Determine Cell Fate Research Articles

Calcium signaling from damaged lysosomes induces cytoprotective stress granules.

Lysosomal damage induces stress granule (SG) formation. However, the importance of SGs in determining cell fate and the precise mechanisms that mediate SG formation in response to lysosomal damage remain unclear. Here, we describe a novel calcium-dependent pathway controlling SG formation, which promotes cellsurvival during lysosomal damage. Mechanistically, the calcium-activated protein ALIX transduces lysosomal damage signals to SG formation by controlling eIF2α phosphorylation after sensing calcium leakage. ALIX enhances eIF2α phosphorylation by promoting the association between PKR and its activator PACT, with galectin-3 inhibiting this interaction; these regulatory events occur on damaged lysosomes. We further find that SG formation plays a crucial role in promoting cell survival upon lysosomal damage caused by factors such as SARS-CoV-2ORF3a, adenovirus, malarial pigment, proteopathic tau, or environmental hazards. Collectively, these data provide insights into the mechanism of SG formation upon lysosomal damage and implicate it in diseases associated with damaged lysosomes and SGs.

Abstract 4120919: Cell physiology and multi-omics analysis revealed disordered embryogenesis as early as mesoderm specification in models of Holt-Oram Syndrome

Introduction: Congenital heart diseases (CHDs) are the leading cause of childhood morbidity and mortality. The dysregulation of several cardiac transcription factors (TFs) leads to CHD. The coordination of several cardiac TFs is required and essential for cardiogenesis. However, the mechanisms to acquire its cardiac cell identity remain unclear. Hypothesis: Mutant Tbx5 dysregulates embryogenesis during mesoderm specification, prior to its expression in the tissues in Holt-Oram syndrome. Methods: Using cellular physiology and multiomics analysis in both human ES cells and a zebrafish model of TBX5 germline mutation. we evaluated embryonic structure and function, prior to the onset of gastrulation in the context of both heterozygous and homozygous TBX5 mutation. Results: Zebrafish time course transcriptome profiles over gastrulation revealed that loss of Tbx5 impacted transcriptional profiles at the blastula stage. Single cell RNA sequencing (scRNA-seq) on 16243 zebrafish blastula stage cells showed loss of Tbx5 impacted transcription noise at the blastula stage prior to the expression of zygotic Tbx5 with associated effects on chromatin accessibility using omni-assay for transposase-accessible chromatin (ATAC) and evidence of aberrant Wnt signaling even at the blastula stage. Embryo-wide cell structure and function were abnormal in both Tbx5 mutant zebrafish heterozygotes or homozygotes. To validate Undifferentiated human ES cell H3K4me3 Cleavage Under Targets&Release Using Nuclease (CUT&RUN) also showed abnormal Wnt signaling in TBX5 homozygous mutation and TBX5 CUT&RUN showed aberrant mesoderm pathway. Calcium imaging analysis demonstrated the lowest excitation frequency in TBX5 homozygous mutation prior to mesoderm specification. TBX5 homozygous human ES derived mesoderm cells exhibited low expression levels of mesoderm marker genes compared to TBX5 wild type mesoderm. Conclusion: Integrating single cell physiology and multi-omics technologies, we idneifified fundamental dysregulation of embryogenesis in mutant cardiac-restricted gene disorder prior to mesoderm specification or the zygotic expression of the mutant gene. These findings suggest that Tbx5 started to determine cell fate prior to mesoderm specification by altering chromatin accessibilities and histone modification. Tbx5 affected mesoderm differentiation by influencing Wnt signaling and cell physiology.

CCRG-01. MYT1 BLOCKADE AS A NOVEL GLIOMA THERAPEUTICS THROUGH ABROGATIING OF THE G2/M CELL CYCLE CHECKPOINT

Abstract BACKGROUND The cell cycle is tightly regulated by checkpoints, which play a vital role in controlling its progression and timing. Cancer cells exploit the G2/M checkpoint, which serves as a resistance mechanism against genotoxic anticancer treatments, allowing for DNA repair prior to cell division. Manipulating cell cycle timing has emerged as a potential strategy to augment the effectiveness of DNA damage-based therapies. METHODS In this study, we conducted a forward genome-wide CRISPR/Cas9 screening with repeated exposure to the alkylating agent temozolomide (TMZ) to investigate the mechanisms underlying tumor cell survival under genotoxic stress. The screening hits were validated through in patient derived glioma cells and xenografts. RESULTS Our findings revealed that canonical DNA repair pathways, including the Ataxia–telangiectasia mutated (ATM)/Fanconi and mismatch repair, determine cell fate under genotoxic stress. Notably, we identified the critical role of PKMYT1, in ensuring cell survival. Depletion of PKMYT1 led to overwhelming TMZ-induced cytotoxicity in cancer cells. Isobologram analysis demonstrated potent drug synergy between alkylating agents and a Myt1 kinase inhibitor, RP-6306. Mechanistically, inhibiting Myt1 forced G2/M-arrested cells into an unscheduled transition to the mitotic phase without complete resolution of DNA damage. This forced entry into mitosis, along with persistent DNA damage, resulted in severe mitotic abnormalities. Ultimately, these aberrations led to mitotic exit with substantial apoptosis. Preclinical animal studies demonstrated that the combination regimen involving TMZ and RP-6306 prolonged the overall survival of glioma-bearing mice.

Bmgsb is involved in the determination of cell fate by affecting the cell cycle genes in the silk gland of Bombyx mori

Silk gland is the only organ of silkworm that can produce silk protein, which is a natural macromolecular protein complex and widely utilized in various fields such as biomaterials and biomedicine. The development of silk gland and the expression patterns of silk protein crucial for the silk industry. In this study, the function of a transcription factor Bmgsb was investigated with CRISPR/Cas9 and transgenic system. It was found that the homozygous individuals in the Bmgsb KO line experienced spinning failure and pupae death, the AMSG exhibited defects, and the ASG displayed abnormal curvature. These phenotypes were accompanied by increased DNA endoreplication and significantly upregulated expression of fibroin genes in the ASG. RT-qPCR results confirmed significant upregulation of cell cycle-related genes, including cyclin G and cyclin T in the Bmgsb KO line. Furthermore, ectopic expression of Bmgsb in the PSG weakened PSG curvature, inhibited DNA endoreplication, and downregulated the expression of fibroin genes. These findings strongly suggest that Bmgsb plays a crucial role in determining cell fate in the silk gland and regulating the expression of silk protein through the cyclin pathway. Our research provides a theoretical foundation for further studies on organ differentiation and have implications for the silk industry.

Senataxin Attenuates DNA Damage Response Activation and Suppresses Senescence

Oxidative stress, driven by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), induces DNA double-strand breaks (DSBs) that compromise genomic integrity. The DNA Damage Response (DDR), primarily mediated by ATM and ATR kinases, is crucial for recognizing and repairing DSBs. Senataxin (SETX), a DNA/RNA helicase, is critical in resolving R-loops, with mutations in SETX associated with neurodegenerative diseases. This study uncovers a novel function of senataxin in modulating DDR and its impact on cellular senescence. Senataxin is shown to be crucial not only for DSB repair but also for determining cell fate under oxidative stress. SETX knockout cells show impaired DSB repair and prolonged ATM/ATR signaling detected by Western blotting, leading to increased senescence, as indicated by elevated β-galactosidase activity following H2O2 exposure and I-PpoI-induced DSBs. Wild-type cells exhibit higher apoptosis levels compared to SETX knockout cells under H2O2 treatment, suggesting that senataxin promotes apoptosis over senescence in oxidative stress. This indicates that senataxin plays a protective role against the accumulation of senescent cells, potentially mitigating age-related cellular decline and neurodegenerative disease progression. These findings highlight senataxin as a critical mediator in DDR pathways and a potential therapeutic target for conditions where cellular senescence contributes to disease pathology.

Distinct Essentiality of the Mitochondrial Respiratory Chain in Proliferating Cells in Vivo

Mitochondrial respiratory chain (RC) activity is essential for in vivo cell proliferation, particularly in cancer, CD4+ and CD8+ T cells, and endothelial cells involving ATP production and biosynthesis. The RC is essential for the oxidative tricarboxylic acid (TCA) cycle to produce intermediates that funnel into anabolic pathways to synthesize lipids, proteins, and nucleotides. By contrast, mitochondrial respiration has a distinct role in other proliferating cells including regulatory T cells (Tregs) and stem cells whereby mitochondria are dispensable for in vivo cell proliferation but determine cell fate and function through several signaling mechanisms. In this review, we discuss how the mitochondrial RC is an anabolic engine that supports the proliferation of cancer cells, CD4+ and CD8+ T cells, and endothelial cells while mitochondria serve as central hubs that integrate metabolic signals to control Treg and stem cell fate and function in vivo.

Cell-cell interaction determines cell fate of mesoderm-derived cell in tongue development through Hh signaling.

Dysfunction of primary cilia leads to genetic disorder, ciliopathies, which shows various malformations in many vital organs such as brain. Multiple tongue deformities including cleft, hamartoma, and ankyloglossia are also seen in ciliopathies, which yield difficulties in fundamental functions such as mastication and vocalization. Here, we found these tongue anomalies in mice with mutation of ciliary protein. Abnormal cranial neural crest-derived cells (CNCC) failed to evoke Hh signal for differentiation of mesoderm-derived cells into myoblasts, which resulted in abnormal differentiation of mesoderm-derived cells into adipocytes. The ectopic adipose subsequently arrested tongue swelling formation. Ankyloglossia was caused by aberrant cell migration due to lack of non-canonical Wnt signaling. In addition to ciliopathies, these tongue anomalies are often observed as non-familial condition in human. We found that these tongue deformities could be reproduced in wild-type mice by simple mechanical manipulations to disturb cellular processes which were disrupted in mutant mice. Our results provide hints for possible future treatment in ciliopathies.

AXIN1 boosts antiviral response through IRF3 stabilization and induced phase separation

Axis inhibition protein 1 (AXIN1), a scaffold protein interacting with various critical molecules, plays a vital role in determining cell fate. However, its impact on the antiviral innate immune response remains largely unknown. Here, we identify that AXIN1 acts as an effective regulator of antiviral innate immunity against both DNA and RNA virus infections. In the resting state, AXIN1 maintains the stability of the transcription factor interferon regulatory factor 3 (IRF3) by preventing p62-mediated autophagic degradation of IRF3. This is achieved by recruiting ubiquitin-specific peptidase 35 (USP35), which removes lysine (K) 48-linked ubiquitination at IRF3 K366. Upon virus infection, AXIN1 undergoes a phase separation triggered by phosphorylated TANK-binding kinase 1 (TBK1). This leads to increased phosphorylation of IRF3 and a boost in IFN-I production. Moreover, KYA1797K, a small molecule that binds to the AXIN1 RGS domain, enhances the AXIN1-IRF3 interaction and promotes the elimination of various highly pathogenic viruses. Clinically, patients with HBV-associated hepatocellular carcinoma (HCC) who show reduced AXIN1 expression in pericarcinoma tissues have low overall and disease-free survival rates, as well as higher HBV levels in their blood. Overall, our findings reveal how AXIN1 regulates IRF3 signaling and phase separation-mediated antiviral immune responses, underscoring the potential of the AXIN1 agonist KYA1797K as an effective antiviral agent.

Roles of X-box binding protein 1 in liver pathogenesis.

The prevalence of drug-induced liver injury (DILI) and viral liver infections presents significant challenges in modern healthcare and contributes to considerable morbidity and mortality worldwide. Concurrently, metabolic dysfunction-associated fatty liver disease (MAFLD) has emerged as a major public health concern, reflecting the increasing rates of obesity and leading to more severe complications such as fibrosis and hepatocellular carcinoma. X-box binding protein 1 (XBP1) is a distinct transcription factor with a basic-region leucine zipper structure, whose activity is regulated by alternative splicing in response to disruptions in endoplasmic reticulum (ER) homeostasis and the unfolded protein response (UPR) activation. XBP1 interacts with a key signaling component of the highly conserved UPR and is critical in determining cell fate when responding to ER stress in liver diseases. This review aims to elucidate the emerging roles and molecular mechanisms of XBP1 in liver pathogenesis, focusing on its involvement in DILI, viral liver infections, MAFLD, fibrosis/cirrhosis, and liver cancer. Understanding the multifaceted functions of XBP1 in these liver diseases offers insights into potential therapeutic strategies to restore ER homeostasis and mitigate liver damage.

DEWNA: dynamic entropy weight network analysis and its application to the DNA-binding proteome in A549 cells with cisplatin-induced damage.

Cisplatin is one of the most commonly used chemotherapy drugs for treating solid tumors. As a genotoxic agent, cisplatin binds to DNA and forms platinum-DNA adducts that cause DNA damage and activate a series of signaling pathways mediated by various DNA-binding proteins (DBPs), ultimately leading to cell death. Therefore, DBPs play crucial roles in the cellular response to cisplatin and in determining cell fate. However, systematic studies of DBPs responding to cisplatin damage and their temporal dynamics are still lacking. To address this, we developed a novel and user-friendly stand-alone software, DEWNA, designed for dynamic entropy weight network analysis to reveal the dynamic changes of DBPs and their functions. DEWNA utilizes the entropy weight method, multiscale embedded gene co-expression network analysis and generalized reporter score-based analysis to process time-course proteome expression data, helping scientists identify protein hubs and pathway entropy profiles during disease progression. We applied DEWNA to a dataset of DBPs from A549 cells responding to cisplatin-induced damage across 8 time points, with data generated by data-independent acquisition mass spectrometry (DIA-MS). The results demonstrate that DEWNA can effectively identify protein hubs and associated pathways that are significantly altered in response to cisplatin-induced DNA damage, and offer a comprehensive view of how different pathways interact and respond dynamically over time to cisplatin treatment. Notably, we observed the dynamic activation of distinct DNA repair pathways and cell death mechanisms during the drug treatment time course, providing new insights into the molecular mechanisms underlying the cellular response to DNA damage.

Unraveling developmental patterns and differentiation trajectories in a single developing internode of Moso Bamboo (Phyllostachys edulis)

Bamboo, a significant carbon sink and eco-friendly resource, possesses substantial economic value and ecological benefits. A single internode represents the fundamental unit of bamboo culm, yet research focusing on the pivotal cellular destinies and molecular mechanisms underpinning the growth and development of a single internode remains comparatively scarce. In the study, we pioneered the establishment of a high-resolution single-cell transcriptomic atlas for a single internode of Moso bamboo. Utilizing known marker genes, we identified six major cell clusters (meristem, epidermis, phloem, xylem, pre-xylem/phloem, and vascular bundle sheath) and found many potential marker genes in the internode of Moso bamboo. Subsequently, we reconstructed the developmental trajectories of the epidermis and vascular tissues and further unveiled the key regulatory factors determining cell fates. Moreover, ectopic expression of PheIAA15 in Arabidopsis thaliana resulted in a marked reduction in the number of vascular bundles within the stems, as well as a significant decrease in their cross-sectional areas, diverging from existing research in Arabidopsis. The interaction between PheIAA15 and PheWOX4c suggested a potential novel auxin response mechanism in Moso bamboo. We subsequently elucidated that PheIAA15 bound to the promoter region of PheCLE25, thereby down-regulating the expression of PheCLE25, whereas PheWOX4c can activate the transcription of PheCLE25, which suggested that these two factors regulated the expression of PheCLE25 through an antagonistic mechanism. This finding highlighted the critical role of the complex regulatory network established among these elements in the differentiation of vascular tissues in the internodes of Moso bamboo. Overall, the study fills a critical research void concerning internodal development in bamboo plants at the single-cell level, laying a foundation for future studies to unravel the origin and differentiation of vascular bundle cells during internode development in perennial Gramineous plants.

SMARCA5-mediated chromatin remodeling is required for germinal center formation.

The establishment of long-lasting immunity against pathogens is facilitated by the germinal center (GC) reaction, during which B cells increase their antibody affinity and differentiate into antibody-secreting cells (ASC) and memory cells. These events involve modifications in chromatin packaging that orchestrate the profound restructuring of gene expression networks that determine cell fate. While several chromatin remodelers were implicated in lymphocyte functions, less is known about SMARCA5. Here, using ribosomal pull-down for analyzing translated genes in GC B cells, coupled with functional experiments in mice, we identified SMARCA5 as a key chromatin remodeler in B cells. While the naive B cell compartment remained unaffected following conditional depletion of Smarca5, effective proliferation during B cell activation, immunoglobulin class switching, and as a result GC formation and ASC differentiation were impaired. Single-cell multiomic sequencing analyses revealed that SMARCA5 is crucial for facilitating the transcriptional modifications and genomic accessibility of genes that support B cell activation and differentiation. These findings offer novel insights into the functions of SMARCA5, which can be targeted in various human pathologies.

IGF-I concentration determines cell fate by converting signaling dynamics as a bifurcation parameter in L6 myoblasts

Insulin-like growth factor (IGF)-I mediates long-term activities that determine cell fate, including cell proliferation and differentiation. This study aimed to characterize the mechanisms by which IGF-I determines cell fate from the aspect of IGF-I signaling dynamics. In L6 myoblasts, myogenic differentiation proceeded under low IGF-I levels, whereas proliferation was enhanced under high levels. Mathematical and experimental analyses revealed that IGF-I signaling oscillated at low IGF-I levels but remained constant at high levels, suggesting that differences in IGF-I signaling dynamics determine cell fate. We previously reported that differential insulin receptor substrate (IRS)-1 levels generate a driving force for cell competition. Computational simulations and immunofluorescence analyses revealed that asynchronous IRS-1 protein oscillations were synchronized during myogenic processes through cell competition. Disturbances of cell competition impaired signaling synchronization and cell fusion, indicating that synchronization of IGF-I signaling oscillation is critical for myoblast cell fusion to form multinucleate myotubes.

The Protective Effects of Mcl-1 on Mitochondrial Damage and Oxidative Stress in Imiquimod-Induced Cancer Cell Death.

Mitochondria, vital organelles that generate ATP, determine cell fate. Dysfunctional and damaged mitochondria are fragmented and removed through mitophagy, a mitochondrial quality control mechanism. The FDA-approved drug IMQ, a synthetic agonist of Toll-like receptor 7, exhibits antitumor activity against various skin malignancies. We previously reported that IMQ promptly reduced the level of the antiapoptotic Mcl-1 protein and that Mcl-1 overexpression attenuated IMQ-triggered apoptosis in skin cancer cells. Furthermore, IMQ profoundly disrupted mitochondrial function, promoted mitochondrial fragmentation, induced mitophagy, and caused cell death by generating high levels of ROS. However, whether Mcl-1 protects mitochondria from IMQ treatment is still unknown. In this study, we demonstrated that Mcl-1 overexpression induced resistance to IMQ-induced apoptosis and reduced both IMQ-induced ROS generation and oxidative stress in cancer cells. Mcl-1 overexpression maintained mitochondrial function and integrity and prevented mitophagy in IMQ-treated cancer cells. Furthermore, IL-6 protected against IMQ-induced apoptosis by increasing Mcl-1 expression and attenuating IMQ-induced mitochondrial fragmentation. Mcl-1 overexpression ameliorates IMQ-induced ROS generation and mitochondrial fragmentation, thereby increasing mitochondrial stability and ultimately attenuating IMQ-induced cell death. Investigating the roles of Mcl-1 in mitochondria is a potential strategy for cancer therapy development.

Endoplasmic reticulum stress in diseases.

Theendoplasmic reticulum (ER) is a key organelle in eukaryotic cells, responsible for a wide range of vital functions, including the modification, folding, and trafficking of proteins, as well as the biosynthesis of lipids and the maintenance of intracellular calcium homeostasis. A variety of factors can disrupt the function of the ER, leading to the aggregation of unfolded and misfolded proteins within its confines and the induction of ER stress. A conserved cascade of signaling events known as the unfolded protein response (UPR) has evolved to relieve the burden within the ER and restore ER homeostasis. However, these processes can culminate in cell death while ER stress is sustained over an extended period and at elevated levels. This review summarizes the potential role of ER stress and the UPR in determining cell fate and function in various diseases, including cardiovascular diseases, neurodegenerative diseases, metabolic diseases, autoimmune diseases, fibrotic diseases, viral infections, and cancer. It also puts forward that the manipulation of this intricate signaling pathway may represent a novel target for drug discovery and innovative therapeutic strategies in the context of human diseases.

Combinatorial regulatory states define cell fate diversity during embryogenesis

Cell fate specification occurs along invariant species-specific trajectories that define the animal body plan. This process is controlled by gene regulatory networks that regulate the expression of the limited set of transcription factors encoded in animal genomes. Here we globally assess the spatial expression of ~90% of expressed transcription factors during sea urchin development from embryo to larva to determine the activity of gene regulatory networks and their regulatory states during cell fate specification. We show that >200 embryonically expressed transcription factors together define >70 cell fates that recapitulate the morphological and functional organization of this organism. Most cell fate-specific regulatory states consist of ~15–40 transcription factors with similarity particularly among functionally related cell types regardless of developmental origin. Temporally, regulatory states change continuously during development, indicating that progressive changes in regulatory circuit activity determine cell fate specification. We conclude that the combinatorial expression of transcription factors provides molecular definitions that suffice for the unique specification of cell states in time and space during embryogenesis.

Targeting ROS in cancer: rationale and strategies.

Reactive oxygen species (ROS) in biological systems are transient but essential molecules that are generated and eliminated by a complex set of delicately balanced molecular machineries. Disruption of redox homeostasis has been associated with various human diseases, especially cancer, in which increased ROS levels are thought to have a major role in tumour development and progression. As such, modulation of cellular redox status by targeting ROS and their regulatory machineries is considered a promising therapeutic strategy for cancer treatment. Recently, there has been major progress in this field, including the discovery of novel redox signalling pathways that affect the metabolism of tumour cells as well as immune cells in the tumour microenvironment, and the intriguing ROS regulation of biomolecular phase separation. Progress has also been made in exploring redox regulation in cancer stem cells, the role of ROS in determining cell fate and new anticancer agents that target ROS. This Review discusses these research developments and their implications for cancer therapy and drug discovery, as well as emerging concepts, paradoxes and future perspectives.

A CRISPR/Cas9 screen in embryonic stem cells reveals that Mdm2 regulates totipotency exit

During early embryonic development, the transition from totipotency to pluripotency is a fundamental and critical process for proper development. However, the regulatory mechanisms governing this transition remain elusive. Here, we conducted a comprehensive genome-wide CRISPR/Cas9 screen to investigate the 2-cell-like cells (2CLCs) phenotype in mouse embryonic stem cells (mESCs). This effort led to the identification of ten regulators that play a pivotal role in determining cell fate during this transition. Notably, our study revealed Mdm2 as a significant negative regulator of 2CLCs, as perturbation of Mdm2 resulted in a higher proportion of 2CLCs. Mdm2 appears to influence cell fate through its impact on cell cycle progression and H3K27me3 epigenetic modifications. In summary, the results of our CRISPR/Cas9 screen have uncovered several genes with distinct functions in regulating totipotency and pluripotency at various levels, offering a valuable resource for potential targets in future molecular studies.

Regulation of stomatal development by epidermal, subepidermal and long-distance signals.

Plant leaves consist of three layers, including epidermis, mesophyll and vascular tissues. Their development is meticulously orchestrated. Stomata are the specified structures on the epidermis for uptake of carbon dioxide (CO2) while release of water vapour and oxygen (O2), and thus play essential roles in regulation of plant photosynthesis and water use efficiency. To function efficiently, stomatal formation must coordinate with the development of other epidermal cell types, such as pavement cell and trichome, and tissues of other layers, such as mesophyll and leaf vein. This review summarizes the regulation of stomatal development in three dimensions (3D). In the epidermis, specific stomatal transcription factors determine cell fate transitions and also activate a ligand-receptor- MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) signaling for ensuring proper stomatal density and patterning. This forms the core regulation network of stomatal development, which integrates various environmental cues and phytohormone signals to modulate stomatal production. Under the epidermis, mesophyll, endodermis of hypocotyl and inflorescence stem, and veins in grasses secrete mobile signals to influence stomatal formation in the epidermis. In addition, long-distance signals which may include phytohormones, RNAs, peptides and proteins originated from other plant organs modulate stomatal development, enabling plants to systematically adapt to the ever changing environment.

Lineage-specific CDK activity dynamics characterize early mammalian development.

Cyclin-dependent kinases (CDK) are key regulatory enzymes that regulate proliferation dynamics and cell fate in response to extracellular inputs. It remains largely unknown how CDK activity fluctuates and influences cell commitment in vivo during early mammalian development. Here, we generated a transgenic mouse model expressing a CDK kinase translocation reporter (KTR) that enabled quantification of CDK activity in live single cells. By examining pre- and post-implantation mouse embryos at different stages, we observed a progressive decrease in CDK activity in cells from the trophectoderm (TE) prior to implantation. This drop correlated with the establishment of an FGF4-dependent signaling gradient through the embryonic-abembryonic axis. Furthermore, we showed that CDK activity levels do not determine cell fate decisions during pre-implantation development. Finally, we uncovered the existence of conserved regulatory mechanisms in mammals by revealing lineage-specific regulation of CDK activity in TE-like human cells.