Imprinting defects on human chromosome 15Horsthemke B. · Buiting K.
Institut für Humangenetik, Universitätsklinikum Essen, Essen (Germany)
The Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are two distinct neurogenetic diseases that are caused by the loss of function of imprinted genes on the proximal long arm of human chromosome 15. In a few percent of patients with PWS and AS, the disease is due to aberrant imprinting and gene silencing. In patients with PWS and an imprinting defect, the paternal chromosome carries a maternal imprint. In patients with AS and an imprinting defect, the maternal chromosome carries a paternal imprint. Imprinting defects offer a unique opportunity to identify some of the factors and mechanisms involved in imprint erasure, resetting and maintenance. In approximately 10% of cases the imprinting defects are caused by a microdeletion affecting the 5′ end of the SNURF-SNRPN locus. These deletions define the 15q imprinting center (IC), which regulates imprinting in the whole domain. These findings have been confirmed and extended in knock-out and transgenic mice. In the majority of patients with an imprinting defect, the incorrect imprint has arisen without a DNA sequence change, possibly as the result of stochastic errors of the imprinting process or the effect of exogenous factors.
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Institut für Humangenetik, Universitätsklinikum Essen
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Manuscript received : 23 May 2005
Accepted in revised form for publication by H. Sasaki,: 3 June 2005.
Number of Print Pages : 8
Number of Figures : 2, Number of Tables : 1, Number of References : 56
Cytogenetic and Genome Research
Vol. 113, No. 1-4, Year 2006 (Cover Date: March 2006)
Journal Editor: Schmid, M. (Würzburg)
ISSN: 1424–8581 (print), 1424–859X (Online)
For additional information: http://www.karger.com/CGR