Prader-Willi Syndrome Methylation-Specific MLPA

Clinical Information

Prader-Willi syndrome is an example of a disorder involving imprinted genes. Imprinted genes are only expressed from either the maternally or paternally derived member of a homologous chromosome pair. Prader-Willi syndrome is characterized by significant infantile hypotonia and feeding difficulties. In early childhood this transitions into excessive eating and morbid obesity. Developmental delay and behavioral problems are common features. Physical characteristics include hypogonadism, short stature, small hands and feet, almond shaped eyes, and hypopigmentation.

Prader-Willi syndrome is caused by the lack of expression of the paternally derived region of chromosome 15 (15q11.2-q13). This lack of expression can be caused by a deletion of the paternal chromosome, maternal uniparental disomy (UPD) of chromosome 15 or more rarely, a defect in the imprinting region.

Technical Information

A methylation sensitive Multiplex Ligation-dependent Probe Amplification (MLPA) assay is used to determine methylation status at 15q11.2-q13 as well as any copy number variants in this region. If an abnormal methylation pattern is identified, then pyrosequencing is performed to quantify the methylation at these sites as needed.

Specimen Requirements

• The preferred sample type is 3-4 ml of peripheral blood collected in an EDTA (purple top) tube. Extracted DNA is also accepted for this test. Blood kits are available by request.
• Send approximately 5µg of extracted DNA at a requested concentration of 90-130 ng/µl.

Transport Instructions

• The blood specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.
• Extracted DNA should be sent at room temperature via overnight delivery.

Prenatal Testing Information

Prenatal diagnosis may be available dependent on ultrasound findings and/or family history. Contact the laboratory prior to sending a prenatal specimen to confirm that requirements for receipt are met. Amniotic fluid must be collected at a minimum of 16 weeks for MS-MLPA results to be informative. CVS samples are not accepted for this methylation-based test. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests.

Prenatal Transport Instructions

Amniotic fluid should be kept at room temperature; do not freeze or refrigerate. Specimen should be sent by courier or overnight mail to arrive at the laboratory the next day. FedEx is preferred.
The blood specimen should be kept at room temperature and delivered via overnight shipping. FedEx is preferred. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Please contact the lab with any questions.
Extracted DNA should be sent at room temperature via overnight delivery.
Saliva is stable at room temperature and can be delivered via overnight or ground shipping.