Comparative proteomic analysis of proteins involved in oocyte meiotic maturation in mice

Dynamic Changes in Proteome during Yak Oocyte Maturation Analyzed Using iTRAQ Technology

The aim of this study was to investigate protein regulation at different time points during the in vitro maturation of yak oocytes. Yak oocytes at GV, MI, and MII stages were collected during in vitro maturation, and differential proteomics sequencing was performed using iTRAQ technology. GO functional classification indicated that the differential proteins were closely associated with biological processes such as "metabolic processes", and molecular events such as "binding" molecular-function-related categories were active. KOG analysis showed that energy-metabolism-related activities were vigorous during oocyte development from the GV phase to MI phase, and genetic material preparation activities were more active when oocytes developed from the MI stage to MII stage. KEGG pathway analysis showed that the PPAR metabolic pathway, Hippo signaling pathway, and ECM-receptor interaction and metabolic pathway were enriched from the GV to the MI stages. The PI3K-Akt, TGF-β, and phagosome pathways were enriched from the MI stage to the MII stage. These results indicate that transient dynamic changes occurred in the proteome during the maturation of yak oocytes, and the physiological functions mediated by these were also different. The accurate identification of the differential proteins in the three stages of GV, MI, and MII was helpful in further analyzing the molecular regulatory mechanism of yak oocyte maturation.

Porcine oocytes matured in a chemically defined medium are transcriptionally active

The statement that fully-grown porcine oocytes (oocytes from follicles with diameter from 3 to 6 mm) are transcriptionally quiescent is not as strongly supported as it was before. Currently, we know that there is a difference between the transcription profile of germinal vesicle (GV) and metaphase II (MII) oocytes. The goal of our study was to compare the transcription profile of GV, germinal vesicle breakdown (GVBD), metaphase I (MI), and MII oocytes matured in the chemically defined medium FLI. Oocytes were sequenced, and the results were subsequently validated using quantitative reverse transcription polymerase chain reaction (RT-qPCR). We detected multiple differentially transcribed mRNAs, of which many were upregulated. Among them we found mRNAs necessary for protein production, mitochondrial functions and cytoplasmic maturation. Collectively, these data support the hypothesis that transcription activity in fully-grown porcine oocytes is necessary for key processes during their successful maturation in vitro in a chemically defined maturation medium.

Female reproduction-specific proteins, origins in marine species, and their evolution in the animal kingdom

The survival of a species largely depends on the ability of individuals to reproduce, thus perpetuating their life history. The advent of metazoans (i.e. pluricellular animals) brought about the evolution of specialized tissues and organs, which in turn led to the development of complex protein regulatory pathways. This study sought to elucidate the evolutionary relationships between female reproduction-associated proteins by analyzing the transcriptomes of representative species from a selection of marine invertebrate phyla. Our study identified more than 50 reproduction-related genes across a wide evolutionary spectrum, from Porifera to Vertebrata. Among these, a total of 19 sequences had not been previously reported in at least one phylum, particularly in Porifera. Moreover, most of the structural differences between these proteins did not appear to be determined by environmental pressures or reproductive strategies, but largely obeyed a distinguishable evolutionary pattern from sponges to mammals.

Proteomic-based identification of oocyte maturation-related proteins in mouse germinal vesicle oocytes

Oocyte proteins play an important role in oocyte maturation, fertilization and embryonic development. However, the protein composition of mouse germinal vesicle (GV) oocytes is still unclear. Using one-dimensional Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (1D SDS-PAGE) and Reverse-phase liquid chromatography tandem mass spectrometry (RP-LC-MS/MS), we constructed a protein profile of mouse GV oocytes. First, our proteomics profile identified 1,405 different proteins from 11,000 mouse GV oocytes lacking zona pellucida. Second, with detailed bioinformatics analysis, a group of proteins that play an essential role in oocyte maturation was screened. In addition, the expression and localization of suppressor of G2 allele of skp1(SUGT1, also called SGT1), heterogeneous nuclear ribonucleoprotein K (Hnrpk), Seruin, Cullin1(Clu1) and nuclear distribution protein C (Nudc) in mouse ovaries and early embryos were also captured and investigated in this study. Moreover, the protein profile was submitted to the Proteomics Identifications Database (PRIDE) and is available via ProteomeXchange with the identifier PXD014314. Our research provides valuable resources for the study of oocyte proteins and oocyte maturation and helps to clarify the mechanisms of oocyte maturation.

Early cleavage of preimplantation embryos is regulated by tRNAGln-TTG-derived small RNAs present in mature spermatozoa

tRNA-derived small RNAs (tsRNAs) from spermatozoa could act as acquired epigenetic factors and contribute to offspring phenotypes. However, the roles of specific tsRNAs in early embryo development remain to be elucidated. Here, using pigs as a research model, we probed the tsRNA dynamics during spermatogenesis and sperm maturation and demonstrated the delivery of tsRNAs from semen-derived exosomes to spermatozoa. By microinjection of antisense sequences into in vitro fertilized oocytes and subsequent single-cell RNA-seq of embryos, we identified a specific functional tsRNA group (termed here Gln-TTGs) that participate in the early cleavage of porcine preimplantation embryos, probably by regulating cell cycle-associated genes and retrotransposons. We conclude that specific tsRNAs present in mature spermatozoa play significant roles in preimplantation embryo development.

Proteomic analysis of germinal vesicles in the domestic cat model reveals candidate nuclear proteins involved in oocyte competence acquisition

STUDY QUESTION

Do nuclear proteins in the germinal vesicle (GV) contribute to oocyte competence acquisition during folliculogenesis?

SUMMARY ANSWER

Proteomic analysis of GVs identified candidate proteins for oocyte competence acquisition, including a key RNA processing protein-heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1).

WHAT IS KNOWN ALREADY

The domestic cat GV, which is physiologically similar to the human GV, gains the intrinsic ability to resume meiosis and support early embryo development during the pre-antral-to-antral follicle transition. However, little is known about nuclear proteins that contribute to this developmental process.

STUDY DESIGN SIZE, DURATION

GVs were enriched from pre-antral (incompetent) and antral (competent) follicles from 802 cat ovaries. Protein lysates were subjected to quantitative proteomic analysis to identify differentially expressed proteins in GVs from the two follicular categories.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Two biological replicates (from independent pools of ovaries) of pre-antral versus antral samples were labeled by tandem mass tags and then assessed by liquid chromatography-tandem mass spectrometry. Proteomic data were analyzed according to gene ontology and a protein-protein interaction network. Immunofluorescent staining and protein inhibition assays were used for validation.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 174 nuclear proteins was identified, with 54 being up-regulated and 22 down-regulated (≥1.5-fold) after antrum formation. Functional protein analysis through gene ontology over-representation tests revealed that changes in molecular network within the GVs during this transitional phase were related to chromatin reorganization, gene transcription, and maternal RNA processing and storage. Protein inhibition assays verified that hnRNPA2B1, a key nuclear protein identified, was required for oocyte meiotic maturation and subsequent blastocyst formation.

LARGE SCALE DATA

Data are available via ProteomeXchange with identifier PXD007211.

LIMITATIONS REASONS FOR CAUTION

Proteins identified by proteomic comparison may (i) be involved in processes other than competence acquisition during the pre-antral-to-antral transition or (ii) be co-expressed in other macrostructures besides the GV. Expressional and functional validations should be performed for candidate proteins before downstream application.

WIDER IMPLICATIONS OF THE FINDINGS

Collective results generated a blueprint to better understand the molecular mechanisms involved in GV competence acquisition and identified potential nuclear competence markers for human fertility preservation.

STUDY FUNDING AND COMPETING INTEREST(S)

Funded by the National Center for Research Resources (R01 RR026064), a component of the National Institutes of Health (NIH) and currently by the Office of Research Infrastructure Programs/Office of the Director (R01 OD010948). The authors declare that there is no conflict of interest.

Missing and overexpressing proteins in domestic cat oocytes following vitrification and in vitro maturation as revealed by proteomic analysis

Background

The domestic cat serves as an animal model for assisted reproductive studies of endangered felid species. To date, there are no data on the protein alterations following cryopreservation of oocytes in felid family.

Methods

Immature (germinal vesicle) domestic cat oocytes were vitrified in the vitrification solution containing 35% ethylene glycol, 20% DMSO and 0.5 mM sucrose. The vitrified-warmed oocytes were matured (metaphase II) in vitro and subjected to proteomic analysis using 1DE SDS-PAGE prefractionation combined with LC–MS/MS.

Results

A total of 1712 proteins were identified in in vitro matured oocytes. Of the 1712 proteins, 1454 proteins were found in both groups, whereas, 258 proteins were differentially expressed between control and vitrified-warmed groups. In vitrified-warmed oocytes, the missing proteins were membrane and nuclear proteins; whereas, apoptosis and DNA repair proteins were overrepresented.

Conclusions

The identified missing and overexpressed proteins in vitrified-warmed oocytes represent potential markers of cryoinjuries and the developmental pathways of oocytes. The findings of differential expressed proteins may contribute to effective ways of proteome analysis of oocyte/embryo quality in order to assess safety of cryopreservation in felid species.

Pnma5 is essential to the progression of meiosis in mouse oocytes through a chain of phosphorylation

PNMA (paraneoplastic antigen MA) family includes Pnma1–6. Although other members have been found to be involved in paraneoplastic neurological disorders, death receptor-dependent apoptosis, and tumorigenesis, Pnma5 was thought to be a female fertility factor, as indicated by one genome-wide study. But until now there have not been any further functional studies about Pnma5 in female meiosis. Our preliminary study indicated that Pnma5 might play important roles in meiosis. To further address this, Pnma5 was knocked down in in-vitro maturated (IVM) mouse oocytes, which are common models for mammalian female meiosis, by specific siRNA, and results showed that the loss of Pnma5 significantly delayed the progression of meiosis I and increased chromosome segregation errors during anaphase I. In in-vitro fertilization (IVF), Pnma5 knockdown caused significantly lower fertilization. To assess how it affects meiosis, Pnma5 knockdown was found to significantly decrease the stability of spindle microtubules and altered F-actin organization within actin cap regions, cause significantly abnormal mitochondria aggregation and lower ATP concentration. Next we have found that phosphorylation at Thr533 re-located Pnma5 strongly to spindles & cortex and was required for the phosphorylation of Akt and Gsk3β, while Src and Erk1/2 phosphorylation was required for the phosphorylation of Pnma5, indicating that phosphorylated Pnma5 is the active form and subsequently activates Akt and Gsk3β. Collectively this study suggests that Pnma5 is important for meiosis and is the pivot of Src→Erk1/2→Pnma5→Akt→Gsk3β pathway.

Intact cell MALDI-TOF mass spectrometry on single bovine oocyte and follicular cells combined with top-down proteomics: A novel approach to characterise markers of oocyte maturation

Intact cell MALDI-TOF mass spectrometry (ICM-MS) was adapted to bovine follicular cells from individual ovarian follicles to obtain the protein/peptide signatures (<17kDa) of single oocytes, cumulus cells (CC) and granulosa cells (GC), which shared a total of 439 peaks. By comparing the ICM-MS profiles of single oocytes and CC before and after in vitro maturation (IVM), 71 different peaks were characterised, and their relative abundance was found to vary depending on the stage of oocyte meiotic maturation. To identify these endogenous biomolecules, top-down workflow using high resolution MS/MS (TD HR-MS) was performed on the protein extracts from oocytes, CC and GC. The TD HR-MS proteomic approach allowed for: (1) identification of 386 peptide/proteoforms encoded by 194 genes; and (2) characterisation of proteolysis products likely resulting from the action of kallikreins and caspases. In total, 136 peaks observed by ICM-MS were annotated by TD HR-MS (ProteomeXchange PXD004892). Among these, 16 markers of maturation were identified, including IGF2 binding protein 3 and hemoglobin B in the oocyte, thymosins beta-4 and beta-10, histone H2B and ubiquitin in CC. The combination of ICM-MS and TD HR-MS proved to be a suitable strategy to identify non-invasive markers of oocyte quality using limited biological samples.

BIOLOGICAL SIGNIFICANCE

Intact cell MALDI-TOF mass spectrometry on single oocytes and their surrounding cumulus cells, coupled to an optimised top-down HR-MS proteomic approach on ovarian follicular cells, was used to identify specific markers of oocyte meiotic maturation represented by whole low molecular weight proteins or products of degradation by specific proteases.

Discovery of porcine maternal factors related to nuclear reprogramming and early embryo development by proteomic analysis

Background

Differentiated cell nuclei can be reprogrammed to a pluripotent state in several ways, including incubation with oocyte extracts, transfer into enucleated oocytes, and induced pluripotent stem cell technology. Nuclear transfer-mediated reprogramming has been proven to be the most efficient method. Maternal factors stored in oocytes have critical roles on nuclear reprogramming and early embryo development, but remain elusive.

Results

In this study, we showed most of porcine oocytes became nuclear matured at 33 h of IVM and the rate had no significant difference with oocytes at 42 h of IVM (p > 0.05). Moreover, the cleavage and blastocyst rates of SCNT and PA embryos derived from 42O were significantly higher than that of 33O (p < 0.05). But 33O could sustain IVF embryo development with higher cleavage and blastocyst rates comparing to 42O (p < 0.05). To clarify the development potential difference between 33O and 42O, 18 differentially expressed proteins were identified by proteomic analysis, and randomly selected proteins were confirmed by Western blot. Bioinformatic analysis of these proteins revealed that 33O highly synthesized proteins related to fertilization, and 42O was rich in nuclear reprogramming factors.

Conclusions

These results present a unique insight into maternal factors related to nuclear reprogramming and early embryo development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-015-0074-5) contains supplementary material, which is available to authorized users.

Application of gel-based proteomic technique in female reproductive investigations

Recently, gel-based proteomics has been increasingly applied to investigate proteins involved in female reproductive tract in healthy and disease states. Gel-based proteomics coupled by mass spectrometry (MS) facilitate the identification of new proteins playing roles in cellular and molecular interactions underlying female reproductive biology and it is a useful method to identify novel biomarkers of diseases by studying thousands of proteins simultaneously involved in female reproductive tract in healthy state compared to disease state. This review will discuss the best studies areas contributed to female reproductive biology in which gel-based proteomics coupled by MS has been applied to generate proteome of female reproductive tract in a healthy state.

Quantitative proteomics reveals the dynamics of protein changes during Drosophila oocyte maturation and the oocyte-to-embryo transition

The onset of development is marked by two major, posttranscriptionally controlled, events: oocyte maturation (release of the prophase I primary arrest) and egg activation (release from the secondary meiotic arrest). Using quantitative mass spectrometry, we previously described proteome remodeling during Drosophila egg activation. Here, we describe our quantitative mass spectrometry-based analysis of the changes in protein levels during Drosophila oocyte maturation. This study presents the first quantitative survey, to our knowledge, of proteome changes accompanying oocyte maturation in any organism and provides a powerful resource for identifying both key regulators and biological processes driving this critical developmental window. We show that Muskelin, found to be up-regulated during oocyte maturation, is required for timely nurse cell nuclei clearing from mature egg chambers. Other proteins up-regulated at maturation are factors needed not only for late oogenesis but also completion of meiosis and early embryogenesis. Interestingly, the down-regulated proteins are predominantly involved in RNA processing, translation, and RNAi. Integrating datasets on the proteome changes at oocyte maturation and egg activation uncovers dynamics in proteome remodeling during the change from oocyte to embryo. Notably, 66 proteins likely act uniquely during late oogenesis, because they are up-regulated at maturation and down-regulated at activation. We find down-regulation of this class of proteins to be mediated partially by APC/C(CORT), a meiosis-specific form of the E3 ligase anaphase promoting complex/cyclosome (APC/C).

Molecular signatures of bovine embryo developmental competence

Assessment of the developmental capacity of early bovine embryos is still an obstacle. Therefore, the present paper reviews all current knowledge with respect to morphological criteria and environmental factors that affect embryo quality. The molecular signature of an oocyte or embryo is considered to reflect its quality and to predict its subsequent developmental capacity. Therefore, the primary aim of the present review is to provide an overview of reported correlations between molecular signatures and developmental competence. A secondary aim of this paper is to present some new strategies to enable concomitant evaluation of the molecular signatures of specific embryos and individual developmental capacity.

Maternal age effect on mouse oocytes: new biological insight from proteomic analysis

The long-standing view of ‘immortal germline vs mortal soma’ poses a fundamental question in biology concerning how oocytes age in molecular terms. A mainstream hypothesis is that maternal ageing of oocytes has its roots in gene transcription. Investigating the proteins resulting from mRNA translation would reveal how far the levels of functionally available proteins correlate with mRNAs and would offer novel insights into the changes oocytes undergo during maternal ageing. Gene ontology (GO) semantic analysis revealed a high similarity of the detected proteome (2324 proteins) to the transcriptome (22 334 mRNAs), although not all proteins had a cognate mRNA. Concerning their dynamics, fourfold changes of abundance were more frequent in the proteome (3%) than the transcriptome (0.05%), with no correlation. Whereas proteins associated with the nucleus (e.g. structural maintenance of chromosomes and spindle-assembly checkpoints) were largely represented among those that change in oocytes during maternal ageing; proteins associated with oxidative stress/damage (e.g. superoxide dismutase) were infrequent. These quantitative alterations are either impoverishing or enriching. Using GO analysis, these alterations do not relate in any simple way to the classic signature of ageing known from somatic tissues. Given the lack of correlation, we conclude that proteome analysis of mouse oocytes may not be surrogated with transcriptome analysis. Furthermore, we conclude that the classic features of ageing may not be transposed from somatic tissues to oocytes in a one-to-one fashion. Overall, there is more to the maternal ageing of oocytes than mere cellular deterioration exemplified by the notorious increase of meiotic aneuploidy.

Proteomes of animal oocytes: what can we learn for human oocytes in the in vitro fertilization programme?

Oocytes are crucial cells for mammalian reproduction, yet the molecular principles underlying oocyte development are only partially understood. Therefore, contemporary proteomic approaches have been used increasingly to provide new insights into oocyte quality and maturation in various species such as mouse, pig, and cow. Especially, animal studies have helped in elucidating the molecular status of oocytes during in vitro maturation and other procedures of assisted reproduction. The aim of this review is to summarize the literature on mammalian oocyte proteome and secretome research in the light of natural and assisted reproduction and on lessons to be learned for human oocytes, which have so far remained inaccessible for proteome analysis.

Identification and characterization of an oocyte factor required for porcine nuclear reprogramming

Nuclear reprogramming of somatic cells can be induced by oocyte factors. Despite numerous attempts, the factors responsible for successful nuclear reprogramming remain elusive. In the present study, we found that porcine oocytes with the first polar body collected at 42 h of in vitro maturation had a stronger ability to support early development of cloned embryos than porcine oocytes with the first polar body collected at 33 h of in vitro maturation. To explore the key reprogramming factors responsible for the difference, we compared proteome signatures of the two groups of oocytes. 18 differentially expressed proteins between these two groups of oocytes were discovered by mass spectrometry (MS). Among these proteins, we especially focused on vimentin (VIM). A certain amount of VIM protein was stored in oocytes and accumulated during oocyte maturation, and maternal VIM was specifically incorporated into transferred somatic nuclei during nuclear reprogramming. When maternal VIM function was inhibited by anti-VIM antibody, the rate of cloned embryos developing to blastocysts was significantly lower than that of IgG antibody-injected embryos and non-injected embryos (12.24 versus 22.57 and 21.10%; p < 0.05), but the development of in vitro fertilization and parthenogenetic activation embryos was not affected. Furthermore, we found that DNA double strand breaks dramatically increased and that the p53 pathway was activated in cloned embryos when VIM function was inhibited. This study demonstrates that maternal VIM, as a genomic protector, is crucial for nuclear reprogramming in porcine cloned embryos.

Proteomic analysis of eggs from Mytilus edulis females differing in mitochondrial DNA transmission mode

Many bivalves have an unusual mechanism of mitochondrial DNA (mtDNA) inheritance called doubly uniparental inheritance (DUI) in which distinctly different genomes are inherited through the female (F genome) and male (M genome) lineages. In fertilized eggs that will develop into male embryos, the sperm mitochondria remain in an aggregation, which is believed to be delivered to the primordial germ cells and passed to the next generation through the sperm. In fertilized eggs that will develop into female embryos, the sperm mitochondria are dispersed throughout the developing embryo and make little if any contribution to the next generation. The frequency of embryos with the aggregated or dispersed mitochondrial type varies among females. Previous models of DUI have predicted that maternal nuclear factors cause molecular differences among unfertilized eggs from females producing embryos with predominantly dispersed or aggregated mitochondria. We test this hypothesis using females of each of the two types from a natural population. We have found small, yet detectable, differences of the predicted type at the proteome level. We also provide evidence that eggs of females giving the dispersed pattern have consistently lower expression for different proteasome subunits than eggs of females giving the aggregated pattern. These results, combined with those of an earlier study in which we used hatchery lines of Mytilus, and with a transcriptomic study in a clam that has the DUI system of mtDNA transmission, reinforce the hypothesis that the ubiquitin-proteasome system plays a key role in the mechanism of DUI and sex determination in bivalves. We also report that eggs of females giving the dispersed pattern have higher expression for arginine kinase and enolase, enzymes involved in energy production, whereas ferritin, which is involved in iron homeostasis, has lower expression. We discuss these results in the context of genetic models for DUI and suggest experimental methods for further understanding the role of these proteins in DUI.