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LINE1 retrotransposable element 1 OKDB#: 5030
 Symbols: L1RE1 Species: human
 Synonyms: L1.2, LRE1  Locus: 22q12.1 in Homo sapiens


For retrieval of Nucleotide and Amino Acid sequences please go to: OMIM Entrez Gene
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General Comment Maximizing the ovarian reserve in mice by evading LINE-1 genotoxicity. Tharp ME et al. (2020) Female reproductive success critically depends on the size and quality of a finite ovarian reserve. Paradoxically, mammals eliminate up to 80% of the initial oocyte pool through the enigmatic process of fetal oocyte attrition (FOA). Here, we interrogate the striking correlation of FOA with retrotransposon LINE-1 (L1) expression in mice to understand how L1 activity influences FOA and its biological relevance. We report that L1 activity triggers FOA through DNA damage-driven apoptosis and the complement system of immunity. We demonstrate this by combined inhibition of L1 reverse transcriptase activity and the Chk2-dependent DNA damage checkpoint to prevent FOA. Remarkably, reverse transcriptase inhibitor AZT-treated Chk2 mutant oocytes that evade FOA initially accumulate, but subsequently resolve, L1-instigated genotoxic threats independent of piRNAs and differentiate, resulting in an increased functional ovarian reserve. We conclude that FOA serves as quality control for oocyte genome integrity, and is not obligatory for oogenesis nor fertility.//////////////////

NCBI Summary: DISCONTINUED: This record has been withdrawn by HGNC and NCBI. It represented an L1 retrotransposon that is present in multiple copies and outside the scope for our representation.
General function , Epigenetic modifications
Comment
Cellular localization Nuclear
Comment
Ovarian function Follicle endowment, Oogenesis
Comment Expression of Retroelements in Mammalian Gametes and Embryos. Mastora E et al. (2021) Retroelements are genetic mobile elements, expressed during male and female gamete differentiation. Retrotransposons are normally regulated by the methylation machinery, chromatin modifications, non-coding RNAs, and transcription factors, while retrotransposition control is of vital importance in cellular proliferation and differentiation process. Retrotransposition requires a transcription step, by a cellular RNA polymerase, followed by reverse transcription of an RNA intermediate to cDNA and its integration into a new genomic locus. Long interspersed elements (LINEs), human endogenous retroviruses (HERVs), short interspersed elements (SINEs) and SINE-VNTR-Alu elements (SVAs) constitute about half of the human genome, play a crucial role in genome organization, structure and function and interfere with several biological procedures. In this mini review, we discuss recent data regarding retroelement expression (LINE-1, HERVK-10, SVA and VL30) and retrotransposition events in mammalian oocytes and spermatozoa, as well as the importance of their impact on human and mouse preimplantation embryo development.//////////////////Epigenetic modification of long interspersed elements-1 in cumulus cells of mature and immature oocytes from patients with polycystic ovary syndrome. Pruksananonda K et al. (2016) The long interspersed elements (LINE-1, L1s) are a group of genetic elements found in large numbers in the human genome that can translate into phenotype by controlling genes. Growing evidence supports the role of epigenetic in polycystic ovary syndrome (PCOS). The purpose of this study is to evaluate the DNA methylation levels in LINE-1 in a tissue-specific manner using cumulus cells from patients with PCOS compared with normal controls. The study included 19 patients with PCOS and 22 control patients who were undergoing controlled ovarian hyperstimulation. After oocyte retrieval, cumulus cells were extracted. LINE-1 DNA methylation levels were analysed by bisulfite treatment, polymerase chain reaction, and restriction enzyme digestion. The Connection Up- and Down-Regulation Expression Analysis of Microarrays software package was used to compare the gene regulatory functions of intragenic LINE-1. The results showed higher LINE-1 DNA methylation levels in the cumulus cells of mature oocytes in PCOS patients, 79.14 (±2.66) vs. 75.40 (±4.92); p=0.004, but no difference in the methylation of cumulus cells in immature oocytes between PCOS and control patients, 70.33 (±4.79) vs. 67.79 (±5.17); p=0.155. However, LINE-1 DNA methylation levels were found to be higher in the cumulus cells of mature oocytes than in those of immature oocytes in both PCOS and control patients. These findings suggest that the epigenetic modification of LINE-1 DNA may play a role in regulating multiple gene expression that affects the pathophysiology and development of mature oocytes in PCOS.////////////////// A Role for Retrotransposon LINE-1 in Fetal Oocyte Attrition in Mice. Malki S 2014 et al. Fetal oocyte attrition (FOA) is a conserved but poorly understood process of elimination of more than two-thirds of meiotic prophase I (MPI) oocytes before birth. We now implicate retrotransposons LINE-1 (L1), activated during epigenetic reprogramming of the embryonic germline, in FOA in mice. We show that wild-type fetal oocytes possess differential nuclear levels of L1ORF1p, an L1-encoded protein essential for L1 ribonucleoprotein particle (L1RNP) formation and L1 retrotransposition. We demonstrate that experimental elevation of L1 expression correlates with increased MPI defects, FOA, oocyte aneuploidy, and embryonic lethality. Conversely, reverse transcriptase (RT) inhibitor AZT has a profound effect on the FOA dynamics and meiotic recombination, and it implicates an RT-dependent trigger in oocyte elimination in early MPI. We propose that FOA serves to select oocytes with limited L1 activity that are therefore best suited for the next generation. /////////////////////////
Expression regulated by
Comment
Ovarian localization Oocyte
Comment LINE-1 of Evidence for Fetal Oocyte Attrition by Retrotransposon. Chuma S 2014 et al. Fetal oocytes in mammals undergo extensive apoptosis during development. In this issue of Developmental Cell, Malki et?al. (2014) provide insight into how and why such massive oocyte loss occurs through the demonstration that the expression level of LINE-1 retrotransposon defines the survival threshold and thus viability of fetal oocytes. /////////////////////////
Follicle stages
Comment
Phenotypes PCO (polycystic ovarian syndrome)
Mutations 0 mutations
Genomic Region show genomic region
Phenotypes and GWAS show phenotypes and GWAS
Links
OMIM (Online Mendelian Inheritance in Man: an excellent source of general gene description and genetic information.)
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created: June 4, 2014, 1:25 p.m. by: hsueh   email:
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last update: June 30, 2021, 10:14 a.m. by: hsueh    email:



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