Detection of somatic mosaicism in DMD using computer-assisted laser densitometry
- Hospital for Sick Children, Toronto (Canada); and others
Approximately two-thirds of Duchenne muscular dystrophy (DMD) patients have a deletion in the dystrophin gene located at Xp21.1. Two PCR-based multiplex systems have been developed which detect 98% of deletions in affected males. Diagnosis of carrier females requires densitometry of PCR products following gel electrophoresis to calculate dosage of specific exons. We have developed a system in which fluorescently labelled PCR products are analysed using a GENESCANNER automated fragment analyser (ABI). Dosage is determined using computer-assisted laser densitometry (CALD). Recently, we diagnosed somatic mosaicism in the mother of an affected boy using this method. PCR analysis showed that the patient had a deletion that included exons 47-51 of his dystrophin gene. CALD analysis on the patient`s 36-year-old mother revealed a 29-34% reduction in the intensity of the bands corresponding to the deleted region of the gene rather than the 50% reduction normally seen in carrier females. A skin biopsy was obtain and monoclonal fibroblast colonies were tested by CALD for the deletion. Four of the twenty colonies screened were found to be deleted while the remaining colonies had two intact copies of the gene. We conclude that this patient is a somatic mosaic for DMD and that the mutation was the result of a post-zygotic event. This is the only case of somatic mosaicism detected among 800 women from 400 DMD families tested using CALD in our laboratory. At least one other case of possible somatic mosaicism has been reported but not confirmed. Germinal mosaicism is thought to occur in approximately 10% of mothers of sporadic DMD patients. Our findings indicate that somatic mosaicism is a much rarer condition among DMD carriers, thus suggesting that mitotic mutations in the dystrophin gene are more likely to occur later in embryogenesis after differentiation of the germline.
- OSTI ID:
- 134336
- Report Number(s):
- CONF-941009--
- Journal Information:
- American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: Suppl.3 Vol. 55; ISSN AJHGAG; ISSN 0002-9297
- Country of Publication:
- United States
- Language:
- English
Similar Records
Relatively low proportion of dystrophin gene deletions in Israeili Duchenne and Becker muscular dystrophy patients
Electroretinographic genotype-phenotype correlations for mouse and man at the dmd/DMD locus
Related Subjects
BASIC STUDIES
ANIMAL CELLS
AUTOMATION
COMPUTERS
DETECTION
DISEASES
ELECTROPHORESIS
EXONS
FLUORESCENCE
GENE MUTATIONS
GENES
GENETIC MAPPING
HEREDITARY DISEASES
HUMAN X CHROMOSOME
LASERS
MITOSIS
MOSAICISM
MULTIPLEXERS
MUSCLES
MUTATION FREQUENCY
ONTOGENESIS
PATIENTS
POLYMERASE CHAIN REACTION
SOMATIC MUTATIONS