Validation of reference genes for quantitative RT-PCR studies in porcine oocytes and preimplantation embryos

Epigenetic-related transcriptional reprogramming elucidated by identification and validation of a novel reference gene combination for RT-qPCR studies in porcine oocytes of contrasting quality

BACKGROUND

Reliable RT-qPCR results are dependent on appropriate normalisation. Oocyte maturation studies can be challenging in this respect, as the stage of development can distinctively affect reference gene transcript abundance. The aim of this study was to validate the use of reference genes in oocyte in vitro maturation RT-qPCR studies, and thereafter, examine the abundance of transcripts supporting histone modification during oocyte and early embryo development in oocytes of contrasting quality.

METHODS AND RESULTS

Total RNA from oocytes from prepubertal gilts and sows was extracted either directly succeeding follicle aspiration or after 44 h in vitro maturation, followed by RT-qPCR. The stability of YWHAG, HPRT1, ACTB, GAPDH, HMBS and PFKP, was analysed by NormFinder and further cross-validated by assessing results generated following application of different combinations of potential reference genes for normalisation of the RT-qPCR data. Combining ACTB and PFKP generated high stability according to NormFinder and concordant results. Applying this normalisation, gilt derived oocytes displayed significantly higher abundance than oocytes from sows of almost all the epigenetic-related transcripts studied (HDAC2, SIRT1, SALL4, KDM1A, KDM1B, KDM5A), both before and after maturation.

CONCLUSIONS

This study identified the combined use of ACTB and PFKP as the optimal normalisation for porcine oocyte RT-qPCR data. In oocytes collected from prepubertal gilts, transcription did not appear to be silenced at the time of aspiration, and accumulation of transcripts supporting histone modification facilitating proper fertilization and further embryo development seemed delayed. The results imply the epigenetic-related transcripts may have potential as markers of oocyte quality.

Bifenox compromises porcine trophectoderm and luminal epithelial cells in early pregnancy by arresting cell cycle progression and impairing mitochondrial and calcium homeostasis

Bifenox is a widely used herbicide that contains a diphenyl ether group. However its global usage, the cell physiological effects that induce toxicity have not been elucidated. In this study, the effect of bifenox was examined in porcine trophectoderm and uterine epithelial cells to investigate the potential toxicity of the implantation process. To uncover the toxic effects of bifenox, cell viability and apoptosis following treatment with bifenox were evaluated. To investigate the underlying cellular mechanisms, mitochondrial and calcium homeostasis were investigated in both cell lines. In addition, the dysregulation of cell signal transduction and transcriptional alterations were also demonstrated. Bifenox reduced cell viability and significantly increased the number of cells arrested at the sub-G1 stage. Moreover, bifenox depolarized the mitochondrial membrane and upregulated the calcium flux into the mitochondria in both cell lines. Cytosolic calcium flux increased in porcine trophectoderm (pTr) cells and decreased in porcine luminal epithelium (pLE) cells. In addition, bifenox activated the mitogen-activated protein kinase and phosphoinositide 3-kinase signaling pathways. Furthermore, bifenox inhibited the expression of retinoid receptor genes, such as RXRA, RXRB, and RXRG. Chemokine CCL8 was also downregulated at the mRNA level, whereas CCL5 expression remained unchanged. Overall, the results of this study suggest that bifenox deteriorates cell viability by arresting cell cycle progression, damaging mitochondria, and controlling calcium levels in pTr and pLE cells. The present study indicates the toxic potential of bifenox in the trophectoderm and luminal epithelial cells, which can lead to implantation disorders in early pregnancy.

Picolinafen exposure induces ROS accumulation and calcium depletion, leading to apoptosis in porcine embryonic trophectoderm and uterine luminal epithelial cells during the peri-implantation period

The global use of herbicides accounts for more than 48% of total pesticide usage. Picolinafen is a pyridine carboxylic acid herbicide that is predominantly used to control broadleaf weeds in wheat, barley, corn, and soybeans. Despite its widespread use in agriculture, its toxicity in mammals has rarely been studied. In this study, we first identified the cytotoxic effects of picolinafen on porcine trophectoderm (pTr) and luminal epithelial (pLE) cells, which are involved in the implantation process during early pregnancy. Picolinafen treatment significantly decreased the viability of pTr and pLE cells. Our results demonstrate that picolinafen increased the number of sub-G1 phase cells and early/late apoptosis. In addition, picolinafen disrupted mitochondrial function and resulted in the accumulation of intracellular ROS, leading to a reduction in calcium levels in both the mitochondria and cytoplasm of pTr and pLE cells. Moreover, picolinafen was found to significantly inhibit the migration of pTr. These responses were accompanied by the activation of the MAPK and PI3K signal transduction pathways by picolinafen. Our data suggest that the deleterious effects of picolinafen on the viability and migration of pTr and pLE cells might impair their implantation potential.

The effect of age and FSH stimulation on the ovarian follicular response, nuclear maturation, and gene expression of cumulus-oocyte complexes in prepubertal gilts

This study investigated the effects of age and FSH treatment on the ovarian response, follicular fluid (FF) biochemical composition, nuclear maturation, and molecular profile of cumulus-oocytes complexes (COCs) recovered from prepubertal gilts. Thirty-five prepubertal gilts were separated according to age [140 (n = 20) or 160 (n = 15) days], and within each age, the gilts were allotted to receive either 100 mg of FSH [treated; G140+FSH (n = 10) and G160+FSH (n = 7)] or saline solution [control; G140+control (n = 10) and G160+control (n = 8)]. Thus, four experimental groups were included in this study. In the FSH-treated gilts, the percentage of medium follicles increased (P < 0.0001) in the same proportion with which the percentage of small follicles decreased (P < 0.0001). In addition, the glucose concentration in the FF obtained from medium follicles increased (P < 0.05), while that of triglycerides decreased (P < 0.05) in the FSH-treated gilts. The FSH stimulation also improved (P < 0.05) the number of grade I COCs obtained from medium follicles and the meiotic maturation and BCB + rates. FSH treatment only upregulated (P < 0.05) HMGCR expression in immature COCs from prepubertal gilts. The metaphase II and BCB + rates, FF glucose and plasma IGF-1 levels were greater (P < 0.05) in prepubertal gilts at 160 than at 140 days of age. Age had no effect (P > 0.05) on the transcript abundance of the target genes in immature COCs. Hence, oocytes obtained from 140-day-old prepubertal gilts appeared less meiotically competent than those of 160-day-old prepubertal gilts. Our study suggests a possible strategy of using FSH treatment to improve oocyte quantity, quality, and nuclear maturation in 140 and 160-day-old prepubertal gilts.

Vitrification of porcine immature oocytes and zygotes results in different levels of DNA damage which reflects developmental competence to the blastocyst stage

The present study investigated the effects of vitrification of porcine oocytes either at the immature Germinal Vesicle (GV) stage before in vitro maturation (GV-stage oocytes) or at the pronuclear stage after in vitro maturation and fertilization (zygotes) on DNA integrity in relevance with their subsequent embryo development. Vitrification at the GV stage but not at the pronuclear stage significantly increased the abundance of double-strand breaks (DSBs) in the DNA measured by the relative fluorescence after γH2AX immunostaining. Treatment of GV-stage oocytes with cryoprotectant agents alone had no effect on DSB levels. When oocytes were vitrified at the GV stage and subjected to in vitro maturation and fertilization (Day 0) and embryo culture, significantly increased DSB levels were detected in subsequent cleavage-stage embryos which were associated with low cell numbers on Day 2, the upregulation of the RAD51 gene at the 4-8 cell stage (measured by RT-qPCR) and reduced developmental ability to the blastocyst stage when compared with the non-vitrified control. However, total cell numbers and percentages of apoptotic cells (measured by TUNEL) in resultant blastocysts were not different from those of the non-vitrified control. On the other hand, vitrification of zygotes had no effect on DSB levels and the expression of DNA-repair genes in resultant embryos, and their development did not differ from that of the non-vitrified control. These results indicate that during vitrification GV-stage oocytes are more susceptible to DNA damages than zygotes, which affects their subsequent development to the blastocyst stage.

Comparison of reference gene expression stability in mouse skeletal muscle via five algorithms

Real-time quantitative PCR (RT-qPCR) is a widely applied technique for relative quantification of gene expression. In this context, the selection of a suitable reference gene (RG) is an essential step for obtaining reliable and biologically relevant RT-qPCR results. The present study aimed to determine the expression stability of commonly used RGs in mouse skeletal muscle tissue. The expression pattern of eight RGs (ACTB, GAPDH, HPRT, YWHAZ, B2M, PPIA, TUBA and 18S) were evaluated by RT-qPCR in different sample groups classified based on genetic background, muscle tissue type, and growth stage, as well as in a C2C12 myoblast cell line model. Five computational programs were included in the study (comparative ΔCq value, NormFinder, BestKeeper, geNorm, RefFinder) to evaluate the expression stability of RGs. Furthermore, the normalization effects of RGs in soleus (SOL) and gastrocnemius (GAS) muscle tissue were evaluated. Collectively, ACTB, HPRT and YWHAZ were shown to be the most stable RGs, while GADPH and 18S were the least stable. Therefore, the combined use of ACTB, HPRT and YWHAZ is recommended for the normalization of gene expression results in experiments with murine skeletal muscle. The results discussed herein provide a foundation for gene expression analysis by RT-qPCR in mammalian skeletal muscle.

Identification and validation of stable reference genes for quantitative real time PCR in different minipig tissues at developmental stages

Background

Quantitative real time PCR (qPCR) is a powerful tool to evaluate mRNA expression level. However, reliable qPCR results require normalization with validated reference gene(s). In this study, we investigated stable reference genes in seven tissues according to four developmental stages in minipigs. Six candidate reference genes and one target gene (ACE2) were selected and qPCR was performed. BestKeeper, geNorm, NormFinder, and delta Ct method through the RefFinder web-based tool were used to evaluate the stability of candidate reference genes. To verify the selected stable genes, relative expression of ACE2 was calculated and compared with each other.

Results

As a result, HPRT1 and 18S genes had lower SD value, while HMBS and GAPDH genes had higher SD value in all samples. Using statistical algorithms, HPRT1 was the most stable gene, followed by 18S, β-actin, B2M, GAPDH, and HMBS. In intestine, all candidate reference genes exhibited similar patterns of ACE2 gene expression over time, whereas in liver, lung, and kidney, gene expression pattern normalized with stable reference genes differed from those normalized with less stable genes. When normalized with the most stable genes, the expression levels of ACE2 in minipigs highly increased in intestine and kidney at PND28, which is consistent with the ACE2 expression pattern in humans.

Conclusions

We suggest that HPRT1 and 18S are good choices for analyzing all these samples across the seven tissues and four developmental stages. However, this study can be a reference literature for gene expression experiments using minipig because reference gene should be validated and chosen according to experimental conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08830-z.

Altered microfilament dynamics contribute to the formation of diploid metaphase spindles in porcine oocytes which fail to reach the metaphase-II stage during in vitro maturation

Premature meiotic arrest during in vitro maturation (IVM) of porcine oocytes after germinal vesicle breakdown is associated with microfilament degradation. We aimed to clarify (1) if such arrest occurs at the metaphase-I (MI) stage or the oocyte progresses to a so-called diploid metaphase-II (MII) stage and (2) if microfilament degradation is the cause or result of the meiotic arrest. The number and morphology of chromosomes in oocytes showing premature meiotic arrest at 44 h IVM (38 monovalents) was similar to those cultured in the presence of the actin polymerization-inhibitor cytochalasin-B, but different from those of MI-stage (19 bivalents), and MII-stage oocytes (19 monovalents) at 33 and 44 h of IVM, respectively. Immunostaining revealed similar frequencies of microfilament degradation in prematurely arrested and cytochalasin-B-treated oocytes (58.7% and 57.2%, respectively), which were higher (P < 0.05) than those in MI- and MII-stage oocytes (10.6% and 6.8%, respectively). Induction of MI-arrest by nocodazole did not affect microfilament morphology. ATP and mRNA levels of microfilament-related genes in oocytes were similar among all groups. These results suggest that altered microfilament dynamics contribute to the formation of diploid metaphase spindles in oocytes, which fail to reach the MII stage. However, the cause of microfilament degeneration remains unclear.

Dietary Yeast Cell Wall Improves Growth Performance and Prevents of Diarrhea of Weaned Pigs by Enhancing Gut Health and Anti-Inflammatory Immune Responses

Simple Summary

Post-weaning stress can substantially affect performance of weaned pigs as well as overall pig production, and thus, a practical approach is needed to improve their performance by alleviating the stress that can cause intestinal barrier dysfunction of weaned pigs. There are potential ways to solve the concern in swine production, but dietary yeast cell wall in weaner diets may be one possible solution. The results of the present study suggest that dietary yeast cell wall improves growth performance of weaned pigs by enhancing gut health and provide its potential mechanism.

Abstract

Dietary yeast cell wall products (YCW) are recognized as a feed additive due to multifunctional benefits by the biological response modulators. Thus, this study was conducted to verify a potential advantage of YCW for improving growth performance, nutrient digestibility, immune responses, and intestinal health and microbiota of weaned pigs. A total of 112 weaned pigs (7.99 ± 1.10 kg of body weight; 28 days old) were arbitrarily allocated to two experimental treatments with eight pigs (four barrows and four gilts) per pen and seven replicate pens per treatment in a completely randomized block design (block = BW and sex): (1) a basal diet based on corn and soybean meal (CON) and (2) CON + 0.05% YCW. The experimental period was for 4 weeks. There were no differences in final body weight, average daily feed intake, and gain-to-feed ratio between dietary treatments. In contrast, pigs fed YCW had higher average daily gain (p = 0.088) and apparent ileal digestibility of DM (p < 0.05) and energy (p = 0.052) and lower diarrhea frequency (p = 0.083) than those fed control diet (CON). Pigs fed YCW also had a higher (p < 0.05) ratio between villus height and crypt depth, villus width and area, and goblet cell counts in the duodenum and/or jejunum than those fed CON. Dietary YCW decreased (p < 0.05) serum TNF-α and IL–1β of weaned pigs on day 7 and 14, respectively, compared with CON. Furthermore, pigs fed YCW had higher (p < 0.05) ileal gene expression of claudin family, occludin, MUC1, INF-γ, and IL-6 and lower (p < 0.05) that of TNF-α than those fed CON. Lastly, there were no differences in the relative abundance of bacteria at the phylum level between CON and YCW. However, dietary YCW increased (p < 0.05) the relative abundance of genera Prevotella and Roseburia compared with CON. This study provided that dietary YCW improved growth rate, nutritional digestibility, and intestinal health and modified immune responses and intestinal microbiota of weaned pigs.

Reverse transcription priming methods affect normalisation choices for gene expression levels in oocytes and early embryos

Mammalian oocytes and embryos rely exclusively on maternal mRNAs to accomplish early developmental processes. Since oocytes and early embryos are transcriptionally silent after meiotic resumption, most of the synthesised maternal mRNA does not undergo immediate translation but is instead stored in the oocyte. Quantitative RT-PCR is commonly used to quantify mRNA levels, and correct quantification relies on reverse transcription and the choice of reference genes. Different methods for reverse transcription may affect gene expression determination in oocytes. In this study, we examined the suitability of either random or oligo(dT) primers for reverse transcription to be used for quantitative RT-PCR. We further looked for changes in poly(A) length of the maternal mRNAs during oocyte maturation. Our data indicate that depending on the method of reverse transcription, the optimal combination of reference genes for normalisation differed. Surprisingly, we observed a shortening of the poly(A) tail lengths of maternal mRNA as oocytes progressed from germinal vesicle to metaphase II. Overall, our findings suggest dynamic maternal regulation of mRNA structure and gene expression during oocyte maturation and early embryo development.

Lycopene Improves In Vitro Development of Porcine Embryos by Reducing Oxidative Stress and Apoptosis

In vitro culture (IVC) for porcine embryo development is inferior compared to in vivo development because oxidative stress can be induced by the production of excessive reactive oxygen species (ROS) under high oxygen tension in the in vitro environment. To overcome this problem, we investigated the effect of lycopene, an antioxidant carotenoid, on developmental competence and the mechanisms involved in mitochondria-dependent apoptosis pathways in porcine embryos. In vitro fertilized (IVF) embryos were cultured in IVC medium supplemented with 0, 0.02, 0.05, 0.1, or 0.2 μM lycopene. The results indicate that 0.1 μM lycopene significantly increased the rate of blastocyst formation and the total cell numbers, including trophectoderm cell numbers, on Day In terms of mitochondria-dependent apoptosis, IVF embryos treated with 0.1 μM lycopene exhibited significantly decreased levels of ROS, increased mitochondrial membrane potential, and decreased expression of cytochrome c on Days 2 and Furthermore, 0.1 μM lycopene significantly decreased the number and percentage of caspase 3-positive and apoptotic cells in Day-6 blastocysts. In addition, Day-2 embryos and Day-6 blastocysts treated with 0.1 μM lycopene showed significantly reduced mRNA expression related to antioxidant enzymes (SOD1, SOD2, CATALASE) and apoptosis (BAX/BCL2L1 ratio). These results indicate that lycopene supplementation during the entire period of IVC enhanced embryonic development in pigs by regulating oxidative stress and mitochondria-dependent apoptosis.

Fetal gastroschisis: Maternal and fetal methylation profile

OBJECTIVE

The purpose of this study was to describe the genomic deoxyribonucleic acid (DNA) methylation profile in fetuses with gastroschisis, determine whether the profile was inherited, and investigate any possible correlations with maternal risk factors.

METHOD

Genome-wide DNA methylation analysis of 96 blood samples was performed using the Illumina Human Methylation 850K BeadChip. The blood samples were collected as follows: 32 from the umbilical cord of fetuses with gastroschisis, 32 from their respective mothers, 16 from the umbilical cord of fetuses without malformation, and 16 from their respective mothers.

RESULTS

The differential DNA methylation analysis showed a significant difference between the groups. The enrichment analysis resulted in 12 sites related to T-cell activation (p = 0.0128). The sites with different methylation status contained 10 genes, three of which were related to the beta-2-microglobulin gene. The methylation profile observed in the fetuses with gastroschisis was not inherited from the mothers. In addition, there was no association between maternal urinary tract infection, smoking, and alcohol use and different methylated sites.

CONCLUSION

We established the methylation profile of gastroschisis fetuses, which differs from that of normal fetuses. The profile was not inherited and did not correlate with maternal risk factors.

Transplant chimerism in porcine structural vascularized bone allotransplants

BACKGROUND

Bone allotransplant viability can be maintained long-term by implanting arteriovenous (AV) bundles and creating an autogenous neoangiogenic circulation. Only short-term immunosuppression is required. This study investigates the origin of viable osteocytes observed in areas of active bone remodeling in orthotopically transplanted tibiae in a Yucatan mini-pig model.

METHODS

Segmental tibial defects created in female Yucatan minipigs (N = 14) were reconstructed with a matched vascularized composite allotransplant from a male donor. The circulation was microsurgically restored, with simultaneous autogenous AV-bundle implantation in group 1 (N = 7). A ligated AV-bundle was implanted as a no-angiogenesis control in group 2 (N = 7). After 20-weeks, repopulation of the allotransplant was assessed by real-time qPCR measurement of relative copy numbers of a Y chromosome-specific gene (SRY) and an autosomal housekeeping gene, ribosomal protein L4 (RPL4). A lower SRY/RPL4 ratio demonstrates replacement of male allogeneic cells with female, autogenous cells in the sample. Genomic DNA was extracted from cross-sections of the allotransplant, liver and spleen. Additionally, areas of new bone formation within the allotransplant were sampled by laser capture microdissection. A comparison was made between groups as well as male control samples. RNA was extracted from bone as well, as a measure of metabolically active cells.

RESULTS

Laser-captured areas of new bone formation in animals with both normal and ligated AV-bundles were found to have significantly lower relative copy numbers of SRY (p = 0.03) than control specimens from male bone, indicating replacement by female (autogenous) bone-forming cells. Analysis of an entire segment of the allotransplant from Group 1 was similarly reduced (p = 0.04), unlike that from Group 2. RNA expression of SRY was observed in both groups. No chimerism could be found in non-bone tissues (liver and spleen).

CONCLUSION

We observed a significant level of transplant chimerism in areas of new bone formation sampled by laser capture microdissection. The migration of autogenous cells including osteocytes was seen in both groups. Survival of some allogeneic (male) cells was also demonstrable. No microchimerism was found in liver and spleen.

Bovine immunisation with a recombinant peptide derived from synthetic SBm7462® (Bm86 epitope construct) immunogen for Rhipicephalus microplus control

RHIPICEPHALUS MICROPLUS: is the most important ectoparasite of livestock in tropical and subtropical areas around the world. Research focused on developing an efficient vaccine for cattle tick control is a high priority. The aim of this study was to evaluate the rSBm7462® peptide (Bm86-B and T cell epitopes) regarding its properties of immunogenicity, protective effect in cattle and efficacy against R. microplus. This peptide was produced by a fermentative process in the yeast culture system of Komagataella (Pichia) pastoris strain Km 71. The vaccination assay was conducted in a tick-free area using non-splenectomised Holstein Friesian calves, separated into immunisation and control groups. These animals individually received the recombinant peptide and the inoculum without peptide using saponin as an adjuvant at three time points. The calves were challenged 21 days after the last immunisation using 4500 larvae per animal. An indirect ELISA was used to identify the IgG kinetics of serum samples from the calves studied. The qPCR was performed to determine the cytokine gene expression from the total RNA of the cultured PBMCs. Histomorphometry of the germinal centres (GCs) was performed measuring slides with haematoxylin-eosin staining of surgically removed lymph nodes from immunised calves. The antibody response showed a significant induction of high-affinity IgGs in calves immunised with the recombinant peptide in comparison to the controls. The kinetics of antibodies in immunised calves showed a significant increase during the experiment. This increase in high-affinity IgGs correlated with a gradual increase of the GC diameter following each peptide vaccination. Cytokine expression profiles demonstrating an adaptive immune response in calves immunised with rSBm7462® confirmed the T-dependent response. Vaccine efficacy was calculated at 72.4 % following the analysis and fecundity of collected adult female ticks, compared between control and vaccinated groups. These findings demonstrate that this new recombinant peptide is an option for control of R. microplus infestations.

The extracellular calcium-sensing receptor promotes porcine egg activation via calcium/calmodulin-dependent protein kinase II

Extracellular calcium is required for intracellular Ca²⁺ oscillations needed for egg activation, but the regulatory mechanism is still poorly understood. The present study was designed to demonstrate the function of calcium-sensing receptor (CASR), which could recognize extracellular calcium as first messenger, during porcine egg activation. CASR expression was markedly upregulated following egg activation. Functionally, the addition of CASR agonist NPS R-568 significantly enhanced pronuclear formation rate, while supplementation of CASR antagonist NPS2390 compromised egg activation. There was no change in NPS R-568 group compared with control group when the egg activation was performed without extracellular calcium addition. The addition of NPS2390 precluded the activation-dependent [Ca²⁺ ]_i rise. When egg activation was conducted in intracellular Ca²⁺ chelator BAPTA-AM and NPS R-568 containing medium, CASR function was abolished. Meanwhile, CASR activation increased the level of the [Ca²⁺ ]_i effector p-CAMKII, and the presence of KN-93, an inhibitor of CAMKII, significantly reduced the CASR-mediated increasement of pronuclear formation rate. Furthermore, the increase of CASR expression following activation was reversed by inhibiting CAMKII activity, supporting a positive feedback loop between CAMKII and CASR. Altogether, these findings provide a new pathway of egg activation about CASR, as the extracellular Ca²⁺ effector, promotes egg activation via its downstream effector and upstream regulator CAMKII.

Vitrification of porcine cumulus-oocyte complexes at the germinal vesicle stage does not trigger apoptosis in oocytes and early embryos, but activates anti-apoptotic Bcl-XL gene expression beyond the 4-cell stage

The aim of the present study was to clarify whether or not our vitrification procedure at the germinal vesicle (GV)-stage triggers the apoptotic cascade in oocytes and subsequent embryos. Immature porcine cumulus-oocyte complexes were either vitrified and warmed (vitrified group) or subjected to cryoprotectant agents (CPA group) or cultured without any treatment (control). Oocytes of all treatment groups were subjected to in vitro maturation (IVM), fertilization, and embryo culture. Apoptosis was assayed in live oocytes at the end of IVM culture and in cleavage-stage embryos after in vitro fertilization (IVF). We detected similar frequencies of DNA fragmentation, levels of caspase activity, phosphatidylserine externalization, and mRNA levels for pro-apoptotic Bax and CASP3 genes in oocytes at the end of IVM and in early embryos among all groups. However, in the vitrified group, the anti-apoptotic Bcl-XL gene was upregulated in 4–8 cell embryos, which caused an 8-fold significant increase in the Bcl-XL/Bax mRNA ratio compared with the control and CPA groups (P < 0.05). In conclusion, vitrification of porcine oocytes at the GV stage by our method did not trigger the apoptotic cascade in oocytes and subsequent embryos but triggered the upregulation of the anti-apoptotic Bcl-XL gene in embryos.

Differentiating between the effects of heat stress and lipopolysaccharide on the porcine ovarian heat shock protein response1

Heat stress (HS) negatively affects both human and farm-animal health and undermines efficiency in a variety of economically important agricultural variables, including reproduction. HS impairs the intestinal barrier, allowing for translocation of the resident microflora and endotoxins, such as lipopolysaccharide (LPS), from the gastrointestinal lumen into systemic circulation. While much is known about the cellular function of heat shock proteins (HSPs) in most tissues, the in vivo ovarian HSP response to stressful stimuli remains ill-defined. The purpose of this study was to compare the effects of HS or LPS on ovarian HSP expression in pigs. We hypothesized that ovarian HSPs are responsive to both HS and LPS. Altrenogest (15 mg/d) was administered per os for estrus synchronization (14 d) prior to treatment and three animal paradigms were used: (i) gilts were exposed to cyclical HS (31 ± 1.4 °C) or thermoneutral (TN; 20 ± 0.5 °C) conditions immediately following altrenogest withdrawal for 5 d during follicular development; (ii) gilts were subjected to repeated (4×/d) saline (CON) or LPS (0.1 μg/kg BW) i.v. infusion immediately following altrenogest withdrawal for 5 d; and (iii) gilts were subjected to TN (20 ± 1 °C) or cyclical HS (31 to 35 °C) conditions 2 d post estrus (dpe) until 12 dpe during the luteal phase. While no differences were detected for transcript abundances of the assessed ovarian HSP, the protein abundance of specific HSP was influenced by stressors during the follicular and luteal phases. HS during the follicular phase tended (P < 0.1) to increase ovarian protein abundance of HSP90AA1 and HSPA1A, and increased (P ≤ 0.05) HSF1, HSPD1, and HSPB1 compared with TN controls, while HS decreased HSP90AB1 (P = 0.01). Exposure to LPS increased (P < 0.05) HSP90AA1 and HSPA1A and tended (P < 0.1) to increase HSF1 and HSPB1 compared with CON gilts, while HSP90AB1 and HSPD1 were not affected by LPS. HS during the luteal phase increased (P < 0.05) abundance of HSPB1 in corpora lutea (CL), decreased (P < 0.05) CL HSP90AB1, but did not impact HSF1, HSPD1, HSP90AA1, or HSPA1A abundance. Thus, these data support that HS and LPS similarly regulate expression of specific ovarian HSP, which suggest that HS effects on the ovary are in part mediated by LPS.

Oocytes, embryos and pluripotent stem cells from a biomedical perspective

The veterinary and animal science professions are rapidly developing and their inherent and historical connection to agriculture is challenged by more biomedical and medical directions of research. While some consider this development as a risk of losing identity, it may also be seen as an opportunity for developing further and more sophisticated competences that may ultimately feed back to veterinary and animal science in a synergistic way. The present review describes how agriculture-related studies on bovine in vitro embryo production through studies of putative bovine and porcine embryonic stem cells led the way to more sophisticated studies of human induced pluripotent stem cells (iPSCs) using e.g. gene editing for modeling of neurodegeneration in man. However, instead of being a blind diversion from veterinary and animal science into medicine, these advanced studies of human iPSC-derived neurons build a set of competences that allowed us, in a more competent way, to focus on novel aspects of more veterinary and agricultural relevance in the form of porcine and canine iPSCs. These types of animal stem cells are of biomedical importance for modeling of iPSC-based therapy in man, but in particular the canine iPSCs are also important for understanding and modeling canine diseases, as e.g. canine cognitive dysfunction, for the benefit and therapy of dogs.

Reference genes selection for real-time quantitative PCR analysis in mouse germinal vesicle oocytes

Reference gene selection in mouse oocytes is an important task required to perform further adequate analysis of target gene expression levels. In the current work we have analyzed expression stability of the seven most commonly used reference genes (Actb, Eef1e1, Gapdh, H2afz, Ppia, Rpl4 and Ubc) in mouse oocytes at the germinal vesicle (GV) stage. We have performed analysis of expression stability of the above-mentioned reference genes with the three most commonly used software tools: geNorm, BestKeeper and NormFinder. Taking into account the results obtained from all of these programmes Gapdh, Rpl4 and H2afz seem to be suitable candidate reference genes in GV oocytes of mouse.

Effect of EZH2 knockdown on preimplantation development of porcine parthenogenetic embryos

The EZH2 protein endows the polycomb repressive complex 2 (PRC2) with histone lysine methyltransferase activity that is associated with transcriptional repression. Recent investigations have documented crucial roles for EZH2 in mediating X-inactivation, stem cell pluripotency and cancer metastasis. However, there is little evidence demonstrating the maternal effect of EZH2 on porcine preimplantation development. Here, we took parthenogenetic activation embryos to eliminate the confounding paternal influence. We showed that the dynamic expression of EZH2 during early development was accompanied by changes in H3K27me3 levels. Depletion of EZH2 in MII oocytes by small interfering RNA not only impaired embryonic development at the blastocyst stage (P < 0.05), but also disrupted the equilibrium of H3K4me3 and H3K27me3 in the embryo. Interestingly, the expression of TET1, a member of Ten-Eleven Translocation gene family for converting 5-methylcytosine (5 mC) to 5-hydroxymethylcytosine (5hmC), was decreased after EZH2 knockdown, in contrast to the increase of the other two members, TET2 and TET3 (P < 0.05). These results indicate a correlation between histone methylation and DNA methylation, and between EZH2 and TET1. Along with the downregulation of TET1, the expression of the pluripotency gene NANOG was decreased (P < 0.05), which is consistent with a previous finding in mouse ES cells. Meanwhile, the abundance of OCT4 and SOX2 were also down-regulated. Moreover, EZH2 knockdown reduced the capacity of cells in the blastocysts to resist apoptosis. Taken together, our data suggest that EZH2 is integral to the developmental program of porcine parthenogenetic embryos and exerts its function by regulating pluripotency, differentiation and apoptosis.

A new set of reference housekeeping genes for the normalization RT-qPCR data from the intestine of piglets during weaning

The intestinal mucosal development of piglets (Sus scrofa) during the weaning stage is important to their disease susceptibility and later growth. Quantitative real-time PCR (RT-qPCR) is commonly used to screen for differentially expressed genes and, for accurate results, proper reference housekeeping genes are essential. Here we assessed the mRNA expression of 18 well-known candidate reference genes at different parts of the gastrointestinal tract (GIT) of piglets during the weaning process by RT-qPCR assay. GeNorm analysis revealed that B2M/HMBS/HPRT1 were the three most stable reference genes and GAPDH was the least stable gene in the duodenum, jejunum, ileum, colon, and whole GIT. BestKeeper analysis found that B2M/HMBS/PGK11, HMBS/B2M/HPRT1, B2M/HMBS/HSPCB, B2M/HPRT1/HMBS, and B2M/HMBS/HPRT1 were the most stable genes in the duodenum, jejunum, ileum, colon, and whole GIT, respectively, whereas GAPDH, B-actin, and 18S rRNA were the least stable genes at different parts of the GIT. To confirm the crucial role of appropriate housekeeping genes in obtaining reliable results, we analyzed the expression of ALP using each of the 18 reference genes to normalize the RT-qPCR data. We found that the expression levels of ALP normalized using the most stable reference genes (B2M/HMBS/HPRT1) differed greatly from the expression levels obtained when the data were normalized using the least stable genes (GAPDH, B-actin, and 18S). We concluded that B2M/HMBS/HPRT1 were the optimal reference genes for gene expression analysis by RT-qPCR in the intestinal mucosal development stages of piglets at weaning. Our findings provide a set of porcine housekeeping reference genes for studies of mRNA expression in different parts of the pig intestine.

Peri-conceptional nutritional restriction alters transcriptomic profile in the peri-implantation pig embryos

Restricted nutritional consumption during the peri-conceptional period affects the potential for DNA methylation and alters endometrial transcriptomic profile during the peri-implantation period. The restricted diet fed to females during the peri-conceptional period may affect the transcriptomic profile in peri-implantation embryos. In the present study, the transcriptome of embryos of normal-diet-fed gilts was determined and compared with that in embryos of restricted-diet-fed gilts during the peri-implantation period. The restricted-diet-fed gilts were fed forage, in which the dose of proteins and energy had been reduced by 30% compared to the normal diet (Polish Norms of Nutrition). To clarify the issue Agilent's Porcine (V2) Two-Color Gene Expression Microarray 4 × 44 was used. Analysis of the microarray data revealed that the expression of 787 genes with known biological function were consistently altered (496 up- and 291 down-regulated) in embryos. The accurately annotated genes were organized into five categories and 18 subcategories containing 62 biological pathways. The qPCR analysis of ten selected genes [i.e., 5 acid phosphatase, tartrate resistant (ACP5), high mobility group box 2 (HMGB2), prostaglandin-endoperoxide synthase 2 (PTGS2), arachidonate 12-lipoxygenase (ALOX12), adiponectin receptor 2 (ADIPOR2), DNA (cytosine-5)-methyltransferase 1 (DNMT1), steroidogenic acute regulatory protein (STAR), progesterone receptor membrane component 2 (PGRMC2), progestin and adipoQ receptor family member 7 (PAQR7) and serpin family A member 1 (SERPINA1)] confirmed altered gene expression in embryos of restricted-diet-fed gilts. The insight into embryonic transcriptome indicates that female under-nutrition during the peri-conceptional period may create alterations in the pattern of genes expressed in the peri-implantation embryos.

Antimicrobial peptide expression in swine granulosa cells in response to lipopolysaccharide

Antimicrobial peptides (AMP) are host defense peptides present in all species examined. The objective of the current study was to characterize the expression of a group of antimicrobial peptides in ovarian cells, and to investigate their expression response to pathogen ligands. It was found that while PG1 transcript was not detected in the ovary, the expression of BD2 is the highest in small follicle derived granulosa cells (SGC), and its expression decreases during follicular development to large follicle stage (LGC; p < 0.05). The expression of BD2 in cumulus cells also decreased from GV to MII stage of oocyte maturation. ANG4 expression increased in granulosa cells during follicular development from SGC to LGC stage (p < 0.05), although no significant difference was observed in cumulus cells from different stages of oocyte maturation. We further examined AMP expression in follicle cells treated with different toll-like receptor (TLR) ligands which mimic pathogen exposure in the ovary. Of the four TLR ligands examined, lipopolysaccharide (LPS) exposure resulted in a 11.5 fold increase of BD2 expression, and a significant decrease of LYZ in LGC. A similar response pattern in BD2 and LYZ expression was also observed in SGC. These responses of AMP expression to LPS are associated with increased TLR4 signaling pathway component in mRNA and protein level, such as MyD88 and NFkB, and pro-inflammatory cytokines/chemokines, such as IL-6, TNFα and IL-8 (p < 0.05). Our data suggest that AMPs may play a role in innate defense as well as other physiological functions during ovarian follicular development and oocyte maturation.

Effect of Kisspeptin on the Developmental Competence and Early Transcript Expression in Porcine Oocytes Parthenogenetically Activated with Different Methods

Recent studies showed the modulatory effect of kisspeptin (KP) on calcium waves through the cell membrane and inside the cell. Spermatozoon can induce similar ooplasmic calcium oscillations at fertilization to trigger meiosis II. Here, we evaluated the effect of KP supplementation with 6-dimethylaminopurine (6-DMAP) for 4 h on embryonic development after oocyte activation with single electric pulse, 5 µM ionomycin, or 8% ethanol. Compared to control nonsupplemented groups, KP significantly improved embryo developmental competence electric- and ethanol-activated oocytes in terms of cleavage (75.3% and 58.6% versus 64% and 48%, respectively, p < 0.05) and blastocyst development (31.3% and 10% versus 19.3% and 4%, respectively, p < 0.05). MOS expression was increased in electrically activated oocytes in presence of KP while it significantly reduced CCNB1 expression. In ionomycin treated group, both MOS and CCNB1 showed significant increase with no difference between KP and control groups. In ethanol-treated group, KP significantly reduced CCNB1 but no effect was observed on MOS expression. The early alterations in MOS and CCNB1 mRNA transcripts caused by KP may explain the significant differences in the developmental competence between the experimental groups. Kisspeptin supplementation may be adopted in protocols for porcine oocyte activation through electric current and ethanol to improve embryonic developmental competence.

Identification of stable reference genes for quantitative PCR in koalas

To better understand host and immune response to diseases, gene expression studies require identification of reference genes with stable expression for accurate normalisation. This study describes the identification and testing of reference genes with stable expression profiles in koala lymph node tissues across two genetically distinct koala populations. From the 25 most stable genes identified in transcriptome analysis, 11 genes were selected for verification using reverse transcription quantitative PCR, in addition to the commonly used ACTB and GAPDH genes. The expression data were analysed using stable genes statistical software - geNorm, BestKeeper, NormFinder, the comparative ΔCt method and RefFinder. All 13 genes showed relative stability in expression in koala lymph node tissues, however Tmem97 and Hmg20a were identified as the most stable genes across the two koala populations.

SIRT1-dependent modulation of methylation and acetylation of histone H3 on lysine 9 (H3K9) in the zygotic pronuclei improves porcine embryo development

Background

The histone code is an established epigenetic regulator of early embryonic development in mammals. The lysine residue K9 of histone H3 (H3K9) is a prime target of SIRT1, a member of NAD⁺-dependent histone deacetylase family of enzymes targeting both histone and non-histone substrates. At present, little is known about SIRT1-modulation of H3K9 in zygotic pronuclei and its association with the success of preimplantation embryo development. Therefore, we evaluated the effect of SIRT1 activity on H3K9 methylation and acetylation in porcine zygotes and the significance of H3K9 modifications for early embryonic development.

Results

Our results show that SIRT1 activators resveratrol and BML-278 increased H3K9 methylation and suppressed H3K9 acetylation in both the paternal and maternal pronucleus. Inversely, SIRT1 inhibitors nicotinamide and sirtinol suppressed methylation and increased acetylation of pronuclear H3K9. Evaluation of early embryonic development confirmed positive effect of selective SIRT1 activation on blastocyst formation rate (5.2 ± 2.9% versus 32.9 ± 8.1% in vehicle control and BML-278 group, respectively; P ≤ 0.05). Stimulation of SIRT1 activity coincided with fluorometric signal intensity of ooplasmic ubiquitin ligase MDM2, a known substrate of SIRT1 and known limiting factor of epigenome remodeling.

Conclusions

We conclude that SIRT1 modulates zygotic histone code, obviously through direct deacetylation and via non-histone targets resulting in increased H3K9me3. These changes in zygotes lead to more successful pre-implantation embryonic development and, indeed, the specific SIRT1 activation due to BML-278 is beneficial for in vitro embryo production and blastocyst achievement.

Determination of stable reference genes for RT-qPCR expression data in mechanistic pain studies on pig dorsal root ganglia and spinal cord

RNA expression levels for genes of interest must be normalised with appropriate reference or "housekeeping" genes that are stably expressed across samples and treatments. This study determined the most stable reference genes from a panel of 6 porcine candidate genes: beta actin (ACTB), beta-2-microglobulin (B2M), eukaryotic elongation factor 1 gamma-like protein (eEF-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), succinate dehydrogenase complex subunit A (SDHA), Ubiquitin C (UBC) in sacral dorsal root ganglia and spinal cord samples collected from 16 tail docked pigs (2/3rds of tail amputated) 1, 4, 8 and 16weeks after tail injury (4 pigs/time point). Total RNA from pooled samples was measured by SYBRgreen real-time quantitative PCR. Cycle threshold values were analysed using geNorm, BestKeeper and NormFinder PCR analysis software. Average expression stability and pairwise variation values were calculated for each candidate reference gene. GeNorm analysis identified the most stable genes for normalisation of gene expression data to be GAPDH>eEF-1>UBC>B2M>ACTB>SDHA for dorsal root ganglia and ACTB>SDHA>UBC>B2M>GAPDH>eEF-1 for spinal cord samples. Expression stability estimates were verified by BestKeeper and NormFinder analysis. Expression stability varied between genes within and between tissues. Validation of most stably expressed reference genes was performed by normalisation of calcitonin gene related polypeptide beta (CALCB). The results show similar patterns of CALCB expression when the best reference genes selected by all three programs were used. GAPDH, eEF-1 and UBC are suitable reference genes for porcine dorsal root ganglia samples, whereas ACTB, SDHA and UBC are more appropriate for spinal cord samples.

Dormancy and activation of human oocytes from primordial and primary follicles: molecular clues to oocyte regulation

STUDY QUESTION

Do specific transcriptome dynamics in human oocytes from primordial and primary follicles identify novel pathways in oocyte activation?

SUMMARY ANSWER

The transcriptomic profiles in oocytes from primordial and primary follicles, respectively, revealed several new canonical pathways as putative mediators of oocyte dormancy and activation.

WHAT IS KNOWN ALREADY

Cellular signaling pathways including PI3K/AKT and AKT/mTOR as well as TGF-β and IGF signaling are known to regulate the primordial-to-primary transition in mammalian follicle development.

STUDY DESIGN, SIZE, DURATION

We performed a class comparison study on human oocytes from primordial (n = 436) and primary (n = 182) follicles donated by three women having ovarian tissue cryopreserved before chemotherapy.

PARTICIPANTS/MATERIALS, SETTING, METHODS

RNA was extracted from oocytes from primordial and primary follicles isolated by Laser Capture Microdissection, and submitted to the HiSeq Illumina platform. Data mapping, quality control, filtering and expression analysis were performed using Tophat (2.0.4), Cufflinks (2.0.2), BWA (0.6.2) and software R. Modeling of complex biological systems was performed using the IPA® software. Finally, qPCR and immunohistochemistry were employed to explore expression and localization of selected genes and products in human ovarian tissue.

MAIN RESULTS AND THE ROLE OF CHANCE

We found 223 and 268 genes down-regulated and up-regulated, respectively, in the oocytes during the human primordial-to-primary follicle transition (P < 0.05 and/or FPKM fold-change >2). IPA® enrichment analysis revealed known pathways ('mTOR Signaling', 'PI3K/AKT Signaling' and 'PTEN Signaling') as well as enriched canonical pathways not previously associated with human ovarian follicle development such as 'ErB Signaling' and 'NGF Signaling' in the down-regulated category and 'Regulation of eIF4 and P70S6K Signaling' and 'HER-2 Signaling in Breast Cancer' in the up-regulated group. Additionally, immunohistochemistry on human ovarian tissue explored the intraovarian localization of VASA, FOXO1 and eIF4E.

LARGE SCALE DATA

http://users-birc.au.dk/biopv/published_data/ernst_2017/.

LIMITATIONS, REASONS FOR CAUTION

This is a descriptive analysis and no functional studies were performed. The study was based on a limited number of patients and the experimental design could not take into account the natural biological variance in human samples. Therefore, qPCR was used to confirm selected genes alongside immunohistochemical stainings.

WIDER IMPLICATIONS OF THE FINDINGS

This study shows, for the first time, a detailed molecular description of global gene transcription activities in oocytes from primordial and primary follicles, respectively. Knowing the global transcription profiles of human oocyte dormancy and activation are important in developing new clinical applications.

STUDY FUNDING/COMPETING INTEREST(S)

E.H.E. was supported by Health Faculty, Aarhus University and Kong Christian Den Tiendes Fond. K.H. and S.F. were supported by an MRC (UK) project grant MR/M012638/1. K.L.H. was supported by grants from Fonden til Lægevidenskabens Fremme, Kong Christian Den Tiendes Fond. K.L.H. and L.S. were supported by the IDEAS grant from Aarhus University Research Foundation (AUFF). There are no conflicts of interest.

Optimal doses of EGF and GDNF act as biological response modifiers to improve porcine oocyte maturation and quality

It is well documented that both epidermal growth factor (EGF) and glial cell line-derived neurotrophic factor (GDNF) are critical for porcine oocyte maturation, however, little information is known about their mechanism of action in vitro. To gain insight into the mechanisms of action of the optimum doses of EGF and GDNF on porcine oocyte maturation, porcine cumulus–oocyte complexes (COCs) were matured in defined porcine oocyte medium supplemented with EGF, GDNF or a combination of both at varying concentrations (0–100 ng/ml) for 44 h. Nuclear and cytoplasmic maturation were determined in terms of nuclear stage after DNA staining with Hoechst and cortical granule distribution after lectin labeling, respectively. Mature oocytes were subsequently collected for gene expression analysis or subjected to in vitro fertilization and cultured for 7 days. The results showed that EGF and/or GDNF, when administered in a certain dose (50 ng/μl) to the maturation medium, not only effectively improved the synchronization of nuclear and cytoplasmic maturation processes within the oocyte, but enhanced expression of their corresponding receptors in mature oocytes (P < 0.05). Moreover, supplementation with an optimal combination of EGF + GDNF resulted in elevation of TFAM transcripts as well as a decrease of caspase-3 transcripts compared with the other studied groups (P < 0.05). Collectively, our results indicate that treatment of porcine oocytes with specific-dose combinations of EGF and GDNF stimulates oocyte quality and competence by transcriptional modulation of genes involved in oocyte survival and competence.

Methods of RNA preparation affect mRNA abundance quantification of reference genes in pig maturing oocytes

To ensure accurate normalization and quantification of target RNA transcripts using reverse transcription quantitative polymerase chain reaction (RT-qPCR), most studies focus on the identification of stably expressed gene(s) as internal reference. However, RNA preparation methods could also be an important factor, especially for test samples of limited quantity (e.g. oocytes). In this study, we aimed to select appropriate reference gene(s), and evaluate the effect of RNA preparation methods on gene expression quantification in porcine oocytes and cumulus cells during in vitro maturation. Expression profiles of seven genes (GAPDH, 18S, YWHAG, BACT, RPL4, HPRT1 and PPIA) were examined, on RNA samples extracted from cumulus cells (RNeasy Kit) and oocytes (RNeasy Kit and Lysis Kit) during in vitro maturation, respectively. Interestingly, different RNA preparation methods were found to potentially affect the quantification of reference gene expression in pig oocytes cultured in vitro. After geNorm analyses, the most suitable genes for normalization were identified, GAPDH/18S for cumulus cells and YWHAG/BACT for oocytes, respectively. Thus, our results provide useful data and information on the selection of better reference genes and RNA preparation method for related functional studies.

Bisphenol S negatively affects the meotic maturation of pig oocytes

Bisphenol A (BPA), a chemical component of plastics, is a widely distributed environmental pollutant and contaminant of water, air, and food that negatively impacts human health. Concerns regarding BPA have led to the use of BPA-free alternatives, one of which is bisphenol S (BPS). However, the effects of BPS are not well characterized, and its specific effects on reproduction and fertility remain unknown. It is therefore necessary to evaluate any effects of BPS on mammalian oocytes. The present study is the first to demonstrate the markedly negative effects of BPS on pig oocyte maturation in vitro, even at doses lower than those humans are exposed to in the environment. Our results demonstrate (1) an effect of BPS on the course of the meiotic cell cycle; (2) the failure of tubulin fibre formation, which controls proper chromosome movement; (3) changes in the supply of maternal mRNA; (4) changes in the protein amounts and distribution of oestrogen receptors α and β and of aromatase; and (5) disrupted cumulus cell expansion. Thus, these results confirm that BPS is an example of regrettable substitution because this substance exerts similar or even worse negative effects than those of the material it replaced.

CDX2 is essential for cell proliferation and polarity in porcine blastocysts

The role of CDX2 in trophectoderm (TE) cells has been extensively studied, yet the results are contradictory and species specific. Here, CDX2 expression and function were explored in early porcine embryos. Notably, siRNA-mediated gene knockdown and lentivirus-mediated TE-specific gene regulation demonstrated that CDX2 is essential for the maintenance of blastocyst integrity by regulating the BMP4-mediated blastocyst niche and classic protein kinase C (PKC)-mediated TE polarity in mammalian embryos. Mechanistically, CDX2-depleted porcine embryos stalled at the blastocyst stage and exhibited apoptosis and inactive cell proliferation, possibly resulting from BMP4 downregulation. Moreover, TE cells in CDX2-depleted blastocysts displayed defective F-actin apical organization associated with downregulation of PKCα (PRKCA). Collectively, these results provide further insight into the functional diversity of CDX2 in early mammalian embryos.

Candidate Reference Genes Selection and Application for RT-qPCR Analysis in Kenaf with Cytoplasmic Male Sterility Background

Cytoplasmic male sterility (CMS) is a maternally inherited trait that results in the production of dysfunctional pollen. Based on reliable reference gene-normalized real-time quantitative PCR (RT-qPCR) data, examining gene expression profile can provide valuable information on the molecular mechanism of kenaf CMS. However, studies have not been conducted regarding selection of reference genes for normalizing RT-qPCR data in the CMS and maintainer lines of kenaf crop. Therefore, we studied 10 candidate reference genes (ACT3, ELF1A, G6PD, PEPKR1, TUB, TUA, CYP, GAPDH, H3, and 18S) to assess their expression stability at three stages of pollen development in CMS line 722A and maintainer line 722B of kenaf. Five computational statistical approaches (GeNorm, NormFinder, ΔCt, BestKeeper, and RefFinder) were used to evaluate the expression stability levels of these genes. According to RefFinder and GeNorm, the combination of TUB, CYP, and PEPKR1 was identified as an internal control for the accurate normalization across all sample set, which was further confirmed by validating the expression of HcPDIL5-2a. Furthermore, the combination of TUB, CYP, and PEPKR1 was used to differentiate the expression pattern of five mitochondria F₁F₀-ATPase subunit genes (atp1, atp4, atp6, atp8, and atp9) by RT-qPCR during pollen development in CMS line 722A and maintainer line 722B. We found that atp1, atp6, and atp9 exhibited significantly different expression patterns during pollen development in line 722A compared with line 722B. This is the first systematic study of reference genes selection for CMS and will provide useful information for future research on the gene expressions and molecular mechanisms underlying CMS in kenaf.

Common and specific transcriptional signatures in mouse embryos and adult tissues induced by in vitro procedures

Stressful environmental exposures incurred early in development can affect postnatal metabolic health and susceptibility to non-communicable diseases in adulthood, although the molecular mechanisms by which this occurs have yet to be elucidated. Here we use a mouse model to investigate how assorted in vitro exposures restricted exclusively to the preimplantation period affect transcription both acutely in embryos and long-term in subsequent offspring adult tissues, to determine if reliable transcriptional markers of in vitro stress are present at specific developmental time points and throughout development. Each in vitro fertilization or embryo culture environment led to a specific and unique blastocyst transcriptional profile, but we identified a common 18-gene and 9-pathway signature of preimplantation embryo manipulation that was present in all in vitro embryos irrespective of culture condition or method of fertilization. This fingerprint did not persist throughout development and there was no clear transcriptional cohesion between adult IVF offspring tissues or compared to their preceding embryos, indicating a tissue-specific impact of in vitro stress on gene expression. However, the transcriptional changes present in each IVF tissue were targeted by the same upstream transcriptional regulators, which provide insight as to how acute transcriptional responses to stressful environmental exposures might be preserved throughout development to influence adult gene expression.

Promise and Ontological Ambiguity in the In vitro Meat Imagescape: From Laboratory Myotubes to the Cultured Burger

In vitro meat (IVM), also known as cultured meat, involves growing cells into muscle tissue to be eaten as food. The technology had its most high-profile moment in 2013 when a cultured burger was cooked and tasted in a press conference. Images of the burger featured in the international media and were circulated across the Internet. These images-literally marks on a two-dimensional surface-do important work in establishing what IVM is and what it can do. A combination of visual semiotics and narrative analysis shows that images of IVM afford readings of their story that are co-created by the viewer. Before the cultured burger, during 2011, images of IVM fell into four distinct categories: cell images, tissue images, flowcharts, and meat in a dish images. The narrative infrastructure of each image type affords different interpretations of what IVM can accomplish and what it is. The 2013 cultured burger images both draw upon and depart from these image types in an attempt to present IVM as a normal food stuff, and as 'matter in place' when placed on the plate. The analysis of individual images and the collection of images about a certain object or subject-known as the imagescape-is a productive approach to understanding the ontology and promise of IVM and is applicable to other areas of social life.

Verification of suitable and reliable reference genes for quantitative real-time PCR during adipogenic differentiation in porcine intramuscular stromal-vascular cells

Intramuscular fat (IMF) is an important trait influencing meat quality, and intramuscular stromal-vascular cell (MSVC) differentiation is a key factor affecting IMF deposition. Quantitative real-time PCR (qPCR) is often used to screen the differentially expressed genes during differentiation of MSVCs, where proper reference genes are essential. In this study, we assessed 31 of previously reported reference genes for their expression suitability in porcine MSVCs derived form longissimus dorsi with qPCR. The expression stability of these genes was evaluated using NormFinder, geNorm and BestKeeper algorithms. NormFinder and geNorm uncovered ACTB, ALDOA and RPS18 as the most three stable genes. BestKeeper identified RPL13A, SSU72 and DAK as the most three stable genes. GAPDH was found to be the least stable gene by all of the three software packages, indicating it is not an appropriate reference gene in qPCR assay. These results might be helpful for further studies in pigs that explore the molecular mechanism underlying IMF deposition.

Selection of reliable reference genes in eutopic and ectopic endometrium for quantitative expression studies

PURPOSE

Physiological changes during menstrual cycle cause the endometrium and endometriosis to develop specific kind of tissues, especially in regard to the gene expression profiles, which may include also housekeeping genes, commonly used as reference genes (RGs) in quantitative studies. Reverse transcription, followed by quantitative polymerase chain reaction (RT-qPCR) is the most precise and commonly used method in gene expression studies. In order to reduce effects of technical approaches and biological variability of gene's expression level, the studies often employ RGs in experimental data normalization. However, the expression of RGs is not always stable and depends on several variables. Thus, the selection of appropriate RG is one of the most significant steps to obtain reliable results in RT-qPCR-based methods.

MATERIAL AND METHODS

With the usage of RT-qPCR, we researched the expression of seven genes (ACTB, B2M, G6PD, GAPD, GUSB, HPRT and PPIA) as reliable reference genes in eutopic and ectopic endometrial tissue specimens obtained during standard surgery of women of reproductive age. Stability of expression level was analyzed by the most universal MS Excel plug-ins including: geNorm, NormFinder and BestKeeper. The descriptive statistics were evaluated using Statistica software.

RESULTS

The distribution of threshold (Ct) values was not equal. We identified genes with higher expression level (referring to Ct values) such as ACTB and B2M, medium e.g., GAPD and low expression level, e.g., G6PD and HPRT. We demonstrated that the stability of the analyzed reference genes was not homogenous, and different algorithms pointed to PPIA, GAPD and B2M as the most stable ones in eutopic and ectopic endometrium. On the contrary to these, GUSB and G6PD were the most unstable ones.

CONCLUSIONS

In RT-qPCR-based analyses of gene expression level in eutopic and ectopic endometrium, we strongly recommend that a minimum of two reference genes are to be used and we determined that the most suitable seem to be PPIA and GAPD.

Cdx2 represses Oct4 function via inducing its proteasome-dependent degradation in early porcine embryos

Reciprocal repression of inner cell mass specific factor OCT4 and trophectoderm specific factor CDX2 promotes mouse first lineage segregation. Studies in mouse embryonic stem (ES) cells revealed that they bind to each other's regulatory regions to reciprocally suppress transcription, additionally they form protein complex for mutual antagonism. However, so far the molecular interaction of Oct4 and Cdx2 in other mammal's early embryo is not yet investigated. Here, over-expression of Cdx2 in early porcine embryo showed CDX2 represses Oct4 through neither the transcriptional repression nor forming repressive complex, but promoting OCT4 nuclear export and proteasomal degradation. The results showed novel molecular regulation of CDX2 on Oct4, and provided important clues for clarifying the mechanism of interaction between CDX2 and Oct4 in embryo of mammals other than mouse.

The Extracellular Calcium-Sensing Receptor (CASR) Regulates Gonadotropins-Induced Meiotic Maturation of Porcine Oocytes

Gonadotropins and epidermal growth factor (EGF) play crucial roles in promoting oocyte maturation. The regulatory network downstream of these key factors is not well understood. The present study was designed to investigate the role of the calcium-sensing receptor (CASR) in porcine oocyte in vitro maturation. CASR expression was up-regulated in oocytes matured in gonadotropin-containing medium. Cortical distribution of CASR was enhanced with gonadotropins but not EGF. Supplementation of a CASR agonist (NPS R-568) in the gonadotropin (FSH and/or LH)-containing maturation medium significantly enhanced oocyte nuclear maturation. Addition of NPS2390, a CASR antagonist, compromised oocyte nuclear maturation. Furthermore, increased cortical distribution and decreased expression of CASR was observed after the NPS R-568 treatment. Oocytes treated with NPS R-568 had higher concentration of CYCLIN B1, decreased reactive oxygen species, and increased glutathione levels, indicative of advanced cytoplasmic maturation. In contrast, NPS2390 treatment compromised oocyte cytoplasmic maturation. A higher blastocyst formation rate after parthenogenetic activation was observed when oocytes were matured in the presence of the CASR agonist, NPS R-568. MAPK3/1 phosphorylation was increased during in vitro maturation and after NPS R-568 treatment, and decreased following CASR antagonist supplementation. Taken together, our data showed that the CASR is a gonadotropin-regulated factor that promotes porcine oocyte maturation in a MAPK-dependent manner.

Endogenously produced hydrogen sulfide is involved in porcine oocyte maturation in vitro

Hydrogen sulfide, one of three known gasotransmitters, is involved in physiological processes, including reproductive functions. Oocyte maturation and surrounding cumulus cell expansion play an essential role in female reproduction and subsequent embryonic development. Although the positive effects of exogenous hydrogen sulfide on maturing oocytes are well known, the role of endogenous hydrogen sulfide, which is physiologically released by enzymes, has not yet been described in oocytes. In this study, we observed the presence of Cystathionine β-Synthase (CBS), Cystathionine γ-Lyase (CTH) and 3-Mercaptopyruvate Sulfurtransferase (3-MPST), hydrogen sulfide-releasing enzymes, in porcine oocytes. Endogenous hydrogen sulfide production was detected in immature and matured oocytes as well as its requirement for meiotic maturation. Individual hydrogen sulfide-releasing enzymes seem to be capable of substituting for each other in hydrogen sulfide production. However, meiosis suppression by inhibition of all hydrogen sulfide-releasing enzymes is not irreversible and this effect is a result of M-Phase/Maturation Promoting Factor (MPF) and Mitogen-Activated Protein Kinase (MAPK) activity inhibition. Futhermore, cumulus expansion expressed by hyaluronic acid (HA) production is affected by the inhibition of hydrogen sulfide production. Moreover, quality changes of the expanded cumuli are indicated. These results demonstrate hydrogen sulfide involvement in oocyte maturation as well as cumulus expansion. As such, hydrogen sulfide appears to be an important cell messenger during mammalian oocyte meiosis and adequate cumulus expansion.

Reference gene selection for quantitative gene expression studies during biological invasions: A test on multiple genes and tissues in a model ascidian Ciona savignyi

As invasive species have successfully colonized a wide range of dramatically different local environments, they offer a good opportunity to study interactions between species and rapidly changing environments. Gene expression represents one of the primary and crucial mechanisms for rapid adaptation to local environments. Here, we aim to select reference genes for quantitative gene expression analysis based on quantitative Real-Time PCR (qRT-PCR) for a model invasive ascidian, Ciona savignyi. We analyzed the stability of ten candidate reference genes in three tissues (siphon, pharynx and intestine) under two key environmental stresses (temperature and salinity) in the marine realm based on three programs (geNorm, NormFinder and delta Ct method). Our results demonstrated only minor difference for stability rankings among the three methods. The use of different single reference gene might influence the data interpretation, while multiple reference genes could minimize possible errors. Therefore, reference gene combinations were recommended for different tissues - the optimal reference gene combination for siphon was RPS15 and RPL17 under temperature stress, and RPL17, UBQ and TubA under salinity treatment; for pharynx, TubB, TubA and RPL17 were the most stable genes under temperature stress, while TubB, TubA and UBQ were the best under salinity stress; for intestine, UBQ, RPS15 and RPL17 were the most reliable reference genes under both treatments. Our results suggest that the necessity of selection and test of reference genes for different tissues under varying environmental stresses. The results obtained here are expected to reveal mechanisms of gene expression-mediated invasion success using C. savignyi as a model species.

Combination effects of epidermal growth factor and glial cell line-derived neurotrophic factor on the in vitro developmental potential of porcine oocytes

The developmental potential of in vitro matured porcine oocytes is still lower than that of oocytes matured and fertilized in vivo. Major problems that account for the lower efficiency of in vitro production include the improper nuclear and cytoplasmic maturation of oocytes. With the aim of improving this issue, the single and combined effects of epidermal growth factor (EGF) and glial cell line-derived neurotrophic factor (GDNF) on oocyte developmental competence were investigated. Porcine cumulus-oocyte cell complexes (COCs) were matured in serum-free medium supplemented with EGF (0, 10 or 50 ng/ml) and/or GDNF (0, 10 or 50 ng/ml) for 44 h, and subsequently subjected to fertilization and cultured for 7 days in vitro. The in vitro-formed blastocysts derived from selected growth factor groups (i.e. EGF = 50 ng/ml; GDNF = 50 ng/ml; EGF = 50 ng/ml + GDNF = 50 ng/ml) were also used for mRNA expression analysis, or were subjected to Hoechst staining. The results showed that the addition of EGF and/or GDNF during oocyte maturation dose dependently enhanced oocyte developmental competence. Compared with the embryos obtained from control or single growth factor-treated oocytes, treatment with the combination of EGF and GDNF was shown to significantly improve oocyte competence in terms of blastocyst formation, blastocyst cell number and blastocyst hatching rate (P < 0.05), and also simultaneously induced the expression of BCL-xL and TERT and suppressed the expression of caspase-3 in resulting blastocysts (P < 0.05). These results suggest that both GDNF and EGF may play an important role in the regulation of porcine in vitro oocyte maturation and the combination of these growth factors could promote oocyte competency and blastocyst quality.

The protective effect of follicular fluid against the emerging mycotoxins alternariol and beauvericin

Porcine granulosa cells were cultured in the absence or presence of 10% porcine follicular fluid (FF) at different concentrations (0-20 μM) of the mycotoxins alternariol (AOH) and beauvericin (BEA). The analyses were performed after exposure to these mycotoxins in a medium supplemented or not with FF harvested from gilts and sows. Cell enzymatic activity and nuclear membrane integrity were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and ethidium homodimer-1 labelling. Trolox equivalent antioxidant capacity was measured to calculate the capacity of the cells to counteract reactive oxygen species. qRT-PCR was used to determine the relative gene expression of efflux transporters (ABCG1 and ABCG2) as well CYP11 and CYP19. Mycotoxin cytotoxicity was more related to enzymatic activity than to nuclear membrane damage and no direct relationship with oxidative stress was observed, except when cells were exposed to AOH. In this case, medium supplementation with FF from sows increased the antioxidant capacity of the cells. AOH did not regulate gene expression in the present conditions, but 5 μM BEA led to the up-regulation of ABCG2 gene expression and a down-regulation of CYP19 expression. In conclusion, follicular fluid from sows is capable to decrease toxicity of AOH and of BEA.

Distinct differences in global gene expression profiles in non-implanted blastocysts and blastocysts resulting in live birth

Results from animal models points towards the existence of a gene expression profile that is distinguishably different in viable embryos compared with non-viable embryos. Knowledge of human embryo transcripts is however limited, in particular with regard to how gene expression is related to clinical outcome. The purpose of the present study was therefore to determine the global gene expression profiles of human blastocysts. Next Generation Sequencing was used to identify genes that were differentially expressed in non-implanted embryos and embryos resulting in live birth. Three trophectoderm biopsies were obtained from morphologically high quality blastocysts resulting in live birth and three biopsies were obtained from non-implanting blastocysts of a comparable morphology. Total RNA was extracted from all samples followed by complete transcriptome sequencing. Using a set of filtering criteria, we obtained a list of 181 genes that were differentially expressed between trophectoderm biopsies from embryos resulting in either live birth or no implantation (negative hCG), respectively. We found that 37 of the 181 genes displayed significantly differential expression (p<0.05), e.g. EFNB1, CYTL1 and TEX26 and TESK1, MSL1 and EVI5 in trophectoderm biopsies associated with live birth and non-implanting, respectively. Out of the 181 genes, almost 80% (145 genes) were up-regulated in biopsies from un-implanted embryos, whereas only 20% (36 genes) showed an up-regulation in the samples from embryos resulting in live birth. Our findings suggest the presence of molecular differences visually undetectable between implanted and non-implanted embryos, and represent a proof of principle study.

Removal of O-GlcNAcylation is important for pig preimplantation development

Glucose has been recognized as an energy source for a long time, but it has recently been suggested that the hexosamine biosynthesis pathway (HBP) and downstream protein O-GlcNAcylation have important functions in mouse preimplantation development. Thus, whether or not O-GlcNAcylation was present and what functions O-GlcNAcylation has in pig preimplantation development were investigated in the present study. The expressions of mRNA of glutaminefructose-6-phosphate aminotransferase (Gfpt), O-GlcNAc transferase (Ogt) and O-GlcNAcase (Oga), which are involved in the HBP and O-GlcNAc cycling, were examined in pig parthenogenetic diploids at each preimplantation developmental stage. Gfpt and Ogt were detected in diploids at all stages. Though Oga was detected at all stages except the 4-cell stage, OGA proteins were detected in diploids from the 2-cell to blastocyst stage. Furthermore, O-GlcNAcylated proteins in MII oocytes and diploids were also detected by immunofluorescence at every stage. Inhibition of OGT by 4.0 mM BADGP did not affect development up to the blastocyst stage, while inhibition of OGA by 300 µM PUGNAc decreased the proportion of diploids beyond the 4-cell stage. Four-cell diploids cultured with PUGNAc until 48 h developed to the blastocyst stage after culture in a PUGNAc-free medium until 144 h after electrostimulation. RNA polymerase II (Pol II) phosphorylation, which indicates the onset of mRNA transcription, was detected in nuclei of diploids in the control group at 48 h but not in the PUGNAc-treated group. These results indicate that HBP and O-GlcNAcylation have important functions in pig preimplantation development and that inhibition of OGA is fatal for development. It is also suggested that OGA inhibition disrupts normal Pol II regulation and may cause a zygotic gene activation error.

Evaluation of housekeeping genes for normalizing real-time quantitative PCR assays in pig skeletal muscle at multiple developmental stages

Quantitative PCR (qPCR) requires a constantly expressed housekeeping gene as an internal control, the expression of which is similar in different biological samples. In the present study, we evaluated the applicability and compared the consistency of the gene expression of 16 reference genes, i.e., 10 common and 6 candidate genes, through qPCR assays in pig skeletal muscles at multiple developmental stages. The stability of these 16 potential reference genes was investigated using the geNorm and NormFinder methods. Our results indicated that DRAP1 and RNF7 were the most appropriate combination to normalize gene expression in the Yorkshire samples, the combination of DRAP1 and WSB2 were appropriate in the Tongcheng samples, H3F3A and DRAP1 in prenatal periods, DRAP1 and RNF7 in postnatal periods, and the combination of DRAP1 and WSB2 was most suitable for accurate normalization in whole samples. This result provides a strong basis for similar studies in pigs that explore the molecular mechanisms underlying skeletal muscle development.

Selection and validation of reference genes for qRT-PCR expression analysis of candidate genes involved in olfactory communication in the butterfly Bicyclus anynana

Real-time quantitative reverse transcription PCR (qRT-PCR) is a technique widely used to quantify the transcriptional expression level of candidate genes. qRT-PCR requires the selection of one or several suitable reference genes, whose expression profiles remain stable across conditions, to normalize the qRT-PCR expression profiles of candidate genes. Although several butterfly species (Lepidoptera) have become important models in molecular evolutionary ecology, so far no study aimed at identifying reference genes for accurate data normalization for any butterfly is available. The African bush brown butterfly Bicyclus anynana has drawn considerable attention owing to its suitability as a model for evolutionary ecology, and we here provide a maiden extensive study to identify suitable reference gene in this species. We monitored the expression profile of twelve reference genes: eEF-1α, FK506, UBQL40, RpS8, RpS18, HSP, GAPDH, VATPase, ACT3, TBP, eIF2 and G6PD. We tested the stability of their expression profiles in three different tissues (wings, brains, antennae), two developmental stages (pupal and adult) and two sexes (male and female), all of which were subjected to two food treatments (food stress and control feeding ad libitum). The expression stability and ranking of twelve reference genes was assessed using two algorithm-based methods, NormFinder and geNorm. Both methods identified RpS8 as the best suitable reference gene for expression data normalization. We also showed that the use of two reference genes is sufficient to effectively normalize the qRT-PCR data under varying tissues and experimental conditions that we used in B. anynana. Finally, we tested the effect of choosing reference genes with different stability on the normalization of the transcript abundance of a candidate gene involved in olfactory communication in B. anynana, the Fatty Acyl Reductase 2, and we confirmed that using an unstable reference gene can drastically alter the expression profile of the target candidate genes.