Table 1.

Genomic Testing used in Maternal 15q Duplication Syndrome

Duplication 1MethodSensitivity
ProbandAt-risk family members
4.5- to 12-Mb duplication at 15q11.2-q13.1 (incl PWACR)
ISCN: seq[GRCh38] dup(15)(q11.2-13.1) chr15:g. 22,782,170-28,134,728dup 2
ClinGen ID: ISCA-37404 3 or ISCA-37478 4		CMA 5,6100%100%
Targeted duplication analysis 7NA 8100%

PWACR = Prader-Willi/Angelman critical region

1.

See Molecular Genetics for details of the duplication and genes of interest included in this region.

2.

Standardized clinical annotation and interpretation for genomic variants from the Clinical Genome Resource (ClinGen) project (formerly the International Standards for Cytogenomic Arrays [ISCA] Consortium). Genomic coordinates represent the minimum duplication size associated with the 15q11.2-q13.1 recurrent duplication as designated by ClinGen. Duplication coordinates may vary slightly based on array design used by the testing laboratory. Note that the size of the duplication as calculated from these genomic positions may differ from the expected duplication size due to the presence of segmental duplications near breakpoints. The phenotype of significantly larger or smaller duplications within this region may be clinically distinct from the 15q11.2-q13.1 recurrent duplication (see Genetically Related Disorders).

3.

Class 1 duplication, approximately 6 Mb, extending from BP1 to BP3

4.

Class 2 duplication, approximately 5 Mb, extending from BP2 to BP3

5.

Chromosomal microarray analysis (CMA) using oligonucleotide or SNP arrays. CMA designs in current clinical use target the 15q11.2-q13.1 region. Note: Maternal 15q duplication may not have been detectable by older oligonucleotide or BAC platforms.

6.

FISH or cytogenetic analysis (e.g., G-banded chromosome study) should be completed as a follow up to CMA in most instances in order to determine whether the duplication is interstitial or contained within a supernumerary chromosome. Although CMA results may indicate whether the duplication is interstitial, this is not common.

7.

Targeted duplication analysis methods can include FISH, quantitative PCR (qPCR), and multiplex ligation-dependent probe amplification (MLPA) as well as other targeted quantitative methods.

8.

Targeted duplication analysis is not appropriate for diagnosis of an individual in whom the 15q11.2-q13.1 duplication was not detected by CMA designed to target this region.

From: Maternal 15q Duplication Syndrome

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