Angelman Syndrome Methylation-Specific MLPA

Clinical Information

Angelman 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. Angelman syndrome is characterized by significant developmental delay or intellectual disability, severe speech impairment, an ataxic gait, and inappropriate happy behavior including excessive laughing and smiling. Other physical concerns include microcephaly, seizures, wide mouth and a prominent mandible.

Angelman syndrome is caused by the lack of expression of the maternally inherited region of chromosome 15 (15q11.2-q13). This lack of expression can be caused by a deletion of the maternal chromosome, paternal uniparental disomy (UPD), a variant in the UBE3A gene in this region, or an imprinting defect.

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 and saliva are also accepted for this test. Blood and saliva kits are available by request.
• Saliva samples must be submitted in an approved saliva kit.
• Send approximately 5µg of extracted DNA at a requested concentration of 90-130 ng/µl. Bead-based extraction is strongly discouraged for MS-MLPA.

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.
• Saliva is stable at room temperature and can be delivered via overnight or ground shipping.
• 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 Specimen Requirements

• Amniotic Fluid: Direct amniotic fluid will be accepted for analysis given there is sufficient volume for back-up culture to be established. A back-up culture at a reference lab OR Greenwood lab is required. Additional charges may apply if cell culture is required after receipt of the sample. If sending direct fluid for molecular analysis only, 10-20 ml of amniotic fluid is requested. Chromosome studies will require an additional 10-15 ml of fluid.
• CVS samples are not accepted for this methylation-based test.
• Maternal Sample: A maternal sample is required. Accepted maternal sample types include blood in an EDTA/lavender top tube, saliva, or extracted DNA. Please refer to the specimen requirements above for more information.

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.
• Please refer to the transport instructions above for sending the maternal sample.