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Bolfa P, Wang P, Nair R, Rajeev S, Armien AG, Henthorn PS, Wood T, Thrall MA, Giger U. Hereditary β-mannosidosis in a dog: Clinicopathological and molecular genetic characterization. Mol Genet Metab 2019; 128:137-143. [PMID: 31439511 PMCID: PMC6864274 DOI: 10.1016/j.ymgme.2019.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 08/05/2019] [Accepted: 08/09/2019] [Indexed: 11/30/2022]
Abstract
Hereditary β-mannosidosis causing progressive lysosomal neuropathy and other clinical signs, has been previously described in humans, Nubian goats, and Salers cattle. Here we report the clinicopathological, metabolic, and molecular genetic features of canine beta-mannosidase (MANBA, EC 3.2.1.25) deficiency. A 1-year-old male mix-breed dog from St. Kitts was presented with progressive stumbling, weakness, and regurgitation. Vacuolated lymphocytes were observed on the blood film. Postmortem findings included marked enlargement of nerves, megaesophagus, and internal hydrocephalus. Vacuolated macrophages, neurons, and secretory epithelial cells suggested an oligosaccharide storage disease. Plasma concentration of the β-mannosidosis specific oligosaccharide was approximately 75 fold that of controls. The plasma beta-mannosidase activity was severely reduced to ~5% of controls; five other lysosomal acid hydrolase activities were increased or within their normal reference interval. Genomic sequencing of this dog's MANBA gene identified a homozygous exonic five bp tandem duplication in the penultimate exon of the MANBA gene (c.2377_2381dupTATCA) which results in a reading frame shift, altering the subsequent amino acid sequence and creating a premature stop codon. The truncated beta-mannosidase enzyme is expected to be dysfunctional. This enzyme deficiency causes the accumulation of un-degraded oligosaccharides in cells, which affect the myelination of the peripheral and central nervous systems. This insertion was not encountered in 121 and 80-screened samples from dogs on St. Kitts (all were homozygous for wild-type) and Philadelphia region (wild-type), respectively. In conclusion, canine β-mannosidosis has similar clinicopathological features with some human patients, but milder signs than in ruminants and more severe than in knockout mice. Hence, dogs with β-mannosidosis could become a valuable disease model for the human disease.
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Affiliation(s)
- Pompei Bolfa
- Department of Biomedical Sciences, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, Saint Kitts and Nevis.
| | - Ping Wang
- Section of Medical Genetics (PennGen), School of Veterinary Medicine, University of Pennsylvania, 3900 Delancey St., Philadelphia, PA 19104-6010, USA
| | - Rajeev Nair
- Department of Clinical Sciences, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, Saint Kitts and Nevis
| | - Sreekumari Rajeev
- Department of Biomedical Sciences, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, Saint Kitts and Nevis
| | - Anibal G Armien
- Ultrastructural Pathology Unit, Veterinary Diagnostic Laboratory, University of Minnesota, 1333 Gortner Avenue, St. Paul, MN 55108, USA
| | - Paula S Henthorn
- Section of Medical Genetics (PennGen), School of Veterinary Medicine, University of Pennsylvania, 3900 Delancey St., Philadelphia, PA 19104-6010, USA
| | - Tim Wood
- Biochemical Genetics Laboratory, Greenwood Genetic Center, 106 Gregor Mendel Circle, Greenwood, SC 29646, USA
| | - Mary Anna Thrall
- Department of Biomedical Sciences, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, Saint Kitts and Nevis
| | - Urs Giger
- Section of Medical Genetics (PennGen), School of Veterinary Medicine, University of Pennsylvania, 3900 Delancey St., Philadelphia, PA 19104-6010, USA
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β-Mannosidosis caused by a novel homozygous intragenic inverted duplication in MANBA. Cold Spring Harb Mol Case Stud 2019; 5:mcs.a003954. [PMID: 30886116 PMCID: PMC6549551 DOI: 10.1101/mcs.a003954] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/04/2019] [Indexed: 11/25/2022] Open
Abstract
β-Mannosidosis is a lysosomal storage disorder characterized by accumulation of disaccharides due to deficiency of the lysosomal enzyme β-mannosidase. The disease is caused by mutations in MANBA and is extremely rare in humans. Although the clinical presentation is heterogeneous, common symptoms include various degrees of developmental delay, behavioral disturbances, hearing loss, and frequent infections. We report a 15-yr-old girl presenting with mild intellectual disability, sensorineural hearing loss, severe behavioral disturbances, dysmorphic traits, and evolving angiokeratomas. Copy-number variation analysis of next-generation sequencing (NGS) data indicated increased coverage in exons 8-11 of MANBA Low β-mannosidase activity (1 µkatal/kg protein, refv 25-40) established the diagnosis of β-mannosidosis. Whole-genome sequencing (WGS) and cDNA analysis revealed a novel homozygous intragenic inverted duplication in MANBA, where a 13.1-kb region between introns 7 and 11 was duplicated and inserted in an inverted orientation, creating a 67-base nonduplicated gap at the insertion point. Both junctions showed microhomology regions. The inverted duplication resulted in exon skipping of exons 8-9 or 8-10. Our report highlights the importance of copy-number variation analysis of data from NGS and in particular the power of WGS in the identification and characterization of copy-number variants.
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