A nonsense mutation in the LIMP-2 gene associated with progressive myoclonic epilepsy and nephrotic syndrome

Hum Mol Genet. 2008 Jul 15;17(14):2238-43. doi: 10.1093/hmg/ddn124. Epub 2008 Apr 17.

Abstract

The main clinical features of two siblings from a consanguineous marriage were progressive myoclonic epilepsy without intellectual impairment and a nephrotic syndrome with a strong accumulation of C1q in capillary loops and mesangium of kidney. The biochemical analysis of one of the patients revealed a normal beta-glucocerebrosidase activity in leukocytes, but a severe enzymatic deficiency in cultured skin fibroblasts. This deficiency suggested a defect in the intracellular sorting pathway of this enzyme. The sequence analysis of the gene encoding LIMP-2 (SCARB2), the sorting receptor for beta-glucocerebrosidase, confirmed this hypothesis. A homozygous nonsense mutation in codon 178 of SCARB2 was found in the patient, whereas her healthy parents were heterozygous for the mutation. Besides lacking immunodetectable LIMP-2, patient fibroblasts also had decreased amounts of beta-glucocerebrosidase, which was mainly located in the endoplasmic reticulum, as assessed by its sensitivity to Endo H. This is the first report of a mutation in the SCARB2 gene associated with a human disease, which, contrary to earlier proposals, shares no features with Charcot-Marie-Tooth disease both at the clinical and neurophysiological levels.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Base Sequence
  • Codon, Nonsense*
  • Female
  • Fibroblasts / enzymology
  • Glucosylceramidase / genetics
  • Glucosylceramidase / metabolism
  • Humans
  • Leukocytes / enzymology
  • Lysosome-Associated Membrane Glycoproteins / genetics*
  • Lysosome-Associated Membrane Glycoproteins / metabolism
  • Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase / metabolism
  • Myoclonic Epilepsies, Progressive / enzymology
  • Myoclonic Epilepsies, Progressive / genetics*
  • Myoclonic Epilepsies, Progressive / metabolism
  • Nephrotic Syndrome / enzymology
  • Nephrotic Syndrome / genetics*
  • Nephrotic Syndrome / metabolism
  • Phenotype
  • Receptors, Scavenger / genetics*
  • Receptors, Scavenger / metabolism
  • Skin / enzymology

Substances

  • Codon, Nonsense
  • Lysosome-Associated Membrane Glycoproteins
  • Receptors, Scavenger
  • SCARB2 protein, human
  • Glucosylceramidase
  • Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase