The intestinal epithelium is the tissue with the highest cell turnover rate. 100’s of millions of cells are generated everyday in the intestine yet all these cells die in less than a week. This tremendous regenerative power is sustained by a population of intestinal stem cells (ISCs). It was believed that ISCs represent an homogeneous population of rapidly dividing cells. In this work we reveal that ISCs adopt two discrete states, one of then defined by the expression of the RNA binding protein Mex3a and characterized by a slow proliferation mode. These slow cycling ISCs contribute to all intestinal lineages with a delayed kinetics. During homeostasis, Mex3a+ cells continually shift into the rapidly dividing, self-renewing ISC pool. Chemotherapy and radiation preferentially target rapidly dividing ISCs but spare the Mex3a+ cell population, which regenerates the intestinal epithelium following this toxic insult. Thus, Mex3a marks a reserve-like stem cell population within the intestinal epithelium.
Every year, a committee of experts sits down with a tough job to do: from among all ICREA publications, they must find a handful that stand out from all the others. This is indeed a challenge. The debates are sometimes heated and always difficult but, in the end, a shortlist of 24 publications is produced. No prize is awarded, and the only additional acknowledge is the honour of being chosen and highlighted by ICREA. Each piece has something unique about it, whether it be a particularly elegant solution, the huge impact it has in the media or the sheer fascination it generates as a truly new idea. For whatever the reason, these are the best of the best and, as such, we are proud to share them here.
LIST OF SCIENTIFIC HIGHLIGHTS
The intestine has a reservoir of stem cells that are resistant to chemotherapy (2017)
Batlle Gómez, Eduard (IRB Barcelona)view details
Size matters for aquatic communities and ecosystems (2017)
Brucet, Sandra (UVIC)view details
Freshwater ecosystems have particularly high biodiversity and provide ecosystem services essential to human well-being. However, the biodiversity of these habitats is declining at an alarming and unprecedented rate due to human activities. One of the major consequences of biodiversity decline is the loss of ecological functions and ecosystem services. For this reason, major efforts are invested at quantifying the relationship between biodiversity and ecosystem functions. Nevertheless, the estimation of biodiversity is often complex and time-consuming.
An alternative to the taxonomical approach to assessing biodiversity and ecosystem processes is to study the body size structure (i.e. relationship between organisms’ body size and their density) of the community. Body size is a fundamental attribute of organisms because many physiological rates are size-dependent. Body size also determines ecological structures and processes such as population abundance, predator–prey interactions and the resilience of the food webs.
The research on size structure of aquatic communities at ICREA has recently been quite productive. Based on a large database of fish communities in European lakes, we have shown that competition and predation are key drivers of the size structure. We also provided evidence that higher size diversity of prey may drive a higher size diversity of predators, or vice versa. Size structure of aquatic communities also respond systematically to environmental disturbance, such as changes in land use in subtropical streams or shifts in temperature and resource availability in Mediterranean lakes. Thus, metrics based on size structure could be used as comprehensive indicators of ecosystem health, together with traditional taxonomic approaches. Finally, by performing an experiment in lake Mývatn (Iceland), we demonstrated that changes in size structure across the aquatic food web are related to shifts in the efficiency of energy transfer. Thus, our studies underpin the importance of taking into account organisms’ size when assessing ecosystem processes and human impacts.
Christians living in a Muslim World? Radiocarbon dating of the cemetery over the forum of Pollentia (Mallorca, Balearic Islands) (2017)
Cau Ontiveros, Miguel Ángel (UB)view details
The Roman city of Pollentia (Alcúdia) is one of the main cities for the study of the Roman period in Spain. Archaeological excavations conducted since 1923 have uncovered the forum, residential quarters, the theater and several necropolises among other remains. The city was founded after the conquest of the Balearics by Quintus Caecilius Metellus in 123 BCE. At the end of the 3rd century CE, a fire destroyed many parts of the city. However, the city continued inhabited through the Vandal (455 CE), Byzantine (534 CE) and the Islamic (902/903 CE) occupations.
Over the forum area, a large necropolis with more than 300 graves has been excavated since 1980. This cemetery was traditionally dated to the 4th century CE, right after the fire. However, recent excavations have yielded data to question this dating. The types of inhumation graves, the disposition of the bodies and the lack of goods suggest that is a Christian cemetery from the late antique period but dated at least after the 7th century CE.
In order to obtain an absolute chronology, 14C dating was applied to thirteen bone samples. The results are striking as the dates, ranging mainly from the tenth to the twelfth centuries, fall into the Islamic period (902/903-1229). Muslims were buried in a lateral position with the head towards the East and these graves did not follow Muslim practices. The results are extremely important because provide archaeological evidence for the existence of non-Muslim communities on the island in that period. The graves had typologies and rituals of deposition of the bodies seen in other Christian cemeteries. Were they Christians? If so, were they descendants of the Christian communities that inhabited the city in Late Antiquity or newcomers introduced by the Muslims? Were they Jews? The mystery remains unsolved, but the archaeological identification of a non-Muslim community living in a Muslim world in the Balearics opens new possibilities for the study of these minorities as well as on interaction, tolerance, and co-existence issues, linking in this way past and present.
How plants use their own endogneous genetics to limit and compartmentalize beneficial and harmful metals (2017)
Christou, Paul (UdL)view details
Rice is a staple crop for more than 50% of the world population. Insufficient levels of Fe and Zn in the seed cause deficiency diseases in populations relying on rice as the main source of calories. More than 2 billion people suffer from Fe deficiency anemia and Zn deficiency. Rice grown on contaminated soils also causes cadmium (Cd) toxicity. Therefore, biofortification strategies that enhance Fe and Zn levels in rice endosperm should do so without also encouraging the accumulation of Cd. The maximum levels of Fe and Zn reported in seeds of biofortified rice are well below the Recommended Daily Intake. This suggests an upper limit for Fe and Zn accumulation in the seed. Metal homeostasis acts to prevent the seed becoming overloaded with these metals, but the underlying mechanisms are largely unknown. Nicotianamine (NA) and deoxymugenic acid (DMA) are endogenous metal chelating molecules; increasing the amount of NA or DMA in the plant increases the accumulation of Fe and Zn in the seeds. NA and DMA are synthesized from S-adenosylmethionine in three steps involving nicotianamine synthase (NAS), nicotianamine aminotransferase (NAAT) and DMA synthase (DMAS).
We generated transgenic rice lines co-expressing NAS and NAAT. These plants accumulated higher levels of NA and DMA and promoted the accumulation of Fe and Zn in seeds Increasing the external supply of Fe affected the uptake of Fe and Zn into the roots and the mobilization of these metals in the aboveground organs, but compensatory mechanisms involving sequestration in leaves have a buffering effect and impose strict limits on the accumulation of metals in the seed. Surprisingly, the preferential retention of Fe and Zn in the seed led to the competitive exclusion of Cd, halving the amount of Cd. This can provide a useful strategy to increase the abundance of metal nutrients in rice while ensuring that toxic metals are exported to the bran. Such strategies could help simultaneously to address micronutrient deficiency and heavy metal toxicity in communities that rely predominantly on cereal-based diets.
Photonic Quantum State Transfer between disparate Quantum Nodes (2017)
de Riedmatten, Hugues (ICFO)view details
Classical information networks such as the internet have revolutionized our way of transmitting and processing data. Now, scientists are trying to build the quantum version of such networks, which hold promise to provide radically new capabilities compared to their classical counterparts. Quantum information networks (consisting of matter quantum nodes and quantum communication channels) could for example enable perfectly secure data transmission, enhanced data processing via distributed quantum computing or advanced clock synchronization applications. While it is generally agreed that photons are the best choice to transmit quantum information, the optimal matter system for building the quantum nodes is still an open question, as each system provides different functionalities. Therefore, the implementation of a hybrid network has been proposed, searching to combine the best capabilities of different material systems.
In a recent study, published in Nature, ICFO researchers led by ICREA Prof. Hugues de Riedmatten, have achieved an elementary “hybrid” quantum network link and demonstrated for the first time photonic quantum communication between two very distinct quantum nodes placed in different laboratories, using a single photon as information carrier.
In their study, the ICFO researchers used two very distinct quantum nodes functioning at different wavelengths: the emitting node was a laser-cooled cloud of Rubidium atoms and the receiving node a crystal doped with Praseodymium ions. They transmitted a qubit from one system to the other, using quantum frequency conversion techniques. The qubit emitted by the cold atomic ensemble was first converted to telecom wavelength, then transmitted to another laboratory via an optical fiber and finally converted to the frequency of the crystal, where it was absorbed and stored.
The results of the study have shown that two very different quantum systems can be connected and can communicate by means of a single photon. The ability to perform back- and forth-conversion of photonic qubits at the telecom C-band wavelength shows that these systems would be completely compatible with the current telecom networks.
Uncovering the underlying mechanisms and whole-brain dynamics of deep brain stimulation for Parkinson's disease. (2017)
Deco, Gustavo (UPF)view details
Deep brain stimulation, or DBS, has relieved the symptoms of more than 150,000 patients suffering from Parkinson’s disease. However, the functional mechanisms of this treatment have not yet been clarified. Now, thanks to the recent efforts of an international group of researchers, these mechanisms have been published in Scientific Reports.
The research was designed and conducted by Victor Saenger and Gustavo Deco, of the Center for Brain and Cognition (CBC) at Universitat Pompeu Fabra, and Morten Kringelbach, University of Oxford. The results show that using DBS in the subthalamic nucleus in patients with Parkinson’s disease balances global brain dynamics.
In the study, the researchers measured brain activity using Functional Magnetic Resonance imaging in ten patients with Parkinson’s disease before and during DBS treatment. Through large scale mathematical models of the brain they have shown the global effects created by such stimulation. Artificial stimulation has also been applied in a simulated brain exposing the brain regions that show greatest treatment efficacy.
“This method helps us to understand what regions are responsible for changing the brain activity of patients with Parkinson’s disease to the type of activity found in healthy persons. It is the first study to show that DBS treatment, despite being localized, has a global effect”, states Victor Saenger, of the Center for Brain and Cognition at UPF and first author of the article. He adds that “this method allows us also to understand why DBS treatment is so effective. Now we can find more effective stimulation regions without the need for clinical interventions”.
According to Morten Kringelbach of the University of Oxford, “the perspective of this study shows that we are now able to use computational models of brain activity to simulate the effects of brain stimulation and thus predict the result. In the long term, we hope to use these methods to make personalized interventions to achieve individual benefits”. However, he warns that “it is very important to consider the risks and ethical aspects of using something as invasive as the DBS method”.