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Monk D.,Bellvitge Institute for Biomedical | Arnaud P.,Montpellier University | Frost J.M.,University College London | Frost J.M.,Kings College London | And 10 more authors.
Nucleic Acids Research | Year: 2011

Imprinted retrotransposed genes share a common genomic organization including a promoter-associated differentially methylated region (DMR) and a position within the intron of a multi-exonic 'host' gene. In the mouse, at least one transcript of the host gene is also subject to genomic imprinting. Human retrogene orthologues are imprinted and we reveal that human host genes are not imprinted. This coincides with genomic rearrangements that occurred during primate evolution, which increase the separation between the retrogene DMRs and the host genes. To address the mechanisms governing imprinted retrogene expression, histone modifications were assayed at the DMRs. For the mouse retrogenes, the active mark H3K4me2 was associated with the unmethylated paternal allele, while the methylated maternal allele was enriched in repressive marks including H3K9me3 and H4K20me3. Two human retrogenes showed monoallelic enrichment of active, but not of repressive marks suggesting a partial uncoupling of the relationship between DNA methylation and repressive histone methylation, possibly due to the smaller size and lower CpG density of these DMRs. Finally, we show that the genes immediately flanking the host genes in mouse and human are biallelically expressed in a range of tissues, suggesting that these loci are distinct from large imprinted clusters. © 2011 The Author(s). Source

Porta-de-la-Riva M.,Bellvitge Institute for Biomedical Research | Porta-de-la-Riva M.,Bellvitge Institute for Biomedical | Fontrodona L.,Bellvitge Institute for Biomedical Research | Villanueva A.,Bellvitge Institute for Biomedical Research | And 3 more authors.
Journal of Visualized Experiments | Year: 2012

Research into the molecular and developmental biology of the nematode Caenorhabditis elegans was begun in the early seventies by Sydney Brenner and it has since been used extensively as a model organism 1. C. elegans possesses key attributes such as simplicity, transparency and short life cycle that have made it a suitable experimental system for fundamental biological studies for many years 2. Discoveries in this nematode have broad implications because many cellular and molecular processes that control animal development are evolutionary conserved 3. C. elegans life cycle goes through an embryonic stage and four larval stages before animals reach adulthood. Development can take 2 to 4 days depending on the temperature. In each of the stages several characteristic traits can be observed. The knowledge of its complete cell lineage 4,5 together with the deep annotation of its genome turn this nematode into a great model in fields as diverse as the neurobiology 6, aging 7,8, stem cell biology 9 and germ line biology 10. An additional feature that makes C. elegans an attractive model to work with is the possibility of obtaining populations of worms synchronized at a specific stage through a relatively easy protocol. The ease of maintaining and propagating this nematode added to the possibility of synchronization provide a powerful tool to obtain large amounts of worms, which can be used for a wide variety of small or high-throughput experiments such as RNAi screens, microarrays, massive sequencing, immunoblot or in situ hybridization, among others. Because of its transparency, C. elegans structures can be distinguished under the microscope using Differential Interference Contrast microscopy, also known as Nomarski microscopy. The use of a fluorescent DNA binder, DAPI (4',6-diamidino-2-phenylindole), for instance, can lead to the specific identification and localization of individual cells, as well as subcellular structures/defects associated to them.© JoVE 2006-2012.All Rights Reserved. Source

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