Acute loss of Cited2 impairs Nanog expression and decreases self-renewal of mouse embryonic stem cells

Screening Preeclampsia Genes and the Effects of CITED2 on Trophoblastic Function

Purpose

Preeclampsia (PE) is a serious complication of obstetrics and represents a significant challenge in terms of understanding its underlying mechanism. It has been shown that a number of disorders involve dysregulation of the CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 2 (CITED2). However, the relationship between PE and CITED2 is still mostly unclear. This work aimed to confirm the hub genes linked to PE and explore the roles of CITED2 in trophoblast using experimental and bioinformatic methods.

Methods

To determine the hub genes, bioinformatics research was performed on two datasets from the Gene Expression Omnibus (GEO) public database. Immune infiltration analysis and enrichment analysis were also used to identify the related pathways and immune cells. PCR and WB were then used to validate the mRNA and protein levels of CITED2 in the PE samples. Finally, the expression of CITED2 was knocked down using siRNA to investigate the function of CITED2 in trophoblast development in vitro.

Results

The study's findings showed that the NOTCH signaling pathways, glycolysis, and hypoxia were the main areas of enrichment for the six PE-related genes that were tested. The results of immune infiltration suggest that activated NK cells and regulatory T cells may play an important role in this process. CITED2 was significantly upregulated in the PE placenta. In functional tests, the knockdown of CITED2 may enhance apoptosis while suppressing migration, invasion, and proliferation of cells.

Conclusion

This study offers important proof that CITED2 influences trophoblast cell function and may one day be a therapeutic target for PE.

Charting the Path: Navigating Embryonic Development to Potentially Safeguard against Congenital Heart Defects

Congenital heart diseases (CHDs) are structural or functional defects present at birth due to improper heart development. Current therapeutic approaches to treating severe CHDs are primarily palliative surgical interventions during the peri- or prenatal stages, when the heart has fully developed from faulty embryogenesis. However, earlier interventions during embryonic development have the potential for better outcomes, as demonstrated by fetal cardiac interventions performed in utero, which have shown improved neonatal and prenatal survival rates, as well as reduced lifelong morbidity. Extensive research on heart development has identified key steps, cellular players, and the intricate network of signaling pathways and transcription factors governing cardiogenesis. Additionally, some reports have indicated that certain adverse genetic and environmental conditions leading to heart malformations and embryonic death may be amendable through the activation of alternative mechanisms. This review first highlights key molecular and cellular processes involved in heart development. Subsequently, it explores the potential for future therapeutic strategies, targeting early embryonic stages, to prevent CHDs, through the delivery of biomolecules or exosomes to compensate for faulty cardiogenic mechanisms. Implementing such non-surgical interventions during early gestation may offer a prophylactic approach toward reducing the occurrence and severity of CHDs.

CITED2 coordinates key hematopoietic regulatory pathways to maintain the HSC pool in both steady-state hematopoiesis and transplantation

Hematopoietic stem cells (HSCs) reside at the apex of the hematopoietic differentiation hierarchy and sustain multilineage hematopoiesis. Here, we show that the transcriptional regulator CITED2 is essential for life-long HSC maintenance. While hematopoietic-specific Cited2 deletion has a minor impact on steady-state hematopoiesis, Cited2-deficient HSCs are severely depleted in young mice and fail to expand upon aging. Moreover, although they home normally to the bone marrow, they fail to reconstitute hematopoiesis upon transplantation. Mechanistically, CITED2 is required for expression of key HSC regulators, including GATA2, MCL-1, and PTEN. Hematopoietic-specific expression of anti-apoptotic MCL-1 partially rescues the Cited2-deficient HSC pool and restores their reconstitution potential. To interrogate the Cited2→Pten pathway in HSCs, we generated Cited2;Pten compound heterozygous mice, which had a decreased number of HSCs that failed to reconstitute the HSC compartment. In addition, CITED2 represses multiple pathways whose elevated activity causes HSC exhaustion. Thus, CITED2 promotes pathways necessary for HSC maintenance and suppresses those detrimental to HSC integrity.

Role of CITED2 in stem cells and cancer

Cbp/P300 interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) is a transcription co-factor that interacts with several other transcription factors and co-factors, and serves critical roles in fundamental cell processes, including proliferation, apoptosis, differentiation, migration and autophagy. The interacting transcription factors or co-factors of CITED2 include LIM homeobox 2, transcription factor AP-2, SMAD2/3, peroxisome proliferator-activated receptor γ, oestrogen receptor, MYC, Nucleolin and p300/CBP, which regulate downstream gene expression, and serve important roles in the aforementioned fundamental cell processes. Emerging evidence has demonstrated that CITED2 serves an essential role in embryonic and adult tissue stem cells, including hematopoietic stem cells and tendon-derived stem/progenitor cells. Additionally, CITED2 has been reported to function in different types of cancer. Although the functions of CITED2 in different tissues vary depending on the interaction partner, altered CITED2 expression or altered interactions with transcription factors or co-factors result in alterations of fundamental cell processes, and may affect stem cell maintenance or cancer cell survival. The aim of this review is to summarize the molecular mechanisms of CITED2 function and how it serves a role in stem cells and different types of cancer based on the currently available literature.

CITED2 and the modulation of the hypoxic response in cancer

CITED2 (CBP/p300-interacting transactivator with Glu/Asp-rich C-terminal domain, 2) is a ubiquitously expressed protein exhibiting a high affinity for the CH1 domain of the transcriptional co-activators CBP/p300, for which it competes with hypoxia-inducible factors (HIFs). CITED2 is particularly efficient in the inhibition of HIF-1α-dependent transcription in different contexts, ranging from organ development and metabolic homeostasis to tissue regeneration and immunity, being also potentially involved in various other physiological processes. In addition, CITED2 plays an important role in inhibiting HIF in some diseases, including kidney and heart diseases and type 2-diabetes. In the particular case of cancer, CITED2 either functions by promoting or suppressing cancer development depending on the context and type of tumors. For instance, CITED2 overexpression promotes breast and prostate cancers, as well as acute myeloid leukemia, while its expression is downregulated to sustain colorectal cancer and hepatocellular carcinoma. In addition, the role of CITED2 in the maintenance of cancer stem cells reveals its potential as a target in non-small cell lung carcinoma and acute myeloid leukemia, for example. But besides the wide body of evidence linking both CITED2 and HIF signaling to carcinogenesis, little data is available regarding CITED2 role as a negative regulator of HIF-1α specifically in cancer. Therefore, comprehensive studies exploring further the interactions of these two important mediators in cancer-specific models are sorely needed and this can potentially lead to the development of novel targeted therapies.

Exogenous WNT5A and WNT11 proteins rescue CITED2 dysfunction in mouse embryonic stem cells and zebrafish morphants

Mutations and inadequate methylation profiles of CITED2 are associated with human congenital heart disease (CHD). In mouse, Cited2 is necessary for embryogenesis, particularly for heart development, and its depletion in embryonic stem cells (ESC) impairs cardiac differentiation. We have now determined that Cited2 depletion in ESC affects the expression of transcription factors and cardiopoietic genes involved in early mesoderm and cardiac specification. Interestingly, the supplementation of the secretome prepared from ESC overexpressing CITED2, during the onset of differentiation, rescued the cardiogenic defects of Cited2-depleted ESC. In addition, we demonstrate that the proteins WNT5A and WNT11 held the potential for rescue. We also validated the zebrafish as a model to investigate cited2 function during development. Indeed, the microinjection of morpholinos targeting cited2 transcripts caused developmental defects recapitulating those of mice knockout models, including the increased propensity for cardiac defects and severe death rate. Importantly, the co-injection of anti-cited2 morpholinos with either CITED2 or WNT5A and WNT11 recombinant proteins corrected the developmental defects of Cited2-morphants. This study argues that defects caused by the dysfunction of Cited2 at early stages of development, including heart anomalies, may be remediable by supplementation of exogenous molecules, offering the opportunity to develop novel therapeutic strategies aiming to prevent CHD.

Cited2 regulates proliferation and survival in young and old mouse cardiac stem cells

Background

Cardiac stem cells (CSCs) exhibit age-dependent characteristics. Cited2 has been implicated in the regulation of heart development; however, there is little known about how Cited2 affects CSC aging.

Results

Cited2 mRNA and protein level was downregulated in aging heart tissue and CSCs. Old (O)-CSCs showed decreased differentiation and proliferation capacities as compared to Young (Y)-CSCs, the decrease in cell proliferation, increase in apoptosis, and cell cycle arrest in G0/G1 phase in CSCs are mediated by knocdown CITED2expression in (Y)-CSCs.

Conclusions

Cited2 plays an important role in cell cycle progression and in maintaining the balance between CSC proliferation and apoptosis in the process of aging without influencing cell fate decisions. These findings have important implications for cell-based therapies for heart repair.

Electronic supplementary material

The online version of this article (10.1186/s12860-019-0207-2) contains supplementary material, which is available to authorized users.

Bioenergetic Changes Underline Plasticity of Murine Embryonic Stem Cells

Murine embryonic stem cells (mESCs) are endowed by a time-dependent window of plasticity during their early commitment steps. Indeed, while mESCs deprived of leukemia inhibitory factor (LIF) for 24 hours revert to their naive pluripotent state after subsequent LIF readdition, cells deprived of LIF for 48 hours are no longer efficient in reverting, upon LIF addition, and undergo irreversible differentiation. We investigated undisclosed bioenergetic profiles of early mESC-derived committed cells versus their undifferentiated states in order to reveal specific bioenergetic changes associated with mESC plasticity. Multiparametric bioenergetic analysis revealed that pluripotent (+LIF) and reversibly committed cells (-LIF24h) are energetically flexible, depending on both oxidative phosphorylation (OXPHOS) and glycolysis. They exhibit high mitochondrial respiration in the presence of the main energetic substrates and can also rely on glycolysis in the presence of OXPHOS inhibitor. Inhibition of the glycolysis or mitochondrial respiration does not change drastically the expression of pluripotency genes, which remain well expressed. In addition, cells treated with these inhibitors keep their capacity to differentiate efficiently upon embryoid bodies formation. Transition from metabolically active mESCs to irreversibly committed cells is associated with a clear change in mitochondrial network morphology, to an increase of adenosine triphosphate (ATP) produced from glycolysis and a decline of ATP turnover and of the mitochondrial activity without change in the mitochondrial mass. Our study pointed that plasticity window of mESCs is associated with the bivalent energetic metabolism and potency to shift to glycolysis or OXPHOS on demand. LIF removal provokes glycolytic metabolic orientation and consecutive loss of the LIF-dependent reversion of cells to the pluripotent state. Stem Cells 2019;37:463-475.

Insights into the Etiology of Mammalian Neural Tube Closure Defects from Developmental, Genetic and Evolutionary Studies

The human neural tube defects (NTD), anencephaly, spina bifida and craniorachischisis, originate from a failure of the embryonic neural tube to close. Human NTD are relatively common and both complex and heterogeneous in genetic origin, but the genetic variants and developmental mechanisms are largely unknown. Here we review the numerous studies, mainly in mice, of normal neural tube closure, the mechanisms of failure caused by specific gene mutations, and the evolution of the vertebrate cranial neural tube and its genetic processes, seeking insights into the etiology of human NTD. We find evidence of many regions along the anterior–posterior axis each differing in some aspect of neural tube closure—morphology, cell behavior, specific genes required—and conclude that the etiology of NTD is likely to be partly specific to the anterior–posterior location of the defect and also genetically heterogeneous. We revisit the hypotheses explaining the excess of females among cranial NTD cases in mice and humans and new developments in understanding the role of the folate pathway in NTD. Finally, we demonstrate that evidence from mouse mutants strongly supports the search for digenic or oligogenic etiology in human NTD of all types.

The transcription factor Vezf1 represses the expression of the antiangiogenic factor Cited2 in endothelial cells

Formation of the vasculature by angiogenesis is critical for proper development, but angiogenesis also contributes to the pathogenesis of various disorders, including cancer and cardiovascular diseases. Vascular endothelial zinc finger 1 (Vezf1), is a Krüppel-like zinc finger protein that plays a vital role in vascular development. However, the mechanism by which Vezf1 regulates this process is not fully understood. Here, we show that Vezf1^−/− mouse embryonic stem cells (ESC) have significantly increased expression of a stem cell factor, Cbp/p300-interacting transactivator 2 (Cited2). Compared with WT ESCs, Vezf1^−/− ESCs inefficiently differentiated into endothelial cells (ECs), which exhibited defects in the tube-formation assay. These defects were due to reduced activation of EC-specific genes concomitant with lower enrichment of histone 3 acetylation at Lys²⁷ (H3K27) at their promoters. We hypothesized that overexpression of Cited2 in Vezf1^−/− cells sequesters P300/CBP away from the promoters of proangiogenic genes and thereby contributes to defective angiogenesis in these cells. This idea was supported by the observation that shRNA-mediated depletion of Cited2 significantly reduces the angiogenic defects in the Vezf1^−/− ECs. In contrast to previous studies that have focused on the role of Vezf1 as a transcriptional activator of proangiogenic genes, our findings have revealed a role for Vezf1 in modulating the expression of the antiangiogenic factor Cited2. Vezf1 previously has been characterized as an insulator protein, and our results now provide insights into the mechanism, indicating that Vezf1 can block inappropriate, nonspecific interactions of promoters with cis-located enhancers, preventing aberrant promoter activation.

The SIN3A/HDAC Corepressor Complex Functionally Cooperates with NANOG to Promote Pluripotency

Although SIN3A is required for the survival of early embryos and embryonic stem cells (ESCs), the role of SIN3A in the maintenance and establishment of pluripotency remains unclear. Here, we find that the SIN3A/HDAC corepressor complex maintains ESC pluripotency and promotes the generation of induced pluripotent stem cells (iPSCs). Members of the SIN3A/HDAC corepressor complex are enriched in an extended NANOG interactome and function in transcriptional coactivation in ESCs. We also identified a critical role for SIN3A and HDAC2 in efficient reprogramming of somatic cells. Mechanistically, NANOG and SIN3A co-occupy transcriptionally active pluripotency genes in ESCs and also co-localize extensively at their genome-wide targets in pre-iPSCs. Additionally, both factors are required to directly induce a synergistic transcriptional program wherein pluripotency genes are activated and reprogramming barrier genes are repressed. Our findings indicate a transcriptional regulatory role for a major HDAC-containing complex in promoting pluripotency.

PRDM15 safeguards naive pluripotency by transcriptionally regulating WNT and MAPK-ERK signaling

The transcriptional network acting downstream of LIF, WNT and MAPK-ERK to stabilize mouse embryonic stem cells (ESCs) in their naive state has been extensively characterized. However, the upstream factors regulating these three signaling pathways remain largely uncharted. PR-domain-containing proteins (PRDMs) are zinc-finger sequence-specific chromatin factors that have essential roles in embryonic development and cell fate decisions. Here we characterize the transcriptional regulator PRDM15, which acts independently of PRDM14 to regulate the naive state of mouse ESCs. Mechanistically, PRDM15 modulates WNT and MAPK-ERK signaling by directly promoting the expression of Rspo1 (R-spondin1) and Spry1 (Sprouty1). Consistent with these findings, CRISPR-Cas9-mediated disruption of PRDM15-binding sites in the Rspo1 and Spry1 promoters recapitulates PRDM15 depletion, both in terms of local chromatin organization and the transcriptional modulation of these genes. Collectively, our findings uncover an essential role for PRDM15 as a chromatin factor that modulates the transcription of upstream regulators of WNT and MAPK-ERK signaling to safeguard naive pluripotency.

Ectopic expression of CITED2 prior to reprogramming, promotes and homogenises the conversion of somatic cells into induced pluripotent stem cells

Cited2 plays crucial roles in mouse embryonic stem cells self-renewal, the initiation of the somatic reprogramming process into induced pluripotent stem cells (iPSC) and the suppression of cell senescence. Here, we investigated the potential of CITED2 expression in combination with the Oct4, Sox2, Klf4 and c-Myc factors for reprogramming of primary mouse embryonic fibroblasts (MEF) at passage 2 and 4. The ectopic CITED2 expression in primary MEF prior to the onset of the reprogramming process, generated iPSC with less variability in the expression of endogenous pluripotency-related genes. In contrast, part of the MEF reprogrammed without ectopic expression of CITED2 at passage 4 originated partially reprogrammed iPSC or pre-iPSC. However, the overexpression of CITED2 in the pre-iPSC was insufficient to complete the reprogramming process into iPSC. These results indicated that ectopic CITED2 expression at the onset of the reprogramming process in combination with the reprogramming factors promotes a complete and homogeneous conversion of somatic cells into iPSC.

Downregulation of CITED2 contributes to TGFβ-mediated senescence of tendon-derived stem cells

Tendon-derived stem cells (TDSCs) are multipotent adult stem cells with potential applications in tendon and tendon-bone junction repair. However, cellular characteristics change during in vitro passaging. Therefore, elucidation of the molecular and cellular mechanisms of tendon aging will be essential for the development of TDSC-based therapies. The aim of this study is to investigate the effect of CITED2, a nuclear regulator and transforming growth factor β2 (TGFβ2) on TDSC proliferation and senescence by comparing cells derived from Achilles tendon biopsies of young individuals (Y-TDSC) with those of older patients (O-TDSC). Our results showed that CITED2 mRNA and protein expression levels were significantly higher in Y-TDSCs than in O-TDSCs and O-TDSCs displayed decreased proliferation and increased senescence compared with Y-TDSCs. Furthermore, high levels of CITED2 protein expression in Y-TDSCs correlated with the downregulation of SP1 and p21 and the upregulation of MYC, potentially indicating the mechanism by which CITED2 upregulates TDSC proliferation. TGFβ2 was found to downregulate the expression of the CITED2 gene and knockdown of CITED2 abolished the effect of TGFβ2 on TDSC proliferation and senescence. Thus, the downregulation of CITED2 contributes to TGFβ-mediated senescence providing an insight into the molecular and cellular mechanisms that contribute to tendon aging and degeneration. Our findings may aid the development of cell-based therapies for tendon repair.

CITED2 in breast carcinoma as a potent prognostic predictor associated with proliferation, migration and chemoresistance

CITED2 (Cbp/p300‐interacting transactivator, with Glu/Asp‐rich carboxy‐terminal domain, 2) is a member of the CITED family and is involved in various cellular functions during development and differentiation. Mounting evidence suggests the importance of CITED in the progression of human malignancies, but the significance of CITED2 protein has not yet been examined in breast carcinoma. Therefore, in the present study, we examined the clinical significance and the biological functions of CITED2 in breast carcinoma by immunohistochemistry and in vitro study. CITED2 immunoreactivity was detected in breast carcinoma tissues, and it was significantly higher compared to those in morphologically normal mammary glands. CITED2 immunoreactivity was significantly associated with stage, pathological T factor, lymph node metastasis, histological grade, HER2 and Ki‐67, and inversely correlated with estrogen receptor. Moreover, the immunohistochemical CITED2 status was significantly associated with increased incidence of recurrence and breast cancer‐specific death of the breast cancer patients, and multivariate analyses demonstrated CITED2 status as an independent worse prognostic factor for disease‐free and breast cancer‐specific survival. Subsequent in vitro experiments showed that CITED2 expression significantly increased proliferation activity and migration property in MCF‐7and S KBR‐3 breast carcinoma cells. Moreover, CITED2 caused chemoresistance to epirubicin and 5‐fluorouracil, but not paclitaxel, in these cells, and it inhibited p53 accumulation after 5‐fluorouracil treatment in MCF‐7 cells. These results suggest that CITED2 plays important roles in the progression and chemoresistance of breast carcinoma and that CITED2 status is a potent prognostic factor in breast cancer patients.

CITED2 Cooperates with ISL1 and Promotes Cardiac Differentiation of Mouse Embryonic Stem Cells

The transcriptional regulator CITED2 is essential for heart development. Here, we investigated the role of CITED2 in the specification of cardiac cell fate from mouse embryonic stem cells (ESC). The overexpression of CITED2 in undifferentiated ESC was sufficient to promote cardiac cell emergence upon differentiation. Conversely, the depletion of Cited2 at the onset of differentiation resulted in a decline of ESC ability to generate cardiac cells. Moreover, loss of Cited2 expression impairs the expression of early mesoderm markers and cardiogenic transcription factors (Isl1, Gata4, Tbx5). The cardiogenic defects in Cited2-depleted cells were rescued by treatment with recombinant CITED2 protein. We showed that Cited2 expression is enriched in cardiac progenitors either derived from ESC or mouse embryonic hearts. Finally, we demonstrated that CITED2 and ISL1 proteins interact physically and cooperate to promote ESC differentiation toward cardiomyocytes. Collectively, our results show that Cited2 plays a pivotal role in cardiac commitment of ESC.

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Overexpression of CITED2 in ESC promotes cardiogenesis upon differentiation

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Cited2 depletion reduces ESC ability to generate cardiac cells

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Cited2 expression is enriched in cardiac progenitors

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CITED2 and ISL1 cooperate to promote ESC differentiation toward cardiomyocytes

FBXL5 modulates HIF-1α transcriptional activity by degradation of CITED2

CITED2 is a ubiquitously expressed nuclear protein exhibiting a high affinity for the cysteine-histidine-rich domain 1 (CH1) of the transcriptional co-activators CBP/p300. CITED2 is particularly efficient in the inhibition of the hypoxia-inducible factor-1α (HIF-1α) dependent transcription by competing with it for the interaction with the CH1 domain. Here we report a direct and specific interaction between CITED2 and the F-box and leucine rich repeat protein 5 (FBXL5), a substrate adaptor protein which is part of E3 ubiquitin ligase complexes mediating protein degradation by the proteasome. We demonstrated that depletion of FBXL5 by RNA interference led to an increase of CITED2 protein levels. Conversely, overexpression of FBXL5 caused the decrease of CITED2 protein levels in a proteasome-dependent manner, and impaired the interaction between CITED2 and the CH1 domain of p300 in living cells. In undifferentiated mouse embryonic stem cells, the overexpression of FBXL5 also reduced Cited2 protein levels. Finally, we evidenced that FBXL5 overexpression and the consequent degradation of CITED2 enabled the transcriptional activity of the N-terminal transactivation domain of HIF-1α. Collectively, our results highlighted a novel molecular interaction between CITED2 and FBXL5, which might regulate the steady state CITED2 protein levels and contribute to the modulation of gene expression by HIF-1α.