Myoadenylate deaminase deficiency caused by alternative splicing due to a novel intronic mutation in the AMPD1 gene.
We have examined two Caucasian brothers with myoadenylate deaminase (AMPD) deficiency who presented with exercise intolerance and muscle cramps. Allele-specific PCR amplification assays demonstrated that the common Q12X (C34T) and P48L (C143T) mutations were not found within their AMPD1 genes. Further analysis revealed that both brothers were compound heterozygotes for a previously reported K287I (A860T) mutation in exon 7 and a novel deletion within intron 2 (IVS2-(4-7)delCTTT). The intronic deletion appears to affect the splicing machinery since characterization of AMPD1 mRNA from skeletal muscle of one brother identified multiple alternatively spliced transcripts resulting in multiple deletions in exon 3, the complete deletion of either exon 3 or exons 3 and 4, and the activation of a cryptic splice site that resulted in an insertion at the 5' end of exon 4. The predominant transcript contains a 51 base deletion at the 5' end of exon 3 that is predicted to produce a functional form of AMPD containing a 17-amino acid residue deletion within its N-terminal region. Analysis of 137 Caucasian normal control patients determined that the K287I mutation is relatively frequent (5.1% carrier frequency), whereas the IVS2-(4-7)delCTTT mutation is rare and not present in 274 chromosomes.
Isackson
Paul J
PJ
Department of Pediatrics, Division of Genetics, State University of New York at Buffalo, Buffalo, NY 14209, USA.
Bujnicki
Heather
H
Harding
Cary O
CO
Vladutiu
Georgirene D
GD
D000659:AMP Deaminase / Q000235:genetics*; D000328:Adult; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D004247:DNA; D015444:Exercise; D006801:Humans; D007438:Introns; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D012333:RNA, Messenger / Q000235:genetics
D012333:RNA, Messenger; D004247:DNA; D000659:AMP Deaminase