A start codon CMT1X mutation associated with transient encephalomyelitis causes complete loss of Cx32

Irene Sargiannidou, Gun Ha Kim, Styliana Kyriakoudi, Baik-Lin Eun, Kleopas A. Kleopa

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

X-linked Charcot-Marie-Tooth disease (CMTX1) results from numerous mutations in the GJB1 gene encoding the gap junction protein connexin32 (Cx32) and is one of the commonest forms of inherited neuropathy. Owing to the expression of Cx32 not only in Schwann cells but also in oligodendrocytes, a subset of CMT1X patients develops central nervous system (CNS) clinical manifestations in addition to peripheral neuropathy. While most GJB1 mutations appear to cause peripheral neuropathy through loss of Cx32 function, the cellular mechanisms underlying the CNS manifestations remain controversial. A novel start codon GJB1 mutation (p.Met1Ile) has been found in a CMT1X patient presenting with recurrent episodes of transient encephalomyelitis without apparent signs of peripheral neuropathy. In order to clarify the functional consequences of this mutation, we examined the cellular expression of two different constructs cloned from genomic DNA including the mutated start codon. None of the cloned constructs resulted in detectable expression of Cx32 by immunocytochemistry or immunoblot, although mRNA was produced at normal levels. Furthermore, co-expression with the other major oligodendrocyte connexin, Cx47, had no negative effect on GJ formation by Cx47. Finally, lysosomal and proteasomal inhibition in cells expressing the start codon mutant constructs failed to recover any detection of Cx32 as a result of impaired protein degradation. Our results indicate that the Cx32 start codon mutation is equivalent to a complete loss of the protein with failure of translation, although transcription is not impaired. Thus, complete loss of Cx32 function is sufficient to produce CNS dysfunction with clinical manifestations.

Original languageEnglish
Pages (from-to)193-200
Number of pages8
JournalNeurogenetics
Volume16
Issue number3
DOIs
Publication statusPublished - 2015 Jul 20

Fingerprint

Encephalomyelitis
Initiator Codon
Peripheral Nervous System Diseases
Mutation
Connexins
Central Nervous System
Oligodendroglia
Charcot-Marie-Tooth Disease
Schwann Cells
Proteolysis
Immunohistochemistry
Messenger RNA
DNA
Genes
Proteins

Keywords

  • ADEM
  • Connexin32
  • Gap junctions
  • Start codon mutation
  • X-linked Charcot-Marie-Tooth disease

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)
  • Cellular and Molecular Neuroscience

Cite this

A start codon CMT1X mutation associated with transient encephalomyelitis causes complete loss of Cx32. / Sargiannidou, Irene; Kim, Gun Ha; Kyriakoudi, Styliana; Eun, Baik-Lin; Kleopa, Kleopas A.

In: Neurogenetics, Vol. 16, No. 3, 20.07.2015, p. 193-200.

Research output: Contribution to journalArticle

Sargiannidou, Irene ; Kim, Gun Ha ; Kyriakoudi, Styliana ; Eun, Baik-Lin ; Kleopa, Kleopas A. / A start codon CMT1X mutation associated with transient encephalomyelitis causes complete loss of Cx32. In: Neurogenetics. 2015 ; Vol. 16, No. 3. pp. 193-200.
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