Genetic defect in muscle phosphofructokinase deficiency. Abnormal splicing of the muscle phosphofructokinase gene due to a point mutation at the 5'-splice site.

The genetic defect in muscle phosphofructokinase deficiency (type VII glycogenosis, Tarui disease) was investigated. Six cDNAs for muscle phosphofructokinase, including a full-length clone, were isolated from a non-amplified library of muscle from a patient. By sequence analysis of these clones, a 75-base in-frame deletion was identified. The rest of the sequence was identical to that of the normal cDNA, except for a silent base transition at position 516 (ACT (Thr) to ACC (Thr]. The deletion was located in the 3'-terminal region of exon 13 (numbered with reference to the rabbit muscle phosphofructokinase gene (Lee, C.-P., Kao, M.-C., French, B.A., Putney, S.D., and Chang, S.H. (1987) J. Biol. Chem. 262, 4195-4199]. Genomic DNA of the patient was amplified by polymerase chain reaction. Sequence analysis of the amplified DNA revealed a point mutation from G to T at the 5'-end of intron 13. This mutation changed the normal 5'-splice site of CAG:GTATGG to CAG:TTATGG. A cryptic splice site of ACT:GTGAGG located 75 bases upstream from the normal splice site was recognized and spliced in the patient.