Diagnosing Lysosomal Storage Disorders: The GM2 Gangliosidoses

Patricia Hall1, Sara Minnich2, Claire Teigen3, Kimiyo Raymond2

1 Department of Human Genetics, Emory University, Atlanta, 2 Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, 3 GeneDx, Gaithersburg, Maryland
Publication Name:  Current Protocols in Human Genetics
Unit Number:  Unit 17.16
DOI:  10.1002/0471142905.hg1716s83
Online Posting Date:  October, 2014
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The GM2 gangliosidoses are a group of autosomal recessive lysosomal storage disorders caused by defective β‐hexosaminidase. There are three clinical conditions in this group: Tay‐Sachs disease (TSD), Sandhoff disease (SD), and hexosaminidase activator deficiency. The three conditions are clinically indistinguishable. TSD and SD have been identified with infantile, juvenile, and adult onset forms. The activator deficiency is only known to present with infantile onset. Diagnosis of TSD and SD is based on decreased hexosaminidase activity and a change in the percentage of activity between isoforms. There are no biochemical tests currently available for activator deficiency. This unit provides a detailed procedure for identifying TSD and SD in affected individuals and carriers from leukocyte samples, the most robust sample type available. Curr. Protoc. Hum. Genet. 83:17.16.1‐17.16.8. © 2014 by John Wiley & Sons, Inc.

Keywords: Tay‐Sachs disease; Sandhoff disease; hexosaminidase; GM2 gangliosidosis

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Table of Contents

  • Reagents and Solutions
  • Commentary
  • Literature Cited
  • Tables
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Basic Protocol 1:

  • Whole blood specimen (ACD‐B): 10 ml is preferred, 5 ml is the minimum (samples must be shipped on wet ice; do not freeze whole blood)
  • 5% dextran solution (see recipe)
  • 0.7%, 0.9% (w/v) and 1.8% (w/v) NaCl (see recipe)
  • Protein assay kit (e.g., BioRad)
  • 0.6% bovine serum albumin (BSA; see recipe)
  • Substrate: 4‐methylumbelliferyl‐2‐acetamido‐2‐deoxy‐β‐D‐glucopyranoside (see recipe)
  • Stop buffer: 0.25 M glycine carbonate buffer (see recipe)
  • Standard: 4‐methylumbelliferone (see recipe)
  • 5‐ml conical polypropylene tubes
  • Refrigerated centrifuge
  • Probe sonicator (e.g., Misonix 3000)
  • 12 × 75–mm polystyrene tubes
  • Water bath (capable of 37°C and 51.5°C)
  • 96‐well flat‐bottom polystyrene microtiter plate (Corning Costar, cat. no. 3915) or 1.2‐ml polypropylene 8‐strip cluster tubes (plate selection should be compatible with fluorometer used)
  • Plate fluorometer
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Literature Cited

Literature Cited
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  Bley, A.E., Giannikopoulos, O.A., Hayden, D., Kubilus, K., Tifft, C.J., and Eichler, F.S. 2011. Natural history of infantile G(M2) gangliosidosis. Pediatrics 128:e1233‐e1241.
  Cao, Z., Petroulakis, E., Salo, T., and Triggs‐Raine, B. 1997. Benign HEXA mutations, C739T(R247W) and C745T(R249W), cause beta‐hexosaminidase A pseudodeficiency by reducing the alpha‐subunit protein levels. J. Biol. Chem. 272:14975‐14982.
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