51
|
Tarailo-Graovac M, Sinclair G, Stockler-Ipsiroglu S, Van Allen M, Rozmus J, Shyr C, Biancheri R, Oh T, Sayson B, Lafek M, Ross CJ, Robinson WP, Wasserman WW, Rossi A, van Karnebeek CDM. The genotypic and phenotypic spectrum of PIGA deficiency. Orphanet J Rare Dis 2015; 10:23. [PMID: 25885527 PMCID: PMC4348372 DOI: 10.1186/s13023-015-0243-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 02/18/2015] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Phosphatidylinositol glycan biosynthesis class A protein (PIGA) is one of the enzymes involved in the biosynthesis of glycosylphosphatidylinositol (GPI) anchor proteins, which function as enzymes, adhesion molecules, complement regulators and co-receptors in signal transduction pathways. Until recently, only somatic PIGA mutations had been reported in patients with paroxysmal nocturnal hemoglobinuria (PNH), while germline mutations had not been observed, and were suspected to result in lethality. However, in just two years, whole exome sequencing (WES) analyses have identified germline PIGA mutations in male patients with XLIDD (X-linked intellectual developmental disorder) with a wide spectrum of clinical presentations. METHODS AND RESULTS Here, we report on a new missense PIGA germline mutation [g.15342986C>T (p.S330N)] identified via WES followed by Sanger sequencing, in a Chinese male infant presenting with developmental arrest, infantile spasms, a pattern of lesion distribution on brain MRI resembling that typical of maple syrup urine disease, contractures, dysmorphism, elevated alkaline phosphatase, mixed hearing loss (a combination of conductive and sensorineural), liver dysfunction, mitochondrial complex I and V deficiency, and therapy-responsive dyslipidemia with confirmed lipoprotein lipase deficiency. X-inactivation studies showed skewing in the clinically unaffected carrier mother, and CD109 surface expression in patient fibroblasts was 57% of that measured in controls; together these data support pathogenicity of this mutation. Furthermore, we review all reported germline PIGA mutations (1 nonsense, 1 frameshift, 1 in-frame deletion, five missense) in 8 unrelated families. CONCLUSIONS Our case further delineates the heterogeneous phenotype of this condition for which we propose the term 'PIGA deficiency'. While the phenotypic spectrum is wide, it could be classified into two types (severe and less severe) with shared hallmarks of infantile spasms with hypsarrhythmia on EEG and profound XLIDD. In severe PIGA deficiency, as described in our patient, patients also present with dysmorphic facial features, multiple CNS abnormalities, such as thin corpus callosum and delayed myelination, as well as hypotonia and elevated alkaline phosphatase along with liver, renal, and cardiac involvement; its course is often fatal. The less severe form of PIGA deficiency does not involve facial dysmorphism and multiple CNS abnormalities; instead, patients present with milder IDD, treatable seizures and generally a longer lifespan.
Collapse
Affiliation(s)
- Maja Tarailo-Graovac
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada.
| | - Graham Sinclair
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Biochemical Genetics Laboratory, Department of Pathology, BC Children's Hospital, University of British Columbia, Vancouver, Canada.
| | - Sylvia Stockler-Ipsiroglu
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Margot Van Allen
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Jacob Rozmus
- Division of Hematology, Oncology & BMT, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Casper Shyr
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada.
| | - Roberta Biancheri
- Department of Paediatric Neurology, Children's Hospital Oxford, John Radcliffe Hospital, Oxford, UK.
| | - Tracey Oh
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Bryan Sayson
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada.
| | - Mirafe Lafek
- Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada.
| | - Colin J Ross
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Wendy P Robinson
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Wyeth W Wasserman
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Department of Medical Genetics, University of British Columbia, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| | - Andrea Rossi
- Department of Neuroradiology, Istituto Giannina Gaslini, Via Gerolamo Gaslini 5, I-16147, Genoa, Italy.
| | - Clara D M van Karnebeek
- Centre for Molecular Medicine and Therapeutics, Vancouver, Canada. .,Treatable Intellectual Disability Endeavour in British Columbia, Vancouver, Canada. .,Division of Biochemical Diseases, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, Canada. .,Child & Family Research Institute, Vancouver, BC, Canada.
| |
Collapse
|
54
|
Murakami Y, Tawamie H, Maeda Y, Büttner C, Buchert R, Radwan F, Schaffer S, Sticht H, Aigner M, Reis A, Kinoshita T, Jamra RA. Null mutation in PGAP1 impairing Gpi-anchor maturation in patients with intellectual disability and encephalopathy. PLoS Genet 2014; 10:e1004320. [PMID: 24784135 PMCID: PMC4006728 DOI: 10.1371/journal.pgen.1004320] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 03/07/2014] [Indexed: 02/07/2023] Open
Abstract
Many eukaryotic cell-surface proteins are anchored to the membrane via glycosylphosphatidylinositol (GPI). There are at least 26 genes involved in biosynthesis and remodeling of GPI anchors. Hypomorphic coding mutations in seven of these genes have been reported to cause decreased expression of GPI anchored proteins (GPI-APs) on the cell surface and to cause autosomal-recessive forms of intellectual disability (ARID). We performed homozygosity mapping and exome sequencing in a family with encephalopathy and non-specific ARID and identified a homozygous 3 bp deletion (p.Leu197del) in the GPI remodeling gene PGAP1. PGAP1 was not described in association with a human phenotype before. PGAP1 is a deacylase that removes an acyl-chain from the inositol of GPI anchors in the endoplasmic reticulum immediately after attachment of GPI to proteins. In silico prediction and molecular modeling strongly suggested a pathogenic effect of the identified deletion. The expression levels of GPI-APs on B lymphoblastoid cells derived from an affected person were normal. However, when those cells were incubated with phosphatidylinositol-specific phospholipase C (PI-PLC), GPI-APs were cleaved and released from B lymphoblastoid cells from healthy individuals whereas GPI-APs on the cells from the affected person were totally resistant. Transfection with wild type PGAP1 cDNA restored the PI-PLC sensitivity. These results indicate that GPI-APs were expressed with abnormal GPI structure due to a null mutation in the remodeling gene PGAP1. Our results add PGAP1 to the growing list of GPI abnormalities and indicate that not only the cell surface expression levels of GPI-APs but also the fine structure of GPI-anchors is important for the normal neurological development. Glycosylphosphatidylinositols (GPI) are glycolipid anchors that anchor various proteins to the cell surface. At least 26 genes are involved in biosynthesis and modification of the GPI anchors. Recently, mutations in eight of those genes have been described. Although those mutations do not fully abolish the functions of encoded enzymes, they lead to a decreased expression of surface GPI-anchored proteins and to different forms of intellectual disability. Here we report a mutation in PGAP1 that encodes a protein that modifies the GPI anchor. We found that the mutation leads to a full loss of PGAP1 enzyme activity, but that the patient cells still express normal levels of surface GPI-anchored proteins. However, the GPI anchors have an abnormal lipid structure that is resistant to cleavage by phosphatidylinositol-specific phospholipase C. Our results add PGAP1 to the growing list of GPI abnormalities that cause intellectual disability and indicate that the fine structure of GPI-anchors is also important for a normal neurological development.
Collapse
Affiliation(s)
- Yoshiko Murakami
- Research Institute for Microbial Diseases and WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
- * E-mail: (YM); (RAJ)
| | - Hasan Tawamie
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Yusuke Maeda
- Research Institute for Microbial Diseases and WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Christian Büttner
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Rebecca Buchert
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Farah Radwan
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Stefanie Schaffer
- Department of Internal Medicine 5, Hematology and Oncology, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Heinrich Sticht
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Michael Aigner
- Department of Internal Medicine 5, Hematology and Oncology, University of Erlangen-Nürnberg, Erlangen, Germany
| | - André Reis
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Taroh Kinoshita
- Research Institute for Microbial Diseases and WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Rami Abou Jamra
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
- * E-mail: (YM); (RAJ)
| |
Collapse
|
55
|
Belet S, Fieremans N, Yuan X, Van Esch H, Verbeeck J, Ye Z, Cheng L, Brodsky BR, Hu H, Kalscheuer VM, Brodsky RA, Froyen G. Early frameshift mutation in PIGA identified in a large XLID family without neonatal lethality. Hum Mutat 2014; 35:350-5. [PMID: 24357517 DOI: 10.1002/humu.22498] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 12/12/2013] [Indexed: 11/09/2022]
Abstract
The phosphatidylinositol glycan class A (PIGA) protein is a member of the glycosylphosphatidylinositol anchor pathway. Germline mutations in PIGA located at Xp22.2 are thought to be lethal in males. However, a nonsense mutation in the last coding exon was recently described in two brothers with multiple congenital anomalies-hypotonia-seizures syndrome 2 (MCAHS2) who survived through birth likely because of the hypomorphic nature of the truncated protein, but died in their first weeks of life. Here, we report on a frameshift mutation early in the PIGA cDNA (c.76dupT; p.Y26Lfs*3) that cosegregates with the disease in a large family diagnosed with a severe syndromic form of X-linked intellectual disability. Unexpectedly, CD59 surface expression suggested the production of a shorter PIGA protein with residual functionality. We provide evidence that the second methionine at position 37 may be used for the translation of a 36 amino acids shorter PIGA. Complementation assays confirmed that this shorter PIGA cDNA was able to partially rescue the surface expression of CD59 in a PIGA-null cell line. Taken together, our data strongly suggest that the early frameshift mutation in PIGA produces a truncated hypomorph, which is sufficient to rescue the lethality in males but not the MCAHS2-like phenotype.
Collapse
Affiliation(s)
- Stefanie Belet
- Human Genome Laboratory, VIB Center for the Biology of Disease, Leuven, Belgium; Human Genome Laboratory, Department of Human Genetics, KU Leuven, Leuven, Belgium
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|