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University of Iowa Diagnostic Laboratories (UIDL) Department of Pathology Room 5231, RCP Iowa City, Iowa 52242-1181 319-384-7212 Tel 319-384-7213 Fax |
PRADER-WILLI and
ANGELMAN SYNDROME INFORMATION
| Background and Methodology: |
Prader-Willi syndrome (PWS) is caused by a deficiency of paternal gene expression on chromosome 15q. Approximately 70% of all PWS patients have a 15q11-q13 deletion on the paternally contributed chromosome 15. Approximately 28% of all PWS patients lack the paternal chromosome 15 by maternal unipaternal disomy (UPD(15)). The remaining cases of PWS have mutations leading to errors in the imprinting process that cause non expression of the paternally contributed genes on 15q11-q13. The direct DNA test for PWS is accomplished by detecting the patient's methylation imprint on 15q11-q13 with a Southern blot procedure using a methylation sensitive restriction enzyme and a 15q11-q12 probe (SNRPN). Angelman syndrome (AS) is caused by a deficiency of maternal gene expression on chromosome 15q. Approximately 70% of all AS patients have a 15q11-q13 deletion on the maternally contributed chromosome 15. Approximately 3%-5% of all AS patients lack the maternal chromosome 15 by paternal unipaternal disomy (UPD(15)). The remaining non deletion, non UPD AS cases are due to mutations leading to abnormal imprinting or to mutations in the UBE3A gene. The direct DNA test for AS is accomplished by detecting the patient's methylation imprint on 15q11-q13 as described above. This test will not detect mutations in the UBE3A gene. |
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| Selected References: |
ASHG/ACMG Report. Diagnostic Testing for Prader-Willi and Angelman Syndromes: Report of the ASHG/ACMG Test and Technology Transfer Committee. American Society of Human Genetics/American College of Medical Genetics Test and Technology Transfer Committee (1996). Am. J. Hum. Genet., Vol 58: 1085-1088. Sutcliffe et al., (1994) Deletions of a Differentially Methylated CpG Island at the SNRPN Gene Define a Putative Imprinting Control Region. Nature, Vol 8:52-58. OMIM reference #176270 PWS, #105830 AS. |
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