The South Side Of Jupiter, Observed By The Voyager 1 Space Probe On March 1, 1979.

Checking Cancer At Its Origin..

In a first, the lab led by Leonard Zon at Boston Children’s Hospital has visualised the emergence of the primary melanoma cell in transgenic zebrafish that harbour the human oncogenic BRAFV600E mutation in melanocytes. This cancerous state is characterised in maturing fish by the formation of neural crest progenitors [NCPs], which are the predecessors of melanocytes and are only seen in the embryonic stage of healthy zebrafish.

The Zon lab placed the human mutated oncogene, BRAFV600E (a characteristic of benign human nevi/moles) under the control of a melanocyte-specific promoter and introduced it into the zebrafish. Generations of this transgenic fish were engineered such that they were also deficient in functional p53 (loss of function mutation). They used previous findings that in healthy zebrafish, a gene called crestin is expressed only in the embryonic NCPs and never throughout maturity, but is re-expressed selectively in melanomatous cells during adulthood. crestin was cloned adjacent to a reporter, enhanced green fluorescent protein [EGFP] for live imaging purposes.

The developmental phases of the fish, that were by now triple transgenic (for human BRAFV600E, p53 LOF and crestin:EGFP) were observed by live imaging; ~21 days after fertilisation, the expression of crestin:EGFP localised precisely to the (future) melanoma sites, and the very first triple-transgenic (individual) cells that went on to form larger masses of cells were also observed. To summarise, melanoma formation was observed in three stages: individual fluorescent cells, followed by these cells multiplying to form groups of <50 cells, and lastly these groups forming raised lesions. This consistently held true, with all 30 observed individual cells turning into 30 lesions. These results are illustrated in Figure 1.

Figure 1. In the top left box, a single cell is visualised as it multiplies into a group of melanoma cells (top right). The bottom images show the raised melanoma lesion as observed by the naked eye and by live imaging. The green fluorescence emitted from EGFP indicates that it is localised only to the melanoma (as is crestin expression), that is, it has not metastasised elsewhere. 

These pre-cancerous cells were also shown to be self-sustaining and tumourigenic: when fish scales containing the mutant cells were transplanted to another part of the same fish (auto-transplant) or to another fish (allo-transplant) that was also exposed to radiation, the cells proliferated in the new site, as well as penetrated the hypodermis underneath (Figure 2).

Figure 2. The fluorescence indicates a single scale being auto-transplanted elsewhere on the same fish. As the days progress, the patch expands as well, and after day 33, the cells penetrate deeper into the hypodermis and thrive independently, and excising the transplanted scale proves futile. 

Role of Transcription Factor sox10

sox10 is a master TF in NCP and its over-expression has been correlated with increased crestin expression, and accordingly, sox10 over expression in the transgenic melanocytes accelerated the melanoma onset. Following the logical train of thought that sox10 promotes melanoma progression, it was then targeted by CRISPR-Cas9 and inactivated in the transgenic cells. This resulted in a delayed onset of melanoma (180 days) compared to the controls (133 days). sox10 is also known to be expressed in most human melanoma cell lines. Moreover, the DNA element that acts as the binding site for Sox10 is also found in a hyper-acetylated [H3K27Ac], super-enhancer state. This is an epigenetic alteration and may prove a useful target in therapy (ex. HAT inhibitors).

Summary

The key finding clears up a hitherto ambiguous association between a reversion to stem/progenitor cell-like status and cancer: it indicates that the apparent devolution of a specialised cell to a primitive cellular state is not a consequence of cancer progression, but that it is an hallmark of pre-cancerous cells that may contribute to tumour progression. The rarity of melanoma formation among the mutant cells also suggests that the double mutant [BRAFV600E; p53 LOF] is not the only factor to influence the onset. Experimentally, crestin expression was a definitive prelude to formation of nevi which transformed into full-fledged raised melanomas in that spot.

This discovery has two chronological applications: first, of the many susceptible melanocytes harbouring the mutated oncogene, we can find out which are most likely to enter the melanoma state. Peaks in the expression profile of sox2, or a couple other TFs, dlx2 and tfap2, can prove to be a telltale pre-melanoma signature and thus be used in diagnosis. Secondly, by doing so, these can be better targeted early on before they’ve disseminated and become virtually untreatable.

Kaufman CK, Mosimann C, Fan ZP, Yang S, Thomas AJ, Ablain J, et al. A zebrafish melanoma model reveals emergence of neural crest identity during melanoma initiation. Science. 2016;351[6272]:aad2197–aad2197.

Collective memory in bacteria

Individual bacterial cells have short memories. But groups of bacteria can develop a collective memory that can increase their tolerance to stress. This has been demonstrated experimentally for the first time in a study by Eawag and ETH Zurich scientists published in PNAS.

Roland Mathis, Martin Ackermann. Response of single bacterial cells to stress gives rise to complex history dependence at the population level. PNAS, March 7, 2016 DOI: 10.1073/pnas.1511509113

Experimental set-up with the bacterium Caulobacter crescentus in microfluidic chips: each chip comprises eight channels, with a bacterial population growing in each channel. The bacteria are attached to the glass surface by an adhesive stalk. When the bacterial cells divide, one of the two daughter cells remains in the channel, while the other is washed out. Using time-lapse microscopy, bacterial cell-division cycles and survival probabilities can thus be reconstructed. Credit: Stephanie Stutz

Quote from #JaneGoodall primatologist and anthropologist. More quotes like this to inspire you in my new journal I Love Science, in stores March but ready for preorder now! #womeninscience #ilovescience #anthropology #scientificliteracy

Marrow Christmas and a Happy New Smear!

A very seasonal smear made from red marrow extracted from the iliac crest of a donor’s pelvis prior to transplantation.

Happy Holidays everyone

i♡histo

The image amazingly captures a single moment in time during the development of thousands of red and white blood cells.

Many of the small cells that are visible, like the ones forming the snowman’s carrot nose, do not have a nucleus. These are brand new erythrocytes (red blood cells) that are ready to exit the bone and enter the blood stream.

The other, slightly larger cells that have nuclei, like the snowman’s eyes and his top button, are either precursors to these erythrocytes (they will mature and lose their nucleus) or are precursors to the other blood cells in our body, the leukocytes (white blood cells): lymphocytes, monocytes, neutrophils, eosinophils and basophils.

In addition, the bone marrow is home to the cells that form platelets. These are huge multinucleated cells aptly named megakaryocytes - perhaps the cell at the bottom right.

It is possible to identify each mature cell and its precursor based upon its morphology and staining at higher magnification. High or low levels of these cells can indicate disease or cancers of the blood.

A Brand-New Human Organ Has Been Identified

Your body now has an extra organ — meet the mesentery.

A mighty membrane that twists and turns through the gut is starting the new year with a new classification: the structure, called the mesentery, has been upgraded to an organ.

Scientists have known about the structure, which connects a person’s small and large intestines to the abdominal wall and anchors them in place, according to the Mayo Clinic. However, until now, it was thought of as a number of distinct membranes by most scientists. Interestingly, in one of its earliest descriptions, none other than Leonardo da Vinci identified the membranes as a single structure, according to a recent review.

One of the smoothest, most beautiful color changes I’ve ever seen.

The reaction is methoxymethyl deprotection of one of my agonists with concentrated HCl in acetonitrile as my solvent. The color change doesn’t happen in THF!

(Image caption: The brain of a fruit fly contains many different regions responsible for processing sight, smell and taste in addition to regions for controlling movement. This image shows the results of a new method which automatically identifies these brain regions. Each color represents a different brain region. The authors used this method to discover specific areas involved in processing of visual information in the fly. The technique could also be used to refine our understanding of vertebrate brains)

Identifying Brain Regions Automatically

Using the example of the fruit fly, a team of biologists led by Prof. Dr. Andrew Straw has identified patterns in the genetic activity of brain cells and taken them as a basis for drawing conclusions about the structure of the brain. The research, published in Current Biology, was conducted at the University of Freiburg and at the Research Institute of Molecular Pathology (IMP) in Vienna, Austria.

The newly developed method focuses on enhancers, DNA segments responsible for enhancing transcription of RNA at specific locations and developmental times in an organism. The research started with a database of three-dimensional images showing individual enhancer activity. The team used an automatic pattern finding algorithm to identify genetic activity patterns shared across the images. They noticed that, in some cases, these patterns seemed to correspond with specific brain regions. To demonstrate the functionality of their method, the biologists began by applying it to regions of the fruit fly brain whose anatomy is already well known – namely, those responsible for the sense of smell. The activity patterns of the enhancers traced the already familiar anatomy of these regions.

Then the biologists used the new method to study brain regions responsible for vision. These experiments led to new insights into the anatomy of these areas: In addition to eleven already known regions, the activity patterns of the enhancers revealed 14 new regions, each of which presumably serves a different function for the fruit fly’s sense of sight. The researchers now aim to conduct further studies to determine which regions are responsible for which functions.

Andrew Straw has served since January 2016 as professor of behavioral neurobiology and animal physiology at the University of Freiburg’s Faculty of Biology and is a member of the Bernstein Center Freiburg (BCF). Before their move to Freiburg, he and his research assistants Karin Panser and Dr. Laszlo Tirian worked at the Research Institute of Molecular Pathology in Vienna in collaboration with Dr. Florian Schulze, Virtual Reality and Visualization Research Center GmbH (VRVis). The goal of Straw’s research is to achieve a better understanding of the structure and function of the brain. He hopes this basic research will ultimately help in the design of therapies for patients suffering from neurological diseases affecting specific regions of the brain.

Results and visualizations: https://strawlab.org/braincode

Clear as Day

The more light your eyes can take in, the better the picture you see, and the lens at the front of your eye is transparent to help this. Most body cells contain lots of membranes – they have important roles like manufacturing cellular components, but they scatter light and aren’t transparent. Cells in the lens become transparent by losing all but their most vital internal membranes as they develop and move towards the middle of the lens: the central cells (shown here in a chick’s eye) are flatter, with rounder nuclei (blue). It wasn’t known how the membranes were lost until recently, when scientists discovered a structure called the excisosome. This forms inside cells and breaks down the membranes, possibly by stripping them apart into the proteins and lipids they’re made of. Current research implies that excisosomes form in the lenses of all animals, helping us understand how our eyes develop.

Written by Esther Redhouse White

Image from work by M.Joseph Costello and colleagues

Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, USA

Image originally published under a Creative Commons Licence (BY 4.0)

Published in PLOS One, August 2016

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Organic Chemistry, Part 2/6

Reaction Mechanisms: Electrophilic addition to double bonds, SN2, SN1, E1, E2, and the decision tree

Next week: EAS, NAS, pericyclic reactions, Claisen rearrangements, and radical reactions!

Part 1

Blood is red, urine is yellow, and faeces are brown. Why? Chemistry*!  *Disclaimer: shout-outs to biology and physics too.