Identification of Prader-Willi Syndrome mosaicism by fluorescent in situ hybridization
- Magee Womens Hospital, Pittsburgh, PA (United States)
- Rehabilitation Institute, Pittsburgh, PA (United States)
Prader-Willi Syndrome (PWS) is a microdeletion syndrome involving an interstitial deletion of region q11-q13 on the paternal chromosome 15. We report 2 cases of PWS that were analyzed using FISH and were found to be mosaic for a normal cell line and a deleted cell line. Case 1 was diagnosed as an atypical PWS who was cytogenetically normal. She is a 38 y.o. white female displaying some but not all of the features of PWS. Case 2 is a 23 y.o. white male with a classical deletion of chromosome 15q11-q13. He displays very typical features of PWS. He was also noted to be albino. FISH analysis was performed on PHA stimulated lymphocytes. We examined four loci: D15S11, SNRPN, D15S10, and GABRB3. The number of cells examined for each locus ranged from 46 to 75. Case 1 was deleted at 3 of the 4 loci (D15S11, SNRPN and GABRB3) in 30% of her cells. The D15S10 locus was not deleted. This may account for the atypical features displayed by this patient. It also suggests that this chromosome is rearranged resulting in the retention of the interstitial locus. The exact nature of the rearrangement needs to be determined. Case 2 was deleted at all four loci in 60% of the cells analyzed. This result was unexpected because his deletion was identified cytogenetically, but mosaicism was not detected. These are the first reported cases of mosaic PWS diagnosed using FISH. The use of cytogenetics alone requires high resolution banding to accurately identify the deletion. This makes the detection of small deletions in every cell difficult and the determination of mosaicism almost impossible. Our results suggest that mosaicism may be occurring more frequently than previously thought and may account for some of the atypical cases. Studies are in progress to determine the effect of mosaicism on methylation at genes located within this region which are imprinted and are thought to be involved in the etiology of Prader-Willi Syndroms.
- OSTI ID:
- 133729
- 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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