title: LINEs in mice: features, families, and potential roles in early development.
abstract: Approximately half of the mammalian genome is composed of repetitive elements, including LINE-1 (L1) elements. Because of their potential ability to transpose and integrate into other regions of the genome, their activation represents a threat to genome stability. Molecular pathways have emerged to tightly regulate and repress their transcriptional activity, including DNA methylation, histone modifications, and RNA pathways. It has become evident that Line-L1 elements are evolutionary diverse and dedicated repression pathways have been recently uncovered that discriminate between evolutionary old and young elements, with RNA-directed silencing mechanisms playing a prominent role. During periods of epigenetic reprogramming in development, specific classes of repetitive elements are upregulated, presumably due to the loss of most heterochromatic marks in this process. While we have learnt a lot on the molecular mechanisms that regulate Line-L1 expression over the last years, it is still unclear whether reactivation of Line-L1 after fertilization serves a functional purpose or it is a simple side effect of reprogramming.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM U964, Université de Strasbourg, 67404, Illkirch, France.
authors.forename: Joanna W
authors.initials: JW
authors.lastname: Jachowicz
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM U964, Université de Strasbourg, 67404, Illkirch, France. metp@igbmc.fr.
authors.forename: Maria-Elena
authors.initials: ME
authors.lastname: Torres-Padilla
mesh_terms: D000818:Animals; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006657:Histones / Q000378:metabolism; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics* / Q000502:physiology; D008297:Male; D051379:Mice; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D014158:Transcription, Genetic
chemical_list: D006657:Histones
keywords: Epigenetic reprogramming; Line-L1; Transposable elements