title: Exogenous retroelement integration in sperm and embryos affects preimplantation development.
abstract: Retroelement transcripts are present in male and female gametes, where they are typically regulated by methylation, noncoding RNAs and transcription factors. Such transcripts are required for occurrence of retrotransposition events, while failure of retrotransposition control may exert negative effects on cellular function and proliferation. In order to investigate the occurrence of retrotransposition events in mouse epididymal spermatozoa and to address the impact of uncontrolled retroelement RNA expression in early preimplantation embryos, we performed in vitro fertilization experiments using spermatozoa preincubated with plasmid vectors containing the human retroelements LINE-1, HERVK-10 or the mouse retroelement VL30, tagged with an enhanced green fluorescence (EGFP) gene-based cassette. Retrotransposition events in mouse spermatozoa and embryos were detected using PCR, FACS analysis and confocal microscopy. Our findings show that: (i) sperm cell incorporates exogenous retroelements and favors retrotransposition events, (ii) the inhibition of spermatozoa reverse transcriptase can decrease the retrotransposition frequency in sperm cells, (iii) spermatozoa can transfer exogenous human or mouse retroelements to the oocyte during fertilization and (iv) retroelement RNA overexpression affects embryo morphology and impairs preimplantation development. These findings suggest that the integration of exogenous retroelements in the sperm genome, as well as their transfer into the mouse oocyte, could give rise to new retrotransposition events and genetic alterations in mouse spermatozoa and embryos.
authors.affiliation: Laboratory of Medical Genetics and Human ReproductionMedical School, Ioannina University, Ioannina, Greece.
authors.forename: C
authors.initials: C
authors.lastname: Kitsou
authors.affiliation: Laboratory of Medical Genetics and Human ReproductionMedical School, Ioannina University, Ioannina, Greece.
authors.forename: L
authors.initials: L
authors.lastname: Lazaros
authors.affiliation: Foundation for Research & Technology-Hellas Institute of Molecular Biology and BiotechnologyDepartment of Biomedical Research, Ioannina, Greece.
authors.forename: S
authors.initials: S
authors.lastname: Bellou
authors.affiliation: Hematology LaboratoryUnit of Molecular Biology, Ioannina University Hospital, Ioannina, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Vartholomatos
authors.affiliation: Laboratory of Medical Genetics and Human ReproductionMedical School, Ioannina University, Ioannina, Greece.
authors.forename: P
authors.initials: P
authors.lastname: Sakaloglou
authors.affiliation: Laboratory of Medical Genetics and Human ReproductionMedical School, Ioannina University, Ioannina, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Hatzi
authors.affiliation: Department of NeurologyMedical School, Ioannina University, Ioannina, Greece.
authors.forename: S
authors.initials: S
authors.lastname: Markoula
authors.affiliation: Laboratory of Medical Genetics and Human ReproductionMedical School, Ioannina University, Ioannina, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Zikopoulos
authors.affiliation: Department of General BiologyMedical School, Ioannina University, Ioannina, Greece.
authors.forename: T
authors.initials: T
authors.lastname: Tzavaras
authors.affiliation: Laboratory of Medical Genetics and Human ReproductionMedical School, Ioannina University, Ioannina, Greece igeorgio@uoi.gr.
authors.forename: I
authors.initials: I
authors.lastname: Georgiou
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D047108:Embryonic Development / Q000235:genetics*; D004822:Epididymis / Q000166:cytology / Q000378:metabolism; D005260:Female; D005306:Fertilization / Q000502:physiology*; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D051379:Mice; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D016133:Polymerase Chain Reaction; D018626:Retroelements / Q000235:genetics*; D013094:Spermatozoa / Q000378:metabolism*
chemical_list: D018626:Retroelements