FISH Analysis:
(Prader-Willi Syndrome & Angelman Syndrome)
The American College of Medical Genetics has described two approaches to laboratory diagnosis. The first approach, to be used in cases with a high degree of suspicion of AS or PWS, is DNA methylation analysis which will detect cases caused by deletion, UPD or imprint defects. DNA methylation analysis can distinguish between the maternal methylated and paternal unmethylated copies of a gene in the 15q11.2 region. An exclusively paternal pattern is observed in cases of AS due to deletion, UPD and imprint control mutations. An exclusively maternal pattern is observed in cases of PWS due to deletion, UPD and imprint control mutations. If the results are negative, chromosome and FISH analysis should be performed to rule out chromosome abnormalities.
TESTING METHODOLOGY:
Fluoresescence in situ hybridization (FISH) is the application of fluorescently-labeled DNA probes to metaphase chromosomes or interphase nuclei for the detection of chromosome abnormalities such as aneuploidy, structural rearrangements, and microdeletions. The assay uses the D15S10 or SNRPN gene probe, for AS and PWS, respectively, and two chromosome 15 control probes. Analysis is based on fluorescent signals present in 10 to 20 labeled metaphases.
SPECIMEN REQUIREMENTS:
Newborn: minimum 1-2 mL
Child/Adult: prefer 2 tubes of 3-5 mL
Transport at ambient temperature. Specimen cannot be frozen.
Prenatal testing: Please contact the laboratory for instructions.
Contact the Cytogenetics Laboratory at 918-502-1721 to obtain further information.
TURNAROUND TIME: 10 days
CPT CODES: 88271, 88273, 88230, 88291