Molecular mechanisms of McArdle's disease (muscle glycogen phosphorylase deficiency). RNA and DNA analysis.

Abstract

Lack of muscle glycogen phosphorylase activity leads to McArdle's disease, a rare metabolic myopathy. To investigate its molecular basis at the nucleic acid level, we isolated muscle phosphorylase cDNA clones from a human cDNA library in Escherichia coli plasmid pBR 322. Subcloning of one insertion of M13 bacteriophage permitted its definite identification by sequencing. Northern blot experiments revealed one specific messenger RNA of 3.4 kilobases found uniquely in tissues expressing muscle phosphorylase.We show that McArdle's disease exhibits a molecular heterogeneity at the messenger RNA level. In eight unrelated cases of McArdle's disease in which no inactive proteins had been detected, we assayed muscle biopsies for phosphorylase mRNA by Northern blotting. In five cases, no muscle phosphorylase mRNA could be detected, while in three other cases, normal length mRNA was present in lower amounts.Moreover, Southern blot analysis of DNA isolated from white blood cells in four McArdle patients revealed no major deletion or rearrangements of the phosphorylase gene as compared with controls.

The Na‐G Ion Channel Is Transcribed from a Single Promoter Controlled by Distinct Neuron‐ and Schwann Cell‐Specific DNA Elements

“…Total genomic DNA was isolated from tail biopsies as described (Davis et al, 1986). The presence of the transgene and copy number were evaluated as described by Southern (1975 with modifications as described (Gautron et al., 1987). Founder mice were crossed and analysis carried out on offspring, to avoid mosaicim and transgenes with multiple insertion sites, except for the ‐1,050‐intron founder mice, which were analyzed directly.…”

Expression of muscle-type phosphorylase in innervated and aneural cultured muscle of patients with myophosphorylase deficiency.

“…Slab gel IEF (as used in this study) offers clear advantages in both definition and separation over the assays used in the previous studies (36 (4,(39)(40)(41). A forthcoming report seems to indicate in many l * | patients the presence of a point mutation introducing a stop codon in the first exon of the gene (4 la).…”

“…Molecular studies of myophosphorylase deficiency revealed that in most cases the protein is absent and the mRNA is missing or greatly reduced (4)(5)(6), in some patients there is a normal amount of either full-length or shorter mRNA, and in a few patients an inactive protein of normal or reduced size can be shown by immunoreaction with anti-M-GP antiserum (5)(6)(7)(8)(9). In human tissues there are three different isoforms ofglycogen phosphorylase (GP) ( 10), which are encoded by three separate genes (1 1-13).…”

Clinical utility gene card for McArdle disease

“…It is exclusively caused by recessive variants in the PYGM gene, which codes for the skeletal muscle glycogen phosphorylase (myophosphorylase) enzyme [1,2]. The myophosphorylase enzyme is the first enzyme in the process to breakdown glycogen stores in skeletal muscle.…”