Biological Mechanisms Impacting Pre-Implantation Embryo Development

It is estimated that one out of four couples in developed countries are affected by infertility. Assisted reproductive technologies (ART) have made crucial advancements in helping couples achieve the goal of parenthood. However, one of the many challenges facing this patient population is the failure of embryo implantation into the uterus during in vitro fertilization (IVF). The transfer of seemingly good-quality embryos can often result in a negative pregnancy outcome. There are many factors that can contribute to implantation potential, including embryo aneuploidy, advanced maternal age, and sperm and oocyte quality among many others. However, little is understood regarding the molecular mechanisms responsible for embryo development during the window of implantation.Therefore, the overall aim of this thesis was to understand the biological and epigenetic mechanisms during embryo implantation development by specifically investigating:(1) How both maternal age and/or chromosome constitution affect microRNA profiles and downstream target RNAs of pre-implantation blastocysts, (2) the hypothesis that advanced maternal age is impacting the overall transcriptome of the developing embryo, (3) if methylation alterations are present in aneuploid blastocysts and if this contributes to implantation potential, (4) how different types of infertility diagnoses are impacting the transcriptome of the pre-implantation blastocyst, and (5) if it is possible to detect polymorphisms in patients with premature diminished ovarian reserve and if methylation alterations are found in the germline of embryos from this infertile population which affect implantation potential.The conclusions of these aims are as follows:Both chromosome constitution, as well as advanced maternal age, affect miRNA profiles of the developing blastocyst. MiR-93 was found to be exclusively expressed in women of advanced maternal age and further up-regulated in aneuploid embryos. The increased expression of this miRNA was additionally found to result in a down-regulation of SIRT1, its target gene, which likely affects the oxidative stress defense mechanisms of the embryo, thereby reducing implantation potential. Additionally, an overall decreased global transcriptome was observed in maternally aged blastocysts, impacting biological pathways involved in cell growth and invasion which are vital to pre-implantation embryo development.Epigenetic alterations were also observed in aneuploid blastocysts. A hypomethylated state was revealed but only in monosomic embryos and only in the chromosome involved in the error. Decreased expression of developmental genes located on the chromosome of error were also observed. In contrast, the trisomic blastocyst displayed transcriptional dosage compensatory mechanisms for the presence of the additional chromosome. This might partially explain the difference in implantation potential between trisomic and monosomic embryos.Underlying infertility diagnosis was also found to have a significant impact on the blastocyst transcriptome. Alterations were observed for all infertility etiologies examined. Biological and molecular processes of the altered transcriptomes revealed both similarities, as well as differences, across the groups. Similarities included alterations to reproductive genes, cell adhesion, and response to stimulus genes among others. These processes are characterized by cells that are able to proliferate, migrate, and attach and are all crucial to embryo development and implantation. Lastly, young women with premature diminished ovarian reserve (DOR) were found to have critical variants in DNA sequence. Utilizing exome sequencing, a panel of single-nucleotide polymorphisms (SNPs) was able to distinguish DOR wome

Infertility diagnosis has a significant impact on the transcriptome of developing blastocysts

STUDY QUESTION: Is the human blastocyst transcriptome associated with infertility diagnosis, specifically: polycystic ovaries (PCO), male factor (MF) and unexplained (UE)? SUMMARY ANSWER: The global blastocyst transcriptome was significantly altered in association with a PCO, MF and UE infertility diagnosis. WHAT IS KNOWN ALREADY: Infertility diagnosis has an impact on the probability for a successful outcome following an IVF cycle. Limited information is known regarding the relationship between a specific infertility diagnosis and blastocyst transcription during preimplantation development. STUDY DESIGN, SIZE, DURATION: Blastocysts created during infertility treatment from patients with specific infertility diagnoses (PCO, MF and UE) were analyzed for global transcriptome compared to fertile donor oocyte blastocysts (control). PARTICIPANTS/MATERIALS, SETTING, METHODS: Surplus cryopreserved blastocysts were donated with patient consent and institutional review board approval. Female patients were <38 years old with male patients <40 years old. Blastocysts were grouped according to infertility diagnosis: PCO (n = 50), MF (n = 50), UE (n = 50) and fertile donor oocyte controls (n = 50). Pooled blastocysts were lysed for RNA isolation followed by microarray analysis using the SurePrint G3 Human Gene Expression Microarray. Validation was performed on significant genes of interest using real-time quantitative PCR (RT-qPCR). MAIN RESULTS AND THE ROLE OF CHANCE: Transcription alterations were observed for all infertility etiologies compared to controls, resulting in differentially expressed genes: PCO = 869, MF = 348 and UE = 473 (P 2-fold). Functional annotation of biological and molecular processes revealed both similarities, as well as differences, across the infertility groups. All infertility etiologies displayed transcriptome alterations in signal transducer activity, receptor binding, reproduction, cell adhesion and response to stimulus. Blastocysts from PCO patients were also enriched for apoptotic genes while MF blastocysts displayed enrichment for genes involved in cancer processes. Blastocysts from couples with unexplained infertility displayed transcription alterations related to various disease states, which included mechanistic target of rapamycin (mTOR) and adipocytokine signaling. RT-qPCR validation confirmed differential gene expression for the following genes: BCL2 like 10 (BCL2L10), heat shock protein family A member 1A (HSPA1A), heat shock protein family A member 1B (HSPA1B), activating transcription factor 3 (ATF3), fibroblast growth factor 9 (FGF9), left-right determination factor 1 (LEFTY1), left-right determination factor 2 (LEFTY2), growth differentiation factor 15 (GDF15), inhibin beta A subunit (INHBA), adherins junctions associated protein 1 (AJAP1), cadherin 9 (CDH9) and laminin subunit alpha 4 (LAMA4) (P 2-fold)

Compromised global embryonic transcriptome associated with advanced maternal age

Purpose To investigate the global transcriptome and associated embryonic molecular networks impacted with advanced maternal age (AMA). Methods Blastocysts derived from donor oocyte IVF cycles with no male factor infertility (< 30 years of age) and AMA blastocysts (≥ 42 years) with no other significant female factor infertility or male factor infertility were collected with informed patient consent. RNA sequencing libraries were prepared using the SMARTer® Ultra® Low Kit (Clontech Laboratories) and sequenced on the Illumina HiSEQ 4000. Bioinformatics included Ingenuity® Pathway Analysis (Qiagen) with ViiA™7 qPCR utilized for gene expression validation (Applied Biosystems). Results A total of 2688 significant differentially expressed transcripts were identified to distinguish the AMA blastocysts from young, donor controls. 2551 (95%) of these displayed decreased transcription in the blastocysts from older women. Pathway analysis revealed three altered molecular signaling networks known to be critical for embryo and fetal development: CREBBP, ESR1, and SP1. Validation of genes within these networks confirmed the global decreased transcription observed in AMA blastocysts (P < 0.05). Conclusions A significant, overall decreased global transcriptome was observed in blastocysts from AMA women. The ESR1/SP1/CREBBP pathway, in particular, was found to be a highly significant upstream regulator impacting biological processes that are vital during embryonic patterning and pre-implantation development. These results provide evidence that AMA embryos are compromised on a cell signaling level which can repress the embryo’s ability to proliferate and implant, contributing to a deterioration of reproductive outcomes

The impact of infertility diagnosis on embryo-endometrial dialogue

Initial stages of implantation involve bi-directional molecular crosstalk between the blastocyst and endometrium. This study investigated an association between infertility etiologies, specifically advanced maternal age (AMA) and endometriosis, on the embryo-endometrial molecular dialogue prior to implantation. Co-culture experiments were performed with endometrial epithelial cells (EEC) and cryopreserved day 5 blastocysts (n?=?41???Grade 3BB) donated from patients presenting with AMA or endometriosis, compared to fertile donor oocyte controls. Extracellular vesicles isolated from co-culture supernatant were analyzed for miRNA expression and revealed significant alterations correlating to AMA or endometriosis. Specifically, AMA resulted in 16 miRNAs with increased expression (P???0.05) and strong evidence for negative regulation toward 206 target genes. VEGFA, a known activator of cell adhesion, displayed decreased expression (P???0.05), validating negative regulation by 4 of these increased miRNAs: miR-126; 150; 29a; 29b (P???0.05). In endometriosis patients, a total of 10 significantly altered miRNAs displayed increased expression compared to controls (miR-7b; 9; 24; 34b; 106a; 191; 200b; 200c; 342-3p; 484) (P???0.05), targeting 1014 strong evidence-based genes. Three target genes of miR-106a (CDKN1A, E2F1 and RUNX1) were independently validated. Functional annotation analysis of miRNA-target genes revealed enriched pathways for both infertility etiologies, including disrupted cell cycle regulation and proliferation (P???0.05). These extracellular vesicle-bound secreted miRNAs are key transcriptional regulators in embryo-endometrial dialogue and may be prospective biomarkers of implantation success. One of the limitations of this study is that it was a stimulated, in vitro model and therefore may not accurately reflect the in-vivo environment

Risk estimation of distant metastasis in node-negative, estrogen receptor-positive breast cancer patients using an RT-PCR based prognostic expression signature

<p>Abstract</p> <p>Background</p> <p>Given the large number of genes purported to be prognostic for breast cancer, it would be optimal if the genes identified are not confounded by the continuously changing systemic therapies. The aim of this study was to discover and validate a breast cancer prognostic expression signature for distant metastasis in untreated, early stage, lymph node-negative (N-) estrogen receptor-positive (ER+) patients with extensive follow-up times.</p> <p>Methods</p> <p>197 genes previously associated with metastasis and ER status were profiled from 142 untreated breast cancer subjects. A "metastasis score" (MS) representing fourteen differentially expressed genes was developed and evaluated for its association with distant-metastasis-free survival (DMFS). Categorical risk classification was established from the continuous MS and further evaluated on an independent set of 279 untreated subjects. A third set of 45 subjects was tested to determine the prognostic performance of the MS in tamoxifen-treated women.</p> <p>Results</p> <p>A 14-gene signature was found to be significantly associated (p < 0.05) with distant metastasis in a training set and subsequently in an independent validation set. In the validation set, the hazard ratios (HR) of the high risk compared to low risk groups were 4.02 (95% CI 1.91–8.44) for the endpoint of DMFS and 1.97 (95% CI 1.28 to 3.04) for overall survival after adjustment for age, tumor size and grade. The low and high MS risk groups had 10-year estimates (95% CI) of 96% (90–99%) and 72% (64–78%) respectively, for DMFS and 91% (84–95%) and 68% (61–75%), respectively for overall survival. Performance characteristics of the signature in the two sets were similar. Ki-67 labeling index (LI) was predictive for recurrent disease in the training set, but lost significance after adjustment for the expression signature. In a study of tamoxifen-treated patients, the HR for DMFS in high compared to low risk groups was 3.61 (95% CI 0.86–15.14).</p> <p>Conclusion</p> <p>The 14-gene signature is significantly associated with risk of distant metastasis. The signature has a predominance of proliferation genes which have prognostic significance above that of Ki-67 LI and may aid in prioritizing future mechanistic studies and therapeutic interventions.</p

An international effort towards developing standards for best practices in analysis, interpretation and reporting of clinical genome sequencing results in the CLARITY Challenge

There is tremendous potential for genome sequencing to improve clinical diagnosis and care once it becomes routinely accessible, but this will require formalizing research methods into clinical best practices in the areas of sequence data generation, analysis, interpretation and reporting. The CLARITY Challenge was designed to spur convergence in methods for diagnosing genetic disease starting from clinical case history and genome sequencing data. DNA samples were obtained from three families with heritable genetic disorders and genomic sequence data were donated by sequencing platform vendors. The challenge was to analyze and interpret these data with the goals of identifying disease-causing variants and reporting the findings in a clinically useful format. Participating contestant groups were solicited broadly, and an independent panel of judges evaluated their performance. RESULTS: A total of 30 international groups were engaged. The entries reveal a general convergence of practices on most elements of the analysis and interpretation process. However, even given this commonality of approach, only two groups identified the consensus candidate variants in all disease cases, demonstrating a need for consistent fine-tuning of the generally accepted methods. There was greater diversity of the final clinical report content and in the patient consenting process, demonstrating that these areas require additional exploration and standardization. CONCLUSIONS: The CLARITY Challenge provides a comprehensive assessment of current practices for using genome sequencing to diagnose and report genetic diseases. There is remarkable convergence in bioinformatic techniques, but medical interpretation and reporting are areas that require further development by many groups

Corona cell RNA sequencing from individual oocytes revealed transcripts and pathways linked to euploid oocyte competence and live birth.

Corona cells surround the oocyte and maintain a close relationship through transzonal processes and gap junctions, and may be used to assess oocyte competence. In this study, the corona cell transcriptome of individual cumulus oocyte complexes (COCs) was investigated. Isolated corona cells were collected from COCs that developed into euploid blastocysts and were transferred in a subsequent frozen embryo transfer. Ten corona cell samples underwent RNA-sequencing to generate unique gene expression profiles. Live birth was compared with negative implantation after the transfer of a euploid blastocyst using bioinformatics and statistical analysis. Individual corona cell samples produced a mean of 21.2 million sequence reads, and 307 differentially expressed transcrpits (P < 0.05; fold change ?2). Enriched pathway analysis showed Wnt signalling, mitogen-activated protein kinases signalling, focal adhesion and tricarboxylic acid cycle to be affected by implantation outcome. The Wnt/beta-catenin signalling pathway, including genes APC, AXIN and GSK3B, were independently validated by real-time quantitative reverse transcription. Individual, corona cell transcriptome was successfully generated using RNA-sequencing. Key genes and signalling pathways were identified in association with implantation outcome after the transfer of a euploid blastocyst in a frozen embryo transfer. These data could provide novel biomarkers for the non-invasive assessment of embryo viability

Epigenetic Dysregulation Observed in Monosomy Blastocysts Further Compromises Developmental Potential.

Epigenetic mechanisms such as DNA methylation regulate genomic imprinting and account for the distinct non-equivalence of the parental genomes in the embryo. Chromosomal aneuploidy, a major cause of infertility, distorts this highly regulated disparity by the presence or absence of chromosomes. The implantation potential of monosomy embryos is negligible compared to their trisomy counterparts, yet the cause for this is unknown. This study investigated the impact of chromosomal aneuploidy on strict epigenetically regulated domains, specifically imprinting control regions present on aneuploid chromosomes. Donated cryopreserved human IVF blastocysts of transferable quality, including trisomy 15, trisomy 11, monosomy 15, monosomy 11, and donor oocyte control blastocysts were examined individually for DNA methylation profiles by bisulfite mutagenesis and sequencing analysis of two maternally methylated imprinting control regions (ICRs), SNRPN (15q11.2) and KCNQ1OT1 (11p15.5), and one paternally methylated imprinting control region, H19 (11p15.5). Imprinted genes within the regions were also evaluated for transcript abundance by RT-qPCR. Overall, statistically significant hypermethylated and hypomethylated ICRs were found in both the trisomy and monosomy blastocysts compared to controls, restricted only to the chromosome affected by the aneuploidy. Increased expression was observed for maternally-expressed imprinted genes in trisomy blastocysts, while a decreased expression was observed for both maternally- and paternally-expressed imprinted genes in monosomy blastocysts. This epigenetic dysregulation and altered monoallelic expression observed at imprinting control regions in aneuploid IVF embryos supports euploid embryo transfer during infertility treatments, and may specifically highlight an explanation for the compromised implantation potential in monosomy embryos