Associated with Genomic Imprinting

Figure 6-7 Prader-Willi syndrome (PWS) and Angelman syndrome (AS). A, PWS in a image-year-old boy with obesity, hypogonadism, and small hands and feet who also has short stature and developmental delay. B, Angelman syndrome in a 4-year-old girl. Note wide stance and position of arms. C, Chromosomal microarray detection of approximately 5-Mb deletion in 15q11.2-q13.1 (red). D, Schematic of the 15q11.2-q13 region. The PWS region (shaded in blue) contains a series of imprinted genes (blue) that are expressed only from the paternal copy. The AS region (shaded in pink) contains two imprinted genes that are expressed only from the maternal copy, including the UBE3A gene, which is imprinted in the central nervous system and mutations in which can cause AS. The region is flanked by nonimprinted genes (purple) that are expressed from both maternal and paternal copies. Common deletions of the PWS/AS region, caused by recombination between pairs of segmental duplications, are shown in green at the bottom. Smaller deletions of the imprinting center (IC; orange) and of a subset of genes in the small nucleolar RNA (snoRNA) gene cluster can also lead to PWS. cen, Centromere; tel, telomere. See Sources & Acknowledgments.


Genomic Mechanisms Causing Prader-Willi and Angelman Syndromes

Mechanism Prader-Willi Syndrome Angelman Syndrome
15q11.2-q13 deletion ≈70% (paternal) ≈70% (maternal)
Uniparental disomy ≈20-30% (maternal) ≈7% (paternal)
Imprinting center mutation ≈2.5% ≈3%
Gene mutations Rare (small deletions within snoRNA gene cluster) ≈10% (UBE3A mutations)
Unidentified <1% ≈10%

snoRNA, Small nucleolar RNA.

Data from Cassidy SB, Schwartz S, Miller JL, et al: Prader-Willi syndrome. Genet Med 14:10-26, 2012; Dagli AI, Williams CA: Angelman syndrome. In Pagon RA, Adam MP, Bird TD, et al, editors: GeneReviews [Internet], Seattle, 1993-2013, University of Washington, Seattle,

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Nov 27, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Associated with Genomic Imprinting

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