Establishing the epigenetic status of the Prader-Willi/Angelman imprinting center in the gametes and embryo

Department of Cellular Biochemistry and Human Genetics, The Hebrew University, Hadassah Medical School, Jerusalem, Israel.
Human Molecular Genetics (Impact Factor: 6.39). 12/2004; 13(22):2767-79. DOI: 10.1093/hmg/ddh290
Source: PubMed


The Prader-Willi/Angelman imprinted domain on human chromosome 15q11-q13 is regulated by an imprinting control center (IC) composed of a sequence around the SNRPN promoter (PWS-SRO) and a sequence located 35 kb upstream (AS-SRO). We have previously hypothesized that the primary imprint is established on AS-SRO, which then confers imprinting on PWS-SRO. Here we examine this hypothesis using a transgene that includes both AS-SRO and PWS-SRO sequences and carries out the entire imprinting process. The epigenetic features of this transgene resemble those previously observed on the endogenous locus, thus allowing analyses in the gametes and early embryo. We demonstrate that the primary imprint is in fact established in the gametes, creating a differentially methylated CpG cluster (DMR) on AS-SRO, presumably by an adjacent de novo signal (DNS). The DMR and DNS bind specific proteins: an allele-discrimination protein (ADP) and a de novo methylation protein, respectively. ADP, being a maternal protein, is involved in both the establishment of DMR in the gametes and in its maintenance through implantation when methylation of PWS-SRO on the maternal allele takes place. Importantly, while the AS-SRO is required in the gametes to confer methylation on PWS-SRO, it is dispensable later in development.

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Available from: Aharon Razin, Sep 20, 2015
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    • "We hypothesized that these intrinsic characteristics of imprinted gene promoters make them attractive candidates for methylation sensors. Perhaps one of the best-studied examples is the Prader-Willi Angelman region, in which an imprinted DMR resides at the small nuclear ribonucleoprotein polypeptide N (Snrpn) gene promoter region controlling its parent-of-origin monoallelic expression (Buiting et al., 1995; Kantor et al., 2004). Furthermore, Snrpn is expressed in most of the tissues and thus serves as an attractive candidate to generate a DNA methylation reporter. "
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    ABSTRACT: Mammalian DNA methylation plays an essential role in development. To date, only snapshots of different mouse and human cell types have been generated, providing a static view on DNA methylation. To enable monitoring of methylation status as it changes over time, we establish a reporter of genomic methylation (RGM) that relies on a minimal imprinted gene promoter driving a fluorescent protein. We show that insertion of RGM proximal to promoter-associated CpG islands reports the gain or loss of DNA methylation. We further utilized RGM to report endogenous methylation dynamics of non-coding regulatory elements, such as the pluripotency-specific super enhancers of Sox2 and miR290. Loci-specific DNA methylation changes and their correlation with transcription were visualized during cell-state transition following differentiation of mouse embryonic stem cells and during reprogramming of somatic cells to pluripotency. RGM will allow the investigation of dynamic methylation changes during development and disease at single-cell resolution.
    Cell 10/2015; 163(1):218-229. DOI:10.1016/j.cell.2015.08.046 · 32.24 Impact Factor
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    • "However, it is important to note that the potential divergence between the human and mouse H19 ICRs is not indicative that all imprinting processes at all imprinted loci have diverged between the two lineages. For example, transgenic mice containing sequence from the human Prader-Willi/Angelman syndrome domain successfully imprint the transgene [95–97], and subsequent experiments have found several cis-acting elements and protein binding complexes that function at the transgenic locus [98]. Similarly, a differentially methylated region near two paternally expressed human genes, HYMAI and PLAG1, was concluded to be an imprint control region following transgenic mouse experiments in which it successfully acquired differential methylation and conferred imprinting of an eGFP reporter gene [99]. "
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    ABSTRACT: Non-model organisms are generally more difficult and/or time consuming to work with than model organisms. In addition, epigenetic analysis of model organisms is facilitated by well-established protocols, and commercially-available reagents and kits that may not be available for, or previously tested on, non-model organisms. Given the evolutionary conservation and widespread nature of many epigenetic mechanisms, a powerful method to analyze epigenetic phenomena from non-model organisms would be to use transgenic model organisms containing an epigenetic region of interest from the non-model. Interestingly, while transgenic Drosophila and mice have provided significant insight into the molecular mechanisms and evolutionary conservation of the epigenetic processes that target epigenetic control regions in other model organisms, this method has so far been under-exploited for non-model organism epigenetic analysis. This paper details several experiments that have examined the epigenetic processes of genomic imprinting and paramutation, by transferring an epigenetic control region from one model organism to another. These cross-species experiments demonstrate that valuable insight into both the molecular mechanisms and evolutionary conservation of epigenetic processes may be obtained via transgenic experiments, which can then be used to guide further investigations and experiments in the species of interest.
    03/2012; 2012:689819. DOI:10.1155/2012/689819
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    • "It is possible that duplications/insertions that do not remove or disrupt the IC act as a barrier to the interaction of AS-SRO-like elements with PWS-SRO-like elements and lead to aberrant epigenetic modification [Wu and Sun, 2006]. Multicopy transgenes containing intact human AS-SRO and PWS-SRO show correct parent-oforigin-dependent methylation of the PWS-SRO that occurs after fertilization [Kantor et al., 2004]. "
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    ABSTRACT: The 15q11-q13 PWS/AS critical region involves genes that are characterized by genomic imprinting. Multiple repeat elements within the region mediate rearrangements, including interstitial duplications, interstitial triplications, and supernumerary isodicentric marker chromosomes, as well as the deletions that cause Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Recently, duplications of maternal origin concerning the same critical region have been implicated in autism spectrum disorders (ASD). We present a 6-month-old girl carrying a de novo duplication of maternal origin of the 15q11.2-q14 PWS/AS region (17.73 Mb in size) [46,XX,dup(15)(q11.2-q14)] detected with a high-resolution microarray-based comparative genomic hybridization (array-CGH). The patient is characterized by severe hypotonia, obesity, microstomia, long eyelashes, hirsutism, microretrognathia, short nose, severe psychomotor retardation, and multiple episodes of drug-resistant epileptic seizures, while her brain magnetic resonance imaging (MRI) documented partial corpus callosum dysplasia. In our patient the duplicated region is quite large extending beyond the Prader-Willi-Angelman critical region (PWACR), containing a number of genes that have been shown to be involved in ASD, exhibiting a severe phenotype, beyond the typical PWS/AS clinical manifestations. Reporting of similar well-characterized clinical cases with clearly delineated breakpoints of the duplicated region will clarify the contribution of specific genes to the phenotype.
    American Journal of Medical Genetics Part A 08/2010; 152A(8):1925-32. DOI:10.1002/ajmg.a.33447 · 2.16 Impact Factor
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