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Presence of aggregates of smooth endoplasmic reticulum in MII oocytes affects oocyte development competence: a molecular-based evidence

ABSTRACT: The oocytes presenting SERa are considered dysmorphic and have been associated with reduced embryological outcome and an increased risk of congenital anomalies. Therefore, in 2011 the Alpha/ESHRE Consensus strongly recommended not to inseminate MII oocytes displaying SERa (SERa+). Not all Centers follow this recommendation and some Authors reported that SERa+ can lead to healthy newborns. Moreover, no experimental data about the effect of SERa presence on the oocyte molecular status are available. To date the question whether or not SERa+ oocytes should be discarded as well as the opportunity to review or not the ESHRE consensus are still open for debate. This study included 28 women, < 38 years aged, without any ovarian pathology, undergoing IVF treatment. Supernumerary MII oocytes with no sign of morphological alterations and SERa+ oocytes were donated after written informed consent. A total of 31 oocytes without SERa (SERa-) and 24 SERa+ oocytes were analyzed. Pools of ≈10 oocytes for both group were prepared. Total RNA was extracted from each pool, amplified, labelled and hybridized on oligonucleotide microarrays. Analyses were performed by R software using the limma package. The expression profiles of SERa+ oocytes significantly differed from those of SERa- oocytes in 488 probe sets corresponding to 102 down-regulated and 283 up-regulated unique transcripts. Gene Ontology analysis by DAVID bioinformatics resource disclosed that three main biological processes were significantly down-regulated in SERa+ oocytes respect to SERa- oocytes: i) genes involved in cell and mitotic nuclear division, spindle assembly, chromosome partition and G2/M transition of mitotic cell cycle; ii) organization of cytoskeleton and microtubules; iii) mitochondrial structure and activity. Among the transcripts up-regulated in SERa+ oocytes, the most significantly (P= 0.002) enriched GO term was “GoLoco motif” including RAP1GAP, GPSM3, and GPSM1 genes. Data validation in a larger cohort of samples would be beneficial, although we applied stringent criteria for gene selection (fold-change >3 or <1/3 and FDR<0.1). Surveys on clinical outcomes, malformation rates, and follow-up of babies born after transfer of embryos from SERa+ oocytes are necessary. For the first time we provide information on molecular status of SERa+ oocytes, highlighting possible correlations among presence of SERa, altered oocyte physiology and reduced developmental competence. Based on our findings, we believe that it is far too early for an eventual revision of the 2011 Alpha/ESHRE Consensus on the issue and presence of SERa should be still a “red flag” in clinical IVF practices.

ORGANISM(S): Homo sapiens

PROVIDER: GSE106222 | GEO | 2018/05/10

REPOSITORIES: GEO

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Project description:Study question: Does storage time impact on transcriptome of slowly frozen cryopreserved human metaphase II (MII) oocytes? Summary answer: For the first time, we demonstrate that the length of cryostorage has no effect on the gene expression profile of human metaphase II oocytes. What is known already: Oocyte cryopreservation is a largely-used technique in IVF for storage of surplus oocytes, as well as for fertility preservation (i.e., women undergoing gonadotoxic therapies) and oocyte donation programs. Although it is known that cryopreservation negatively impacts on oocyte physiology and it is associated with decrease of transcripts, no experimental data about the effect of storage time on the oocyte molecular profile are available to date. Study design, size, duration: This study included 27 women undergoing IVF treatment, < 38 years aged, without any ovarian pathology. Surplus MII oocytes were donated after written informed consent. A total of 31 non-cryopreserved oocytes and 68 surviving slow-frozen/rapid-thawed oocytes (32 oocytes cryostored for 3 years and 36 cryostored for 6 years) were analyzed. Participants/materials, setting, methods: Pools of ?10 oocytes for each group were prepared. Total RNA was extracted from each pool, amplified, labeled and hybridized on 4x44K v2 microarrays (Agilent). Analyses were performed by R v3.1.3 software using the limma package v3.22.7. Main results and the role of chance: Comparison of gene expression profiles between surviving thawed oocytes after 3 and 6 years of storage in liquid nitrogen found no differently expressed genes. The expression profiles of cryopreserved MII oocytes significantly differed from those of non-cryopreserved oocytes in 107 probe sets corresponding to 73 down-regulated and 29 up-regulated unique transcripts. Gene Ontology analysis by DAVID bioinformatics resource disclosed that cryopreservation deregulates genes involved in oocyte function and early embryo development, such as chromosome organization, RNA splicing and processing, cell cycle process, response to DNA damage stimulus, cellular response to stress and DNA repair, calcium ion binding, malate dehydrogenase activity, mitochondrial membrane respiratory chain. Among the probes significantly up-regulated in cryopreserved oocytes, 2 corresponded to ovary-specific expressed large intergenic noncoding (linc)RNAs. This study included 27 women undergoing IVF treatment, < 38 years aged, without any ovarian pathology. Surplus MII oocytes were donated after written informed consent. A total of 31 non-cryopreserved oocytes and 68 surviving slow-frozen/rapid-thawed oocytes (32 oocytes cryostored for 3 years and 36 cryostored for 6 years) were analyzed.

Project description:Study question: Does storage time impact on transcriptome of slowly frozen cryopreserved human metaphase II (MII) oocytes? Summary answer: For the first time, we demonstrate that the length of cryostorage has no effect on the gene expression profile of human metaphase II oocytes. What is known already: Oocyte cryopreservation is a largely-used technique in IVF for storage of surplus oocytes, as well as for fertility preservation (i.e., women undergoing gonadotoxic therapies) and oocyte donation programs. Although it is known that cryopreservation negatively impacts on oocyte physiology and it is associated with decrease of transcripts, no experimental data about the effect of storage time on the oocyte molecular profile are available to date. Study design, size, duration: This study included 27 women undergoing IVF treatment, < 38 years aged, without any ovarian pathology. Surplus MII oocytes were donated after written informed consent. A total of 31 non-cryopreserved oocytes and 68 surviving slow-frozen/rapid-thawed oocytes (32 oocytes cryostored for 3 years and 36 cryostored for 6 years) were analyzed. Participants/materials, setting, methods: Pools of ≈10 oocytes for each group were prepared. Total RNA was extracted from each pool, amplified, labeled and hybridized on 4x44K v2 microarrays (Agilent). Analyses were performed by R v3.1.3 software using the limma package v3.22.7. Main results and the role of chance: Comparison of gene expression profiles between surviving thawed oocytes after 3 and 6 years of storage in liquid nitrogen found no differently expressed genes. The expression profiles of cryopreserved MII oocytes significantly differed from those of non-cryopreserved oocytes in 107 probe sets corresponding to 73 down-regulated and 29 up-regulated unique transcripts. Gene Ontology analysis by DAVID bioinformatics resource disclosed that cryopreservation deregulates genes involved in oocyte function and early embryo development, such as chromosome organization, RNA splicing and processing, cell cycle process, response to DNA damage stimulus, cellular response to stress and DNA repair, calcium ion binding, malate dehydrogenase activity, mitochondrial membrane respiratory chain. Among the probes significantly up-regulated in cryopreserved oocytes, 2 corresponded to ovary-specific expressed large intergenic noncoding (linc)RNAs.

Project description:Background: Early embryonic development is governed by maternal transcripts stored within the oocyte during oogenesis. Transcriptional activity of the oocyte ultimately dictates its developmental potential and may be influenced by maternal age, resulting in reduced competence of oocytes derived from women of advanced age, compared with the young. In the current study, RNA-Seq was used to perform transcriptome profiling of human GV and MII oocytes derived from young and advanced maternal age women. Participants/Materials and Methods: Cumulus dissection from donated oocytes was performed. GV and MII oocytes underwent deep RNA sequencing using the SMART-Seq v4 Ultra Low Input RNA protocol (Takara-Clontech, USA) and Nextera XT DNA library preparation kit (Illumina, USA). Data processing, quality assessment and bioinformatics analysis were performed using source-software, including FastQC, HISAT2, StringTie, edgeR and DAVID. Results: Following deep single-cell RNA-Seq on GV and MII oocytes, hundreds of transcripts were significantly differentially expressed between young maternal age (YMA) and advanced maternal age (AMA) groups, with the most significant biological processes relating to mitochondrial reserves. The GV to MII transition shares common biological processes between young and AMA groups, however, some genes involved in mitochondria function were altered during ageing. A decrease in mitochondrial-related transcripts was also observed during the GV to MII transition. However, there was a much greater reduction of mitochondrial-related transcripts in MII oocytes of AMA. This observation was confirmed when YMA MII oocytes were compared with the AMA MII group with mitochondrial-related transcripts being significantly higher expressed in the YMA group, including biological processes, such as mitochondrial electron transport and ATP biosynthetic process. These results indicate a higher energy potential in YMA MII oocytes that is decreased with age. Other significantly higher biological processes in the YMA MII group include transcripts involved in the regulation of ubiquitin-dependent degradation. Lack of these transcripts could lead to a non-appropriate removal of oogenesis remnants following fertilisation in the AMA MII group. Discussion: Understanding reproductive ageing effects at the RNA level in human oocytes may reveal differences in the mechanisms regulating the GV to MII transition that impact on oocyte quality in YMA and AMA patients. Further investigations of the up-/down-regulated transcripts during ageing could guide and improved IVF outcomes for AMA patients.

Project description:Study Question: What effects do maternal age and oocyte maturation stage have on the human oocyte transcriptome that may be associated with oocyte developmental potential? Summary Answer: Although polyadenylated transcript abundance changes during human oocyte maturation irrespective of age, young (YNG) and advanced maternal age (AMA) metaphase II (MII) oocytes exhibit divergent transcriptomes. What is known already: Maternal age and maturation stage affect oocyte polyadenylated transcript abundance in human oocytes. Although RNA-Seq analysis of single human MII oocytes has been conducted, comparison of the germinal vesicle (GV) and MII oocyte transcriptomes has not been investigated using RNA-Seq, a technique that could provide novel insight into oocyte maturation and age-associated aberrations in gene expression. Participants / materials, settings, methods: Patients undergoing infertility treatment at the Colorado Center for Reproductive Medicine (Lone Tree, CO, USA) underwent ovarian stimulation with FSH and received hCG for final follicular maturation prior to ultrasound guided egg retrieval. Unused GV oocytes obtained at retrieval were donated for transcriptome analysis. Single oocytes were stored (at -80°C in PicoPure RNA Extraction Buffer; Thermo Fisher Scientific, USA) immediately upon verification of immaturity or after undergoing in vitro oocyte maturation (24 hour incubation), representing GV and MII samples, respectively. After isolating RNA and generating single oocyte RNA-Seq libraries (SMARTer Ultra Low Input RNA HV kit; Clontech, USA), Illumina sequencing (100 bp paired-end reads in HiSeq 2500) and bioinformatics analysis (CLC Genomics Workbench, DESeq2, Weighted Gene Correlation Network Analysis (WGCNA), 3’UTR motif analysis, Ingenuity Pathway Analysis) were performed. Main results and the role of chance: Within the 12,770 expressed genes in human oocytes (reads per kilobase per million mapped reads (RPKM) > 0.4 in at least 3 of 5 replicates for a minimum of one sample type), 458 and 3,506 genes significantly (adjusted p < 0.05 and log2 fold change > 1) increased and decreased in polyadenylated transcript abundance during oocyte maturation, respectively. The differentially expressed genes were enriched (FDR < 0.05) for biological functions and canonical pathways related to cell cycle and mitochondrial function. The majority (76%) and minority (25%) of up- and down-regulated transcripts with a complete 3’UTR were predicted to be targets of cytoplasmic polyadenylation (910 total genes), respectively. Differential gene expression analysis between young and advanced maternal age oocytes (within stage) identified 1 and 255 genes that significantly differed (adjusted p < 0.1 and log2 fold change > 1) in polyadenylated transcript abundance for GV and MII oocytes, respectively. These genes included CDK1, NLRP5, and PRDX1, which have been reported to affect oocyte developmental potential and be markers of oocyte quality. Despite similarity in transcript abundance between GV oocytes irrespective of age, divergent expression patterns emerged during oocyte maturation. These age-specific differentially expressed genes were enriched (FDR < 0.05) for functions and pathways associated with mitochondria, cell cycle, and cytoskeleton. Gene modules generated by WGCNA (based on gene expression) and patient traits related to oocyte quality (e.g. age and blastocyst development) were determined to be correlated (p < 0.05) and enriched (FDR < 0.05) for functions and pathways associated with oocyte maturation. Limitations, reasons for caution: The human oocytes used in the current study were obtained from patients with varying causes of infertility (e.g. decreased oocyte quality and oocyte quality-independent factors), possibly affecting oocyte gene expression. Oocytes in this study were retrieved at the GV stage following hCG administration and the MII oocytes were derived by in vitro maturation of patient oocytes, which has the benefit of identifying intrinsic differences between samples, but may not be completely representative of in vivo matured oocytes. Thus, these factors should be considered when interpreting the results. Wider Implications of the findings: Transcriptome profiles of young and advanced maternal age oocytes, particularly at the MII stage, suggest aberrant transcript abundance contributes to the age-associated decline in fertility.

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Presence of aggregates of smooth endoplasmic reticulum in MII oocytes affects oocyte development competence: a molecular-based evidence

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