Angelman syndrome

Angelman syndrome is a neurodevelopmental disorder that can cause developmental delay, microcephaly, intellectual disability, and epilepsy. Genetic testing can assist with clarifying a diagnosis, and lead to tailored management recommendations and genetic counseling. 

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Test Code 7029
Turnaround Time (TAT) 2-4 weeks
Number of Genes 2
Specimen Requirements Click here

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Mutation Detection Rate

This testing can detect >99.9% of described sequencing and deletion/duplication mutations in UBE3A (analytical sensitivity). Methylation studies can detect >99.9% of methylation abnormalities of 15q11-13, when present (analytic sensitivity).

Test Description

Genomic deoxyribonucleic acid (gDNA) is isolated from the patient’s specimen using a standardized methodology and quantified. Sequence enrichment of the targeted coding exons and adjacent intronic nucleotides is carried out by a bait-capture methodology using long biotinylated oligonucleotide probes, followed by polymerase chain reaction (PCR) and next generation sequencing (NGS).

Additional Sanger sequencing is performed for any regions missing or with insufficient read depth coverage for reliable heterozygous variant detection. Reportable small insertions and deletions, potentially homozygous variants, variants in regions complicated by pseudogene interference, and single nucleotide variant calls not satisfying 100x depth of coverage and 40% het ratio thresholds are verified by Sanger sequencing.This assay targets all coding domains, and well into the flanking 5’ and 3’ ends of all the introns and untranslated regions. Gross deletion/duplication analysis for available genes is performed utilizing a targeted chromosomal microarray. Specific Site Analysis for known familial mutations, carrier screening, and prenatal diagnosis is also available.

Methylation analysis to assess the presence or absence of the maternal copy of the 15q11.2-q13 chromosomal region associated with Angelman syndrome can be ordered as a stand-alone test, or with a reflex option to UBE3A gene sequencing and deletion/duplication analysis. Methylation analysis is performed using methylation specific multiplex ligation probe amplification analysis (MS-MLPA, MRC-Holland kit# ME028-B2). This analysis can also detect the absence of the paternal copy of the 15q11.2-q13 chromosomal region, which is associated with Prader-Willi syndrome.

 

1. Mu W, et al. Sanger confirmation is required to achieve optimal sensitivity and specificity in next-generation sequencing panel testing. J Mol Diagn. 2016. 18(6):923-932.

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