The Scizzle Team
Bacteriophage/animal symbiosis at mucosal surfaces
The mucosal surfaces of animals, which are the major entry points for pathogenic bacteria, are also known to contain bacteriophages. In this study, Barr et al. characterized the role of these mucus associated phages. Phages were more commonly found on mucosal surfaces than other environments and adhere to mucin glycoproteins via hypervariable immunoglobulin like domains. Bacteriophage pre-treatment of mucus producing cells provided protection from bacterial induced death, but this was not the case for cells that did not produce mucus. These studies show that there may be a symbiotic relationship between bacteriophages and multicellular organisms which provides bacterial prey for the phages and antimicrobial protection for the animals.
Interlocking gear system discovered in jumping insects
Champion jumping insects need to move their powerful hind legs in synchrony to prevent spinning. Burrows and Sutton studied the mechanism of high speed jumping in Issus coleoptratus juveniles and found the first ever example in nature of an interlocking gear system. The gears are located on the trochantera (leg segments close to the body’s midline) and ensure both hind legs move together when Issus is preparing and jumping. As the insect matures, the gear system is lost, leaving the adults to rely on friction between trochantera for leg synchronization.
HIV-1 capsid hides virus from immune system
Of the two strains of HIV, HIV-1 is the more virulent and can avoid the human immune response, whereas HIV-2 is susceptible. This may be due to the fact that HIV-2 infects dendritic cells, which detect the virus and induce an innate immune response. HIV-1 cannot infect dendritic cells unless it is complexed with the HIV-2 protein Vpx, and even then the immune response isn’t induced until late in the viral life cycle, after integration into the host genome. Lahaye et al. found that only viral cDNA synthesis is required for viral detection by dendritic cells, not genome integration. Mutating the capsid proteins of HIV-1 showed that the capsid prevents sensing of HIV-1 cDNA until after the integration step. This new insight into how HIV-1 escapes immune detection may help HIV vaccine development.
Transcription factor binding in exons affects protein evolution
Many amino acids are specified by multiple codons that are not present in equal frequencies in nature. Organisms display biases towards particular codons, and in this study Stamatoyannopoulos et al. reveal one explanation. They find that transcription factors bind within exonic coding sequences, providing a selective pressure determining which codon is used for that particular amino acid. These codons are called duons for their function as both an amino acid code and a transcription factor binding site.
Down syndrome is caused by the most common chromosomal abnormality in live-born humans: Trisomy 21. The association of the syndrome with an extra (or partial extra) copy of chromosome 21 was established in 1959. In the subsequent fifty years a number of advances have been made using mouse models, but there are still many unanswered questions about exactly why the presence of this extra chromosome should lead to the observed defects. An ideal experimental strategy would be to turn off the extra chromosome in human trisomy 21 cells and compare the “corrected” version of these cells with the original trisomic cells. This is exactly what a team led by Jeanne Lawrence at the University of Massachusetts Medical School has done. Down syndrome is not the only human trisomy disorder: trisomy 13 (Patau syndrome) and trisomy 18 (Edward’s syndrome), for example, produce even more severe effects, with life expectancy usually under one to two years. Inducible chromosome silencing of cells from affected individuals could therefore also provide insights into the molecular and cellular etiology of these diseases.
Grow your own brain
By growing organs in a dish researchers can easily monitor and manipulate the organs’ development, gaining valuable insights into how they normally develop and which genes are involved. Now, however, a team of scientists from Vienna and Edinburgh have found a way to grow embryonic “brains” in culture, opening up a whole world of research possibilities. Their technique, published in Nature, has also already provided a new insight into the etiology of microcephaly, a severe brain defect.
[box style=”rounded”]Scizzling extra: In general, 2013 was a great year for growing your own kidneys, potentially a limb and liver. What organ will be next? [/box]
Sparking metastatic cell growth
A somewhat controversial paper published in Nature Cell Biology this year showed that the perivescular niche regulates breast tumor cells dormancy. The paper showed how disseminated breast tumor cells (DTC) are kept dormant and how they can be activated and aggressively metastasize. Based on the paper, this is due to the interaction of interaction with the microvascularate, where thrombospondin-1 (TSP-1) induces quiescence in DTC and TGF-beta1 and periosstin induces DTC growth. This work opens the door for potential therapeutic against tumor relapse.
Fear memories inherited epigenetically
Scientists showed that behavioral experiences can shape mice epigenetically in a way that is transmittable to offspring. Male mice conditioned to fear an odor showed hypomethylation for the respective odor receptor in their sperm; offspring of these mice showed both increased expression of this receptor, and increased sensitivity to the odor that their fathers had been conditioned on. Does this suggest that memories can be inherited?
Grid cells found in humans
Scientists have long studied rats in a maze, but what about humans? An exciting paper last August demonstrated that we, like out rodent counterparts, navigate in part using hippocampal grid cells. Initially identified in the entorhinal cortex of rats back in 2005, grid cells have the interesting activity pattern of firing in a hexagonal grid in the spatial environment and as such are thought to underlie the activity of place cells. Since then grid cells have been found in mice, rats, and monkeys, and fMRI data has suggested grid cells in humans. This paper used electrophysiological recordings to document grid cell activity in humans.
Sleep facilitates metabolic clearance
Sleep is vital to our health, but researchers have never been entirely sure why. It turns out part of the function of sleep may be washing waste products from the brain, leaving it clean and refreshed for a new day of use. Exchange of cerebral spinal fluid (CSF), which is the primary means of washing waste products from the brain, was shown to be significantly higher when animals were asleep compared to waking. This improved flow was traced back to increased interstitial space during sleep, and resulted in much more efficient clearance of waste products. Thus, sleep may be crucial to flushing metabolites from the brain, leaving it fresh and ready for another day’s work.
[box style = “rounded”] Robert adds: As a college student my friends and I always had discussions about sleep and it was also this mysterious black box of why we actually need to sleep. Studies could show the effects of lack of sleep such as poor cognition and worse memory but this paper linked it to an actual mechanism by which this happens. First of all I found it very impressive that the researchers trained mice to sleep under the microscope. On top of that showing the shrinkage of the neurons and the flow of cerebrospinal fluid which cleans out metabolites finally linked the cognitive aspects of sleep deprivation to the physical brain. [/box]
Poverty impedes cognitive function
People who are struggling financially often find it difficult to escape poverty, in part due to apparently poor decision making. Investigators demonstrated that part of this vicious cycle may arise from cognitive impairment as a direct result of financial pressures. The researchers found that thinking about finances reduced performance on cognitive tasks in participants who were struggling, but not in those who were financially comfortable. Furthermore, farmers demonstrated poorer cognitive performance before harvest, at a time of relative poverty, compared to after harvest when money was more abundant.
2013 has definitely been the year of the gut microbiome! Studies have shown that diet affects the composition of trillions of microorganisms in the human gut, and there is also a great deal of evidence pointing towards the gut microbiome affecting an individual’s susceptibility to a number of diseases. Recently published in Cell,
Hsiao and colleagues report that gut microbiota also affect behavior, specifically in autism spectrum disorder (ASD). Using a mouse model displaying ASD behavioral features, the researchers saw that probiotic treatment not only altered microbial composition, but also corrected gastrointestinal epithelial barrier defects and reduced leakage of metabolites, as demonstrated by an altered serum metabolomic profile. Additionally, a number of ASD behaviors were improved, including communication, anxiety, and sensorimotor behaviors. The researchers further showed that a particular metabolite abundant in ASD mice but lowered with probiotic treatment is the cause of certain behavioral abnormalities, indicating that gut bacteria-specific effects on the mammalian metabolome influence host behavior.
Your skin – their home
A paper published in Nature examined the diversity of the fungal and bacterial communities that call our skin home. The analysis done in this study revealed that the physiologic attributes and topography of skin differentially shape these two microbial communities. The study opens the door for studying how the pathogenic and commensal fungal and bacterial communities interact with each other and how it affects the maintenance of human health.
Discovery of new male-female interaction can help control malaria
A study published in PLOS Biology provided the first demonstration of an interaction between a male allohormone and a female protein in insects. The identification of a previously uncharacterized reproductive pathway in A. Gambiae has promise for the development of tools to control malaria-transmitting mosquito populations and interfere with the mating-induced pathway of oogenesis, which may have an effect on the development of Plasmodium malaria parasites.
[box style = “rounded”]Chris adds: “My friend chose this paper to present at journal club one week, because he thought it was well written, interesting etc etc. Unbeknownst to him, one of the paper’s authors was visiting us at the time. We sit down for journal club and one of the PIs comes in, sees the guy and exclaims (with mock exasperation) “you can’t be here!” Me and the presenter look at one another, confused. He presents journal club, and luckily enough, the paper is so well written, that he can’t really criticize it!” [/box]
Using grapefruit to deliver chemotherapy
Published in Nature Communications, this paper describes how nanoparticles can be made from edible grapefruit lipids and used to deliver different types of therapeutic agents, including medicinal compounds, short interfering RNA, DNA expression vectors, and proteins to different types of cells. Grapefruit-derived nanovectors demonstrated the ability to inhibit tumor growth in two tumor animal models. Moreover, the grapefruit nanoparticles used in this study had no detectable toxic effects, could be manipulated or modified to target specific cells/ tissues, and were economical to create. Grapefruits may have a bad reputation for interfering with drugs, but perhaps in the future we will be using grapefruit products to deliver drugs more effectively!
In May, a new technique called CLARITY to effectively make tissue transparent through a new fixation technique was published in Nature. This new process has allowed them to clearly see neuron connection networks not possible before because they can now view the networks in thicker tissue sections. This new advancement will help researchers be able to better map the brain, but this new technology can also be to create 3-D images of other tissues such as cancer. This new ability allows us to gain better insight into the macroscopic networks within a specific tissue type.
This year, the CRISPR technique was developed as an efficient gene-targeting method. The benefit of this method over the use of TALENS or a zinc-finger knockout is it allows for the rapid generation of mice that have multiple genetic mutations in just one step. The following review gives even more information on this new technique and compares its usefulness to that of TALENS and zinc-finger knockouts. Further, just couple of weeks ago, two back-to-back studies in Cell Stem Cell using the CRISPR-Cas9 system to cure diseases in mice and human stem cells. In the first study the system was used in mice to correct the Crygc gene that causes cataracts; in the second study the CRSPR-Cas9 system was used to correct the CFTR locus in cultured intestinal stem cells of CF patients. These findings serve as a proof-of-concept that diseases caused by a single mutation can be “fixed” with genome editing using the CRISPR-Cas9 system.
What was your favorite paper this year? Let us know! And of course – use Scizzle to stay on top of your favorite topics and authors.