Null mutations and lethal congenital form of glycogen storage disease type IV

Muscular and Neurodegenerative Disease Unit, Department of Pediatrics, Istituto Giannina Gaslini, University of Genova, Largo G. Gaslini 5, I-16147 Genova, Italy.
Biochemical and Biophysical Research Communications (Impact Factor: 2.3). 09/2007; 361(2):445-50. DOI: 10.1016/j.bbrc.2007.07.074
Source: PubMed


Glycogen branching enzyme deficiency (glycogen storage disease type IV, GSD-IV) is a rare autosomal recessive disorder of the glycogen synthesis with high mortality. Two female newborns showed severe hypotonia at birth and both died of cardiorespiratory failure, at 4 and 12 weeks, respectively. In both patients, muscle biopsies showed deposits of PAS-positive diastase-resistant material and biochemical analysis in cultured fibroblasts showed markedly reduced glycogen branching enzyme activity. Direct sequencing of GBE1 gene revealed that patient 1 was homozygous for a novel c.691+5 g>c in intron 5 (IVS5+5 g>c). RT-PCR analysis of GBE1 transcripts from fibroblasts cDNA showed that this mutation produce aberrant splicing. Patient 2 was homozygous for a novel c.1643G>A mutation leading to a stop at codon 548 in exon 13 (p.W548X). These data underscore that in GSD-IV a severe phenotype correlates with null mutations, and indicate that RNA analysis is necessary to characterize functional consequences of intronic mutations.

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