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Background Genomic imprinting results from the resistance of germline epigenetic marks to reprogramming in the early embryo for a small number of mammalian genes. Genetic, epigenetic or environmental insults that prevent imprints from evading reprogramming may result in imprinting disorders, which impact growth, development, behaviour and metabolism. We aimed to identify genetic defects causing imprinting disorders by whole-exome sequencing in families with one or more members affected by multilocus imprinting disturbance. Methods Whole-exome sequencing was performed in 38 pedigrees where probands had multilocus imprinting disturbance, in five of whom maternal variants in NLRP5 have previously been found. Results We now report 15 further pedigrees in which offspring had disturbance of imprinting, while their mothers had rare, predicted-deleterious variants in maternal effect genes, including NLRP2, NLRP7 and PADI6. As well as clinical features of well-recognised imprinting disorders, some offspring had additional features including developmental delay, behavioural problems and discordant monozygotic twinning, while some mothers had reproductive problems including pregnancy loss. Conclusion The identification of 20 putative maternal effect variants in 38 families affected by multilocus imprinting disorders adds to the evidence that maternal genetic factors affect oocyte fitness and thus offspring development. Testing for maternal-effect genetic variants should be considered in families affected by atypical imprinting disorders.

Molecular genetic testing for the 11p15-associated imprinting disorders Silver-Russell and Beckwith-Wiedemann syndrome (SRS, BWS) is challenging because of the molecular heterogeneity and complexity of the affected imprinted regions. With the growing knowledge on the molecular basis of these disorders and the demand for molecular testing, it turned out that there is an urgent need for a standardized molecular diagnostic testing and reporting strategy. Based on the results from the first external pilot quality assessment schemes organized by the European Molecular Quality Network (EMQN) in 2014 and in context with activities of the European Network of Imprinting Disorders (EUCID.net) towards a consensus in diagnostics and management of SRS and BWS, best practice guidelines have now been developed. Members of institutions working in the field of SRS and BWS diagnostics were invited to comment, and in the light of their feedback amendments were made. The final document was ratified in the course of an EMQN best practice guideline meeting and is in accordance with the general SRS and BWS consensus guidelines, which are in preparation. These guidelines are based on the knowledge acquired from peer-reviewed and published data, as well as observations of the authors in their practice. However, these guidelines can only provide a snapshot of current knowledge at the time of manuscript submission and readers are advised to keep up with the literature.Copyright © 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

Molecular genetic testing for the 11p15-associated imprinting disorders Silver-Russell and Beckwith-Wiedemann syndrome (SRS, BWS) is challenging because of the molecular heterogeneity and complexity of the affected imprinted regions. With the growing knowledge on the molecular basis of these disorders and the demand for molecular testing, it turned out that there is an urgent need for a standardized molecular diagnostic testing and reporting strategy. Based on the results from the first external pilot quality assessment schemes organized by the European Molecular Quality Network (EMQN) in 2014 and in context with activities of the European Network of Imprinting Disorders (EUCID.net) towards a consensus in diagnostics and management of SRS and BWS, best practice guidelines have now been developed. Members of institutions working in the field of SRS and BWS diagnostics were invited to comment, and in the light of their feedback amendments were made. The final document was ratified in the course of an EMQN best practice guideline meeting and is in accordance with the general SRS and BWS consensus guidelines, which are in preparation. These guidelines are based on the knowledge acquired from peer-reviewed and published data, as well as observations of the authors in their practice. However, these guidelines can only provide a snapshot of current knowledge at the time of manuscript submission and readers are advised to keep up with the literature.

Contains fulltext : 167696.pdf (Publisher’s version ) (Closed access), Genomic imprinting is a mechanism in which gene expression varies depending on parental origin. Imprinting occurs through differential epigenetic marks on the two parental alleles, with most imprinted loci marked by the presence of differentially methylated regions (DMRs). To identify sites of parental epigenetic bias, here we have profiled DNA methylation patterns in a cohort of 57 individuals with uniparental disomy (UPD) for 19 different chromosomes, defining imprinted DMRs as sites where the maternal and paternal methylation levels diverge significantly from the biparental mean. Using this approach we identified 77 DMRs, including nearly all those described in previous studies, in addition to 34 DMRs not previously reported. These include a DMR at TUBGCP5 within the recurrent 15q11.2 microdeletion region, suggesting potential parent-of-origin effects associated with this genomic disorder. We also observed a modest parental bias in DNA methylation levels at every CpG analyzed across approximately 1.9 Mb of the 15q11-q13 Prader-Willi/Angelman syndrome region, demonstrating that the influence of imprinting is not limited to individual regulatory elements such as CpG islands, but can extend across entire chromosomal domains. Using RNA-seq data, we detected signatures consistent with imprinted expression associated with nine novel DMRs. Finally, using a population sample of 4,004 blood methylomes, we define patterns of epigenetic variation at DMRs, identifying rare individuals with global gain or loss of methylation across multiple imprinted loci. Our data provide a detailed map of parental epigenetic bias in the human genome, providing insights into potential parent-of-origin effects.