Retrotransposon expression and incorporation of cloned human and mouse retroelements in human spermatozoa

LINE-1, HERV-K10, and SVA retrotransposons are transcriptionally expressed in human spermatozoa and cloned active retroelements can be incorporated in the human sperm genome, giving rise to de novo retrotransposition events.

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Volume 107, Issue 3, Pages 821–830

Authors:

Leandros Lazaros, Ph.D., Chrysoula Kitsou, Ph.D., Charilaos Kostoulas, B.Sc., Sofia Bellou, Ph.D., Elissavet Hatzi, Ph.D., Paris Ladias, B.Sc., Theodoros Stefos (M.D., Ph.D.), Sofia Markoula, Ph.D., Vasiliki Galani, Ph.D., Georgios Vartholomatos, Ph.D., Theodore Tzavaras, Ph.D., Ioannis Georgiou (Ph.D.)

Abstract:

Objective

To investigate the expression of long interspersed element (LINE) 1, human endogenous retrovirus (HERV) K10, and short interspersed element–VNTR–Alu element (SVA) retrotransposons in ejaculated human spermatozoa by means of reverse-transcription (RT) polymerase chain reaction (PCR) analysis as well as the potential incorporation of cloned human and mouse active retroelements in human sperm cell genome.

Design

Laboratory study.

Setting

University research laboratories and academic hospital.

Patient(s)

Normozoospermic and oligozoospermic white men.

Intervention(s)

RT-PCR analysis was performed to confirm the retrotransposon expression in human spermatozoa. Exogenous retroelements were tagged with a plasmid containing a green fluorescence (EGFP) retrotransposition cassette, and the de novo retrotransposition events were tested with the use of PCR, fluorescence-activated cell sorting analysis, and confocal microscopy.

Main Outcome Measure(s)

Retroelement expression in human spermatozoa, incorporation of cloned human and mouse active retroelements in human sperm genome, and de novo retrotransposition events in human spermatozoa.

Result(s)

RT-PCR products of expressed human LINE-1, HERV-K10, and SVA retrotransposons were observed in ejaculated human sperm samples. The incubation of human spermatozoa with either retrotransposition-active human LINE-1 and HERV-K10 or mouse reverse transcriptase–deficient VL30 retrotransposons tagged with an EGFP-based retrotransposition cassette led to EGFP-positive spermatozo; 16.67% of the samples were positive for retrotransposition. The respective retrotransposition frequencies for the LINE-1, HERV-K10, and VL30 retrotransposons in the positive samples were 0.34 ± 0.13%, 0.37 ± 0.17%, and 0.30 ± 0.14% per sample of 10,000 spermatozoa.

Conclusion(s)

Our results show that: 1) LINE-1, HERV-K10, and SVA retrotransposons are transcriptionally expressed in human spermatozoa; 2) cloned active retroelements of human and mammalian origin can be incorporated in human sperm genome; 3) active reverse transcriptases exist in human spermatozoa; and 4) de novo retrotransposition events occur in human spermatozoa.


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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders. The journal publishes juried original scientific articles in clinical and laboratory research relevant to reproductive endocrinology, urology, andrology, physiology, immunology, genetics, contraception, and menopause. Fertility and Sterility® encourages and supports meaningful basic and clinical research, and facilitates and promotes excellence in professional education, in the field of reproductive medicine.

1 Comments

Go to the profile of Christian Ibekwe
Christian Ibekwe over 1 year ago

Lysogenic phase interaction activity between bacteria like staph aureus or E.coli could generate transposable elements which when incorporated and expressed by human spermatozoa causes either an inserted change or control change in human fertility.This appears to be the mechanism of the male factor in infertility and uterine fibroid formation in the female.Since from your study here this feat occurred 16% of the times in 100000semen,by extrapolation it means that the more ejaculations one gets during heterosexual intercourse the more the likelihood of getting this happening as is common in cassanovas or promiscous folks.Since both bacteria and viruses are normal commensals of the human reproductive tracts,it could also happen between couples when a traumatic breach triggers an infection.