Telomeres are structures located at the ends of chromosomes. Though the sequences in the telomeres do not code for any known genes, they still play an important role. The presence of telomeres helps prevent the destruction of chromosomal DNA underneath.
That is why the shortening of telomeres is linked to aging , while lengthening of the telomeres often happens in cancer cells. The replication and maintenance of telomeres is a complex process.
One of the proteins responsible for telomere maintenance is called CST . This protein is present in all cells from yeast mammals
Mutations
An international team of researchers from France and Portugal has studied a part of this complex called Stn1 in fission yeast Schizosaccharomyces pombe.
Stn1 is controlled by a phosphatase ssu72 . When ssu72 adds phosphorus to Stn1, the protein prevents the elongation of the telomere. If another protein, Cdk1 , attaches to Stn1, then the latter cannot attach to the telomere, and new sequences are added to telomerase. The same mechanism of telomerase regulation is present in mammalian cells. It is vital to understand how the telomeres are maintained, as telomerase is an important protein in cancer development, as well as in aging.
Reference :
“Ssu72 phosphatase is a conserved telomere replication terminator | The EMBO Journal” . Accessed May 17, 2020.
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When cells divide, a specialized structure is formed called mitotic spindle . This spindle is composed of microtubules – complex structures that are composed of several components. Microtubules originate in several spots:
From the so-called mitotic spindle poles. From the chromosomes By branching from the surfaces of already formed microtubules.
The exact steps of branching of microtubules were previously unknown. Three researchers at the Princeton University – Sabine Petry , specializing in molecular biology Howard A. Stone , specializing in engineering, and Joshua W. Shaevitz , a physics professor – have collaborated to reconstruct this process.
The team has used eggs of the Xenopus frog as a model. They have established that new microtubules tend to form on the surface of the pre-existing ones. The researchers have regulated the availability of the three factors that regulate microtubule growth: TPX2 , augmin , and γ-TuRC . The experiments have shown the following sequence: TPX2 is the first to be deposited on the surface of the “old ” microtubule. Augmin and γ-TuRCare bound together. The new microtubule branches are formed. Based on the results of the experiments, a computer model of the microtubule branching was developed. This work was unique as it required the collaboration of specialists from three different fields. It is also crucial for understanding one of the most important questions of cell biology – cellular division.
Sabine Petry , one of the researchers, has received an WICB Junior Award for Excellence in Research for her work.
Reference :
“Spatiotemporal organization of branched microtubule networks | eLife” . Accessed May 17, 2020.
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Some cells in our bodies spend their lives in constant danger. For instance, muscle cells are subject to regular stretching, skin cells
The cellular membranes form “bags caveolae to withstand pressure. In some cases, caveolae can form clusters that are called caveolae rosettes. The cells form so-called stress fibers that help the membrane to bend. A team of researchers has studied the molecular underpinnings of caveolae formation:
They used the culture of human skin cells for their experiments. To create stressful conditions, the cells were either subjected to stretching or were placed in conditions with lower osmotic pressure. The experiments have shown that caveolae are formed with the help of a protein called FBP17 . FBP17 attaches to the caveolae to arrange them in caveolae rosettes. Another protein, c-Abl , regulates the activity of FBP17. c-Abl senses mechanical pressure and blocks the activity of FBP17. Instead of changing the curve of the membrane and formation of caveolae, c-Abl helps release the stress fibers that help withstand mechanical tension. In people with muscular dystrophies, these stress-relieving mechanisms are impaired. By understanding the mechanisms that help the cells cope with stress, it could be possible to treat people with these severe conditions.
Reference :
“An Abl-FBP17 mechanosensing system couples local plasma membrane . Accessed May 17, 2020.
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Right after fertilization, the zygote divides into two cells . Those two cells are called totipotent – they can differentiate into any possible type of cell.
Totipotent cells can potentially grow into the whole embryo, while stem cells do not have this ability and have a certain limit.
Japanese scientists have tried to reprogram differentiated cells into totipotent cells – which have never been achieved before:
In the course of the experiment, the scientists used mouse pluripotent stem cells. The cells underwent a complex reprogramming process, including adding transcription factor Prdm14 . After reprogramming, the cells self-organized into structures that were similar to a blastocyst stage of embryonic development. Blastocysts are structures with an outer structured layer, and a cavity with a mass of undifferentiated cells within that later give rise to the embryo. Artificial blastocytes had a similar structure, and the mass of the cells inside their cavities was pluripotent. The researchers have implanted the blastocysts into mice. The implanted artificial blastocysts could temporarily grow inside the uterus. This achievement could help scientists understand what factors make cells totipotent. These bits of knowledges are essential to several fields of medicine
Reference :
“Induced 2C Expression and Implantation-Competent Blastocyst-like Cysts from Primed Pluripotent Stem Cells: Stem Cell Reports” . Accessed May 17, 2020.
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The cells have a complex system of proteins. Some of them are responsible for shuttling ions in and out of the cell, thus creating an electrical charge. These ion transporter proteins are in turn controlled by another group called phosphoinositides .
It is known that both types of proteins are present in the sperm cells
A team of Japanese researchers was interested in the role of electricity-related protein in the sperm.
They have focused on the VSP – voltage sensing protein that was known to be present in several of organs, including the testes. The researchers have found that VSP is present in the sperm as well. Sperm without VSP was not able to reach the oocyte properly because it was swimming in circles. It was established that VSP controlled the distribution of certain phosphoinositides in the sperm that were crucial for normal sperm orientation and motility. This discovery can help develop new treatments for male infertility.
Reference :
“Polarized PtdIns(4,5)P2 distribution mediated by a voltage-sensing phosphatase (VSP) regulates sperm motility | PNAS” . Accessed May 17, 2020.
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Oxygen is crucial for the normal functioning of cells. Therefore, the studies devoted to various roles of oxygen in the cells were awarded the Nobel Prize through the years. In the year 2019, the award went to the three researchers – William G. Kaelin Jr. , Sir Peter J. Ratcliffe, and Gregg L. Semenza . This trio has discovered another piece of this puzzle: how cells can sense the amount of available oxygen. Each of these scientists has contributed to the discovery of oxygen-sensing mechanism:
It was known at the beginning of the 20th century that when the oxygen levels in the body are low, the kidney cells start producing a hormone called erythropoietin (EPO ). Erythropoietin stimulates the development of new erythrocytes in the blood that can transport more oxygen to the cells of the body.Gregg Semenza has studied the regulation of erythropoietin gene in response to different oxygen levels.In course of his experiments, Semenza has discovered a protein called hypoxia-inducible factor. This factor binds to regulatory segments of the EPO gene in response to a reduction in oxygen levels. Semenza has also discovered the genes responsible for the HIF components , HIF-1α and ARNT . William Kaelin Jr. was studying the VHL gene and has discovered that this gene codes for a protein that controls responses to hypoxia. When VHL is absent in the cells, many hypoxia -linked genes are activated, and it can lead to the development of certain cancers. Sir Peter Ratcliffe has found that VHL interacts with HIF-1α, a part of the HIF complex, and induces its degradation when oxygen levels are normal. Later, both Kaelin and Ratcliffe have discovered prolyl hydrolases, specialized enzymes that mark HIF-1α fordestruction in the presence of normal oxygen levels. All three discoveries were crucial in our understanding of how cells react to various oxygen levels. As this mechanism is disrupted many of conditions from infections to cancer and infarction, this research was crucial for medicine and fundamental research alike.
Reference :
“The Nobel Prize in physiology . Accessed May 17, 2020.
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The year of 2019 has shown how much we actually do not know about the inner workings of the cell. For example, though not presented in the current article, there were multiple experiments devoted to the formation and activity of microtubules: from the physical forces driving their movement to the fact that microtubules may contribute to diabetes development.
Other laboratories devoted their work to previously overlooked structures, such as cilia in kidney cells or flagella of the archae a. As we can see, new types of cells are found in unexpected situations – such as hair follicles or immune system in diabetes patients.
Modern cell biology intersects with multiple disciplines: computer science, biochemistry, medicine, and genetics. Here are the top 15 cell biology discoveries in 2018.
All recent advances in cell biology points to one conclusion – it would be impossible to find remedies for many known diseases unless we would understand the smallest units of our bodies – the cells – better.
Cite This Page
“Murphy and Petry win awards for excellence in cell biology” . Accessed May 17, 2020. Link .“Mystery solved about the machines that move your genes” . Accessed May 17, 2020. Link .“New role for microtubules in diabetes” . Accessed May 17, 2020. Link .“Primary cilia and the exocyst are linked to urinary extracellular vesicle production and content” . Accessed May 17, 2020. Link .“The structure of the periplasmic FlaG-FlaF complex and its essential role for archaellar swimming motility | Nature Microbiology” . Accessed May 17, 2020. Link .
