Involvement of the STAT5 signaling pathway in the regulation of mouse preimplantation development

Signaling pathway regulators in preimplantation embryos

Embryonic development during the preimplantation stages is highly sensitive and critically dependent on the reception of signaling cues. The precise coordination of diverse pathways and signaling factors is essential for successful embryonic progression. Even minor disruptions in these factors can result in physiological dysfunction, fetal malformations, or embryonic arrest. This issue is particularly evident in assisted reproductive technologies, such as in vitro fertilization, where embryonic arrest is frequently observed. A detailed understanding of these pathways enhances insight into the fundamental mechanisms underlying cellular processes and their contributions to embryonic development. The significance of elucidating signaling pathways and their regulatory factors in preimplantation development cannot be overstated. The application of this knowledge in laboratory settings has the potential to support strategies for modeling developmental stages and diseases, drug screening, therapeutic discovery, and reducing embryonic arrest. Furthermore, using various factors, small molecules, and pharmacological agents can enable the development or optimization of culture media for enhanced embryonic viability. While numerous pathways influence preimplantation development, this study examines several critical signaling pathways in this contex.

The dynamic landscape of enhancer-derived RNA during mouse early embryo development

Enhancer-derived RNAs (eRNAs) play critical roles in diverse biological processes by facilitating their target gene expression. However, the abundance and function of eRNAs in early embryos are not clear. Here, we present a comprehensive eRNA atlas by systematically integrating publicly available datasets of mouse early embryos. We characterize the transcriptional and regulatory network of eRNAs and show that different embryo developmental stages have distinct eRNA expression and regulatory profiles. Paternal eRNAs are activated asymmetrically during zygotic genome activation (ZGA). Moreover, we identify an eRNA, MZGAe1, which plays an important function in regulating mouse ZGA and early embryo development. MZGAe1 knockdown leads to a developmental block from 2-cell embryo to blastocyst. We create an online data portal, M2ED2, to query and visualize eRNA expression and regulation. Our study thus provides a systematic landscape of eRNA and reveals the important role of eRNAs in regulating mouse early embryo development.

Interleukin-6 stimulates in vitro development of late-stage ovine embryos

The effect of interleukin-6 (IL-6) supplementation during the different phases of in vitro embryo culturing (IVC) on embryo development and embryonic gene expression was studied in ovine. IL-6 was added to IVC medium during the late phases (72-192 h; 5, 10, and 25 ng/ml IL-6) or entire period (0-192 h; 10 ng/ml IL-6) of IVC to determine its effect on embryo development. Further, the effect of IL-6 (10 ng/ml) supplementation at the 72 h of IVC on gene expressions associated with JAK/STAT signalling and pluripotency in 8-16 cell embryos (1 h post-supplementation) and compact morulae (48 h post-supplementation), and apoptosis and primitive endoderm (PrE) development in compact morulae was investigated. The supplementation of 10 ng/ml IL-6 during the late phases of IVC significantly (P < 0.05) increased blastocyst formation (35.2 ± 1.52%) compared to the control (21.1 ± 1.11%), and 5 ng/ml (25.9 ± 2.98%) or 25 ng/ml (16.5 ± 0.73%) IL-6 groups. Conversely, IL-6 (10 ng/ml) treatment throughout the IVC period significantly (P < 0.05) decreased the rate of cleavage (55.4 ± 1.57%) and blastocyst formation (14.5 ± 1.28%) compared to the control group (65.8 ± 1.35% and 21.5 ± 0.97%, respectively). In 8-16 cell embryos and compact morulae, the IL-6 treatment significantly (P < 0.05) affected the expression of genes associated with JAK/STAT signalling and pluripotency. Further, the treatment significantly (P < 0.05) downregulated BAX and CASP3, and upregulated GATA6 expression in compact morulae. In conclusion, IL-6 supplementation affected the in vitro development of ovine embryos in a dose- and time-dependent manner. The beneficial effect of IL-6 on the development of late-stage embryos was mediated through the changes in gene expressions associated with JAK/STAT signalling, pluripotency, apoptosis and PrE development.

Histone Arginine Methyltransferase CARM1-Mediated H3R26me2 Is Essential for Morula-to-Blastocyst Transition in Pigs

Coactivator-associated arginine methyltransferase 1 (CARM1) is involved in both establishment of first pluripotent lineage and pluripotency maintenance of embryonic stem cells (ESCs) in mice. However, the histone substrates and role of CARM1 in early embryonic development remain largely unknown. Here, we show that CARM1 specifically catalyzes H3R26me2 to promote porcine blastocyst formation. The putative histone substrates of CARM1, including H3R2me2, H3R17me2, and H3R26me2, are present in pig early embryos. The changes of CARM1 mRNA during early embryogenesis parallel that of H3R26me2. Functional studies using a combinational approach of chemical inhibition and RNA interference (RNAi) showed that catalytic activity inhibition of CARM1 protein or knockdown (KD) of CARM1 mRNA did not alter the levels of both H3R2me2 and H3R17me2, but significantly reduced H3R26me2 levels in porcine embryos. Furthermore, CARM1 inhibition or KD did not affect embryo development to the 2-cell, 4-cell, 8-cell, and morula stages, but severely compromised blastocyst development. CARM1 knocked down embryos that developed to the blastocyst stage had fewer total cells, inner cell mass (ICM), and trophectoderm (TE) cells. Mechanistically, single embryo RNA-sequencing analysis revealed that CARM1 KD altered the transcriptome characterized by downregulation of key genes associated with Hippo and PI3K-AKT signaling pathways. Taken together, these results demonstrate that CARM1 specifically catalyzes H3R26me2 in porcine embryos and participates in blastocyst development.

Genotypic divergence in mouse oocyte transcriptomes: possible pathways to hybrid vigor impacting fertility and embryogenesis

What causes hybrid vigor phenotypes in mammalian oocytes and preimplantation embryos? Answering this question should provide new insight into determinants of oocyte and embryo quality and infertility. Hybrid vigor could arise through a variety of mechanisms, many of which must operate through posttranscriptional mechanisms affecting oocyte mRNA accumulation, stability, translation, and degradation. The differential regulation of such mRNAs may impact essential pathways and functions within the oocyte. We conducted in-depth transcriptome comparisons of immature and mature oocytes of C57BL/6J and DBA/2J inbred strains and C57BL/6J × DBA/2J F1 (BDF1) hybrid oocytes with RNA sequencing, combined with novel computational methods of analysis. We observed extensive differences in mRNA expression and regulation between parental inbred strains and between inbred and hybrid genotypes, including mRNAs encoding proposed markers of oocyte quality. Unique BDF1 oocyte characteristics arise through a combination of additive dominance and incomplete dominance features in the transcriptome, with a lesser degree of transgressive mRNA expression. Special features of the BDF1 transcriptome most prominently relate to histone expression, mitochondrial function, and oxidative phosphorylation. The study reveals the major underlying mechanisms that contribute to superior properties of hybrid oocytes in a mouse model.

Long non-coding RNAs involved in the regulatory network during porcine pre-implantation embryonic development and iPSC induction

Long non-coding RNAs (lncRNA) play a key role in the orchestration of transcriptional regulation during development and many other cellular processes. The importance of the regulatory co-expression network was highlighted in the identification of the mechanism of these processes in humans and mice. However, elucidation of the properties of porcine lncRNAs involved in the regulatory network during pre-implantation embryonic development and fibroblast reprogramming to induced pluripotent stem cell (iPSC) has been limited to date. Using a weighted gene co-expression network analysis, we constructed the regulatory network and determined that the novel lncRNAs were functionally involved in key events of embryonic development during the pre-implantation period; moreover, reprogramming could be delineated by a small number of potentially functional modules of co-expressed genes. These findings indicate that lncRNAs may be involved in the transcriptional regulation of zygotic genome activation, first lineage segregation and somatic reprogramming to pluripotency. Furthermore, we performed a conservation and synteny analysis with the significant lncRNAs involved in these vital events and validated the results via experimental assays. In summary, the current findings provide a valuable resource to dissect the protein coding gene and lncRNA regulatory networks that underlie the progressive development of embryos and somatic reprogramming.

Different co-culture systems have the same impact on bovine embryo transcriptome

During the last few years, several co-culture systems using either BOEC or VERO feeder cells have been developed to improve bovine embryo development and these systems give better results at high oxygen concentration (20%). In parallel, the SOF medium, used at 5% O2, has been developed to mimic the oviduct fluid. Since 2010s, the SOF medium has become popular in improving bovine embryo development and authors have started to associate this medium to co-culture systems. Nevertheless, little is known about the putative benefit of this association on early development. To address this question, we have compared embryo transcriptomes in four different culture conditions: SOF with BOEC or VERO at 20% O2, and SOF without feeders at 5% or 20% O2. Embryos have been analyzed at 16-cell and blastocyst stages. Co-culture systems did not improve the developmental rate when compared to 5% O2. Direct comparison of the two co-culture systems failed to highlight major differences in embryo transcriptome at both developmental stages. Both feeder cell types appear to regulate the same cytokines and growth factors pathways, and thus to influence embryo physiology in the same way. In blastocysts, when compared to culture in SOF at 5% O2, BOEC or VERO seems to reduce cell survival and differentiation by, at least, negatively regulating STAT3 and STAT5 pathways. Collectively, in SOF medium both blastocysts rate and embryo transcriptome suggest no influence of feeder origin on bovine early development and no beneficial impact of co-culture systems when compared to 5% O2.

Female tract cytokines and developmental programming in embryos

In the physiological situation, cytokines are pivotal mediators of communication between the maternal tract and the embryo. Compelling evidence shows that cytokines emanating from the oviduct and uterus confer a sophisticated mechanism for 'fine-tuning' of embryo development, influencing a range of cellular events from cell survival and metabolism, through division and differentiation, and potentially exerting long-term impact through epigenetic remodelling. The balance between survival agents, including GM-CSF, CSF1, LIF, HB-EGF and IGFII, against apoptosis-inducing factors such as TNFα, TRAIL and IFNg, influence the course of preimplantation development, causing embryos to develop normally, adapt to varying maternal environments, or in some cases to arrest and undergo demise. Maternal cytokine-mediated pathways help mediate the biological effects of embryo programming, embryo plasticity and adaptation, and maternal tract quality control. Thus maternal cytokines exert influence not only on fertility and pregnancy progression but on the developmental trajectory and health of offspring. Defining a clear understanding of the biology of cytokine networks influencing the embryo is essential to support optimal outcomes in natural and assisted conception.

Survival response of hippocampal neurons under low oxygen conditions induced by Hippophae rhamnoides is associated with JAK/STAT signaling

Janus activated kinase/signal transducers and activators of transcription (JAK/STATs) pathway are associated with various neuronal functions including cell survival and inflammation. In the present study, it is hypothesized that protective action of aqueous extract of Hippophae rhamnoides in hippocampal neurons against hypoxia is mediated via JAK/STATs. Neuronal cells exposed to hypoxia (0.5% O2) display higher reactive oxygen species with compromised antioxidant status compared to unexposed control cells. Further, these cells had elevated levels of pro-inflammatory cytokines; tumor necrosis factor α and interleukin 6 and nuclear factor κappa B. Moreover, the expression of JAK1 was found to be highly expressed with phosphorylation of STAT3 and STAT5. Cells treated with JAK1, STAT3 and STAT5 specific inhibitors resulted in more cell death compared to hypoxic cells. Treatment of cells with extract prevented oxidative stress and inflammatory response associated with hypoxia. The extract treated cells had more cell survival than hypoxic cells with induction of JAK1 and STAT5b. Cells treated with extract having suppressed JAK1 or STAT3 or STAT5 expression showed reduced cell viability than the cell treated with extract alone. Overall, the findings from these studies indicate that the aqueous extract of Hippophae rhamnoides treatment inhibited hypoxia induced oxidative stress by altering cellular JAK1, STAT3 and STAT5 levels thereby enhancing cellular survival response to hypoxia and provide a basis for possible use of aqueous extract of Hippophae rhamnoides in facilitating tolerance to hypoxia.

Expression pattern of STAT5A gene during early bovine embryogenesis

Growth hormone (GH) plays an important role in early embryo development. It has been shown to activate multiple pathways, the most comprehensively studied being the STAT/JAK (Signal transducers and activators of transcription/Janus kinase) pathway. The objective of the present study was to investigate STAT5A gene expression during early bovine embryogenesis. Real-time polymerase chain reaction (RT-PCR) was used to measure the abundance of STAT5A transcripts. The mRNA was present at all stages of preimplantation bovine embryos investigated. The most abundant STAT5A expression occurred at the 2-cell stage. Expression was markedly reduced between the 4-cell and 8-cell stages, coinciding with the known time of embryo genome activation and loss of maternal mRNAs. This finding suggests that the embryonic STAT5A gene is primarily activated by maternal gene products.

Suppressor of cytokine signalling-6 promotes neurite outgrowth via JAK2/STAT5-mediated signalling pathway, involving negative feedback inhibition

Background

Suppressors of cytokine signalling (SOCS) protein family are key regulators of cellular responses to cytokines and play an important role in the nervous system. The SOCS6 protein, a less extensively studied SOCS family member, has been shown to induce insulin resistance in the retina and promote survival of the retinal neurons. But no reports are available about the role of SOCS6 in neuritogenesis. In this study, we examined the role of SOCS6 in neurite outgrowth and neuronal cell signalling.

Methodology/Principal Findings

The effect of SOCS6 in neural stem cells differentiation was studied in neural stem cells and PC12 cell line. Highly elevated levels of SOCS6 were found upon neural cell differentiation both at the mRNA and protein level. Furthermore, SOCS6 over-expression lead to increase in neurite outgrowth and degree of branching, whereas SOCS6 knockdown with specific siRNAs, lead to a significant decrease in neurite initiation and extension. Insulin-like growth factor-1 (IGF-1) stimulation which enhanced neurite outgrowth of neural cells resulted in further enhancement of SOCS6 expression. Jak/Stat (Janus Kinase/Signal Transducer And Activator Of Transcription) pathway was found to be involved in the SOCS6 mediated neurite outgrowth. Bioinformatics study revealed presence of putative Stat binding sites in the SOCS6 promoter region. Transcription factors Stat5a and Stat5b were involved in SOCS6 gene upregulation leading to neuronal differentiation. Following differentiation, SOCS6 was found to form a ternary complex with IGFR (Insulin Like Growth Factor-1 Receptor) and JAK2 which acted in a negative feedback loop to inhibit pStat5 activation.

Conclusion/Significance

The current paradigm for the first time states that SOCS6, a SOCS family member, plays an important role in the process of neuronal differentiation. These findings define a novel molecular mechanism for Jak2/Stat5 mediated SOCS6 signalling.

Ouabain stimulates a Na+/K+-ATPase-mediated SFK-activated signalling pathway that regulates tight junction function in the mouse blastocyst

The Na(+)/K(+)-ATPase plays a pivotal role during preimplantation development; it establishes a trans-epithelial ionic gradient that facilitates the formation of the fluid-filled blastocyst cavity, crucial for implantation and successful pregnancy. The Na(+)/K(+)-ATPase is also implicated in regulating tight junctions and cardiotonic steroid (CTS)-induced signal transduction via SRC. We investigated the expression of SRC family kinase (SFK) members, Src and Yes, during preimplantation development and determined whether SFK activity is required for blastocyst formation. Embryos were collected following super-ovulation of CD1 or MF1 female mice. RT-PCR was used to detect SFK mRNAs encoding Src and Yes throughout preimplantation development. SRC and YES protein were localized throughout preimplantation development. Treatment of mouse morulae with the SFK inhibitors PP2 and SU6656 for 18 hours resulted in a reversible blockade of progression to the blastocyst stage. Blastocysts treated with 10(-3) M ouabain for 2 or 10 minutes and immediately immunostained for phosphorylation at SRC tyr418 displayed reduced phosphorylation while in contrast blastocysts treated with 10(-4) M displayed increased tyr418 fluorescence. SFK inhibition increased and SFK activation reduced trophectoderm tight junction permeability in blastocysts. The results demonstrate that SFKs are expressed during preimplantation development and that SFK activity is required for blastocyst formation and is an important mediator of trophectoderm tight junction permeability.

Characterizing the developmental pathways TTF-1, NKX2-8, and PAX9 in lung cancer

We investigated the clinical implications of lung developmental transcription factors (TTF-1, NKX2-8, and PAX9) that we recently discovered as cooperating oncogenes activated by way of gene amplification at chromosome 14q13 in lung cancer. Using stable transfectants of human bronchial epithelial cells, RNA expression profiles (signatures) representing activation of the biological pathways defined by each of the 3 genes were determined and used to risk stratify a non-small-cell lung cancer (NSCLC) clinical data set consisting of 91 early stage tumors. Coactivation of the TTF-1 and NKX2-8 pathways identified a cluster of patients with poor survival, representing approximately 20% of patients with early stage NSCLC, whereas activation of individual pathways did not reveal significant prognostic power. Importantly, the poor prognosis associated with coactivation of TTF-1 and NKX2-8 was validated in 2 other independent clinical data sets. Furthermore, lung cancer cell lines showing coactivation of the TTF-1 and NKX2-8 pathways were shown to exhibit resistance to cisplatin, the standard of care for the treatment of NSCLC. This suggests that the cohort of patients with coactivation of TTF-1 and NKX2-8 pathways appears to be resistant to standard cisplatin therapy, suggesting the need for alternative therapies in this cohort of high-risk patients.

Monoallelic maternal expression of STAT5A affects embryonic survival in cattle

Background

Reproductive disorders and infertility are surprisingly common in the human population as well as in other species. The decrease in fertility is a major cause of cow culling and economic loss in the dairy herd. The conception rate has been declining for the past 30–50 years. Conception rate is the product of fertilization and embryonic survival rates. In a previous study, we have identified associations of several single nucleotide polymorphisms (SNPs) in the signal transducer and activator 5A (STAT5A) with fertilization and survival rates in an in vitro experimental system. The objectives of this study are to fine map the STAT5A region in a search for causative mutations and to investigate the parent of origin expression of this gene.

Results

We have performed a total of 5,222 fertilizations and produced a total of 3,696 in vitro fertilized embryos using gametes from 440 cows and eight bulls. A total of 37 SNPs were developed in a 63.4-kb region of genomic sequence that includes STAT5A, STAT3, and upstream and downstream sequences of these genes. SNP153137 (G/C) in exon 8 of STAT5A was associated with a significant variability in embryonic survival and fertilization rate compared to all other examined SNPs. Expression analysis revealed that STAT5A is primarily monoallelically expressed in early embryonic stages but biallelically expressed in later fetal stages. Furthermore, the occurrence of monoallelic maternal expression of STAT5A was significantly higher in blastocysts, while paternal expression was more frequent in degenerative embryos.

Conclusion

Our results imply that STAT5A affects embryonic survival in a manner influenced by developmental stage and allele parent of origin.

Signaling pathways and preimplantation development of mammalian embryos

The mammalian preimplantation embryo is a critical and unique stage in embryonic development. This stage includes a series of crucial events: the transition from oocyte to embryo, the first cell divisions, and the establishment of cellular contacts. These events are regulated by multiple signal-transduction pathways. In this article we describe patterns of stage-specific expression in several signal-transduction pathways and try to give a profile of the signaling transduction network in preimplantation development of mammalian embryo.