Long noncoding RNA 2193 regulates meiosis through global epigenetic modification and cytoskeleton organization in pig oocytes

Roles of histone post-translational modifications in meiosis†

Histone post-translational modifications, such as phosphorylation, methylation, acetylation, and ubiquitination, play vital roles in various chromatin-based cellular processes. Meiosis is crucial for organisms that depend on sexual reproduction to produce haploid gametes, during which chromatin undergoes intricate conformational changes. An increasing body of evidence is clarifying the essential roles of histone post-translational modifications during meiotic divisions. In this review, we concentrate on the post-translational modifications of H2A, H2B, H3, and H4, as well as the linker histone H1, that are required for meiosis, and summarize recent progress in understanding how these modifications influence diverse meiotic events. Finally, challenges and exciting open questions for future research in this field are discussed. Summary Sentence  Diverse histone post-translational modifications exert important effects on the meiotic cell cycle and these "histone codes" in meiosis might lead to the development of novel therapeutic strategies against reproductive diseases.

Spatiotemporal regulation of maternal mRNAs during vertebrate oocyte meiotic maturation

Vertebrate oocytes face a particular challenge concerning the regulation of gene expression during meiotic maturation. Global transcription becomes quiescent in fully grown oocytes, remains halted throughout maturation and fertilization, and only resumes upon embryonic genome activation. Hence, the oocyte meiotic maturation process is largely regulated by protein synthesis from pre-existing maternal messenger RNAs (mRNAs) that are transcribed and stored during oocyte growth. Rapidly developing genome-wide techniques have greatly expanded our insights into the global translation changes and possible regulatory mechanisms during oocyte maturation. The storage, translation, and processing of maternal mRNAs are thought to be regulated by factors interacting with elements in the mRNA molecules. Additionally, posttranscriptional modifications of mRNAs, such as methylation and uridylation, have recently been demonstrated to play crucial roles in maternal mRNA destabilization. However, a comprehensive understanding of the machineries that regulate maternal mRNA fate during oocyte maturation is still lacking. In particular, how the transcripts of important cell cycle components are stabilized, recruited at the appropriate time for translation, and eliminated to modulate oocyte meiotic progression remains unclear. A better understanding of these mechanisms will provide invaluable insights for the preconditions of developmental competence acquisition, with important implications for the treatment of infertility. This review discusses how the storage, localization, translation, and processing of oocyte mRNAs are regulated, and how these contribute to oocyte maturation progression.

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.

LncRNA affects epigenetic reprogramming of porcine embryo development by regulating global epigenetic modification and the downstream gene SIN3A

The study of preimplantation development is of great significance to reproductive biology and regenerative medicine. With the development of high-throughput deep sequencing technology, it has been found that lncRNAs play a very important role in the regulation of embryonic development. In this study, key lncRNAs that regulate embryonic development were screened by analyzing the expression pattern of lncRNAs in porcine in vivo fertilization (IVV) embryos. By knocking down lncRNA expression in in vitro fertilization (IVF) embryos, we investigated its function and mechanism of regulating embryonic development. The results showed that the expression pattern of lncRNA was consistent with the time of gene activation. The lncRNAs were highly expressed in the 4-cell to blastocyst stage but barely expressed in the oocytes and 2-cell stage. So we speculated this part of lncRNAs may regulate gene expression. The lncRNA LOC102165808 (named lncT because the gene near this lncRNA is TFAP2C) was one of them. The knockdown (KD) of lncT inhibited embryonic development, resulting in decreased H3K4me3, H3K4me2, and H3K9me3, and increased DNA methylation. Meanwhile, RNAseq showed SIN3A was the top decreased gene in lncT-KD embryos. There was a severe blastocyst formation defect in SIN3A-KD embryos. Both lncT and SIN3A could affect NANOG and induce more cell apoptosis. In conclusion, the knockdown of lncT inhibits embryonic development by regulating H3K4me3, H3K4me2, DNA methylation, pluripotency gene, and apoptosis, and SIN3A is one of the downstream genes of lncT in regulating embryonic development.

Granulosa Cells Improved Mare Oocyte Cytoplasmic Maturation by Providing Collagens

Assisted reproductive technology has important clinical applications and commercial values in the horse industry. However, this approach is limited largely by the low efficiency of oocyte in vitro maturation (IVM), especially cytoplasmic maturation. To improve the efficiency of mare oocyte IVM, we evaluated the effects of co-culture with cumulus–oocyte complexes (COCs) and granulosa cells (GCs) from follicles with small (<15 mm) and large diameters (>35 mm). Our results showed that oocyte nucleus maturation was not significantly improved by co-culturing with GCs. Interestingly, the cytoplasmic maturation of oocytes, defined by the distribution of cortical granules and mitochondria, as well as reactive oxygen species (ROS) levels, improved dramatically by co-culture with GCs, especially those derived from small follicles. Moreover, GCs promoted cumulus cell expansion by upregulating the expression of BMP15 in oocytes. To determine the mechanism underlying the effects of GCs, the transcriptomes of GCs from large and small follicles were compared. Expression levels of COL1A2, COL6A1, and COL6A2 were significantly higher in GCs from small follicles than in those from large follicles. These three genes were enriched in the extracellular matrix proteins-receptor interaction pathway and were involved in the regulation of collagens. Taken together, our results suggest that co-culture with GCs is beneficial to oocyte cytoplasmic maturation, and the increased expression of COL1A2, COL6A1, and COL6A2 improve the mare oocyte IVM system via the regulation of collagen.

Mechanisms of Oogenesis-Related Long Non-coding RNAs in Porcine Ovaries Treated With Recombinant Pig Follicle-Stimulating Hormone

Reproductive efficiency is of significant importance in pork production for it has a great impact on economic success. Ovulation rate is an early component of reproduction efficiency of pigs, and it contributes to the upper limit of litter size. In this study, we used the newly developed recombinant pig follicle stimulating hormone (rpFSH) instead of traditional PMSG to increase ovulation rate of pigs in order to achieve higher litter size, for it was better at stimulating ovulation, and showed more cheaper and greener. However, relatively little is known about the underlying genetic bases and molecular mechanisms. Consequently, an experiment was carried out in ovaries of replacement gilts to screen the key genes and lncRNAs that affect the fecundity of pigs by RNA-seq technology. Twenty gilts were divided into two groups, including 10 rpFSH treatment pigs and 10 control animals. After slaughtering and collecting the phenotypic data, ovaries of five pigs in each group were selected for RNA-seq. Total RNA was extracted to construct the library and then sequence on an Illumina Hiseq 4000 system. A comprehensive analysis of mRNAs and long non-coding RNAs (lncRNAs) from 10 samples was performed with bioinformatics. The phenotypic data showed that rpFSH treatment groups had the higher (P < 0.01) ovarian weight and more mature follicles. The RNA-seq results showed that a total of 43,499 mRNAs and 21,703 lncRNAs were identified, including 21,300 novel lncRNAs and 403 known lncRNAs, of which 585 mRNAs and 398 lncRNAs (P < 0.05) were significantly differentially expressed (DE) between the two groups of rpFSH treatment group and controlled group. GO and KEGG annotation analysis indicated that the target genes of DE lncRNAs and DE mRNAs were related to prolactin receptor activity, mitophagy by induced vacuole formation, and meiotic spindle. Moreover, we found that NR5A2 (nuclear receptor subfamily 5, group A, member 2), a target gene of lncRNA MSTRG.3902.1, was involved in regulating follicular development, ovulation, and estrogen production. Our study provided a catalog of lncRNAs and mRNAs associated with ovulation of rpFSH treatment, and they deserve further study to deepen the understanding of biological processes in the regulation of ovaries of rpFSH treatment pigs.

Transcriptome Analysis of mRNAs and Long Non-Coding RNAs During Subsequent Embryo Development of Porcine Cloned Zygotes After Vitrification

Cryopreservation of porcine cloned zygotes has important implications for biotechnology and biomedicine research; however, lower embryo developmental potential remains an urgent problem to be resolved. For exploring the sublethal cryodamages during embryo development, this study was designed to acquire the mRNA and long non-coding RNA (lncRNA) profiles of 2-cells, 4-cells and blastocysts derived from vitrified porcine cloned zygotes using transcriptome sequencing. We identified 167 differentially expressed (DE) mRNAs and 516 DE lncRNAs in 2-cell stage, 469 DE mRNAs and 565 lncRNAs in 4-cell stage, and 389 DE mRNAs and 816 DE lncRNAs in blastocyst stage. Functional enrichment analysis revealed that the DE mRNAs during embryo development were involved in many regulatory mechanisms related to cell cycle, cell proliferation, apoptosis, metabolism and others. Moreover, the target genes of DE lncRNAs in the three embryonic stages were also enriched in many key GO terms or pathways such as “defense response”, “linoleic acid metabolic process”, “embryonic axis specification”, “negative regulation of protein neddylation”, etc., In conclusion, the present study provided comprehensive transcriptomic data about mRNAs and lncRNAs for the vitrified porcine cloned zygotes during different developmental stages, which contributed to further understand the potential cryodamage mechanisms responsible for impaired embryo development.

Brain and Pituitary Transcriptome Analyses Reveal the Differential Regulation of Reproduction-Related LncRNAs and mRNAs in Cynoglossus semilaevis

Long noncoding RNAs (lncRNAs) have been identified to be involved in half-smooth tongue sole (Cynoglossus semilaevis) reproduction. However, studies of their roles in reproduction have focused mainly on the ovary, and their expression patterns and potential roles in the brain and pituitary are unclear. Thus, to explore the mRNAs and lncRNAs that are closely associated with reproduction in the brain and pituitary, we collected tongue sole brain and pituitary tissues at three stages for RNA sequencing (RNA-seq), the 5,135 and 5,630 differentially expressed (DE) mRNAs and 378 and 532 DE lncRNAs were identified in the brain and pituitary, respectively. The RNA-seq results were verified by RT-qPCR. Moreover, enrichment analyses were performed to analyze the functions of DE mRNAs and lncRNAs. Interestingly, their involvement in pathways related to metabolism, signal transduction and endocrine signaling was revealed. LncRNA-target gene interaction networks were constructed based on antisense, cis and trans regulatory mechanisms. Moreover, we constructed competing endogenous RNA (ceRNA) networks. In summary, this study provides mRNA and lncRNA expression profiles in the brain and pituitary to understand the molecular mechanisms regulating tongue sole reproduction.

Grape Seed Proanthocyanidin Ameliorates FB1-Induced Meiotic Defects in Porcine Oocytes

Fumonisin B₁ (FB₁), as the most prevalent and toxic fumonisin, poses a health threat to humans and animals. The cytotoxicity of FB₁ is closely related to oxidative stress and apoptosis. The purpose of this study is to explore whether Grape seed proanthocyanidin (GSP), a natural antioxidant, could alleviate the meiotic maturation defects of oocytes caused by FB₁ exposure. Porcine cumulus oocyte complexes (COCs) were treated with 30 μM FB₁ alone or cotreated with 100, 200 and 300 μM GSP during in vitro maturation for 44 h. The results show that 200 μM GSP cotreatment observably ameliorated the toxic effects of FB₁ exposure, showing to be promoting first polar body extrusion and improving the subsequent cleavage rate and blastocyst development rate. Moreover, 200 μM GSP cotreatment restored cell cycle progression, reduced the proportion of aberrant spindles, improved actin distribution and protected mitochondrial function in FB₁-exposed oocytes. Furthermore, reactive oxygen species (ROS) generation was significantly decreased and the mRNA levels of CAT, SOD2 and GSH-PX were obviously increased in the 200 μM GSP cotreatment group. Notably, the incidence of early apoptosis and autophagy level were also significantly decreased after GSP cotreatment and the mRNA expression levels of BAX, CASPASE3, LC3 and ATG5 were markedly decreased, whereas BCL2 and mTOR were observably increased in the oocytes after GSP cotreatment. Together, these results indicate that GSP could exert significant preventive effects on FB₁-induced oocyte defects by ameliorating oxidative stress through repairing mitochondrial dysfunction.

Single cell RNA-seq reveals genes vital to in vitro fertilized embryos and parthenotes in pigs

Successful early embryo development requires the correct reprogramming and configuration of gene networks by the timely and faithful execution of zygotic genome activation (ZGA). However, the regulatory principle of molecular elements and circuits fundamental to embryo development remains largely obscure. Here, we profiled the transcriptomes of single zygotes and blastomeres, obtained from in vitro fertilized (IVF) or parthenogenetically activated (PA) porcine early embryos (1- to 8-cell), focusing on the gene expression dynamics and regulatory networks associated with maternal-to-zygote transition (MZT) (mainly maternal RNA clearance and ZGA). We found that minor and major ZGAs occur at 1-cell and 4-cell stages for both IVF and PA embryos, respectively. Maternal RNAs gradually decay from 1- to 8-cell embryos. Top abundantly expressed genes (CDV3, PCNA, CDR1, YWHAE, DNMT1, IGF2BP3, ARMC1, BTG4, UHRF2 and gametocyte-specific factor 1-like) in both IVF and PA early embryos identified are of vital roles for embryo development. Differentially expressed genes within IVF groups are different from that within PA groups, indicating bi-parental and maternal-only embryos have specific sets of mRNAs distinctly decayed and activated. Pathways enriched from DEGs showed that RNA associated pathways (RNA binding, processing, transport and degradation) could be important. Moreover, mitochondrial RNAs are found to be actively transcribed, showing dynamic expression patterns, and for DNA/H3K4 methylation and transcription factors as well. Taken together, our findings provide an important resource to investigate further the epigenetic and genome regulation of MZT events in early embryos of pigs.

A novel lincRNA identified in buffalo oocytes with protein binding characteristics could hold the key for oocyte competence

Studying the maternal oocyte-specific genes, in farm animals is a significant step towards delineating the underlying mechanisms that regulate oocyte quality, early embryonic development and survival. With the creation of buffalo oocyte-specific subtracted cDNA library, it has raised new questions which need to be answered. The present study has characterized one of the ESTs selected from the library and highlighted its importance in the oocyte quality. The selected EST was made full length by RLM-RACE and four transcript variants were identified. Bioinformatics analysis indicated the novelty of full-length transcript along with conserved intergenic nature. The largest transcript was identified as long intergenic noncoding RNA based upon coding potential calculator output. The expression analysis at different hours of oocyte maturation showed a significant variation in developmentally competent oocytes to that of incompetent ones. Along with this, the transcript was also found to have protein binding ability which was confirmed by RNA electrophoretic mobility shift assay. The protein used in the experiment was isolated from oocyte and cumulus cells via sonication. A novel lincRNA has been reported here that might have an important role in maturation of oocytes, inferred from its relative gene expression study and protein binding characteristics.

Integrated lncRNA and mRNA Transcriptome Analyses in the Ovary of Cynoglossus semilaevis Reveal Genes and Pathways Potentially Involved in Reproduction

Long non-coding RNAs (lncRNAs) have been reported to be involved in multiple biological processes. However, the roles of lncRNAs in the reproduction of half-smooth tongue sole (Cynoglossus semilaevis) are unclear, especially in the molecular regulatory mechanism driving ovarian development and ovulation. Thus, to explore the mRNA and lncRNA mechanisms regulating reproduction, we collected tongue sole ovaries in three stages for RNA sequencing. In stage IV vs. V, we identified 312 differentially expressed (DE) mRNAs and 58 DE lncRNAs. In stage V vs. VI, we identified 1,059 DE mRNAs and 187 DE lncRNAs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that DE mRNAs were enriched in ECM-receptor interaction, oocyte meiosis and steroid hormone biosynthesis pathways. Furthermore, we carried out gene set enrichment analysis (GSEA) to identify potential reproduction related-pathways additionally, such as fatty metabolism and retinol metabolism. Based on enrichment analysis, DE mRNAs with a potential role in reproduction were selected and classified into six categories, including signal transduction, cell growth and death, immune response, metabolism, transport and catabolism, and cell junction. The interactions of DE lncRNAs and mRNAs were predicted according to antisense, cis-, and trans-regulatory mechanisms. We constructed a competing endogenous RNA (ceRNA) network. Several lncRNAs were predicted to regulate genes related to reproduction including cyp17a1, cyp19a1, mmp14, pgr, and hsd17b1. The functional enrichment analysis of these target genes of lncRNAs revealed that they were involved in several signaling pathways, such as the TGF-beta, Wnt signaling, and MAPK signaling pathways and reproduction related-pathways such as the progesterone-mediated oocyte maturation, oocyte meiosis, and GnRH signaling pathway. RT-qPCR analysis showed that two lncRNAs (XR_522278.2 and XR_522171.2) were mainly expressed in the ovary. Dual-fluorescence in situ hybridization experiments showed that both XR_522278.2 and XR_522171.2 colocalized with their target genes cyp17a1 and cyp19a1, respectively, in the follicular cell layer. The results further demonstrated that lncRNAs might be involved in the biological processes by modulating gene expression. Taken together, this study provides lncRNA profiles in the ovary of tongue sole and further insight into the role of lncRNA involvement in regulating reproduction in tongue sole.

Comparative Transcriptome Profiling of mRNA and lncRNA of Ovaries in High and Low Egg Production Performance in Domestic Pigeons (Columba livia)

Egg production performance is one of the most important economic traits in pigeon industry. However, little is known regarding how egg production performance is regulated by long non-coding RNAs (lncRNAs) in pigeons. To evaluate the lncRNAs and mRNAs in ovaries associated with egg production performance in domestic pigeons, high-throughput RNA sequencing of ovaries between high and low egg production performance groups were performed and analyzed in this study. A total of 34,346 mRNAs and 24,601 lncRNAs were identified, including 14,525 known lncRNAs and 10,076 novel lncRNAs, of which 811 mRNAs and 148 lncRNAs (P < 0.05) were significantly differentially expressed (DE) between the groups of high and low egg production performance. GO and KEGG annotation analysis indicated that the target genes of DE lncRNAs and DE mRNAs were related to cell differentiation, ATP binding and methylation. Moreover, we found that FOXK2, a target gene of lncRNA MSTRG.7894.4, was involved in regulating estrogen receptors. Our study provided a catalog of lncRNAs and mRNAs associated with egg production performance, and they deserve further study to deepen the understanding of biological processes in the ovaries of pigeons.

Transcriptomics of Meiosis in the Male Mouse

Molecular studies of meiosis in mammals have been long relegated due to some intrinsic obstacles, namely the impossibility to reproduce the process in vitro, and the difficulty to obtain highly pure isolated cells of the different meiotic stages. In the recent years, some technical advances, from the improvement of flow cytometry sorting protocols to single-cell RNAseq, are enabling to profile the transcriptome and its fluctuations along the meiotic process. In this mini-review we will outline the diverse methodological approaches that have been employed, and some of the main findings that have started to arise from these studies. As for practical reasons most studies have been carried out in males, and mostly using mouse as a model, our focus will be on murine male meiosis, although also including specific comments about humans. Particularly, we will center on the controversy about gene expression during early meiotic prophase; the widespread existing gap between transcription and translation in meiotic cells; the expression patterns and potential roles of meiotic long non-coding RNAs; and the visualization of meiotic sex chromosome inactivation from the RNAseq perspective.

Single-cell RNA-seq reveals mRNAs and lncRNAs important for oocytes in vitro matured in pigs

The faithful execution of molecular programme underlying oocyte maturation and meiosis is vital to generate competent haploid gametes for efficient mammalian reproduction. However, the organization and principle of molecular circuits and modules for oocyte meiosis remain obscure. Here, we employed the recently developed single-cell RNA-seq technique to profile the transcriptomes of germinal vesicle (GV) and metaphase II (MII) oocytes, aiming to discover the dynamic changes of mRNAs and long non-coding RNAs (lncRNAs) during oocyte in vitro meiotic maturation. During the transition from GV to MII, total number of detected RNAs (mRNAs and lncRNAs) in oocytes decreased. Moreover, 1,807 (602 up- and 1,205 down-regulated) mRNAs and 313 (177 up- and 136 down-regulated) lncRNAs were significantly differentially expressed (DE), i.e., more mRNAs down-regulated, but more lncRNAs up-regulated. During maturation of pig oocytes, mitochondrial mRNAs were actively transcribed, eight of which (ND6, ND5, CYTB, ND1, ND2, COX1, COX2 and COX3) were significantly up-regulated. Both DE mRNAs and targets of DE lncRNAs were enriched in multiple biological and signal pathways potentially associated with oocyte meiosis. Highly abundantly expressed mRNAs (including DNMT1, UHRF2, PCNA, ARMC1, BTG4, ASNS and SEP11) and lncRNAs were also discovered. Weighted gene co-expression network analysis (WGCNA) revealed 20 hub mRNAs in three modules to be important for oocyte meiosis and maturation. Taken together, our findings provide insights and resources for further functional investigation of mRNAs/lncRNAs in in vitro meiotic maturation of pig oocytes.

CoQ10 improves meiotic maturation of pig oocytes through enhancing mitochondrial function and suppressing oxidative stress

Coenzyme Q10 (CoQ10) is essential to many fundamental biological processes. However, the effect of CoQ10 on meiotic maturation of pig oocytes still remains elusive. In the present study we aimed to understand the effects of CoQ10 on porcine oocyte maturation, by supplementing different concentrations of CoQ10 (25, 50 and 100 μM) into the maturation medium. We showed that CoQ10 at 50 μM had better capacity to promote the nuclear maturation of pig oocytes derived from both small and large antral follicles. Though the cleavage and blastocyst rates of parthenotes stayed stable, 50 μM CoQ10 treatment could accelerate the development of parthenotes to blastocyst stage, and increase the average cell number of blastocyst. For cumulus-oocyte complexes from large antral follicles categorized by the brilliant cresyl blue (BCB) test, 50 μM CoQ10 treatment could specifically promote the nuclear maturation of poor-quality oocytes in the BCB-negative group. Mitochondrial function of oocytes treated by 50 μM CoQ10 could be boosted, through increasing the levels of mitochondrial membrane potential, ATP production and CoQ6, and changing the pattern of mitochondrial distribution as well. Moreover, 50 μM CoQ10 treatment suppressed the level of reactive oxygen species and reduced the percentage of oocytes with early apoptosis signal. Taken together, CoQ10 could improve the meiotic maturation of pig oocytes, especially for poor-quality oocytes, mainly through enhancing mitochondrial function and suppressing oxidative stress to reduce apoptosis.

Ascorbic acid promotes the reproductive function of porcine immature Sertoli cells through transcriptome reprogramming

Vitamin C (ascorbic acid, AA) can regulate antioxidation and affect many cellular processes. However, the effect of AA on the reproduction of male animals remains less explored. Here, we showed that by supplementing exogenous AA to porcine immature Sertoli cells (iSCs), AA could promote the proliferation, suppress apoptosis, and decrease the global nucleic acid methylation (5 mC and m⁶A) levels of iSCs. After we profiled mRNA and long non-coding RNA (lncRNA) expression by transcriptome sequencing on iSCs (treated by 250 μM AA for 36 h), 1232 mRNAs and 937 lncRNAs were identified to be differentially expressed (DE). Gene enrichment analysis found multiple significantly enriched biological pathways, including oxidoreductase activity, cell proliferation and apoptosis, regulation of hormone level, regulation of catalytic activity, developmental process, ATP metabolism and reproductive process. Specifically, for the reproductive process, 49 up- and 36 down-regulated DE mRNAs (including highly expressed genes, such as Tfcp2l1, Hmgcs1, Mmp7, Fndc3a, and Zfp36l1) are involved. Moreover, AA supplementation could promote the secretion of anti-müllerian hormone, inhibin B and lactate, and enhance the activity of lactate dehydrogenase as well. Taken together, AA could promote the reproductive function of pig iSCs, potentially through reprogramming the global transcriptome, and elevating hormone secretion and metabolite production.

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AA could promote the proliferation, suppress apoptosis, and decrease the global nucleic acid mthylation levels of iSCs.

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AA treatment changed mRNA and lncRNA profiles of iSCs.

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AA treatment significantly disturbed the expression of mRNAs (such as Tfcp2l1, Hmgcs1, Mmp7, Fndc3a, and Zfp36l1) involved in reproductive process.

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AA supplement could promote the secretion of anti-mullerian hormone, inhibin B and lactate, and the activity of lactate dehydrogenase as well.

Single cell RNA-seq reveals molecular pathways altered by 7, 12-dimethylbenz[a]anthracene treatment on pig oocytes

Oocytes of better quality and developmental competence are highly demanded, which is affected by many intrinsic and external factors, including environmental pollutants. We have previously demonstrated that 7, 12-dimethylbenz [a]anthracene (DMBA) reduces the developmental competence of porcine oocytes, by desynchronizing nuclear and ooplasmic maturation. However, the underlying molecular mechanism remains obscure. Here we performed single cell RNA-seq to study the transcriptome changes in DMBA-treated porcine MII oocytes, and identified 19 protein-coding genes and 156 novel long non-coding RNAs (lncRNAs) with abundance to be significantly different (P < 0.05), which enriched in signaling pathways such as glycosphingolipid biosynthesis, nicotine addiction, basal transcription factors and nucleotide excision repair. RT-qPCR on oocyte pools confirmed ornithine aminotransferase (Oat) and serine/arginine-rich splicing factor 4 (Srsf4) to be significantly up- and down-regulated, respectively (P < 0.05). Treating porcine COCs with MAPK and PLC pathway inhibitors suppressed DMBA's effects on increasing PB1 extrusion rate. In addition, DMBA co-incubation with 250 μM vitamin C derivative (l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate, AA2P) and 100 μM co-enzyme Q10 (CoQ10) could significantly reduce the DMBA-induced high ROS level, and partially alleviate the DMBA-induced high PB1 rate, whereas the cleavage and blastocyst rates of parthenotes derived from treated mature oocytes remained to be low. Collectively, our findings indicate that single cell RNA-seq can help reveal the dynamics of molecular signaling pathways for porcine oocytes treated by DMBA, and supplement of anti-oxidative reagents could not sufficiently rescue DMBA-induced defects of porcine oocytes.