Abnormal DLK1/MEG3 imprinting correlates with decreased HERV-K methylation after assisted reproduction and preimplantation genetic diagnosis

Human Endogenous Retroviruses: Friends and Foes in Urology Clinics

Human endogenous retroviruses (HERVs) are originated from ancient exogenous retroviruses, which infected human germ line cells millions of years ago. HERVs have generally lost their replication and retrotransposition abilities, but adopted physiological roles in human biology. Though mostly inactive, HERVs can be reactivated by internal and external factors such as inflammations and environmental conditions. Their aberrant expression can participate in various human malignancies with complex etiology. This review describes the features and functions of HERVs in urological subjects, such as urological cancers and human reproduction. It provides the current knowledge of the HERVs and useful insights helping practice in urology clinics.

A Systems Biology Approach on the Regulatory Footprint of Human Endogenous Retroviruses (HERVs)

Human endogenous retroviruses (HERVs) are a family of endogenous retroviruses that comprise the ~8.93% of the human genome sequence, with a high proportion being human specific. The recent expansion of repeated HERV sequences has offered a framework for genetic and epigenetic innovation. In the current report, a systematic approach is implemented to catalogue regulatory elements within HERVs, as a roadmap to potential functions of HERV sequences in gene networks. ENCODE Project has offered a wealth of epigenetic data based on omics technologies. I analyzed the presence of HERV sequences on consensus cis-regulatory elements (cCREs) from ENCODE data. On the one side, HERVs are in 1 out of 9 cCREs (>100.000 cCREs in total), dispersed within the genome and present in cis-regulatory regions of ~81% of human genes, as calculated following gene enrichment analysis. On the other side, promoter-associated HERV cCREs are present adjacent to (in a 200 bp window) the transcription start sites of 256 human genes. Regulatory network production, followed by centrality analysis led to the discovery of 90 core genes containing HERV-associated promoters. Pathway analysis on the core network genes and their immediate neighbors revealed a regulatory footprint that, among others, is associated with inflammation, chemokine signaling and response to viral infection. Collectively, these results support the concept that the expansion of regulatory sequences derived from HERVs is critical for epigenetic innovation that may have wired together genes into novel transcriptional networks with critical roles in cellular physiology and pathology.

Expression of Retroelements in Mammalian Gametes and Embryos

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.

Influence of conception and delivery mode on stress response marker Oct4B1 and imprinted gene expression related to embryo development: A cohort study

BACKGROUND

Recent scientific data support that the mode of conception and delivery may influence epigenetic regulation and therefore embryo development. Octamer-binding transcription factor 4-B1 (OCT4B1), a novel variant of OCT4 with yet unknown biological function, is suggested to have a potential role in mediating cellular stress response. Furthermore, Insulinlike Growth Factor 2 (IGF2), Mesoderm-specific Transcript (MEST) and paternally expressed gene 10 (PEG10) are genes known as imprinted and are regulated via means of epigenetic regulation. The influence of delivery mode and conception on epigenetic regulation is an active research field.

OBJECTIVE

Our aim was to correlate the expression level of Oct4B1 and the expression and methylation level of IGF2, MEST, and PEG10 imprinted genes with the mode of delivery and conception in the umbilical cord blood of newborns.

MATERIALS AND METHODS

Samples of umbilical cord blood from infants born after vaginal delivery, caesarean section (CS) with the infant in cephalic position and CS due to breech position were examined. Furthermore, the investigation included infants conceived through means of assisted reproductive technology.

RESULTS

No statistically significant differences were found in mRNA expression levels between different modes of conception and delivery (p = 0.96). Oct4B1, IGF2, MEST, and PEG10 expression levels do not seem to be significantly affected by different modes of conception and delivery.

CONCLUSION

These results indicate that the expression and methylation patterns of Oct4B1, IGF2, MEST and PEG10 in umbilical cord blood are not affected by the conception and delivery mode.

Analysis of lncRNA UCA1-related downstream pathways and molecules of cisplatin resistance in lung adenocarcinoma

BACKGROUND

To analyze the lncRNA UCA1-related downstream pathways and molecules of cisplatin resistance in lung adenocarcinoma.

METHODS

We constructed overexpression and siRNA vectors targeting UCA1 and TXNIP and then used next-generation sequencing to compare the UCA1 overexpression and negative control from A549 cell.

RESULTS

It shown that 647 upregulated mRNAs and 633 downregulated differentially expressed mRNAs-related UCA1, and the top ten upregulated mRNAs were CPD, AC007192.1, TGOLN2, LGR4, TFPI, CYP1B1, TOMM6, HLA-B, SLC35F6, and TOP2A, and top ten downregulated mRNAs were TXNIP, SESN2, STC2, HSPA1A, MMP10, CHAC1, DNAJB1, AC004922.1, ATF3, and GABARAPL1. We found TXNIP mRNA expression level was the most significantly downexpressed mRNA. TXNIP mRNA expression level of LAD tissues was clearly lower than the adjacent tissues. UCA1 expression level of cisplatin insensitive group was markedly higher than that of cisplatin-sensitive group, while TXNIP mRNA expression level of cisplatin insensitive group was clearly lower than that of cisplatin-sensitive group. Compared to the BEAS-2B, TXNIP mRNA expression level cut down in A549 and A549/DDP cell and that of A549/DDP cell was lower than A549 cell. After UCA1 overexpression, TXNIP mRNA obviously decreased, while proliferation ability and IC50 of A549 heightened. After knocking down UCA1, TXNIP mRNA was significantly increased, while proliferation ability and IC50 of A549/DDP lowered. PPI analysis result showed that TXNIP could interact with multiple proteins such as TXN, DDIT4, and NLRP3.

CONCLUSION

UCA1 promoted cisplatin resistance by downregulating TXNIP expression in LAD, and TXNIP could interact with multiple proteins. So, UCA1/TXNIP axis might affect cisplatin resistance in LAD.

Epigenetic changes and assisted reproductive technologies

Children conceived by Assisted Reproductive Technologies (ART) are at moderately increased risk for a number of undesirable outcomes, including low birth weight. Whether the additional risk is associated with specific procedures used in ART or biological factors that are intrinsic to infertility has been the subject of much debate, as has the mechanism by which ART or infertility might influence this risk. The potential effect of ART clinical and laboratory procedures on the gamete and embryo epigenomes heads the list of mechanistic candidates that might explain the association between ART and undesirable clinical outcomes. The reason for this focus is that the developmental time points at which ART clinical and laboratory procedures are implemented are precisely the time points at which large-scale reorganization of the epigenome takes place during normal development. In this manuscript, we review the many human studies comparing the epigenomes of ART children with children conceived in vivo, as well as assess the potential of individual ART clinical and laboratory procedures to alter the epigenome.

Alteration in the expression of the renin-angiotensin system in the myocardium of mice conceived by in vitro fertilization

Epidemiological studies have revealed that offspring conceived by in vitro fertilization (IVF) have an elevated risk of cardiovascular malformations at birth, and are more predisposed to cardiovascular diseases. The renin-angiotensin system (RAS) plays an essential role in both the pathogenesis of congenital heart disease in fetuses and cardiovascular dysfunction in adults. This study aimed to assess the relative expression levels of genes in the RAS pathway in mice conceived using IVF, compared to natural mating with superovulation. Results demonstrated that expression of the angiotensin II receptor type 1 (AGTR1), connective tissue growth factor (CTGF), and collagen 3 (COL3), in the myocardial tissue of IVF-conceived mice, was elevated at 3 weeks, 10 weeks, and 1.5 years of age, when compared to their non-IVF counterparts. These data were supported by microRNA microarray analysis of the myocardial tissue of aged IVF-conceived mice, where miR-100, miR-297, and miR-758, which interact with COL3, AGTR1, and COL1 respectively, were upregulated when compared to naturally mated mice of the same age. Interestingly, bisulfite sequencing data indicated that IVF-conceived mice exhibited decreased methylation of CpG sites in Col1. In support of our in vivo investigations, miR-297 overexpression was shown to upregulate AGTR1 and CTGF, and increased cell proliferation in cultured H9c2 cardiomyocytes. These findings indicate that the altered expression of RAS in myocardial tissue might contribute to cardiovascular malformation and/or dysfunction in IVF-conceived offspring. Furthermore, these cardiovascular abnormalities might be the result of altered DNA methylation and abnormal regulation of microRNAs.

Exogenous retroelement integration in sperm and embryos affects preimplantation development

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.

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

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.

Epigenetics: A key paradigm in reproductive health

It is well established that there is a heritable element of susceptibility to chronic human ailments, yet there is compelling evidence that some components of such heritability are transmitted through non-genetic factors. Due to the complexity of reproductive processes, identifying the inheritance patterns of these factors is not easy. But little doubt exists that besides the genomic backbone, a range of epigenetic cues affect our genetic programme. The inter-generational transmission of epigenetic marks is believed to operate via four principal means that dramatically differ in their information content: DNA methylation, histone modifications, microRNAs and nucleosome positioning. These epigenetic signatures influence the cellular machinery through positive and negative feedback mechanisms either alone or interactively. Understanding how these mechanisms work to activate or deactivate parts of our genetic programme not only on a day-to-day basis but also over generations is an important area of reproductive health research.