Spontaneous deletion in the FMR-1 gene in a patient with fragile X syndrome and cherubism
- Oregon Health Sciences Univ., Portland, OR (United States); and others
Fragile X mental retardation results from the transcriptional inactivation of the FMR-1 gene and is commonly caused by the expansion of an unstable CGG trinucleotide repeat located in the first exon of the FMR-1 gene. We describe here a two generation fragile X family in which expansion of the CGG repeat may have resulted in a deletion of a least portion of the FMR-1 gene. One member of this family, AB, carries an apparent deletion of the FMR-1 gene and presents with mental retardation and also cherubism, a feature not usually associated with fragile X syndrome. Cherubism is a condition characterized by a swelling of the lower face and is caused by giant cell lesions of the mandible and maxilla, and often the anterior ends of the ribs. The size of the CGG repeat region in this family was determined by Southern analysis of BglII, EcoRI, and PstI digested genomic DNA, isolated from peripheral blood lymphocytes, using a 558 bp PstI-Xhol fragment specific for the 5{prime}-end of the FMR-1 gene. SB and TB, the mother and maternal half-brother of AB, respectively, were both found to carry an expanded FMR-1 allele with greater than 200 CGG repeats. Negligible hybridization was observed in the DNA of AB. In addition, no amplification was observed when the polymerase chain reaction (PCR) was performed using primers flanking the CGG repeat region. These results are consistent with a deletion of at least the 5{prime} portion of the FMR-1 gene in the majority of peripheral blood lymphocytes. Further work is underway using FMR-1 cDNA probes and additional PCR primers to determine the nature of the molecular lesion in AB`s DNA and determine the relationship of this lesion to his cherubism.
- OSTI ID:
- 134285
- 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
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