IMR Press / FBE / Volume 4 / Issue 6 / DOI: 10.2741/e537

Frontiers in Bioscience-Elite (FBE) is published by IMR Press from Volume 13 Issue 2 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Review

L1 expression and regulation in humans and rodents

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1 School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA

Academic Editor: Kathleen Burns

Front. Biosci. (Elite Ed) 2012, 4(6), 2203–2225; https://doi.org/10.2741/e537
Published: 1 January 2012
(This article belongs to the Special Issue Mobile DNAs in mammalian genomes)
Abstract

Long interspersed elements type 1 (LINE-1s, or L1s) have impacted mammalian genomes at multiple levels. L1 transcription is mainly controlled by its 5’ untranslated region (5’UTR), which differs significantly among active human and rodent L1 families. In this review, L1 expression and its regulation are examined in the context of human and rodent development. First, endogenous L1 expression patterns in three different species—human, rat, and mouse—are compared and contrasted. A detailed account of relevant experimental evidence is presented according to the source material, such as cell lines, tumors, and normal somatic and germline tissues from different developmental stages. Second, factors involved in the regulation of L1 expression at both transcriptional and posttranscriptional levels are discussed. These include transcription factors, DNA methylation, PIWIinteracting RNAs (piRNAs), RNA interference (RNAi), and posttranscriptional host factors. Similarities and differences between human and rodent L1s are highlighted. Third, recent findings from transgenic mouse models of L1 are summarized and contrasted with those from endogenous L1 studies. Finally, the challenges and opportunities for L1 mouse models are discussed.

Keywords
5’UTR
Blastocyst
DNA methylation
Embryonal carcinoma cell
Embryonic stem cell
Gene expression
Gene regulation
Germ cell tumor
L1
LINE-1
Long interspersed element
Morula
Mouse model
Neurogenesis
Non-LTR retrotransposon
ORF1
ORF2
piRNA
Preimplantation
Postimplantation
Primordial germ cell
siRNA
Spermatogenesis
Transcription factor
Transgene
Tumor
Review
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