GOTermMapper (Lewis-Sigler Institute, Princeton University), speculating on six super-clusters: (a) anatomical development, (b) cell division, growth and motility, (c) cell metabolism and catabolism, (d) cell transport, (e) cell structure organization and (f) organ/system-specific processes. This review aims to increase the knowledge on the mechanisms underlying the co-occurrence of tooth agenesis and orofacial clefts, to pave the way for improving targeted (prenatal) molecular diagnosis and finally to reflect on therapeutic or ultimately preventive strategies for these disabling conditions in the future.
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Yin HF, Fang XY, Jin CF, Yin JF, Li JY, Zhao SJ, Miao Q, Song FW. Identification of a novel frameshift mutation in PITX2 gene in a Chinese family with Axenfeld-Rieger syndrome. J Zhejiang Univ Sci B 2014; 15:43-50. [PMID: 24390743 PMCID: PMC3891117 DOI: 10.1631/jzus.b1300053] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Accepted: 07/01/2013] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Axenfeld-Rieger syndrome (ARS) is phenotypically and genetically heterogeneous. In this study, we identified the underlying genetic defect in a Chinese family with ARS. METHODS A detailed family history and clinical data were recorded. The ocular phenotype was documented using slit-lamp photography and systemic anomalies were also documented where available. The genomic DNA was extracted from peripheral blood leukocytes. All coding exons and intron-exon junctions of paired-like homeodomain transcription factor 2 (PITX2) gene and the forkhead box C1 (FOXC1) gene were amplified by polymerase chain reaction (PCR) and screened for mutation by direct DNA sequencing. Variations detected in exon 5 of PITX2 were further evaluated with cloning sequencing. The exon 5 of PITX2 was also sequenced in 100 healthy controls, unrelated to the family, for comparison. Structural models of the wild type and mutant homeodomain of PITX2 were investigated by SWISS-MODEL. RESULTS Affected individuals exhibited variable ocular phenotypes, whereas the systemic anomalies were similar. After direct sequencing and cloning sequencing, a heterozygous deletion/insertion mutation c.198_201delinsTTTCT (p.M66Ifs*133) was revealed in exon 5 of PITX2. This mutation co-segregated with all affected individuals in the family and was not found either in unaffected family members or in 100 unrelated controls. CONCLUSIONS We detected a novel frameshift mutation p.M66Ifs*133 in PITX2 in a Chinese family with ARS. Although PITX2 mutations and polymorphisms have been reported from various ethnic groups, we report for the first time the identification of a novel deletion/insertion mutation that causes frameshift mutation in the homeodomain of PITX2 protein.
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Affiliation(s)
- Hou-fa Yin
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Xiao-yun Fang
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Chong-fei Jin
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Jin-fu Yin
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Jin-yu Li
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Su-juan Zhao
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Qi Miao
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Feng-wei Song
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
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Li Z, Yu M, Tian W. An inductive signalling network regulates mammalian tooth morphogenesis with implications for tooth regeneration. Cell Prolif 2013; 46:501-8. [PMID: 23952789 DOI: 10.1111/cpr.12051] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 05/18/2013] [Indexed: 12/15/2022] Open
Abstract
Sequential and reciprocal epithelial-mesenchymal interactions, essential throughout such aspects of tooth morphogenesis as patterning, size and number of teeth, involves a well-ordered series of inductive and permissive signals that exert global control over cell proliferation, differentiation and organogenesis. In particular, growth factors, transcription factors and their corresponding receptors, as well as other soluble morphogens, make up a regulatory network at the molecular level that synergistically or antagonistically controls intra-/inter-cellular signal transduction during odontogenesis. This review summarizes recent advances in the study of crucial signalling pathways, for example of BMPs, Wnt, Notch, Shh and FGF, with emphasis on the potential integrated signalling network responsible for tooth formation. Our work probes into the complexity of these inductive signalling pathways to promote the understanding of tooth regeneration. Additionally, our study provides further insights into therapeutic strategies for various dental abnormalities in patterning and number, such as tooth agenesis and supernumerary teeth.
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Affiliation(s)
- Z Li
- State Key Laboratory of Oral Disease, West China School of Stomatology, Sichuan University, Chengdu, 610041, China
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Mitsiadis TA, Luder HU. Genetic basis for tooth malformations: from mice to men and back again. Clin Genet 2011; 80:319-29. [DOI: 10.1111/j.1399-0004.2011.01762.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Simard A, Di Giorgio L, Amen M, Westwood A, Amendt BA, Ryan AK. The Pitx2c N-terminal domain is a critical interaction domain required for asymmetric morphogenesis. Dev Dyn 2009; 238:2459-70. [PMID: 19681163 PMCID: PMC3014603 DOI: 10.1002/dvdy.22062] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The paired-like homeodomain transcription factor Pitx2c has an essential role in patterning the left-right axis. However, neither its transcriptional targets nor the molecular mechanisms through which it exerts its patterning function are known. Here we provide evidence that the N-terminal domain of Pitx2c is important for this activity. Overexpression of the Pitx2c N-terminus in ovo randomizes the direction of heart looping, the first morphological asymmetry conserved in vertebrate embryos. In addition, the Pitx2c N-terminal domain blocks the ability of Pitx2c to synergize with Nkx2.5 to transactivate the procollagen lysyl hydroxylase (Plod-1) promoter in transient transfection assays. A five amino acid region containing leucine-41 is required for both of these effects. Our data suggest that the Pitx2c N-terminal domain competes with endogenous Pitx2c for binding to a protein interaction partner that is required for the activation of genes that direct asymmetric morphogenesis along the left-right axis.
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Affiliation(s)
- Annie Simard
- The Research Institute of the McGill University Health Center, Montreal, Quebec
| | | | - Melanie Amen
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX
| | - Ashley Westwood
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX
| | - Brad A. Amendt
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX
| | - Aimee K. Ryan
- The Research Institute of the McGill University Health Center, Montreal, Quebec
- Department of Human Genetics, McGill University, Montreal, Quebec
- Department of Pediatrics, McGill University, Montreal, Quebec
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Wang Y, Wu H, Wu J, Zhao H, Zhang X, Mues G, D'Souza RN, Feng H, Kapadia H. Identification and functional analysis of two novel PAX9 mutations. Cells Tissues Organs 2008; 189:80-7. [PMID: 18701815 DOI: 10.1159/000151448] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The paired-domain transcription factor PAX9 plays a critical role in tooth development, as heterozygous mutations in PAX9 have been shown to be associated with human tooth agenesis. In this study, we report 2 novel missense mutations, gly6arg (G6R) and ser43lys (S43K), in the paired domain of PAX9 in Chinese patients with varying degrees of nonsyndromic tooth agenesis. Excluding third molars, the individual with the G6R mutation was missing 2 mandibular incisors and a maxillary premolar, while the phenotype of individuals with the S43K mutation consisted of peg-shaped upper lateral incisors and missing molars, premolars and canines. As these 2 mutations occur at highly conserved amino acids in the PAX gene family and between different species, we further analyzed the effects of the mutations on the function of the resulting proteins. Immunofluorescence and immunoblotting studies showed that the mutations did not alter nuclear localization in mammalian cells. Gel shift and super shift assays indicate that both mutant proteins bound DNA at a lower level than the normal protein, with G6R having a greater affinity for DNA than S43K. Likewise, the G6R protein was able to transcriptionally activate a Bmp4 promoter construct to a greater extent than S43K. Our finding that the severity of tooth agenesis in the patients was correlated to the DNA-binding capacity of the mutated PAX9 9proteins supports the hypothesis that DNA binding is responsible for the genetic defect.
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Affiliation(s)
- Ying Wang
- Department of Biomedical Sciences, Baylor College of Dentistry, Texas A&M University System Health Science Center, Dallas, Tex., USA
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Maciolek NL, Alward WLM, Murray JC, Semina EV, McNally MT. Analysis of RNA splicing defects in PITX2 mutants supports a gene dosage model of Axenfeld-Rieger syndrome. BMC MEDICAL GENETICS 2006; 7:59. [PMID: 16834779 PMCID: PMC1553432 DOI: 10.1186/1471-2350-7-59] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Accepted: 07/11/2006] [Indexed: 12/02/2022]
Abstract
BACKGROUND Axenfeld-Rieger syndrome (ARS) is associated with mutations in the PITX2 gene that encodes a homeobox transcription factor. Several intronic PITX2 mutations have been reported in Axenfeld-Rieger patients but their effects on gene expression have not been tested. METHODS We present two new families with recurrent PITX2 intronic mutations and use PITX2c minigenes and transfected cells to address the hypothesis that intronic mutations effect RNA splicing. Three PITX2 mutations have been analyzed: a G>T mutation within the AG 3' splice site (ss) junction associated with exon 4 (IVS4-1G>T), a G>C mutation at position +5 of the 5' (ss) of exon 4 (IVS4+5G>C), and a previously reported A>G substitution at position -11 of 3'ss of exon 5 (IVS5-11A>G). RESULTS Mutation IVS4+5G>C showed 71% retention of the intron between exons 4 and 5, and poorly expressed protein. Wild-type protein levels were proportionally expressed from correctly spliced mRNA. The G>T mutation within the exon 4 AG 3'ss junction shifted splicing exclusively to a new AG and resulted in a severely truncated, poorly expressed protein. Finally, the A>G substitution at position -11 of the 3'ss of exon 5 shifted splicing exclusively to a newly created upstream AG and resulted in generation of a protein with a truncated homeodomain. CONCLUSION This is the first direct evidence to support aberrant RNA splicing as the mechanism underlying the disorder in some patients and suggests that the magnitude of the splicing defect may contribute to the variability of ARS phenotypes, in support of a gene dosage model of Axenfeld-Rieger syndrome.
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Affiliation(s)
- Nicole L Maciolek
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Wallace LM Alward
- Department of Ophthalmology, University of Iowa, Iowa City, IA 52242, USA
| | - Jeffrey C Murray
- Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA
| | - Elena V Semina
- Department of Pediatrics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Mark T McNally
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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Idrees F, Bloch-Zupan A, Free SL, Vaideanu D, Thompson PJ, Ashley P, Brice G, Rutland P, Bitner-Glindzicz M, Khaw PT, Fraser S, Sisodiya SM, Sowden JC. A novel homeobox mutation in the PITX2 gene in a family with Axenfeld-Rieger syndrome associated with brain, ocular, and dental phenotypes. Am J Med Genet B Neuropsychiatr Genet 2006; 141B:184-91. [PMID: 16389592 DOI: 10.1002/ajmg.b.30237] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Axenfeld-Rieger Syndrome (ARS) is a genetically heterogeneous birth defect characterized by malformation of the anterior segment of the eye associated with glaucoma. Mutation of the PITX2 homeobox gene has been identified as a cause of ARS. We report a novel Arg5Trp missense mutation in the PITX2 homeodomain, which is associated with brain abnormalities. One patient had a small sella turcica likely to reflect hypoplasia of the pituitary gland and consistent with the critical role identified for Pitx2 in pituitary development in mice. Two patients had an enlarged cisterna magna, one with a malformed cerebellum, and two had executive skills deficits one in isolation and one in association with a below average intellectual capacity. The mutation caused a typical ARS ocular phenotype. All affected had iris hypoplasia, anterior iris to corneal adhesions, and corectopia. The ocular phenotype varied significantly in severity and showed some asymmetry. All affected also had redundant peri-umbilical skin, a hypoplastic maxilla, microdontia, and hypodontia missing between 20 and 27 teeth with an unusual pattern of tooth loss. Dental phenotypes were documented as they are often poorly characterized in ARS patients. All affected individuals showed an absence of first permanent molars with variable absence of other rarely absent teeth: the permanent upper central incisors, maxillary and mandibular first and second molars, and the mandibular canines. Based on the distinctive dental anomalies, we suggest that the dental phenotype can assist in predicting the presence of a PITX2 mutation and the possibility of brain abnormalities.
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Affiliation(s)
- Faisal Idrees
- Developmental Biology Unit, Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust, University College London, London, United Kingdom
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Saadi I, Toro R, Kuburas A, Semina E, Murray JC, Russo AF. An unusual class of PITX2 mutations in Axenfeld-Rieger syndrome. BIRTH DEFECTS RESEARCH. PART A, CLINICAL AND MOLECULAR TERATOLOGY 2006; 76:175-81. [PMID: 16498627 PMCID: PMC4023635 DOI: 10.1002/bdra.20226] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Mutations in the PITX2 homeobox gene are known to contribute to Axenfeld-Rieger syndrome (ARS), an autosomal-dominant developmental disorder. Although most mutations are in the homeodomain and result in a loss of function, there is a growing subset in the C-terminal domain that has not yet been characterized. These mutations are of particular interest because the C-terminus has both inhibitory and stimulatory activities. METHODS In this study we used a combination of in vitro DNA binding and transfection reporter assays to investigate the fundamental issue of whether C-terminal mutations result in gain or loss of function at a cellular level. RESULTS We report a new frameshift mutation in the PITX2 allele that predicts a truncated protein lacking most of the C-terminal domain (D122FS). This newly reported mutant and another ARS C-terminal mutant (W133Stop) both have greater binding than wild-type to the bicoid element. Of interest, the mutants yielded approximately 5-fold greater activation of the prolactin promoter in CHO cells, even though the truncated proteins were expressed at lower levels than the wild-type protein. The truncated proteins also had greater than wild-type activity in 2 other cell lines, including the LS8 oral epithelial line that expresses the endogenous Pitx2 gene. CONCLUSIONS The results indicate that the PITX2 C-terminal domain has inhibitory activity and support the notion that ARS may also be caused by gain-of-function mutations.
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Affiliation(s)
- Irfan Saadi
- Genetics Program, University of Iowa, Iowa City, Iowa
| | - Rafael Toro
- Genetics Program, University of Iowa, Iowa City, Iowa
| | - Adisa Kuburas
- Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa
| | - Elena Semina
- Department of Pediatrics, University of Iowa, Iowa City, Iowa
| | - Jeffrey C. Murray
- Genetics Program, University of Iowa, Iowa City, Iowa
- Department of Pediatrics, University of Iowa, Iowa City, Iowa
| | - Andrew F. Russo
- Genetics Program, University of Iowa, Iowa City, Iowa
- Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa
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