Shiga toxin is a dangerous by-product of certain infectious bacteria, such as strains of Shigella and E. coli, which causes symptoms ranging from intestinal pain to kidney failure and even death. Over 150 million people are afflicted with Shiga toxicosis every year, mostly in developing countries where waterborne diseases are prevalent. It is estimated that Shiga toxins kill more than one million people annually, and is particularly lethal to children. Even in developed countries, Shiga toxicosis remains a threat via foodborne outbreaks.
While exploring the inner workings of the cell, scientists at Carnegie Mellon discovered that Shiga toxin exploits the GPP130 protein found in the Golgi apparatus. As described in their article for the January 20th issue of Science, when a harmful substance enters the cell, it is normally packaged by the Golgi apparatus and sent to the lysosome for degradation. GPP130, however, is an unusual protein that cycles from the Golgi apparatus to endosomes and back without crossing paths with the lysosome. This feature of the GPP130 is utilized by the Shiga toxin which binds to the protein to avoid detection allowing it to remain in the cell where it can cause harm.
However, when high levels of manganese infiltrate the cell, GPP130 alters its pathway to go directly to the lysosome. Beyond a certain point, manganese is also toxic to humans, but the concentrations and methods of administration are already well-documented.
“Manganese is inexpensive. While Shiga toxin affects people in the developed world, it affects far more people in the developing world. An inexpensive, accessible treatment– not a designer drug — is the ideal solution,” says Adam Linstedt, professor of biological sciences at Carnegie Mellon. “While further testing is needed to determine if manganese is a suitable treatment for humans, I’m optimistic that trials should move forward quickly.
Current treatment methods utilize antibiotics to kill the Shiga-excreting bacteria, which actually causes them to lyse (or break apart) and release the toxin in higher concentrations to the detriment of the host. The researchers propose using manganese in conjunction with the antibiotics to neutralize the toxin as well as the bacteria simultaneously. If the scientists are successful in balancing the manganese dosage and the proper supply chain avenues are set up, millions of lives could be saved.
Researchers at the Washington University School of Medicine in St. Louis have discovered that variations in the CD36 gene can alter a human’s sensitivity to the taste of fat in foods. Prior investigation of the CD36 gene in rodent models showed that rats and mice engineered without the CD36 gene no longer had a preference for fatty foods and were not able to digest fat properly. The preference for high-fat foods with higher energy yields is a vital part of the diet.
As noted in their article for the Journal of Lipid Research, not only can people who produce more CD36 protein more easily detect fat, it is estimated that 20% of people have a variant of the CD36 gene associated with making less CD36 protein. 21 participants, all with body mass indexes of 30 or more (within the range of “obese”), and varying degrees of CD36 protein production, were asked to taste and identify three different solutions. One solution contained fatty oil, while the other two were fat-free, but similar in consistency. To avoid cheating by scent and visual cues, the subjects wore nose clips and were tested in a room lit by red lamps. As expected, it was found that participants with genotypes conducive of higher CD36 production were better able to detect the solution containing fat than participants with genotypes less conducive of CD36 production.
“We did the same three-cup test several times with each subject to learn the thresholds at which individuals could identify fat in the solution,” explains Marta Yanina Pepino, PhD, research assistant professor of medicine. “If we had asked, ‘does it taste like fat to you?’ that could be very subjective. So we tried to objectively measure the lowest concentration of fat at which someone could detect a difference… We have to learn what the signal means. It could be how much fat they need to absorb to get the signal of satiety. This is just the tip of the iceberg, the beginning of the story.”
The ultimate goal is to understand how the CD36 gene works in humans, it’s relation to satiety, and how it may play a role in obesity. With such knowledge, researchers may be able to devise new measures and methods aimed at tackling obesity.
Describing their achievement in an article titled “Generation of Chimeric Rhesus Monkeys” for the latest issue of Cell, scientists from Oregon Health & Science University engineered the first successful birth of chimeric Rhesus monkeys. Roku and Hex (shown right) are twins born to the same mother, while Chimero (a singleton) was born to a different surrogate mother at the Oregon National Primate Research Center (ONPRC). All three chimeras are male, though Roku was shown to contain both male and female cells.
A chimera is an organism composed of two or more differing populations of genetically distinct cells and tissues. Chimeric animals are formed from at least four parent cells, (i.e. two fused early embryos). In laboratory research, chimeric animals are valuable tools for investigating questions of genetics and cell lineage.
To conduct the study, surrogate Rhesus monkey females were implanted with in-vitro fertilized blastocysts, which were previously injected by a mix of tagged and untagged embryonic stem cells (ESCs) from multiple donors. After some time, an analysis of mid-term fetuses showed that chimeric tissues were not present. Due to this, further steps were taken to investigate whether the ESCs or the blastocysts were at fault for the lack of chimeric presence. The results showed that monkey blastocysts do not readily incorporate foreign inner cell masses or ESCs. In order to successfully create a chimeric Rhesus monkey, the scientists had to synthesize blastocysts from cells at an even earlier stage of development (totipotent rather than pluripotent cells) for implantation.
Totipotency describes cells that can potentially divide into all cell types, including the placental and fetal cells required for a viable organism (as opposed to pluripotent cells, such as ESCs, which cannot form placental cells). Thus, with the trial and error creation of chimeric Rhesus monkeys, the researchers discovered that higher primate chimeras can only develop from totipotent cells, unlike rodent chimeras, which can develop from a range of donor cell types (including ESCs).
Ultimately, medical applications for human stem cell technology may improve with these findings.
“This is an important development… it points out a key distinction between species and between different kind(s) of stem cells that will impact our understanding of stem cells and their future potential in regenerative medicine,” explains the Cell article co-author and associate scientist of ONPRC’s Division of Reproductive and Developmental Sciences, Shoukhrat Mitalipov, Ph.D.
In Badwater Basin, at the edge of Death Valley National Park, researchers from the University of Nevada, Las Vegas have discovered a new type of magnetic bacteria that could prove useful for a number of biomedical applications. This new bacterium, dubbed BW-1, belongs to a class of magnetic or magnetotactic bacteria characterized by internal structures called magnetosomes which produce magnetic nanocrystals. Magnetic nanocrystals, such as magnetite (Fe3O4) and greigite (Fe3S4) (as found in BW-1), allow bacterium to interact with and navigate magnetic fields.
“The finding is significant in showing that this bacterium has specific genes to synthesize magnetite and greigite, and that the proportion of these magnetosomes varies with the chemistry of the environment,” explains Enriquieta Barrera, program director in the National Science Foundation’s Division of Earth Sciences.
Current studies mostly focus on magnetite-producing bacteria, making BW-1 the first greigite-producing bacteria to have been successfully isolated and cultured. Inspection of BW-1 DNA further revealed two sets of magnetosome genes, likely accounting for its production of both magnetite and greigite.
Greigite, an iron sulfide, indicates that BW-1 represents a new group of sulfate-reducing bacteria in a class dominated by oxygen-reducing bacteria (i.e. that BW-1 produces a sulfate based nanocrystal as opposed to only oxygen based nanocrystals as many other magnetotactic bacteria do). With all these new properties, BW-1 and its magnetic nanocrystals hold potential in cation-based drug delivery and magnetic-particle based imaging, two research areas yet to be explored with the newly isolated compound.
The brain requires activation of many different genes to alter connections between neurons for encoding memories. Neuroscientists at the Massachusetts Institute of Technology have published findings that the Npas4 gene and transcription factor may be a singular instigator and master gene for memory formation in the brain. Npas4 was previously known for activating during new experiences.
As described in their Science article, the researchers investigated the genetic mechanisms of memory formation by monitoring gene activation pathways in mice subjected to contextual fear conditioning. When entering a specific chamber, the mice were given a mild electric shock which caused them to learn within minutes to fear the chamber and freeze upon entering it.
The findings, which indicated that Npas4 turned on very early in the conditioning regimen, set the gene “apart from many other activity-regulated genes”. Further, it was found that activation occurred primarily in the CA3 hippocampal region, an area in the brain required for fast learning.
“We think of the Npas4 as the initial trigger that comes on, and then in turn, in the right spot of the brain, it activates these other downstream targets. Eventually they’re going to modify synapses in a way that’s likely changing synaptic inhibition or some other process that we’re trying to figure out,” says graduate student Kartik Ramamoorthi, lead author of the paper.
To hit the point home, mice did not remember the fear conditioning when the scientists chose to knock out the Npas4 gene, both overall and specifically in the CA3 hippocampal region. Although the study has only identified a few of the genes regulated by Npas4 and only inspected contextual fear conditioning, scientists suspect hundreds more genes are involved in the pathway and that other learning techniques will also involve Npas4.
In the future, the MIT team intends to monitor the neural activity of Npas4 during memory retrieval as well as memory formation, which may someday lead to pinpointing the exact locations of memories in the brain.
Hemophilia refers to a class of genetic disorders characterized by the impairment of blood clotting or coagulation due to the lack of clotting factors normally produced by the liver. Hemophilia type A, for example, results from the deficiency of Clotting Factor VIII while Hemophilia type B results from the lack of Clotting Factor IX. In a recent study published in the New England Journal of Medicine, British researchers at University College London Cancer Institute in collaboration with St. Jude Children’s Research Hospital successfully treated six severe Hemophilia B patients by introducing into them a gene coding for Clotting Factor IX. While past clinical trials using gene therapy were not able to produce lasting expression of clotting factors, this current study shows expression lasting for at least a year. Further, animal models using the same methods have shown genetic expression for up to ten years.
In their study, the scientists used a viral vector (a virus incapacitated of reproduction and infectivity) to carry DNA containing code for Clotting Factor IX. This vector specifically targets the liver where it initiates the production of Clotting Factor IX. All six patients taking part in this study originally produced less than 1% of the normal expected levels of Clotting Factor IX. After a year into the gene therapy trial, the patients were all producing 2 – 12% of the normal levels of Clotting Factor IX (with higher dosages of the viral cocktail corresponding to higher production of Clotting Factor IX). While this appears minute, the research is making steady progress. Perhaps once the gene therapy methods reach optimal potency, the scientists can transition to studying the more prevalent Hemophilia A which requires delivery of a larger gene (for Clotting Factor VIII).
The current treatment for hemophilia B involves injecting clotting factor IX concentrate into patients with the disease. The cost for this can range anywhere from $150,000 to $300,000 a year depending on the frequency of injections needed by the patient. The proposed gene therapy, in addition to its efficacy, would bring down costs for treatment to around $30,000 per patient, since a single treatment would last at least a year as the study has shown. The researchers involved in this study explain their findings below:
