title: Mechanisms of activation of the paternally expressed genes by the Prader-Willi imprinting center in the Prader-Willi/Angelman syndromes domains.
abstract: The Prader-Willi syndrome/Angelman syndrome (PWS/AS) imprinted domain is regulated by a bipartite imprinting control center (IC) composed of a sequence around the SNRPN promoter (PWS-IC) and a 880-bp sequence located 35 kb upstream (AS-IC). The AS-IC imprint is established during gametogenesis and confers repression upon PWS-IC on the maternal allele. Mutation at PWS-IC on the paternal allele leads to gene silencing across the entire PWS/AS domain. This silencing implies that PWS-IC functions on the paternal allele as a bidirectional activator. Here we examine the mechanism by which PWS-IC activates the paternally expressed genes (PEGs) using transgenes that include the PWS-IC sequence in the presence or absence of AS-IC and NDN, an upstream PEG, as an experimental model. We demonstrate that PWS-IC is in fact an activator of NDN. This activation requires an unmethylated PWS-IC in the gametes and during early embryogenesis. PWS-IC is dispensable later in development. Interestingly, a similar activation of a nonimprinted gene (APOA1) was observed, implying that PWS-IC is a universal activator. To decipher the mechanism by which PWS-IC confers activation of remote genes, we performed methylated DNA immunoprecipitation (MeDIP) array analysis on lymphoblast cell lines that revealed dispersed, rather than continued differential methylation. However, chromatin conformation capture (3c) experiments revealed a physical interaction between PWS-IC and the PEGs, suggesting that activation of PEGs may require their proximity to PWS-IC.
authors.affiliation: Department of Developmental Biology and Cancer Research, Institute of Medical Research Israel-Canada,  Hebrew University Hadassah Medical School, Jerusalem 91120,  Israel.
authors.forename: Shiri
authors.initials: S
authors.lastname: Rabinovitz
authors.forename: Yotam
authors.initials: Y
authors.lastname: Kaufman
authors.forename: Guy
authors.initials: G
authors.lastname: Ludwig
authors.forename: Aharon
authors.initials: A
authors.lastname: Razin
authors.forename: Ruth
authors.initials: R
authors.lastname: Shemer
mesh_terms: D017204:Angelman Syndrome / Q000235:genetics*; D000818:Animals; D016632:Apolipoprotein A-I / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015139:Blotting, Southern; D001921:Brain / Q000378:metabolism; D019175:DNA Methylation; D005220:Fathers; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression; D018392:Genomic Imprinting; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D011218:Prader-Willi Syndrome / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D013094:Spermatozoa / Q000378:metabolism; D055517:snRNP Core Proteins / Q000235:genetics
chemical_list: C505693:APOA1 protein, human; D016632:Apolipoprotein A-I; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C069766:necdin; D055517:snRNP Core Proteins