Molecular characterization of the breakpoints of a 12-kb deletion in the NF1 gene in a family showing germ-line mosaicism
- and others
Neurofibromatosis type 1 (NF1) is caused by deletions, insertions, translocations, and point mutations in the NF1 gene, which spans 350 kb on the long arm of human chromosome 17. Although several point mutations have been described, large molecular abnormalities have rarely been characterized in detail. We describe here the molecular breakpoints of a 12-kb deletion of the NF1 gene, which is responsible for the NF1 phenotype in a kindred with two children affected because of germ-line mosaicism in the unaffected father, who has the mutation in 10% of his spermatozoa. The mutation spans introns 31-39, removing 12,021 nt and inserting 30 bp, of which 19 bp are a direct repetition of a sequence located in intron 31, just 4 bp before the 5{prime} breakpoint. The 5{prime} and 3{prime} breakpoints contain the sequence TATTTTA, which could be involved in the generation of the deletion. The most plausible explanation for the mechanism involved in the generation of this 12-kb deletion is homologous/nonhomologous recombination. Since sperm of the father does not contain the corresponding insertion of the 12-kb deleted sequence, this deletion could have occurred within the NF1 chromosome through loop formation. RNA from lymphocytes of one of the NF1 patients showed similar levels of the mutated and normal transcripts, suggesting that the NF1-mRNA from mutations causing frame shifts of the reading frame or stop codons in this gene is not degraded during its processing. The mutation was not detected in fresh lymphocytes from the unaffected father by PCR analysis, supporting the case for true germ-line mosaicism. 30 refs., 3 figs.
- OSTI ID:
- 209895
- Journal Information:
- American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: 5 Vol. 57; ISSN AJHGAG; ISSN 0002-9297
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BASIC STUDIES
CHROMOSOMAL ABERRATIONS
CHROMOSOME BREAKAGE
DNA SEQUENCING
DNA-CLONING
DOMINANT MUTATIONS
GENE MUTATIONS
GENE RECOMBINATION
GENES
HEREDITARY DISEASES
HUMAN CHROMOSOME 17
INTRONS
MOSAICISM
NERVOUS SYSTEM DISEASES
PATIENTS
PHENOTYPE
POLYMERASE CHAIN REACTION
SKELETAL DISEASES
TRANSCRIPTION