End of the semester teaching and a slew of chair duties have kept me away from the blog for a few weeks. But it is now 4:18 am and I am off with a colleague and 10 students for my semi-annual field trip to Oregon Inlet, North Carolina in the Outer Banks for my Marine Biology class. Look for frequent posts about our trip over the next few days.
|
|||||
   |
Two new studies in the journal Nature have leveraged the unique powers of the zebrafish as a model vertebrate to provide answers to this question. George Streisinger of the University of Oregon first developed this cute little pet store fish as a tool to study vertebrate development and gene function in the 1970s. It has since become a prominent player in many areas of biomedical research, and is my model of choice for studying lens development, evolution and cataract. Its use of external fertilization and a see-through egg makes it ideal for visualizing the early stages of development. And with basic molecular techniques you can make specific cell types light up with green fluorescent protein (GFP). This basic approach has now been used to provide further evidence that the initial source of blood stem cells is the lining of the aorta, the largest blood vessel leaving the heart. Previous studies in mice suggested that hematopoietic stem cells (HSCs: which will become all types of blood cells) arise from the endothelial cells lining the ventral surface of the aorta. David Travers’ group at UCSD labelled aortic endothelial cells with GFP and used confocal microscopy to show them moving from the endothelium into the bloodstream (Movie 1). But unlike a proposed mechanism for mammals, these zebrafish HSCs do not enter the arterial bloodstream, but instead move into a neighboring vein. While this detail differs between zebrafish and mammals, Travers’ work shows that similar molecular signaling coordinates the production of the HSCs in both taxa. And in a very cool experiment, they used flow cytometry to isolate these new putative HSCs from zebrafish embryos and confirmed that they indeed became blood stem cells. Movie 1. Live imaging of green HSCs leaving the aortic endothelium. In the second Nature paper, Kissa and Herbomel from the Pasteur Institute in Paris used confocal microscopy to detail how new HSCs can be removed from the lining of the aorta without damaging the integrity of this tube. They document that the differentiating HSCs fold over like a burrito, bringing together the neighboring endothelial cells and joining them together before leaving the tube (Figure 1). This study also confirms that zebrafish HSCs enter the bloodstream through the neighboring vein, not the aorta, and that the process shares similar signaling to mammals. When the authors used synthetic RNA molecules called morpholinos to stop the expression of a known mammalian signaling molecule called Runx1, the movement of HSCs from the aortic lining was highly reduced.  Figure 1. Detachment of HSCs (labeled in green) from the endothelial lining of the zebrafish dorsal aorta. The arrowhead in panel F shows folding in the HSC pulling together two neighboring endothelial cells before it leaves the aorta. So what do these papers add to our understanding of HSC generation? While the source of these cells was already thought to be the endothelial lining of the aorta, these new studies provide the first live visualization and physical description of this process. And while the physical details of the process differ between zebrafish and mammals, the molecular signaling seems to be the same, suggesting that the zebrafish can be a valuable model for further detailing the generation of HSCs and their development into blood stem cells. These studies are just one new example of the zebrafish’s growing influence in biomedical studies. Bertrand, J., Chi, N., Santoso, B., Teng, S., Stainier, D., & Traver, D. (2010). Haematopoietic stem cells derive directly from aortic endothelium during development Nature, 464 (7285), 108-111 DOI: 10.1038/nature08738 Kissa, K., & Herbomel, P. (2010). Blood stem cells emerge from aortic endothelium by a novel type of cell transition Nature, 464 (7285), 112-115 DOI: 10.1038/nature08761 I recently purchased two Flip video cameras for my Senior Capstone biology majors to use when shooting 60 second science videos later this semester. During this past week of spring break I took it on myself to give one a shakedown cruise to see if the built in editing software would do the trick for our class. So I present my first Flip video, edited on Flip software and annotated on YouTube. The topic is the three types of breakers found on sandy beaches – something we are talking about in my marine bio class this coming Monday. Just to entice you, there are dolphins, and my daughter says something funny at the end. Helpful comments always appreciated.
Your average anatomy and physiology textbook shows that all of the different cell types in our blood, such as the red blood cells that carry oxygen and the white blood cells that contribute to our immune system, develop from one stem cell type called a hemocytoblast (see figure below). And because of the importance of understanding the function of blood stem cells to treating many diseases, such as leukemia, this area has attracted lots of research.  A textbook description of blood cell formation. The hemocytoblast is called a multipotent stem cell because it maintains the ability to differentiate into the different types of blood cells. This flexible stem cell “commits” to a different developmental pathway by expressing receptor proteins on its surface for different signaling molecules, that will in turn tell it what to become. The paradigm has been that there is only one type of hemocytoblast, that only becomes committed when a receptor protein is placed on the cell surface. But studies have hinted at the presence of more than one type of hemocytoblast, and a research team based at the Baylor School of Medicine has now identified two of them. The researchers were able to identify and purify two mouse bone marrow stem cell types based on a difference in their interaction with a common cellular dye. When these purified stem cell types were transplanted into mice, the researchers found that each type preferred to make either red blood cells or immune cells. This preference was maintained in the stem cell population as each individual hemocytoblast type produced copies of itself, suggesting that the bias was programmed into the cell. It is not known how these two stem cell types differ, or what mechanism leads to the bias in blood cell production. The researchers found that each stem cell type responded differently to a common signaling molecule used in cellular differentiation, suggesting a possible mechanism. It is possible that there may still be a homogenous population of hemocytoblast precursor cells that predates the differentiation into these two newly found subtypes. But clearly, knowing about the presence of blood stem cells with different behaviors will be important for scientists attempting to harness these cells to treat human disease. I hope to read more about it in the next edition of our textbook. Challen, G., Boles, N., Chambers, S., & Goodell, M. (2010). Distinct Hematopoietic Stem Cell Subtypes Are Differentially Regulated by TGF-beta1 Cell Stem Cell, 6 (3), 265-278 DOI: 10.1016/j.stem.2010.02.002 It speaks for itself:
Thanks to a colleague for tacking this up in their office. I signed up for my Twitter account about two years ago, and then realized that I didn’t really want to let the world know what TV show I was watching, or what my daughter was having for breakfast. I didn’t see the use until noticing that I could follow news stories in real time, keep up with friends, and get updates from professional meetings. But it was not until I started working on this blog again recently that I realized how many scientists are using the platform to disseminate information and network with each other. Oh, and promote their blogs too. It might just be the timing or my naiveté, but it seems like Twitter and science are in a fast growth phase. Some evidence?:
And this past weekend I had my first, prolonged, real time Twitter discussion on academic science careers. Very interesting, lots of fun, and I picked up some new followers and made a great new contact. But one worry – how do you handle the volume of messages? Now, I feel like if I am not monitoring my Twitter stream, I will miss something. Besides the blogs I try to follow, this is another set of information to keep on top of. So, we will see how it goes. Will I keep with it? Don’t know. But I am looking forward to tweeting from the upcoming Fort Lauderdale eye meeting this May. I thought it was time liven up this space a bit. But the changes are more than skin deep. I have added a list in the right sidebar of my favorite posts spanning some of the different topics that I write about. And lower down in the right sidebar I have a section for Ashland science blogs. These will include blogs by student authors from our science departments, most of whom started blogging as part of my senior capstone course on science communication. I keep reading that bloggers need a niche, a focus that sets them apart from the many wonderful science blogs that are out there. As an integrative biologist my interests span from visual ecology, vertebrate evolution and systematics to protein biochemistry and lens development. But I am also deeply involved in mentoring undergraduate research, trying various technologies in my teaching (both new and old) and have developed an interest in exciting students about their ability to communicate science on the web through blogging. Does this all equal a niche? We will see. I hope you keep reading. This week in my undergrad science communication course my students discussed whether it was possible to change an anti-science, denialist perspective with good communication techniques. There was a mix of perspectives, but one view was that people will believe what they want, and will disregard scientific evidence to the contrary.
In a recent Nature editorial, Dan Kahan of Yale Law School criticizes what he sees as the dominant form of science communication:
One of Kahan’s suggestions is that scientific information needs to be presented by diverse voices, so that individuals can get information from people with similar cultural backgrounds. This point was raised by one of my students as well, who argued that blogging has the potential to set up this type of communication. Young science bloggers in particular may have the opportunity to gain the ears of their friends, and help promote scientific thinking, through their social networks. Your thoughts? Bora at A Blog Around the Clock initiated a great discussion on young science bloggers and why they do not always stick with their blogs. Bora was kind enough to talk about my senior capstone course at Ashland University in which my students start team science blogs to hone their science communication skills. Only one of my former students has kept with their blog once the class was over. So why is that? One former student has commented that they felt uncomfortable blogging on controversial subjects and having their public writing come back to hurt them. And a science journalist friend of mine noted that “the kids stop blogging because, you know, blogging is what old people do”. It’s true that some of my former students share science thoughts on Facebook, but another avoids talking science on FB for fear of being ostracized as a science geek by her non-science friends. The most common comment I read was that without a critical mass of people reading your stuff, there just wasn’t the motivation/guilt to get a blogger over the inertia of writing that next post. I definitely felt this when I started this blog, and I remember the excitement of actually getting some comments. Maybe we “minor” science bloggers, either young or old(er) just need to band together. We can be our own community, encouraging each other to write, guaranteeing that there are at least some people waiting for that next post. So I would encourage you to check out the two blogs below from my former students (and this one too!):
And while you are at it, check out some great student (or recently student) blogs and let them know you are reading:
As I approach the one year anniversary of my last blog post this seemed like an opportune time to break my blogjam (shoot, already in Urban Dictionary). Ironically this past year has been filled with blogging. I currently post actively to four blogs, and as I wrote about a year ago, I have started using blogs as teaching tools in my courses. I am now teaching my Department’s senior capstone course for the second time with a focus on science communication, and have students starting and contributing to their own science blogs. Students in my current Marine Biology and Anatomy and Physiology courses are also blogging, and I started a Science News Blog to promote our science programs at Ashland University. Now you can see why I have been neglecting A Fish Eye View. I plan to post more about this experiment in using blogging as a platform to teach science communication skills to students. But for now I would like to thank Bora at A Blog Around the Clock for mentioning the work that my students are doing. He points out the excellent writing on these student blogs, but asks the question why they do not stick to blogging after leaving the course and graduating from college. This is true of last year’s class, with one exception. I have some thoughts on this that I will share in future posts. I can also ask the students themselves in our next meeting. I invite you to see what our students are writing. And feel free to leave them an encouraging comment.
|
||||
|
Copyright © 2012 A Fish Eye View - All Rights Reserved |
|||||
Recent Comments