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POMT2 gene

Overview

Gene (OMIM No.)
Function of gene/protein
  • Protein: protein O-mannosyltransferase 2 (POMT2)
  • POMT2 is part of the POMT enzyme complex (together with POMT1) which is involved in the glycosylation of alpha-dystroglycan (DAG1)
  • DAG1 helps maintain tissue structure in skeletal muscles and the brain
Clinical phenotype
(OMIM phenotype no.)
  • Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A, 2 (#613150)
  • Also known as Walker-Warburg syndrome (WWS)/Muscle Eye Brain Disease (MEB)
  • Muscular dystrophy-dystroglycanopathy (congenital with mental retardation), type B, 2 (#613156)
  • Muscular dystrophy-dystroglycanopathy (limb-girdle), type C, 2 (#613158)
  • Defects in the glycosylation of alpha-dystroglycans cause 3 overlapping syndromes/dystroglycanopathies: WWS, MEB and Fukuyama type Congenital Muscular Dystrophy (FCMD; (#253800)
  • WWS—most severe phenotype; MEB—intermediate phenotype; FCMD—mildest phenotype
  • Phenotype severity is determined by the extent which the mutation affects DAG1 glycosylation
Inheritance
  • Autosomal recessive
Ocular features
Systemic features
  • Congenital muscular dystrophy
  • Brain anomalies (cobblestone lissencephaly, hydrocephalus, hypoplastic cerebellar vermis, macrocephaly, microcephaly or anencephaly)
  • Severe hypotonia
  • Occasional seizures
  • Intellectual disability
  • Developmental delays
  • Patients with WWS have a severely limited lifespan with significant CNS and ocular anomalies
Key investigations
  • B-scan USS to measure axial length to document microphthalmia
  • Electrophysiology to determine visual potential
  • Measurement of intraocular pressure
  • Gonioscopy (if tolerated/EUA) or anterior segment OCT to identify angle abnormalities and any associated anterior segment dysgenesis
  • MRI brain and orbit
  • Systemic assessment with a paediatrician and other relevant specialists
  • Bloods (elevated creatinine kinase)
  • Skeletal muscle biopsy
Molecular diagnosisNext generation sequencing
  • Targeted gene panels
  • Whole genome sequencing
ManagementOcularSystemic
  • Multidisciplinary approach
Therapies under research
  • None at present
Further information

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References

  1.  Manya H, Chiba A, Yoshida A, et al. Demonstration of mammalian protein O-mannosyltransferase activity: Coexpression of POMT1 and POMT2 required for enzymatic activity. Proc Natl Acad Sci U S A 2004; 101: 500–505
  2.  Francisco R, Pascoal C, Marques-da-Silva D, et al. Keeping an eye on congenital disorders of O-glycosylation: A systematic literature review. J Inherit Metab Dis. 2019;42(1):29-48
  3.  Van Reeuwijk J, Janssen M, Van Den Elzen C, et al. POMT2 mutations cause a-dystroglycan hypoglycosylation and Walker-Warburg syndrome. J Med Genet 2005; 42: 907–912
  4.  Clement E, Mercuri E, Godfrey C, et al. Brain involvement in muscular dystrophies with defective dystroglycan glycosylation. Ann Neurol 2008; 64: 573–582
  5.  Yanagisawa A, Bouchet C, Quijano-Roy S, et al. POMT2 intragenic deletions and splicing abnormalities causing congenital muscular dystrophy with mental retardation. Eur J Med Genet. 2009;52(4):201-206
  6.  Mercuri E, Messina S, Bruno C, et al. Congenital muscular dystrophies with defective glycosylation of dystroglycan: a population study [published correction appears in Neurology. 2019 Aug 20;93(8):371]. Neurology. 2009;72(21):1802-1809
  7.  Godfrey C, Clement E, Mein R, et al. Refining genotype phenotype correlations in muscular dystrophies with defective glycosylation of dystroglycan. Brain. 2007;130(Pt 10):2725-2735

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Updated on November 30, 2020
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