Service de neurologie Institut national de neurologie Tunisie

	Service de Neurologie	Actualités scientifiques

Phenotype and sarcoglycan expression in Tunisian LGMD 2C patients sharing the same del521-T mutation.

Kefi M, Amouri R, Driss A, Ben Hamida C, Ben Hamida M, Kunkel LM, Hentati F.

Institut National de Neurologie, Laboratoire de Neurobiologie Moleculaire, 1007 La Rabta, Tunis, Tunisia.

Limb-girdle muscular dystrophy type 2C is an autosomal recessive muscular disorder caused by mutations in the gene encoding the gamma-sarcoglycan subunit. This gamma-sarcoglycanopathy is prevalent in Tunisia where only one homozygous mutation a 521-T deletion has been identified. The aim of this study was to carry out a comparative clinical and immunocytochemical analysis of Tunisian patients sharing the same gamma-sarcoglycan gene mutation. One hundred and thirty-two patients were classified as severe, moderate or mild according to a calculated severity score. Heterogeneous phenotypes between siblings were encountered in 75% of the families. The severity of the disease was not found to be related to the age of onset. Immunohistochemical studies of muscle biopsy showed a total absence of gamma-sarcoglycan, a normal or slightly reduced alpha and delta-sarcoglycans whereas the expression of beta-sarcoglycan was variable. The residual sarcoglycan expression was not related to the clinical phenotype. In conclusion, the phenotypic variability in sarcoglycanopathies in Tunisia seems to involve a modifying gene controlling the course of the disease.

Identification of novel GDAP1 mutations causing autosomal recessive Charcot-Marie-Tooth disease.

Ammar N, Nelis E, Merlini L, Barisic N, Amouri R, Ceuterick C, Martin JJ, Timmerman V, Hentati F, De Jonghe P.

Molecular Genetics Department, Flanders Interuniversity Institute for Biotechnology (VIB), University of Antwerp (UIA), Universiteitsplein 1, B-2610, Antwerp, Belgium.

Mutations in the ganglioside-induced differentiation-associated protein 1 gene cause either autosomal recessive demyelinating Charcot-Marie-Tooth disease type 4A or autosomal recessive axonal Charcot-Marie-Tooth disease with vocal cord paresis. We sequenced the ganglioside-induced differentiation-associated protein 1 gene in 138 patients from 119 unrelated families diagnosed with either demyelinating or axonal autosomal recessive Charcot-Marie-Tooth disease. We detected six distinct mutant alleles in four families, four of which are novel. Electrophysiological studies show severely slowed motor nerve conduction velocities with severely reduced compound muscle action potentials. However, one patient had a normal conduction velocity in the ulnar nerve. Based on the electrophysiological tests, patients with ganglioside-induced differentiation-associated protein 1 mutations will therefore be classified as either axonal or demyelinating Charcot-Marie-Tooth disease. The neuropathological aspect shows a divergent pattern; nerve biopsies taken from two siblings at the same age and sharing the same ganglioside-induced differentiation-associated protein 1 gene mutation showed a dissimilar severity stage.

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