Molecular competition in G1 controls when cells simultaneously commit to terminally differentiate and exit the cell-cycle
TL;DR: A rapid switch mechanism engages exclusively in G1 to trigger a simultaneous commitment to differentiate and permanently exit from the cell cycle and the differentiation control system is able to couple mitogen and differentiation stimuli to sustain a long-term balance between terminally differentiating cells and maintaining the progenitor cell pool.
Abstract: Terminal differentiation is essential for the development and maintenance of tissues in all multi-cellular organisms and is associated with a permanent exit from the cell cycle. Failure to permanently exit the cell cycle can result in cancer and disease. However, the molecular mechanisms and timing that coordinates differentiation commitment and cell cycle exit are not yet understood. Here using adipogenesis as a model system to track differentiation commitment in live cells, we show that a rapid switch mechanism engages exclusively in G1 to trigger a simultaneous commitment to differentiate and permanently exit from the cell cycle. We identify a signal integration mechanism whereby the strengths of both mitogen and differentiation stimuli control a molecular competition between cyclin D1 and PPARG-induced expression of the CDK inhibitor p21 which in turn regulates if and when the differentiation switch is triggered and when the proliferative window closes. In this way, the differentiation control system is able to couple mitogen and differentiation stimuli to sustain a long-term balance between terminally differentiating cells and maintaining the progenitor cell pool, a parameter of critical importance for enabling proper development of tissue domains and organs.
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TL;DR: In this article , a review of miRNAs and their role in obesity and its included processes, such as adipogenesis and lipid metabolism, is presented, along with recent applications of miRNA as a treatment approach for obesity.
Abstract: In recent decades, obesity has extensively emerged to the level of pandemics. It's significantly associated with serious co-morbidities that could decrease life quality and even life expectancy. Obesity has several determinants, such as age, sex, endocrine, and genetic factors. The miRNAs have emerged as genetic factors affecting obesity. The miRNAs are small noncoding nucleic acids that can modify gene expression and hence, control biological processes. The miRNAs can greatly affect many biological processes in obesity, such as adipogenesis, lipid metabolism, and homeostasis. As a result, the entry of miRNAs in obesity therapeutic approaches has been strongly advised as miRNAs mimics, inhibitors, and stimulators. Hence, this review aims to point out a summarized and updated overview of miRNAs and their roles in obesity and its included processes, such as adipogenesis and lipid metabolism. Besides, we also review recent applications of miRNAs as a treatment approach for obesity.
33 citations
TL;DR: The adipogenesis process is accomplished through two sequential phases; the first includes events favoring the commitment of adipose tissue stem cells/precursors to preadipocytes, while the second involves mechanisms that allow the achievement of full adipocyte differentiation as discussed by the authors .
Abstract: The adipose organ comprises two main fat depots termed white and brown adipose tissues. Adipogenesis is a process leading to newly differentiated adipocytes starting from precursor cells, which requires the contribution of many cellular activities at the genome, transcriptome, proteome, and metabolome levels. The adipogenic program is accomplished through two sequential phases; the first includes events favoring the commitment of adipose tissue stem cells/precursors to preadipocytes, while the second involves mechanisms that allow the achievement of full adipocyte differentiation. While there is a very large literature about the mechanisms involved in terminal adipogenesis, little is known about the first stage of this process. Growing interest in this field is due to the recent identification of adipose tissue precursors, which include a heterogenous cell population within different types of adipose tissue as well as within the same fat depot. In addition, the alteration of the heterogeneity of adipose tissue stem cells and of the mechanisms involved in their commitment have been linked to adipose tissue development defects and hence to the onset/progression of metabolic diseases, such as obesity. For this reason, the characterization of early adipogenic events is crucial to understand the etiology and the evolution of adipogenesis-related pathologies, and to explore the adipose tissue precursors' potential as future tools for precision medicine.
19 citations
TL;DR: Results revealed that CCA-1.1 possesses cytotoxic effects similar to those of PGV-1 on T47D cells, and may be a potential chemotherapeutic/co-chemotherapeutic candidate for estrogen receptor-positive (ER+) breast cancer therapy.
Abstract: An improved compound of pentagamavunone-1 (PGV-1), chemoprevention-curcumin analog 1.1 (CCA-1.1), has been synthesized and proven to have antiproliferative effects against breast cancer cells. This study is designed to investigate the potency of CCA-1.1 alone and in combination with doxorubicin (Dox) on T47D cells in comparison with that of PGV-1. We used the MTT assay to assess cytotoxic activity. Propidium iodide (PI), annexin-V–PI, and DCFDA staining were respectively used to determine cell cycle profiles, apoptosis, and intracellular reactive oxygen species (ROS) levels. Senescent cells were identified using the SA-b-galactosidase assay. Our results revealed that CCA-1.1 possesses cytotoxic effects similar to those of PGV-1 on T47D cells. Synergistic effects during co-treatment with Dox were also observed. CCA-1.1 arrested cell cycle progression at the G2/M phase and limited sub-G1 accumulation, which is correlated with apoptosis. CCA-1.1 alone and in combination with Dox increased senescence and intracellular ROS to a similar level to those achieved by PGV-1. CCA-1.1 alone and in combination with Dox enhanced cytotoxic activity toward T47 cells compared to PGV-1. Thus, this curcumin analog may be a potential chemotherapeutic/co-chemotherapeutic candidate for estrogen receptor-positive (ER+) breast cancer therapy.
6 citations
Cites result from "Molecular competition in G1 control..."
...Differences in the present results may be attributed to differences in the sensitivity of the test systems used to determine cell cycle profiles and apoptosis (Zhao et al., 2019)....
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TL;DR: A control principle for robust cell identity is suggested whereby a core component of the differentiated state also promotes differentiation from its own progenitor state, thus providing an explanation for why maintenance of the mature adipocyte state is so robust.
Abstract: How progenitor cells can attain a distinct differentiated cell identity is a challenging problem given that critical transcription factors are often not unique to a differentiation process and the fluctuating signaling environment in which cells exist. Here we test the hypothesis that a unique differentiated cell identity can result from a core component of the differentiated state doubling up as a signaling protein that also drives differentiation. Using live single-cell imaging in the adipocyte differentiation system, we show that progenitor fat cells (preadipocytes) can only commit to terminally differentiate after upregulating FABP4, a lipid buffer that is highly enriched in mature adipocytes. Upon induction of adipogenesis, we show that after a long delay, cells first abruptly start to engage a positive feedback between CEBPA and PPARG before then engaging, after a second delay, a positive feedback between FABP4 and PPARG. These sequential positive feedbacks both need to engage in order to drive PPARG levels past the threshold for irreversible differentiation. In the last step before commitment, PPARG transcriptionally increases FABP4 expression while fatty-acid loaded FABP4 binds to and increases PPARG activity. Together, our study suggests a control principle for robust cell identity whereby a core component of the differentiated state also promotes differentiation from its own progenitor state.
5 citations
TL;DR: CDK activity sensors are utilized for their ability to visualize the exact moment of cell-cycle commitment, which has provided a breakthrough in understanding the proliferation-quiescence decision.
Abstract: Cyclin-dependent kinase (CDK) sensors have facilitated investigations of the cell cycle in living cells. These genetically encoded fluorescent biosensors change their subcellular location upon activation of CDKs. Activation is primarily regulated by their association with cyclins, which in turn trigger cell-cycle progression. In the absence of CDK activity, cells exit the cell cycle and become quiescent, a key step in stem cell maintenance and cancer cell dormancy. The evolutionary conservation of CDKs has allowed for the rapid development of CDK activity sensors for cell lines and several research organisms, including nematodes, fish, and flies. CDK activity sensors are utilized for their ability to visualize the exact moment of cell-cycle commitment. This has provided a breakthrough in understanding the proliferation-quiescence decision. Further adoption of these biosensors will usher in new discoveries focused on the cell-cycle regulation of development, ageing, and cancer.
3 citations
References
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TL;DR: Kallisto pseudoaligns reads to a reference, producing a list of transcripts that are compatible with each read while avoiding alignment of individual bases, which removes a major computational bottleneck in RNA-seq analysis.
Abstract: We present kallisto, an RNA-seq quantification program that is two orders of magnitude faster than previous approaches and achieves similar accuracy. Kallisto pseudoaligns reads to a reference, producing a list of transcripts that are compatible with each read while avoiding alignment of individual bases. We use kallisto to analyze 30 million unaligned paired-end RNA-seq reads in <10 min on a standard laptop computer. This removes a major computational bottleneck in RNA-seq analysis.
6,468 citations
Additional excerpts
...GRCm38.cdna) using Kallisto(Bray et al., 2016) (v0....
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...The Kallisto output files were read into R using Sleuth, and the transcripts per million (TPM), a measurement of the proportion of transcripts in the RNA pool, was used for downstream differential expression analysis(Pimentel et al., 2017)....
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TL;DR: It is shown that adipocyte number is a major determinant for the fat mass in adults, however, the number of fat cells stays constant in adulthood in lean and obese individuals, even after marked weight loss, indicating that thenumber of adipocytes is set during childhood and adolescence.
Abstract: Obesity is increasing in an epidemic manner in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. Owing to the increase in obesity, life expectancy may start to decrease in developed countries for the first time in recent history. The factors determining fat mass in adult humans are not fully understood, but increased lipid storage in already developed fat cells (adipocytes) is thought to be most important. Here we show that adipocyte number is a major determinant for the fat mass in adults. However, the number of fat cells stays constant in adulthood in lean and obese individuals, even after marked weight loss, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analysing the integration of 14C derived from nuclear bomb tests in genomic DNA. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in early onset obesity, suggesting a tight regulation of fat cell number in this condition during adulthood. The high turnover of adipocytes establishes a new therapeutic target for pharmacological intervention in obesity.
2,098 citations
"Molecular competition in G1 control..." refers background in this paper
...Yet adipocytes are replaced only at a low rate (Spalding et al., 2008), arguing that adipogenesis is a relatively slow process with only a small percentage of progenitor cells differentiating at a given time....
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TL;DR: Time-lapse imaging is performed to explore the spatiotemporal patterns of cell-cycle dynamics during the epithelial-mesenchymal transition of cultured cells, the migration and differentiation of neural progenitors in brain slices, and the development of tumors across blood vessels in live mice.
1,946 citations
"Molecular competition in G1 control..." refers background or methods in this paper
...By combining this live-cell PPARG sensor with a reporter to mark the G1 phase (Sakaue-Sawano et al., 2008), we establish a method that can simultaneously track both cell-cycle progression and the precise commitment point to terminally differentiate....
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...Simultaneous Single-Cell Analysis Shows that Further Entry into the Cell Cycle Is Blocked Once a Cell Reaches the Differentiation Commitment Point in G1 We next made a dual-reporter cell line by transfecting a FUCCI cell cycle reporter (Sakaue-Sawano et al., 2008) into the citrine-PPARG preadipocyte cell line described in Figure 1A (Figure 2A; Videos S1 and S2)....
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...…to terminally differentiate simultaneously in the same cells, we made a dual-reporter cell line by transfecting a FUCCI cell cycle reporter (Sakaue-Sawano et al., 2008) into an OP9 preadipocyte cell line we had previously generated that expressed endogenous citrine-PPARG (Figure…...
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TL;DR: New perspective is gained on the roles played by adipocyte in a variety of homeostatic processes and on the mechanisms used by adipocytes to communicate with other tissues and how these relationships are altered during metabolic disease and how they might be manipulated to restore metabolic health.
1,746 citations
"Molecular competition in G1 control..." refers background in this paper
...During adipogenesis, expression of PPARG, the master transcriptional regulator of adipogenesis, is driven by both external input signals and internal positive feedback loops (Ahrends et al., 2014; Rosen and Spiegelman, 2014) (Figure 1A, top)....
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...As adipogenic stimuli are known to increase the expression of PPARG and other key adipogenic transcription factors (Rosen and Spiegelman, 2014), we next tested how this might affect the competition in G1....
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...Adipogenesis is centered on a master transcriptional regulator, PPARG, whose expression is driven by both external input signals and internal positive feedback loops (Ahrends et al., 2014; Rosen and Spiegelman, 2014) (Figure 1A, top)....
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TL;DR: A detailed understanding of the processes governing adipose tissue formation will be instrumental in combating the obesity epidemic and constitutes a framework for potential antiobesity strategies.
1,620 citations
"Molecular competition in G1 control..." refers background in this paper
...Many terminal cell differentiation processes including adipogenesis and myogenesis are regulated by a cascade of transcription factors (Blais et al., 2005; Farmer, 2006)....
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