Telomere fusions as a signal of term placental aging? A pilot study
The placenta plays an essential role at the beginning of life, nourishing and supporting the fetus, but its life span is limited. In late pregnancy, the placenta develops signs of aging, including inflammation and impaired function, which may complicate pregnancy. Placentas also show another sign of aging - cells with extra or missing chromosomes. Chromosomally abnormal cells could gather in the placenta if they get stranded there and/or if the cells do not separate normally. Chromosome separation goes wrong in aging cells when the DNA sequences, which protect the ends of the chromosomes, erode. When chromosomes lose their protective caps, they fuse which leads to abnormal numbers of chromosomes. In this pilot study, for the first time, we found fusions between the caps in a human placenta when it reaches full term. More studies are needed to decide whether this has an influence on how the placenta works and outcomes of pregnancy.
VITRIFICATION WITH DIMETHYL SULFOXIDE (DMSO) CRYOPROTECTANT ALTERS GENE AND TRANSPOSABLE ELEMENT (TE) EXPRESSION IN HUMAN OOCYTES [Meeting Abstract]
Objective: DMSO alters the epigenetic state of mouse oocytes and human cultured cells. The effect of vitrification with DMSO containing cryoprotectant on gene and TE expression in human oocytes is unknown.
Material(s) and Method(s): A prospective paired controlled cohort laboratory study was performed from February - June 2021. Twenty-four discarded oocytes in the germinal vesical (GV) stage were donated from four patients. All oocytes were paired such that half of the oocytes from each patient were vitrified with DMSO-containing cryoprotectant, while the other half were frozen, unexposed to DMSO. All oocytes underwent RNA sequencing via Switching Mechanism At the end of the 5'-end of the RNA Transcript sequencing 2 (SMARTseq2). Reads containing adapters, bases that could not be determined >10% and low quality reads were excluded. Gene mapping to the human reference genome, followed by gene quantification, were performed. Next, differential gene expression analysis between the two cohorts was performed. Then functional enrichment analyses of dysregulated gene sets were performed with Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Human Disease Ontology (DO). Raw data obtained from RNA sequencing was used to analyze TE transcripts using the BonaFide-TEseq method, which were mapped to specific TE loci using Software for Quantifying Interspersed Repeat Expression (SQuIRE), to identify differentially expressed TEs. Real time-qPCR validated results of selected genes and TEs.
Result(s): Of the 27,837 genes identified by SMARTseq2, 7,331 (26.3%) were differentially expressed (p<0.05). Specifically, 3,987 genes were upregulated and 3,344 genes were downregulated in oocytes exposed to DMSO. Genes involved in chromatin and histone modification, and mitochondrial function, as well as WNT, insulin, MTOR, HIPPO and MAPK signaling pathways were affected by DMSO. There was no significant over expression of human disease ontology terms within our data set. Expression of a number of TEs was also affected by exposure to DMSO, including Alu, endogenous retrovirus family members 1 and K (ERV1, ERVK) and long interspersed nuclear elements 1 (LINE-1). Notably, the effects of DMSO on TE expression were most pronounced in the oldest patient. The expression of TEs was negatively correlated with age, and positively correlated with the expression of PIWI-like protein 2 (PIWIL2), DNA Methyltransferase (DNMT) 3A and 3B.
Conclusion(s): Vitrification with DMSO exposure leads to significant changes in gene and TE expression in human GV oocytes. Future experiments should determine whether MII oocytes respond similarly. Impact Statement: Oocyte vitrification with DMSO containing cryoprotectant induces significant transcriptome changes, including those involving TEs, in human GV oocytes. Further studies are needed to evaluate the clinical significance of these findings. Support: This study was supported by the Stanley H Kaplan Fund.
Prenatal phthalate exposure and placental telomere length: Prenatal DEHP exposure and placental telomere length [Letter]
Impact of superovulation and in vitro fertilization on LINE-1 copy number and telomere length in C57BL/6Â J mice blastocysts
OBJECTIVE:Millions of babies have been conceived by IVF, yet debate about its safety to offspring continues. We hypothesized that superovulation and in vitro fertilization (IVF) promote genomic changes, including altered telomere length (TL) and activation of the retrotransposon LINE-1 (L1), and tested this hypothesis in a mouse model. MATERIAL AND METHODS/METHODS:Experimental study analyzing TL and L1 copy number in C57BL/6Â J mouse blastocysts in vivo produced from natural mating cycles (N), in vivo produced following superovulation (S), or in vitro produced following superovulation (IVF). We also examined the effects of prolonged culture on TL and L1 copy number in the IVF group comparing blastocysts cultured 96Â h versus blastocysts cultured 120Â h. TL and L1 copy number were measured by Real Time PCR. RESULTS:TL in S (nâ€‰=â€‰77; Mean: 1.50â€‰Â±â€‰1.15; pâ€‰=â€‰0.0007) and IVF (nâ€‰=â€‰82; Mean: 1.72â€‰Â±â€‰1.44; pâ€‰<â€‰0.0001) exceeded that in N (nâ€‰=â€‰16; Mean: 0.61â€‰Â±â€‰0.27). TL of blastocysts cultured 120Â h (nâ€‰=â€‰15, Mean: 2.14â€‰Â±â€‰1.05) was significantly longer than that of embryos cultured for 96Â h (nâ€‰=â€‰67, Mean: 1.63â€‰Â±â€‰1.50; pâ€‰=â€‰0.0414). L1 copy number of blastocysts cultured for 120Â h (nâ€‰=â€‰15, Mean: 1.71â€‰Â±â€‰1.49) exceeded that of embryos cultured for 96Â h (nâ€‰=â€‰67, Mean: 0.95â€‰Â±â€‰1.03; pâ€‰=â€‰0.0162). CONCLUSIONS:Intriguingly ovarian stimulation, alone or followed by IVF, produced embryos with significantly longer telomeres compared to in vivo, natural cycle-produced embryos. The significance of this enriched telomere endowment for the health and longevity of offspring born from IVF merit future studies.
Can cell-free DNA (cfDNA) testing alleviate psychological distress in early miscarriage? A commentary
BACKGROUND:Psychological, emotional, and mental distress affects many patients who experience early pregnancy loss (EPL). A common concern is that the patient's actions or choices caused the loss. Understanding the cause of EPL may improve the distress of EPL patients and their partners. Chromosomal abnormalities leading to a significant portion of EPL. Cell-free DNA (cfDNA) testing, a non-invasive test providing high quality information about the chromosomal makeup of a fetus, may offer assurance that a fetal abnormality caused the loss, and provide more certainty or closure in processing EPL. CfDNA may be a useful adjunct to patient-centered care in the setting of EPL. This commentary explores the possibility of cfDNA testing in lessening the emotional distress that often accompanies EPL. METHODS:The peer reviewed literature was explored for manuscripts addressing (1) the potential for cfDNA serum testing for patients experiencing EPL and screening products of conception to determine the cause of EPL; and/or (2) the impact that information might have on the psychological morbidity of EPL for patients and their partners. Themes generated from extracted data were used to generate key questions for future research. RESULTS:Preliminary findings suggest fetal fraction values are instrumental in the success of cfDNA testing, and a successful cfDNA testing experience can have a positive impact on patients. CONCLUSIONS:Ultimately, we conclude cfDNA testing could have a positive impact in patient care and improve the well-being of patients undergoing the emotional toll of EPL by reducing feelings of guilt and providing closure to those who learn the loss was associated with chromosomal abnormality. Further trials and studies that explore the intersection of mental health of EPL on patients should explore the efficacy of cfDNA testing as an adjunct to patient-centered care in these cases.
Primary ovarian insufficiency: a glimpse into the racial and socioeconomic disparities found within third-party reproduction
Objective/UNASSIGNED:To describe a unique case of primary ovarian insufficiency and review the systemic barriers in place that hinder reproductive autonomy for Black women who require third-party reproduction. Design/UNASSIGNED:Case report and review of the literature. Setting/UNASSIGNED:Safety-net hospital in an urban community. Patients/UNASSIGNED:A 36-year-old Black woman, gravida 0, with primary ovarian insufficiency who desires future fertility but is restricted by systemic barriers. Interventions/UNASSIGNED:Chromosome analysis. Main Outcome Measures/UNASSIGNED:Not applicable. Results/UNASSIGNED:Balanced reciprocal translocation between chromosomes 1 and 13: 46,XX,t(1;13)(q25;q14.1). Conclusions/UNASSIGNED:The field of assisted reproductive technology has evolved at an exponential rate, yet it unfortunately benefits some and not all. It is imperative that when we advocate for full spectrum infertility care, that this encompasses everyone. As we continue to further study and develop assisted reproductive technology, we must not forget to consider the factors leading to racial and socioeconomic disparities in reproductive care access, utilization, and outcomes.
Control of LINE-1 Expression Maintains Genome Integrity in Germline and Early Embryo Development
Maintenance of genome integrity in the germline and in preimplantation embryos is crucial for mammalian development. Epigenetic remodeling during primordial germ cell (PGC) and preimplantation embryo development may contribute to genomic instability in these cells, since DNA methylation is an important mechanism to silence retrotransposons. Long interspersed elements 1 (LINE-1 or L1) are the most common autonomous retrotransposons in mammals, corresponding to approximately 17% of the human genome. Retrotransposition events are more frequent in germ cells and in early stages of embryo development compared with somatic cells. It has been shown that L1 activation and expression occurs in germline and is essential for preimplantation development. In this review, we focus on the role of L1 retrotransposon in mouse and human germline and early embryo development and discuss the possible relationship between L1 expression and genomic instability during these stages. Although several studies have addressed L1 expression at different stages of development, the developmental consequences of this expression remain poorly understood. Future research is still needed to highlight the relationship between L1 retrotransposition events and genomic instability during germline and early embryo development.
Zscan4 Contributes to Telomere Maintenance in Telomerase-Deficient Late Generation Mouse ESCs and Human ALT Cancer Cells
Proper telomere length is essential for indefinite self-renewal of embryonic stem (ES) cells and cancer cells. Telomerase-deficient late generation mouse ES cells and human ALT cancer cells are able to propagate for numerous passages, suggesting telomerase-independent mechanisms responding for telomere maintenance. However, the underlying mechanisms ensuring the telomere length maintenance are unclear. Here, using late generation telomerase KO (G4 Terc-/-) ESCs as a model, we show that Zscan4, highly upregulated in G4 Terc-/- ESCs, is responsible for the prolonged culture of these cells with stably short telomeres. Mechanistically, G4 Terc-/- ESCs showed reduced levels of DNA methylation and H3K9me3 at Zscan4 promoter and subtelomeres, which relieved the expression of Zscan4. Similarly, human ZSCAN4 was also derepressed by reduced H3K9me3 at its promoter in ALT U2 OS cells, and depletion of ZSCAN4 significantly shortened telomeres. Our results define a similar conserved pathway contributing to the telomere maintenance in telomerase-deficient late generation mESCs and human ALT U2OS cancer cells.
The cervicovaginal microbiome at time of cerclage [Meeting Abstract]
Prenatal phthalate exposure and placental telomere length [Meeting Abstract]