Human Molecular Genetics, Vol 7, 865-870, Copyright © 1998 by Oxford University Press
S Chang, MJ Rosenberg, H Morton, CA Francomano and LG Biesecker
Glycogen storage disease type VI (GSD6) defines a group of disorders that
cause hepatomegaly and hypoglycemia with reduced liver phosphorylase
activity. The course of these disorders is generally mild, but definitive
diagnosis requires invasive procedures. We analyzed a Mennonite kindred
with an autosomal recessive form of GSD6 to determine the molecular defect
and develop a non-invasive diagnostic test. Linkage analysis was performed
using genetic markers flanking the liver glycogen phosphorylase gene ( PYGL
), which was suspected to be the cause of the disorder on biochemical
grounds. Mennonite GSD6 was linked to the PYGL locus with a multipoint LOD
score of 4.7. The PYGL gene was analyzed for mutations by sequencing
genomic DNA. Sequencing of genomic DNA revealed a splice site abnormality
of the intron 13 splice donor. Confirmation of the genomic mutation was
performed by sequencing RT-PCR products, which showed heterogeneous PYGL
mRNA lacking all or part of exon 13 in affected persons. This study is the
first to demonstrate that a mutation in the PYGL gene can cause GSD6. This
mutation is estimated to be present on 3% of Mennonite chromosomes and the
disease affects 0.1% of that population. Determination of this mutation
provides a basis for the development of a simple and non- invasive
diagnostic test for the disease and the carrier state in this population
and confirms biochemical data showing the importance of this gene in
glucose homeostasis.
ARTICLES
Identification of a mutation in liver glycogen phosphorylase in glycogen storage disease type VI
Laboratory of Genetic Disease Research and Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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