51
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Sukalo M, Tilsen F, Kayserili H, Müller D, Tüysüz B, Ruddy DM, Wakeling E, Ørstavik KH, Snape KM, Trembath R, De Smedt M, van der Aa N, Skalej M, Mundlos S, Wuyts W, Southgate L, Zenker M. DOCK6 mutations are responsible for a distinct autosomal-recessive variant of Adams-Oliver syndrome associated with brain and eye anomalies. Hum Mutat 2015; 36:593-8. [PMID: 25824905 DOI: 10.1002/humu.22795] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 03/27/2015] [Indexed: 12/18/2022]
Abstract
Adams-Oliver syndrome (AOS) is characterized by the association of aplasia cutis congenita with terminal transverse limb defects, often accompanied by additional cardiovascular or neurological features. Both autosomal-dominant and autosomal-recessive disease transmission have been observed, with recent gene discoveries indicating extensive genetic heterogeneity. Mutations of the DOCK6 gene were first described in autosomal-recessive cases of AOS and only five DOCK6-related families have been reported to date. Recently, a second type of autosomal-recessive AOS has been attributed to EOGT mutations in three consanguineous families. Here, we describe the identification of 13 DOCK6 mutations, the majority of which are novel, across 10 unrelated individuals from a large cohort comprising 47 sporadic cases and 31 AOS pedigrees suggestive of autosomal-recessive inheritance. DOCK6 mutations were strongly associated with structural brain abnormalities, ocular anomalies, and intellectual disability, thus suggesting that DOCK6-linked disease represents a variant of AOS with a particularly poor prognosis.
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Affiliation(s)
- Maja Sukalo
- Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany
| | - Felix Tilsen
- Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany
| | - Hülya Kayserili
- Medical Genetics Department, Istanbul Medical Faculty, Istanbul, Turkey.,Medical Genetics Department, School of Medicine, Koc University, Istanbul, Turkey
| | - Dietmar Müller
- Institut für Medizinische Genetik, Klinikum Chemnitz, Chemnitz, Germany
| | - Beyhan Tüysüz
- Department of Pediatric Genetics, Istanbul University, Istanbul, Turkey
| | | | - Emma Wakeling
- North West Thames Regional Genetics Service, North West London Hospitals NHS Trust, Harrow, UK
| | | | - Katie M Snape
- Department of Clinical Genetics, St. George's Healthcare NHS Trust, London, UK
| | - Richard Trembath
- Department of Clinical Genetics, Guy's Hospital, London, UK.,Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Maryse De Smedt
- Department of Medical Genetics, Leuven University Hospital, Leuven, Belgium
| | - Nathalie van der Aa
- Department of Medical Genetics, Antwerp University Hospital, Antwerp, Belgium
| | - Martin Skalej
- Institute of Neuroradiology, University Hospital Magdeburg, Magdeburg, Germany
| | - Stefan Mundlos
- Institute for Medical and Human Genetics Charité, Universitätsmedizin Berlin and Max Planck Institute for Molecular Genetics Berlin, Berlin, Germany
| | - Wim Wuyts
- Department of Medical Genetics, Antwerp University Hospital, Antwerp, Belgium.,Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
| | - Laura Southgate
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,Division of Genetics and Molecular Medicine, King's College London, London, UK
| | - Martin Zenker
- Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany
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52
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Ogawa M, Sawaguchi S, Furukawa K, Okajima T. N-acetylglucosamine modification in the lumen of the endoplasmic reticulum. Biochim Biophys Acta Gen Subj 2015; 1850:1319-24. [PMID: 25791024 DOI: 10.1016/j.bbagen.2015.03.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 03/07/2015] [Accepted: 03/11/2015] [Indexed: 12/25/2022]
Abstract
BACKGROUND O-linked β-N-acetylglucosamine (O-GlcNAc) modification of epidermal growth factor (EGF) domains catalyzed by EGF domain O-GlcNAc transferase (EOGT) is the first example of GlcNAc modification in the lumen of the endoplasmic reticulum (ER). SCOPE OF REVIEW This review summarizes current knowledge on the EOGT-catalyzed O-GlcNAc modification of EGF domains obtained through biochemical characterization, genetic analysis in Drosophila, and identification of human EOGT mutation. Additionally, this review discusses GTDC2-another ER protein homologous to EOGT that catalyzes the GlcNAc modification of O-mannosylated α-dystroglycan-and other components of the biosynthetic pathway involved in GlcNAc modification in the ER lumen. MAJOR CONCLUSIONS GlcNAc modification in the ER lumen has been identified as a novel type of protein modification that regulates specific protein function. Moreover, abnormal GlcNAc modification in the ER lumen is responsible for Adams-Oliver syndrome and Walker-Warburg syndrome. GENERAL SIGNIFICANCE Elucidation of the biological function of GlcNAc modification in the ER lumen will provide new insights into the unique roles of O-glycans, whose importance has been demonstrated in multifunctional glycoproteins such as Notch receptors and α-dystroglyan.
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Affiliation(s)
- Mitsutaka Ogawa
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan; Department of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829, Japan
| | - Shogo Sawaguchi
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan
| | - Koichi Furukawa
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan
| | - Tetsuya Okajima
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan.
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53
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Marneros AG. Genetics of Aplasia Cutis Reveal Novel Regulators of Skin Morphogenesis. J Invest Dermatol 2015; 135:666-672. [DOI: 10.1038/jid.2014.413] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Revised: 09/01/2014] [Accepted: 09/04/2014] [Indexed: 11/09/2022]
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54
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Exome sequencing unravels unexpected differential diagnoses in individuals with the tentative diagnosis of Coffin-Siris and Nicolaides-Baraitser syndromes. Hum Genet 2015; 134:553-68. [PMID: 25724810 DOI: 10.1007/s00439-015-1535-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 02/09/2015] [Indexed: 12/11/2022]
Abstract
Coffin-Siris syndrome (CSS) and Nicolaides-Baraitser syndrome (NCBRS) are rare intellectual disability/congenital malformation syndromes that represent distinct entities but show considerable clinical overlap. They are caused by mutations in genes encoding members of the BRG1- and BRM-associated factor (BAF) complex. However, there are a number of patients with the clinical diagnosis of CSS or NCBRS in whom the causative mutation has not been identified. In this study, we performed trio-based whole-exome sequencing (WES) in ten previously described but unsolved individuals with the tentative diagnosis of CSS or NCBRS and found causative mutations in nine out of ten individuals. Interestingly, our WES analysis disclosed overlapping differential diagnoses including Wiedemann-Steiner, Kabuki, and Adams-Oliver syndromes. In addition, most likely causative de novo mutations were identified in GRIN2A and SHANK3. Moreover, trio-based WES detected SMARCA2 and SMARCA4 deletions, which had not been annotated in a previous Haloplex target enrichment and next-generation sequencing of known CSS/NCBRS genes emphasizing the advantages of WES as a diagnostic tool. In summary, we discuss the phenotypic and diagnostic challenges in clinical genetics, establish important differential diagnoses, and emphasize the cardinal features and the broad clinical spectrum of BAF complex disorders and other disorders caused by mutations in epigenetic landscapers.
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55
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Ohshima H. Oral Biosciences: The annual review 2014. J Oral Biosci 2015. [DOI: 10.1016/j.job.2014.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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56
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Ogawa M, Sawaguchi S, Kawai T, Nadano D, Matsuda T, Yagi H, Kato K, Furukawa K, Okajima T. Impaired O-linked N-acetylglucosaminylation in the endoplasmic reticulum by mutated epidermal growth factor (EGF) domain-specific O-linked N-acetylglucosamine transferase found in Adams-Oliver syndrome. J Biol Chem 2014; 290:2137-49. [PMID: 25488668 DOI: 10.1074/jbc.m114.598821] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Epidermal growth factor (EGF) domain-specific O-linked N-acetylglucosamine (EOGT) is an endoplasmic reticulum (ER)-resident O-linked N-acetylglucosamine (O-GlcNAc) transferase that acts on EGF domain-containing proteins such as Notch receptors. Recently, mutations in EOGT have been reported in patients with Adams-Oliver syndrome (AOS). Here, we have characterized enzymatic properties of mouse EOGT and EOGT mutants associated with AOS. Simultaneous expression of EOGT with Notch1 EGF repeats in human embryonic kidney 293T (HEK293T) cells led to immunoreactivity with the CTD110.6 antibody in the ER. Consistent with the GlcNAc modification in the ER, the enzymatic properties of EOGT are distinct from those of Golgi-resident GlcNAc transferases; the pH optimum of EOGT ranges from 7.0 to 7.5, and the Km value for UDP N-acetylglucosamine (UDP-GlcNAc) is 25 μm. Despite the relatively low Km value for UDP-GlcNAc, EOGT-catalyzed GlcNAcylation depends on the hexosamine pathway, as revealed by the increased O-GlcNAcylation of Notch1 EGF repeats upon supplementation with hexosamine, suggesting differential regulation of the luminal UDP-GlcNAc concentration in the ER and Golgi. As compared with wild-type EOGT, O-GlcNAcylation in the ER is nearly abolished in HEK293T cells exogenously expressing EOGT variants associated with AOS. Introduction of the W207S mutation resulted in degradation of the protein via the ubiquitin-proteasome pathway, although the stability and ER localization of EOGT(R377Q) were not affected. Importantly, the interaction between UDP-GlcNAc and EOGT(R377Q) was impaired without adversely affecting the acceptor substrate interaction. These results suggest that impaired glycosyltransferase activity in mutant EOGT proteins and the consequent defective O-GlcNAcylation in the ER constitute the molecular basis for AOS.
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Affiliation(s)
- Mitsutaka Ogawa
- From the Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, the Department of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829
| | - Shogo Sawaguchi
- From the Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065
| | - Takami Kawai
- From the Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065
| | - Daita Nadano
- the Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601
| | - Tsukasa Matsuda
- the Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601
| | - Hirokazu Yagi
- the Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, and
| | - Koichi Kato
- the Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, and the Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 5-1 Higashiyama Myodaiji, Okazaki 444-8787, Japan
| | - Koichi Furukawa
- From the Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065
| | - Tetsuya Okajima
- From the Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065,
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57
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Stittrich AB, Lehman A, Bodian D, Ashworth J, Zong Z, Li H, Lam P, Khromykh A, Iyer R, Vockley J, Baveja R, Silva E, Dixon J, Leon E, Solomon B, Glusman G, Niederhuber J, Roach J, Patel M. Mutations in NOTCH1 cause Adams-Oliver syndrome. Am J Hum Genet 2014; 95:275-84. [PMID: 25132448 DOI: 10.1016/j.ajhg.2014.07.011] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 07/22/2014] [Indexed: 12/16/2022] Open
Abstract
Notch signaling determines and reinforces cell fate in bilaterally symmetric multicellular eukaryotes. Despite the involvement of Notch in many key developmental systems, human mutations in Notch signaling components have mainly been described in disorders with vascular and bone effects. Here, we report five heterozygous NOTCH1 variants in unrelated individuals with Adams-Oliver syndrome (AOS), a rare disease with major features of aplasia cutis of the scalp and terminal transverse limb defects. Using whole-genome sequencing in a cohort of 11 families lacking mutations in the four genes with known roles in AOS pathology (ARHGAP31, RBPJ, DOCK6, and EOGT), we found a heterozygous de novo 85 kb deletion spanning the NOTCH1 5' region and three coding variants (c.1285T>C [p.Cys429Arg], c.4487G>A [p.Cys1496Tyr], and c.5965G>A [p.Asp1989Asn]), two of which are de novo, in four unrelated probands. In a fifth family, we identified a heterozygous canonical splice-site variant (c.743-1 G>T) in an affected father and daughter. These variants were not present in 5,077 in-house control genomes or in public databases. In keeping with the prominent developmental role described for Notch1 in mouse vasculature, we observed cardiac and multiple vascular defects in four of the five families. We propose that the limb and scalp defects might also be due to a vasculopathy in NOTCH1-related AOS. Our results suggest that mutations in NOTCH1 are the most common cause of AOS and add to a growing list of human diseases that have a vascular and/or bony component and are caused by alterations in the Notch signaling pathway.
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58
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Rymen D, Jaeken J. Skin manifestations in CDG. J Inherit Metab Dis 2014; 37:699-708. [PMID: 24554337 DOI: 10.1007/s10545-014-9678-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 12/01/2013] [Accepted: 01/20/2014] [Indexed: 10/25/2022]
Abstract
The group of congenital disorders of glycosylation (CDG) has expanded tremendously since its first description in 1980, with around 70 distinct disorders described to date. A great phenotypic variability exists, ranging from multisystem disease to single organ involvement. Skin manifestations, although inconsistently present, are part of this broad clinical spectrum. Indeed, the presence of inverted nipples, fat pads and orange peel skin in a patient with developmental delay are considered as a hallmark of CDG, particularly seen in PMM2 deficiency. However, over the years many more dermatological findings have been observed (e.g., ichthyosis, cutis laxa, tumoral calcinosis…). In this review we will discuss the variety of skin manifestations reported in CDG. Moreover, we will explore the possible mechanisms that link a certain glycosylation deficiency to its skin phenotype.
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Affiliation(s)
- D Rymen
- Center for Human Genetics, University of Leuven, Leuven, Belgium,
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59
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Lehman A, Stittrich AB, Glusman G, Zong Z, Li H, Eydoux P, Senger C, Lyons C, Roach JC, Patel M. Diffuse angiopathy in Adams-Oliver syndrome associated with truncating DOCK6 mutations. Am J Med Genet A 2014; 164A:2656-62. [PMID: 25091416 DOI: 10.1002/ajmg.a.36685] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 06/18/2014] [Indexed: 11/11/2022]
Abstract
Adams-Oliver syndrome (AOS) is a rare malformation syndrome characterized by the presence of two anomalies: aplasia cutis congenita of the scalp and transverse terminal limb defects. Many affected individuals also have additional malformations, including a variety of intracranial anomalies such as periventricular calcification in keeping with cerebrovascular microbleeds, impaired neuronal migration, epilepsy, and microcephaly. Cardiac malformations can be present, as can vascular dysfunction in the forms of cutis marmorata telangiectasia congenita, pulmonary vein stenoses, and abnormal hepatic microvasculature. Elucidated genetic causes include four genes in different pathways, leading to a model of AOS as a multi-pathway disorder. We identified an infant with mild aplasia cutis congenita and terminal transverse limb defects, developmental delay and a severe, diffuse angiopathy with incomplete microvascularization. Whole-genome sequencing documented two rare truncating variants in DOCK6, a gene associated with a type of autosomal recessive AOS that recurrently features periventricular calcification and impaired neurodevelopment. We highlight an unexpectedly high frequency of likely deleterious mutations in this gene in the general population, relative to the rarity of the disease, and discuss possible explanations for this discrepancy.
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Affiliation(s)
- Anna Lehman
- Department of Medical Genetics and Child and Family Research Institute, University of British Columbia, Vancouver, Canada
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60
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Alkuraya FS. Genetics and genomic medicine in Saudi Arabia. Mol Genet Genomic Med 2014; 2:369-78. [PMID: 25333061 PMCID: PMC4190871 DOI: 10.1002/mgg3.97] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 06/30/2014] [Indexed: 01/01/2023] Open
Affiliation(s)
- Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center Riyadh, Saudi Arabia ; Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University Riyadh, Saudi Arabia
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61
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Namekata K, Kimura A, Kawamura K, Harada C, Harada T. Dock GEFs and their therapeutic potential: neuroprotection and axon regeneration. Prog Retin Eye Res 2014; 43:1-16. [PMID: 25016980 DOI: 10.1016/j.preteyeres.2014.06.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 06/26/2014] [Accepted: 06/30/2014] [Indexed: 12/17/2022]
Abstract
The dedicator of cytokinesis (Dock) family is composed of atypical guanine exchange factors (GEFs) that activate the Rho GTPases Rac1 and Cdc42. Rho GTPases are best documented for their roles in actin polymerization and they regulate important cellular functions, including morphogenesis, migration, neuronal development, and cell division and adhesion. To date, 11 Dock family members have been identified and their roles have been reported in diverse contexts. There has been increasing interest in elucidating the roles of Dock proteins in recent years and studies have revealed that they are potential therapeutic targets for various diseases, including glaucoma, Alzheimer's disease, cancer, attention deficit hyperactivity disorder and combined immunodeficiency. Among the Dock proteins, Dock3 is predominantly expressed in the central nervous system and recent studies have revealed that Dock3 plays a role in protecting retinal ganglion cells from neurotoxicity and oxidative stress as well as in promoting optic nerve regeneration. In this review, we discuss the current understanding of the 11 Dock GEFs and their therapeutic potential, with a particular focus on Dock3 as a novel target for the treatment of glaucoma and other neurodegenerative diseases.
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Affiliation(s)
- Kazuhiko Namekata
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Atsuko Kimura
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Kazuto Kawamura
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Chikako Harada
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
| | - Takayuki Harada
- Visual Research Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan.
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62
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Li Y, Teng C. Angiopoietin-like proteins 3, 4 and 8: regulating lipid metabolism and providing new hope for metabolic syndrome. J Drug Target 2014; 22:679-87. [PMID: 24960069 DOI: 10.3109/1061186x.2014.928715] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Angiopoietin-like proteins (ANGPTLs) are a group of eight proteins that share structural similarity to the members of the angiopoietin protein family. ANGPTL3 plays a vital role in the regulation of the plasma levels of triglyceride and cholesterol, mainly via reversible inhibition of the lipoprotein lipase activity. ANGPTL4, which functions as a homo-oligomer different from ANGPTL3 and ANGPTL8, not only regulates the plasma levels of triglyceride and prevents the uptake of dietary lipids into adipose tissues but also inhibits intravascular lipolysis. ANGPTL8 (also called betatrophin) has been identified as an important factor in regulating the triglyceride levels and adipose tissue mass as well as in replenishing the adipose tissue triglyceride store. ANGPTL8 acts together with ANGPTL3 to regulate the lipid metabolism, and ANGPTL8 promotes cleavage of ANGPTL3 to augment the activity of ANGPTL3. In addition, ANGPTL8 promotes proliferation of pancreatic β-cells and enhances insulin secretion. The properties of ANGPTLs in regulating the lipid metabolism suggest their application in the target therapy for metabolic syndrome. As ANGPTLs are regulated by several factors and may be involved in certain specific pathways of lipid metabolism, designing drugs that target ANGPTLs or factors regulating ANGPTLs may be an efficient approach to treat metabolic syndrome.
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Affiliation(s)
- Yunchao Li
- Laboratory of Animal Development Biology, College of Life Science, Northeast Forestry University, Ministry of Education , Harbin , China
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63
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Gadea G, Blangy A. Dock-family exchange factors in cell migration and disease. Eur J Cell Biol 2014; 93:466-77. [PMID: 25022758 DOI: 10.1016/j.ejcb.2014.06.003] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 06/10/2014] [Accepted: 06/17/2014] [Indexed: 02/06/2023] Open
Abstract
Dock family proteins are evolutionary conserved exchange factors for the Rho GTPases Rac and Cdc42. There are 11 Dock proteins in mammals, named Dock1 (or Dock180) to Dock11 that play different cellular functions. In particular, Dock proteins regulate actin cytoskeleton, cell adhesion and migration. Not surprisingly, members of the Dock family have been involved in various pathologies, including cancer and defects in the central nervous and immune systems. This review proposes an update of the recent findings regarding the function of Dock proteins, focusing on their role in the control of cell migration and invasion and the consequences in human diseases.
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Affiliation(s)
- Gilles Gadea
- CNRS UMR 5237, Centre de Recherche de Biochimie Macromoléculaire, France; Montpellier University, France
| | - Anne Blangy
- CNRS UMR 5237, Centre de Recherche de Biochimie Macromoléculaire, France; Montpellier University, France.
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64
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Ogawa M, Furukawa K, Okajima T. Extracellular O-linked β- N-acetylglucosamine: Its biology and relationship to human disease. World J Biol Chem 2014; 5:224-230. [PMID: 24921011 PMCID: PMC4050115 DOI: 10.4331/wjbc.v5.i2.224] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 01/20/2014] [Accepted: 04/09/2014] [Indexed: 02/05/2023] Open
Abstract
The O-linked β-N-acetylglucosamine (O-GlcNAc)ylation of cytoplasmic and nuclear proteins regulates basic cellular functions and is involved in the etiology of neurodegeneration and diabetes. Intracellular O-GlcNAcylation is catalyzed by a single O-GlcNAc transferase, O-GlcNAc transferase (OGT). Recently, an atypical O-GlcNAc transferase, extracellular O-linked β-N-acetylglucosamine (EOGT), which is responsible for the modification of extracellular O-GlcNAc, was identified. Although both OGT and EOGT are regulated through the common hexosamine biosynthesis pathway, EOGT localizes to the lumen of the endoplasmic reticulum and transfers GlcNAc to epidermal growth factor-like domains in an OGT-independent manner. In Drosophila, loss of Eogt gives phenotypes similar to those caused by defects in the apical extracellular matrix. Dumpy, a membrane-anchored apical extracellular matrix protein, was identified as a major O-GlcNAcylated protein, and EOGT mediates Dumpy-dependent cell adhesion. In mammals, extracellular O-GlcNAc was detected on extracellular proteins including heparan sulfate proteoglycan 2, Nell1, laminin subunit alpha-5, Pamr1, and transmembrane proteins, including Notch receptors. Although the physiological function of O-GlcNAc in mammals has not yet been elucidated, exome sequencing identified homozygous EOGT mutations in patients with Adams-Oliver syndrome, a rare congenital disorder characterized by aplasia cutis congenita and terminal transverse limb defects. This review summarizes the current knowledge of extracellular O-GlcNAc and its implications in the pathological processes in Adams-Oliver syndrome.
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65
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Abstract
Rho GTPases regulate many essential processes during development, yet the full impact of their upstream regulation through guanine nucleotide exchange factors (GEFs) is only beginning to be appreciated. In this review, Laurin and Côté focus on emerging biological functions of the mammalian Dock family of GEFs in development and disease and discuss how recent discoveries might be exploited for novel therapeutic strategies. Rho GTPases play key regulatory roles in many aspects of embryonic development, regulating processes such as differentiation, proliferation, morphogenesis, and migration. Two families of guanine nucleotide exchange factors (GEFs) found in metazoans, Dbl and Dock, are responsible for the spatiotemporal activation of Rac and Cdc42 proteins and their downstream signaling pathways. This review focuses on the emerging roles of the mammalian DOCK family in development and disease. We also discuss, when possible, how recent discoveries concerning the biological functions of these GEFs might be exploited for the development of novel therapeutic strategies.
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Affiliation(s)
- Mélanie Laurin
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, Quebec H2W 1R7, Canada
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66
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Isrie M, Wuyts W, Van Esch H, Devriendt K. Isolated terminal limb reduction defects: extending the clinical spectrum of Adams-Oliver syndrome and ARHGAP31 mutations. Am J Med Genet A 2014; 164A:1576-9. [PMID: 24668619 DOI: 10.1002/ajmg.a.36486] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 01/20/2014] [Indexed: 11/10/2022]
Abstract
Adams-Oliver syndrome (AOS; OMIM 100300) typically comprises a combination of congenital scalp defects and terminal transverse limb defects. Recently, mutations in ARHGAP31 and RBPJ have been found causing autosomal dominant forms of AOS. We describe a four-generation pedigree with isolated terminal limb defects and a truncating mutation in ARHGAP31. This finding underscores the relevance of sequencing ARHGAP31 in similar cases of isolated limb defects, irrespective of the presence of a complete AOS phenotype. We also highlight the variability of clinical features among mutation carriers, ranging from severe reduction defects to mild as well as clinically unaffected cases suggesting reduced penetrance.
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Affiliation(s)
- Mala Isrie
- Center for Human Genetics, University Hospitals Leuven, KU Leuven, Leuven, Belgium
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Lazarus S, Zankl A, Duncan EL. Next-generation sequencing: a frameshift in skeletal dysplasia gene discovery. Osteoporos Int 2014; 25:407-22. [PMID: 23903953 DOI: 10.1007/s00198-013-2443-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 07/04/2013] [Indexed: 11/26/2022]
Abstract
In the last decade, huge breakthroughs in genetics-driven by new technology and different statistical approaches-have resulted in a plethora of new disease genes identified for both common and rare diseases. Massive parallel sequencing, commonly known as next-generation sequencing, is the latest advance in genetics, and has already facilitated the discovery of the molecular cause of many monogenic disorders. This article describes this new technology and reviews how this approach has been used successfully in patients with skeletal dysplasias. Moreover, this article illustrates how the study of rare diseases can inform understanding and therapeutic developments for common diseases such as osteoporosis.
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Affiliation(s)
- S Lazarus
- University of Queensland, UQ Centre for Clinical Research, Herston, Brisbane, QLD, 4029, Australia
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69
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Exome sequencing greatly expedites the progressive research of Mendelian diseases. Front Med 2014; 8:42-57. [PMID: 24384736 DOI: 10.1007/s11684-014-0303-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 09/30/2013] [Indexed: 12/23/2022]
Abstract
The advent of whole-exome sequencing (WES) has facilitated the discovery of rare structure and functional genetic variants. Combining exome sequencing with linkage studies is one of the most efficient strategies in searching disease genes for Mendelian diseases. WES has achieved great success in the past three years for Mendelian disease genetics and has identified over 150 new Mendelian disease genes. We illustrate the workflow of exome capture and sequencing to highlight the advantages of WES. We also indicate the progress and limitations of WES that can potentially result in failure to identify disease-causing mutations in part of patients. With an affordable cost, WES is expected to become the most commonly used tool for Mendelian disease gene identification. The variants detected cumulatively from previous WES studies will be widely used in future clinical services.
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70
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The application of next-generation sequencing in the autozygosity mapping of human recessive diseases. Hum Genet 2013; 132:1197-211. [PMID: 23907654 DOI: 10.1007/s00439-013-1344-x] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 07/20/2013] [Indexed: 02/08/2023]
Abstract
Autozygosity, or the inheritance of two copies of an ancestral allele, has the potential to not only reveal phenotypes caused by biallelic mutations in autosomal recessive genes, but to also facilitate the mapping of such mutations by flagging the surrounding haplotypes as tractable runs of homozygosity (ROH), a process known as autozygosity mapping. Since SNPs replaced microsatellites as markers for the purpose of genomewide identification of ROH, autozygosity mapping of Mendelian genes has witnessed a significant acceleration. Historically, successful mapping traditionally required favorable family structure that permits the identification of an autozygous interval that is amenable to candidate gene selection and confirmation by Sanger sequencing. This requirement presented a major bottleneck that hindered the utilization of simplex cases and many multiplex families with autosomal recessive phenotypes. However, the advent of next-generation sequencing that enables massively parallel sequencing of DNA has largely bypassed this bottleneck and thus ushered in an era of unprecedented pace of Mendelian disease gene discovery. The ability to identify a single causal mutation among a massive number of variants that are uncovered by next-generation sequencing can be challenging, but applying autozygosity as a filter can greatly enhance the enrichment process and its throughput. This review will discuss the power of combining the best of both techniques in the mapping of recessive disease genes and offer some tips to troubleshoot potential limitations.
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71
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Suzuki D, Yamada A, Kamijo R. The essential roles of the small GTPase Rac1 in limb development. J Oral Biosci 2013. [DOI: 10.1016/j.job.2013.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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72
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Atasoy HI, Tug E, Yavuz T, Cine N. Unique variant of Adams-Oliver syndrome with dilated cardiomyopathy and heart block. Pediatr Int 2013; 55:508-12. [PMID: 23910800 DOI: 10.1111/ped.12011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 09/13/2012] [Accepted: 10/30/2012] [Indexed: 11/26/2022]
Abstract
Reported herein is the case of a 2-year-old boy with Adams-Oliver syndrome who presented with dilated cardiomyopathy and complete atrioventricular block. The patient had aplasia cutis congenita with partial aplasia of the skull bones, and terminal transverse limb malformations characteristic of the disease. Although congenital cardiac malformations may be associated with the syndrome, dilated cardiomyopathy has not been previously reported to be associated with the syndrome.
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Affiliation(s)
- Halil Ibrahim Atasoy
- Department of Pediatrics, Faculty of Medicine, Abant Izzet Baysal University, Bolu, Turkey.
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73
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Cohen I, Silberstein E, Perez Y, Landau D, Elbedour K, Langer Y, Kadir R, Volodarsky M, Sivan S, Narkis G, Birk OS. Autosomal recessive Adams-Oliver syndrome caused by homozygous mutation in EOGT, encoding an EGF domain-specific O-GlcNAc transferase. Eur J Hum Genet 2013; 22:374-8. [PMID: 23860037 DOI: 10.1038/ejhg.2013.159] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Revised: 06/04/2013] [Accepted: 06/19/2013] [Indexed: 02/07/2023] Open
Abstract
Autosomal recessive Adams-Oliver syndrome was diagnosed in three remotely related Bedouin consanguineous families. Genome-wide linkage analysis ruled out association with known Adams-Oliver syndrome genes, identifying a single-homozygosity ∼1.8-Mb novel locus common to affected individuals (LOD score 3.37). Whole-exome sequencing followed by Sanger sequencing identified only a single mutation within this locus, shared by all affected individuals and found in patients from five additional apparently unrelated Bedouin families: a 1-bp deletion mutation in a predicted alternative splice variant of EOGT, leading to a putative truncated protein. RT-PCR demonstrated that the EOGT-predicted alternative splice variant is ubiquitously expressed. EOGT encodes EGF-domain-specific O-linked N-acetylglucosamine transferase, responsible for extracellular O-GlcNAcylation of epidermal growth factor-like domain-containing proteins, and is essential for epithelial cell-matrix interactions. F-actin staining in diseased fibroblasts showed apparently intact cell cytoskeleton and morphology, suggesting the EOGT mutation acts not through perturbation of cytoskeleton but through other mechanisms yet to be elucidated.
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Affiliation(s)
- Idan Cohen
- The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel
| | - Eldad Silberstein
- Department of Plastic and Reconstructive Surgery, Soroka Medical Center, Beer-Sheva, Israel
| | - Yonatan Perez
- The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel
| | - Daniella Landau
- Division of Pediatrics, Soroka Medical Center, Beer-Sheva, Israel
| | - Khalil Elbedour
- The Genetics Institute, Soroka Medical Center, Beer-Sheva, Israel
| | - Yshaia Langer
- 1] The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel [2] The Genetics Institute, Soroka Medical Center, Beer-Sheva, Israel
| | - Rotem Kadir
- The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel
| | - Michael Volodarsky
- The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel
| | - Sara Sivan
- The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel
| | - Ginat Narkis
- The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel
| | - Ohad S Birk
- 1] The Morris Kahn Laboratory of Human Genetics at the National Institute for Biotechnology in the Negev (NIBN) and Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel [2] The Genetics Institute, Soroka Medical Center, Beer-Sheva, Israel
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Abstract
Aplasia cutis congenita (ACC) manifests with localized skin defects at birth of unknown cause, mostly affecting the scalp vertex. Here, genome-wide linkage analysis and exome sequencing was used to identify the causative mutation in autosomal dominant ACC. A heterozygous Arg-to-His missense mutation (p.R930H) in the ribosomal GTPase BMS1 is identified in ACC that is associated with a delay in 18S rRNA maturation, consistent with a role of BMS1 in processing of pre-rRNAs of the small ribosomal subunit. Mutations that affect ribosomal function can result in a cell cycle defect and ACC skin fibroblasts with the BMS1 p.R930H mutation show a reduced cell proliferation rate due to a p21-mediated G1/S phase transition delay. Unbiased comparative global transcript and proteomic analyses of ACC fibroblasts with this mutation confirm a central role of increased p21 levels for the ACC phenotype, which are associated with downregulation of heterogenous nuclear ribonucleoproteins (hnRNPs) and serine/arginine-rich splicing factors (SRSFs). Functional enrichment analysis of the proteomic data confirmed a defect in RNA post-transcriptional modification as the top-ranked cellular process altered in ACC fibroblasts. The data provide a novel link between BMS1, the cell cycle, and skin morphogenesis. Elucidating the pathomechanisms in congenital diseases of the skin provides the opportunity to learn what cellular processes are important during embryonic development of the skin structures. Aplasia cutis congenita (ACC) manifests with localized skin defects, most commonly affecting the scalp skin. Here, global proteomic and transcriptional analyses are combined with genome-wide linkage and exome sequencing approaches to identify the molecular mechanisms involved in ACC. A mutation in the ribosomal GTPase BMS1 is identified in ACC that affects 18S rRNA maturation. This mutation is associated with a p21-mediated G1/S phase transition delay during the cell cycle that inhibits cell proliferation. The findings are consistent with mutations in ribosomal disorders that result in nucleolar stress and a G1/S phase transition delay. Thus, mutations in BMS1 can affect the formation of a highly proliferative tissue during development, such as the rapidly expanding scalp epidermis.
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Affiliation(s)
- Alexander G Marneros
- Cutaneous Biology Research Center, Massachusetts General Hospital, Department of Dermatology, Harvard Medical School, Charlestown, Massachusetts, USA.
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75
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Algaze C, Esplin ED, Lowenthal A, Hudgins L, Tacy TA, Selamet Tierney ES. Expanding the phenotype of cardiovascular malformations in Adams-Oliver syndrome. Am J Med Genet A 2013; 161A:1386-9. [PMID: 23613382 DOI: 10.1002/ajmg.a.35864] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Accepted: 12/27/2012] [Indexed: 11/06/2022]
Abstract
We describe a newborn with a phenotype consistent with Adams-Oliver syndrome and truncus arteriosus. Although cardiovascular malformations associated with this syndrome have been previously published in the literature, this is the first description of truncus arteriosus in a patient with Adams-Oliver syndrome. We review other reports of Adams-Oliver syndrome previously described with cardiovascular malformations, consider possible genetic and embryologic mechanisms, and emphasize the need for cardiology consultation when a diagnosis of Adams-Oliver syndrome is suspected in the differential diagnosis.
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Affiliation(s)
- Claudia Algaze
- Division of Pediatric Cardiology, Department of Pediatrics Lucile Packard Children's Hospital, Stanford University, Stanford, California, USA.
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76
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New findings in genodermatoses. Dermatol Clin 2013; 31:303-15. [PMID: 23557657 DOI: 10.1016/j.det.2012.12.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New technologies are accelerating the pace at which genetic defects leading to inherited skin disease are elucidated. Translation of these genetic discoveries into new therapies for patients with inherited skin diseases has not been as rapid but the pace is now accelerating. This article summarizes recent findings in genetic skin diseases, the scope of advances being made, the role of new DNA analysis technologies in these discoveries, as well as highlighting some examples of how an understanding of the genetic cause of inherited skin diseases can lead to therapeutic interventions for patients.
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77
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Shaheen R, Aglan M, Keppler-Noreuil K, Faqeih E, Ansari S, Horton K, Ashour A, Zaki M, Al-Zahrani F, Cueto-González A, Abdel-Salam G, Temtamy S, Alkuraya F. Mutations in EOGT confirm the genetic heterogeneity of autosomal-recessive Adams-Oliver syndrome. Am J Hum Genet 2013; 92:598-604. [PMID: 23522784 PMCID: PMC3617382 DOI: 10.1016/j.ajhg.2013.02.012] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Revised: 02/19/2013] [Accepted: 02/28/2013] [Indexed: 12/17/2022] Open
Abstract
Adams-Oliver syndrome (AOS) is a rare, autosomal-dominant or -recessive disorder characterized primarily by aplasia cutis congenita and terminal transverse limb defects. Recently, we demonstrated that homozygous mutations in DOCK6 cause an autosomal-recessive form of AOS. In this study, we sought to determine the contribution of DOCK6 mutations to the etiology of AOS in several consanguineous families. In two of the five families studied, we identified two homozygous truncating mutations (a splice-site mutation and a frameshift duplication). DOCK6 sequencing revealed no mutation in the remaining three families, consistent with their autozygosity mapping and linkage-analysis results, which revealed a single candidate locus in 3p14.1 on three different haplotype backgrounds in the three families. Indeed, exome sequencing in one family revealed one missense mutation in EOGT (C3orf64), and subsequent targeted sequencing of this gene revealed a homozygous missense mutation and a homozygous frameshift deletion mutation in the other two families. EOGT encodes EGF-domain-specific O-linked N-acetylglucosamine (O-GlcNAc) transferase, which is involved in the O-GlcNAcylation (attachment of O-GlcNAc to serine and threonine residues) of a subset of extracellular EGF-domain-containing proteins. It has a documented role in epithelial-cell-matrix interactions in Drosophila, in which deficiency of its ortholog causes wing blistering. Our findings highlight a developmental role of O-GlcNAcylation in humans and expand the genetic heterogeneity of autosomal-recessive AOS.
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Affiliation(s)
- Ranad Shaheen
- Department of Genetics, King Faisal Specialist Hospital and Research Center, PO Box 3354, Riyadh 11211, Saudi Arabia
| | - Mona Aglan
- Department of Clinical Genetics, National Research Centre, Cairo 12311, Egypt
| | - Kim Keppler-Noreuil
- Genetic Disease Research Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
| | - Eissa Faqeih
- Department of Pediatrics, Section of Medical Genetics, King Fahad Medical City, PO Box 59046, Riyadh 11525, Saudi Arabia
| | - Shinu Ansari
- Department of Genetics, King Faisal Specialist Hospital and Research Center, PO Box 3354, Riyadh 11211, Saudi Arabia
| | - Kim Horton
- Regional Genetics Consultation Service, University of Iowa, Iowa City, IA 52242-1083, USA
| | - Adel Ashour
- Department of Clinical Genetics, National Research Centre, Cairo 12311, Egypt
| | - Maha S. Zaki
- Department of Clinical Genetics, National Research Centre, Cairo 12311, Egypt
| | - Fatema Al-Zahrani
- Department of Genetics, King Faisal Specialist Hospital and Research Center, PO Box 3354, Riyadh 11211, Saudi Arabia
| | - Anna M. Cueto-González
- Clinical Genetics Service, Hospital Universitari Vall d’Hebrón, Passeig Vall d’Hebrón n° 119-129, Barcelona 08035, Spain
| | - Ghada Abdel-Salam
- Department of Clinical Genetics, National Research Centre, Cairo 12311, Egypt
| | - Samia Temtamy
- Department of Clinical Genetics, National Research Centre, Cairo 12311, Egypt
| | - Fowzan S. Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, PO Box 3354, Riyadh 11211, Saudi Arabia
- Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia
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78
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Alkuraya FS. Discovery of rare homozygous mutations from studies of consanguineous pedigrees. ACTA ACUST UNITED AC 2013; Chapter 6:Unit6.12. [PMID: 23074070 DOI: 10.1002/0471142905.hg0612s75] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The unmasking of recessive mutations by virtue of biparental inheritance of the same ancestral haplotype on which they reside (autozygosity) has provided human geneticists with one of their most powerful tools in unraveling the genetic basis of autosomal recessive disorders. This has historically been achieved by tracking the blocks of homozygosity as surrogates of autozygosity using polymorphic microsatellite markers. Mapping the entire set of autozygous blocks per individual (autozygome) at high resolution became possible with the advent of high-density SNP arrays. The more recent availability of next-generation sequencing has markedly accelerated the rate at which rare recessive mutations are identified by obviating the need to prioritize genes for sequencing within candidate autozygous loci. This unit will review the individual and combined use of these techniques in the context of mapping novel recessive disease genes, as well as potential pitfalls and recommended solutions.
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Affiliation(s)
- Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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79
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Abstract
Small GTPases use GDP/GTP alternation to actuate a variety of functional switches that are pivotal for cell dynamics. The GTPase switch is turned on by GEFs, which stimulate dissociation of the tightly bound GDP, and turned off by GAPs, which accelerate the intrinsically sluggish hydrolysis of GTP. For Ras, Rho, and Rab GTPases, this switch incorporates a membrane/cytosol alternation regulated by GDIs and GDI-like proteins. The structures and core mechanisms of representative members of small GTPase regulators from most families have now been elucidated, illuminating their general traits combined with scores of unique features. Recent studies reveal that small GTPase regulators have themselves unexpectedly sophisticated regulatory mechanisms, by which they process cellular signals and build up specific cell responses. These mechanisms include multilayered autoinhibition with stepwise release, feedback loops mediated by the activated GTPase, feed-forward signaling flow between regulators and effectors, and a phosphorylation code for RhoGDIs. The flipside of these highly integrated functions is that they make small GTPase regulators susceptible to biochemical abnormalities that are directly correlated with diseases, notably a striking number of missense mutations in congenital diseases, and susceptible to bacterial mimics of GEFs, GAPs, and GDIs that take command of small GTPases in infections. This review presents an overview of the current knowledge of these many facets of small GTPase regulation.
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Affiliation(s)
- Jacqueline Cherfils
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Centre deRecherche de Gif, Gif-sur-Yvette, France
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80
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Pakes NK, Veltman DM, Williams RSB. Zizimin and Dock guanine nucleotide exchange factors in cell function and disease. Small GTPases 2012; 4:22-7. [PMID: 23247359 PMCID: PMC3620097 DOI: 10.4161/sgtp.22087] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Zizimin proteins belong to the Dock (Dedicator of Cytokinesis) superfamily of Guanine nucleotide Exchange Factor (GEF) proteins. This family of proteins plays a role in the regulation of Rho family small GTPases. Together the Rho family of small GTPases and the Dock/Zizimin proteins play a vital role in a number of cell processes including cell migration, apoptosis, cell division and cell adhesion. Our recent studies of Zizimin proteins, using a simple biomedical model, the eukaryotic social amoeba Dictyostelium discoideum, have helped to elucidate the cellular role of these proteins. In this article, we discuss the domain structure of Zizimin proteins from an evolutionary viewpoint. We also compare what is currently known about the mammalian Zizimin proteins to that of related Dock proteins. Understanding the cellular functions of these proteins will provide a better insight into their role in cell signaling, and may help in treating disease pathology associated with mutations in Dock/Zizimin proteins.
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Affiliation(s)
- Nicholl K Pakes
- Centre for Biomedical Sciences, Royal Holloway University of London, Surrey, UK
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81
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Genomic analysis of Meckel-Gruber syndrome in Arabs reveals marked genetic heterogeneity and novel candidate genes. Eur J Hum Genet 2012; 21:762-8. [PMID: 23169490 DOI: 10.1038/ejhg.2012.254] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Meckel-Gruber syndrome (MKS, OMIM #249000) is a multiple congenital malformation syndrome that represents the severe end of the ciliopathy phenotypic spectrum. Despite the relatively common occurrence of this syndrome among Arabs, little is known about its genetic architecture in this population. This is a series of 18 Arab families with MKS, who were evaluated clinically and studied using autozygome-guided mutation analysis and exome sequencing. We show that autozygome-guided candidate gene analysis identified the underlying mutation in the majority (n=12, 71%). Exome sequencing revealed a likely pathogenic mutation in three novel candidate MKS disease genes. These include C5orf42, Ellis-van-Creveld disease gene EVC2 and SEC8 (also known as EXOC4), which encodes an exocyst protein with an established role in ciliogenesis. This is the largest and most comprehensive genomic study on MKS in Arabs and the results, in addition to revealing genetic and allelic heterogeneity, suggest that previously reported disease genes and the novel candidates uncovered by this study account for the overwhelming majority of MKS patients in our population.
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82
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Abstract
Angiopoietin-like proteins (ANGPTLs) play major roles in the trafficking and metabolism of lipids. Inactivation of ANGPTL3, a gene located in an intron of DOCK7, results in very low levels of LDL-cholesterol (C), HDL-C and triglyceride (TAG). We identified another ANGPTL family member, ANGPTL8, which is located in the corresponding intron of DOCK6. A variant in this family member (rs2278426, R59W) was associated with lower plasma LDL-C and HDL-C levels in three populations. ANGPTL8 is expressed in liver and adipose tissue, and circulates in plasma of humans. Expression of ANGPTL8 was reduced by fasting and increased by refeeding in both mice and humans. To examine the functional relationship between the two ANGPTL family members, we expressed ANGPTL3 at physiological levels alone or together with ANGPTL8 in livers of mice. Plasma TAG level did not change in mice expressing ANGPTL3 alone, whereas coexpression with ANGPTL8 resulted in hypertriglyceridemia, despite a reduction in circulating ANGPTL3. ANGPTL8 coimmunoprecipitated with the N-terminal domain of ANGPTL3 in plasma of these mice. In cultured hepatocytes, ANGPTL8 expression increased the appearance of N-terminal ANGPTL3 in the medium, suggesting ANGPTL8 may activate ANGPTL3. Consistent with this scenario, expression of ANGPTL8 in Angptl3(-/-) mice failed to promote hypertriglyceridemia. Thus, ANGPTL8, a paralog of ANGPTL3 that arose through duplication of an ancestral DOCK gene, regulates postprandial TAG and fatty acid metabolism by controlling activation of its progenitor, and perhaps other ANGPTLs. Inhibition of ANGPTL8 provides a new therapeutic strategy for reducing plasma lipoprotein levels.
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83
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Sunker A, Alkuraya FS. Identification of MRI1, encoding translation initiation factor eIF-2B subunit alpha/beta/delta-like protein, as a candidate locus for infantile epilepsy with severe cystic degeneration of the brain. Gene 2012; 512:450-2. [PMID: 23124037 DOI: 10.1016/j.gene.2012.10.063] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 06/05/2012] [Accepted: 10/10/2012] [Indexed: 11/17/2022]
Abstract
Several neurodegenerative disorders are known to predominantly affect the white matter of the brain including vanishing white matter disease (VWMD), an autosomal recessive disorder characterized by leukodystrophy of varying severity in addition to variable systemic involvement. We report a consanguineous Arab family with three affected children, all of whom presented with severe neonatal epilepsy and profound neurodegenerative disease characterized by marked leukodystrophy with white matter cavitation mimicking VWMD. We combined autozygome and exome analysis to identify a novel variant in the gene encoding a member of the eIF2B-related family of proteins (MRI1). This is a poorly understood family of proteins of unclear function. Our results represent the first link between a variant in a member of this family and a human disease, and suggest that it converges with the highly homologous eIF2B, known to be mutated in VWMD, on the molecular pathogenesis of neurodegeneration.
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Affiliation(s)
- Asma Sunker
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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84
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Seidahmed MZ, Salih MA, Abdulbasit OB, Shaheed M, Al Hussein K, Miqdad AM, Al Rasheed AK, Alazami AM, Alorainy IA, Alkuraya FS. A novel syndrome of lethal familial hyperekplexia associated with brain malformation. BMC Neurol 2012; 12:125. [PMID: 23101555 PMCID: PMC3488335 DOI: 10.1186/1471-2377-12-125] [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: 12/20/2011] [Accepted: 09/26/2012] [Indexed: 11/17/2022] Open
Abstract
Background Hyperekplexia (HPX) is a rare non-epileptic disorder manifesting immediately after birth with exaggerated persistent startle reaction to unexpected auditory, somatosensory and visual stimuli, and non-habituating generalized flexor spasm in response to tapping of the nasal bridge (glabellar tap) which forms its clinical hallmark. The course of the disease is usually benign with spontaneous amelioration with age. The disorder results from aberrant glycinergic neurotransmission, and several mutations were reported in the genes encoding glycine receptor (GlyR) α1 and β subunits, glycine transporter GlyT2 as well as two other proteins involved in glycinergic neurotransmission gephyrin and collybistin. Methods The phenotype of six newborns, belonging to Saudi Arabian kindred with close consanguineous marriages, who presented with hyperekplexia associated with severe brain malformation, is described. DNA samples were available from two patients, and homozygosity scan to determine overlap with known hyperkplexia genes was performed. Results The kindred consisted of two brothers married to their cousin sisters, each with three affected children who presented antenatally with excessive fetal movements. Postnatally, they were found to have microcephaly, severe hyperekplexia and gross brain malformation characterized by severe simplified gyral pattern and cerebellar underdevelopment. The EEG was normal and they responded to clonazepam. All of the six patients died within six weeks. Laboratory investigations, including metabolic screen, were unremarkable. None of the known hyperkplexia genes were present within the overlapping regions of homozygosity between the two patients for whom DNA samples were available. Conclusions We present these cases as a novel syndrome of lethal familial autosomal recessive hyperekplexia associated with microcephaly and severe brain malformation.
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Affiliation(s)
- Mohammed Zein Seidahmed
- Division of Pediatric Neurology, Department of Pediatrics (39), College of Medicine, King Saud University, P. O. Box 2925, Riyadh, 11461, Saudi Arabia
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85
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Abu-Safieh L, Alrashed M, Anazi S, Alkuraya H, Khan AO, Al-Owain M, Al-Zahrani J, Al-Abdi L, Hashem M, Al-Tarimi S, Sebai MA, Shamia A, Ray-Zack MD, Nassan M, Al-Hassnan ZN, Rahbeeni Z, Waheeb S, Alkharashi A, Abboud E, Al-Hazzaa SAF, Alkuraya FS. Autozygome-guided exome sequencing in retinal dystrophy patients reveals pathogenetic mutations and novel candidate disease genes. Genome Res 2012; 23:236-47. [PMID: 23105016 PMCID: PMC3561865 DOI: 10.1101/gr.144105.112] [Citation(s) in RCA: 209] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Retinal dystrophy (RD) is a heterogeneous group of hereditary diseases caused by loss of photoreceptor function and contributes significantly to the etiology of blindness globally but especially in the industrialized world. The extreme locus and allelic heterogeneity of these disorders poses a major diagnostic challenge and often impedes the ability to provide a molecular diagnosis that can inform counseling and gene-specific treatment strategies. In a large cohort of nearly 150 RD families, we used genomic approaches in the form of autozygome-guided mutation analysis and exome sequencing to identify the likely causative genetic lesion in the majority of cases. Additionally, our study revealed six novel candidate disease genes (C21orf2, EMC1, KIAA1549, GPR125, ACBD5, and DTHD1), two of which (ACBD5 and DTHD1) were observed in the context of syndromic forms of RD that are described for the first time.
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Affiliation(s)
- Leen Abu-Safieh
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
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86
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Rokunohe D, Akasaka E, Rokunohe A, Kaneko T, Matsuzaki Y, Takiyoshi N, Aizu T, Nakano H, Sawamura D. Multiple aplasia cutis congenita lesions located along Blaschko's lines in a patient with tetralogy of Fallot-A. J Dermatol Case Rep 2012; 6:40-2. [PMID: 22826717 DOI: 10.3315/jdcr.2012.1096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 04/05/2012] [Indexed: 11/11/2022]
Abstract
BACKGROUND Aplasia cutis congenita (ACC) is a congenital absence of skin, and a single alopecic lesion on the scalp is the most common form. MAIN OBSERVATION We present a case of ACC with tetralogy of Fallot-A. Differetial diagnosis included Adams-Oliver syndrome and nevus psiloliparus. Interestingly, our patient showed multiple ACC lesions, which were located along Blaschko's lines. CONCLUSIONS As far as we know, our case is the third case of ACC with tetralogy of Fallot-A. Also, this is the first case of ACC associated with Blaschko's lines.
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Affiliation(s)
- Daiki Rokunohe
- Department of Dermatology, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan
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87
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Al-Owain M, Al-Zaidan H, Al-Hassnan Z. Map of autosomal recessive genetic disorders in Saudi Arabia: Concepts and future directions. Am J Med Genet A 2012; 158A:2629-40. [DOI: 10.1002/ajmg.a.35551] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 06/06/2012] [Indexed: 12/23/2022]
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88
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Hassed SJ, Wiley GB, Wang S, Lee JY, Li S, Xu W, Zhao ZJ, Mulvihill JJ, Robertson J, Warner J, Gaffney PM. RBPJ mutations identified in two families affected by Adams-Oliver syndrome. Am J Hum Genet 2012; 91:391-5. [PMID: 22883147 DOI: 10.1016/j.ajhg.2012.07.005] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 05/21/2012] [Accepted: 07/01/2012] [Indexed: 01/17/2023] Open
Abstract
Through exome resequencing, we identified two unique mutations in recombination signal binding protein for immunoglobulin kappa J (RBPJ) in two independent families affected by Adams-Oliver syndrome (AOS), a rare multiple-malformation disorder consisting primarily of aplasia cutis congenita of the vertex scalp and transverse terminal limb defects. These identified mutations link RBPJ, the primary transcriptional regulator for the Notch pathway, with AOS, a human genetic disorder. Functional assays confirmed impaired DNA binding of mutated RBPJ, placing it among other notch-pathway proteins altered in human genetic syndromes.
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Affiliation(s)
- Susan J Hassed
- Department of Pediatrics, University of Oklahoma Health Sciences Center, University of Oklahoma Children's Physicians Building, 1200 Children's Avenue, Oklahoma City, OK 73104, USA.
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89
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POC1A truncation mutation causes a ciliopathy in humans characterized by primordial dwarfism. Am J Hum Genet 2012; 91:330-6. [PMID: 22840364 DOI: 10.1016/j.ajhg.2012.05.025] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 04/08/2012] [Accepted: 05/30/2012] [Indexed: 11/21/2022] Open
Abstract
Primordial dwarfism (PD) is a phenotype characterized by profound growth retardation that is prenatal in onset. Significant strides have been made in the last few years toward improved understanding of the molecular underpinning of the limited growth that characterizes the embryonic and postnatal development of PD individuals. These include impaired mitotic mechanics, abnormal IGF2 expression, perturbed DNA-damage response, defective spliceosomal machinery, and abnormal replication licensing. In three families affected by a distinct form of PD, we identified a founder truncating mutation in POC1A. This gene is one of two vertebrate paralogs of POC1, which encodes one of the most abundant proteins in the Chlamydomonas centriole proteome. Cells derived from the index individual have abnormal mitotic mechanics with multipolar spindles, in addition to clearly impaired ciliogenesis. siRNA knockdown of POC1A in fibroblast cells recapitulates this ciliogenesis defect. Our findings highlight a human ciliopathy syndrome caused by deficiency of a major centriolar protein.
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90
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Rabbani B, Mahdieh N, Hosomichi K, Nakaoka H, Inoue I. Next-generation sequencing: impact of exome sequencing in characterizing Mendelian disorders. J Hum Genet 2012; 57:621-32. [DOI: 10.1038/jhg.2012.91] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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91
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Gilissen C, Hoischen A, Brunner HG, Veltman JA. Disease gene identification strategies for exome sequencing. Eur J Hum Genet 2012; 20:490-7. [PMID: 22258526 PMCID: PMC3330229 DOI: 10.1038/ejhg.2011.258] [Citation(s) in RCA: 310] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 10/31/2011] [Accepted: 12/07/2011] [Indexed: 12/16/2022] Open
Abstract
Next generation sequencing can be used to search for Mendelian disease genes in an unbiased manner by sequencing the entire protein-coding sequence, known as the exome, or even the entire human genome. Identifying the pathogenic mutation amongst thousands to millions of genomic variants is a major challenge, and novel variant prioritization strategies are required. The choice of these strategies depends on the availability of well-phenotyped patients and family members, the mode of inheritance, the severity of the disease and its population frequency. In this review, we discuss the current strategies for Mendelian disease gene identification by exome resequencing. We conclude that exome strategies are successful and identify new Mendelian disease genes in approximately 60% of the projects. Improvements in bioinformatics as well as in sequencing technology will likely increase the success rate even further. Exome sequencing is likely to become the most commonly used tool for Mendelian disease gene identification for the coming years.
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Affiliation(s)
- Christian Gilissen
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences and Institute for Genetic and Metabolic Disorders, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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92
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Aizawa R, Yamada A, Suzuki D, Iimura T, Kassai H, Harada T, Tsukasaki M, Yamamoto G, Tachikawa T, Nakao K, Yamamoto M, Yamaguchi A, Aiba A, Kamijo R. Cdc42 is required for chondrogenesis and interdigital programmed cell death during limb development. Mech Dev 2012; 129:38-50. [PMID: 22387309 DOI: 10.1016/j.mod.2012.02.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 02/16/2012] [Accepted: 02/16/2012] [Indexed: 12/20/2022]
Abstract
Cdc42, a member of the Rho subfamily of small GTPases, is known to be a regulator of multiple cellular functions, including cytoskeletal organization, cell migration, proliferation, and apoptosis. However, its tissue-specific roles, especially in mammalian limb development, remain unclear. To investigate the physiological function of Cdc42 during limb development, we generated limb bud mesenchyme-specific inactivated Cdc42 (Cdc42(fl/fl); Prx1-Cre) mice. Cdc42(fl/fl); Prx1-Cre mice demonstrated short limbs and body, abnormal calcification of the cranium, cleft palate, disruption of the xiphoid process, and syndactyly. Severe defects were also found in long bone growth plate cartilage, characterized by loss of columnar organization of chondrocytes, and thickening and massive accumulation of hypertrophic chondrocytes, resulting in delayed endochondral bone formation associated with reduced bone growth. In situ hybridization analysis revealed that expressions of Col10 and Mmp13 were reduced in non-resorbed hypertrophic cartilage, indicating that deletion of Cdc42 inhibited their terminal differentiation. Syndactyly in Cdc42(fl/fl); Prx1-Cre mice was caused by fusion of metacarpals and a failure of interdigital programmed cell death (ID-PCD). Whole mount in situ hybridization analysis of limb buds showed that the expression patterns of Sox9 were ectopic, while those of Bmp2, Msx1, and Msx2, known to promote apoptosis in the interdigital mesenchyme, were down-regulated. These results demonstrate that Cdc42 is essential for chondrogenesis and ID-PCD during limb development.
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Affiliation(s)
- Ryo Aizawa
- Department of Biochemistry, School of Dentistry, Showa University, Shinagawa-ku, Tokyo 142-8555, Japan
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93
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Abstract
Rapid advances in next-generation sequencing technology are revolutionizing approaches to genomic and epigenomic studies of skin. Deep sequencing of cutaneous malignancies reveals heavily mutagenized genomes with large numbers of low-prevalence mutations and multiple resistance mechanisms to targeted therapies. Next-generation sequencing approaches have already paid rich dividends in identifying the genetic causes of dermatologic disease, both in heritable mutations and the somatic aberrations that underlie cutaneous mosaicism. Although epigenetic alterations clearly influence tumorigenesis, pluripotent stem cell biology, and epidermal cell lineage decisions, labor and cost-intensive approaches long delayed a genome-scale perspective. New insights into epigenomic mechanisms in skin disease should arise from the accelerating assessment of histone modification, DNA methylation, and related gene expression signatures.
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Affiliation(s)
- Jeffrey B Cheng
- Department of Dermatology, University of California, San Francisco, San Francisco, California 94143, USA
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94
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Recessive mutations in ELOVL4 cause ichthyosis, intellectual disability, and spastic quadriplegia. Am J Hum Genet 2011; 89:745-50. [PMID: 22100072 DOI: 10.1016/j.ajhg.2011.10.011] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 10/20/2011] [Accepted: 10/26/2011] [Indexed: 12/21/2022] Open
Abstract
Very-long-chain fatty acids (VLCFAs) play important roles in membrane structure and cellular signaling, and their contribution to human health is increasingly recognized. Fatty acid elongases catalyze the first and rate-limiting step in VLCFA synthesis. Heterozygous mutations in ELOVL4, the gene encoding one of the elongases, are known to cause macular degeneration in humans and retinal abnormalities in mice. However, biallelic ELOVL4 mutations have not been observed in humans, and murine models with homozygous mutations die within hours of birth as a result of a defective epidermal water barrier. Here, we report on two human individuals with recessive ELOVL4 mutations revealed by a combination of autozygome analysis and exome sequencing. These individuals exhibit clinical features of ichthyosis, seizures, mental retardation, and spasticity-a constellation that resembles Sjögren-Larsson syndrome (SLS) but presents a more severe neurologic phenotype. Our findings identify recessive mutations in ELOVL4 as the cause of a neuro-ichthyotic disease and emphasize the importance of VLCFA synthesis in brain and cutaneous development.
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