June 2015

Zebrafish make their own sunscreen

Zebrafish make their own sunscreen

Osborn, R.A., Almabruk, K.H., Holzwarth, G., Asamizu, S., LaDu, J., Kean, K.M., Karplus, P.A., Tanguay, R.L., Bakalinsky, A.T., Mahmud, T. (2015). De novo synthesis of a sunscreen compound in vertebrates. eLIFE.

A compound known as gadusol is responsible for protecting many animals, like the zebrafish, from the sun’s harmful ultraviolet radiation, a new study from Oregon State University finds.

Researchers originally believed that the zebrafish obtained gadusol from eating algae, which has long been known to naturally produce the compound. As it turns out, many fish, amphibians, birds and reptiles seem to have developed the ability to produce gadusol through “natural genetic engineering”.

“The ability to make gadusol, which was first discovered in fish eggs, clearly has some evolutionary value to be found in so many species,” remarked study lead author Taifo Mahmud. “We know it provides UV-B protection, it makes a pretty good sunscreen. But there may also be roles it plays as an antioxidant, in stress response, embryonic development and other functions.”

Mahmud and his team also discovered a way to produce high volumes of gadusol from yeast, which could potentially be applied to commercial sunscreens. Mahmud also notes that ingestion of gadusol could possibly provide a sunscreen that protects the body from the inside.

More from Oregon State University: http://oregonstate.edu/ua/ncs/archives/2015/may/no-lotions-needed-many-animal-species-produce-their-own-sunscreen

Read full research here: http://elifesciences.org/content/elife/4/e05919.full.pdf

New zebrafish model should speed research on parasite that causes toxoplasmosis

New zebrafish model should speed research on parasite that causes toxoplasmosis

Researchers at Oregon State University have found a method to speed the search for new therapies to treat toxoplasmosis – by successfully infecting zebrafish with Toxoplasma gondii.

The findings were just published in the Journal of Fish Diseases, in work supported by the Tartar Foundation and the National Institutes of Health.

  1. gondii, a protozoan parasite, can infect a wide range of hosts, and is one of the most prevalent parasites in the world. It has been estimated to infect about one-third of the human race. Treatment can be difficult because parasites often have biologic similarities to the hosts they infect.

Zebrafish have been found in recent years to be an excellent model for biomedical research because they reproduce rapidly, bear many similarities to human genetics and biological systems, and can be used in “high throughput” technologies to literally test hundreds of compounds in a fairly short period of time.

“This advance may provide a very efficient tool for the discovery of new therapies for this parasitic infection,” said Justin Sanders, an OSU postdoctoral fellow and lead author on the study. “With it we should be able to more easily screen a large library of compounds, at much less expense, and look at things that are unknown or have never been considered as a possible treatment.”

Although it infects many animals, T. gondii infection has never been observed prior to this in fish. But the OSU researchers found that by raising the temperature of the water in which zebrafish lived to a warmer-than-normal 98.6 degrees, or the temperature of a human body, they could become infected with the parasite but also survive.

T. gondii affects a wide range of mammals and birds, and cats are actually one of the most routine hosts,” said Michael Kent, a professor of microbiology in the OSU College of Science. “It can cause congenital defects, which is one reason that pregnant women are told not to clean the catbox. Many people become infected for life. These chronic infections can cause serious eye disease and can be fatal to people with weakened immune systems.

“New therapies would clearly be of value, and now we have a better way to find them,” he said.

This work was done in collaboration with researchers from the University of Chicago, Albert Einstein College of Medicine, and the U.S. Department of Agriculture.

The study this story is based on is available online: http://onlinelibrary.wiley.com/doi/10.1111/jfd.12393/full

Original article: http://oregonstate.edu/ua/ncs/archives/2015/may/new-zebrafish-model-should-speed-research-parasite-causes-toxoplasmosis

Murcia University honours Dr. Leonard Zon

Murcia University honours Dr. Leonard Zon

Jorge Galindo-Villegas, Murcia University, Spain

On April 21st, 2015, Dr. Len Zon, Director of the Stem Cell Program at Children’s Hospital Boston at Harvard Medical School (USA), was made Doctor Honoris Causa by Murcia University, Spain. The academic ceremony was presided over by the Honorable Rector Magnificus José Orihuela Calatayud and several distinguished members of the University community. The ceremony took place in the auditorium “Hermenegildo Lumeras de Castro” located beneath the Faculty of Chemistry which faces the Faculty of Biology, on the Espinardo campus. The ceremony, which was broadcast live, included the performance of different pieces by the chamber orchestra of Murcia University. Len’s promoter was Dr. Victoriano Mulero, Professor of the Department of Cell Biology and Histology, who gave the Laudatio speech.

The ceremony began with the entrance of the academic authorities to the sound of Andante, which was followed by the opening speech given by the Rector Orihuela Calatayud. The General Secretary of the University, Santiago M. Alvarez Carreño proceeded to read out the agreement made by the Board of Governors to the proposal made by the Department of Cell Biology and Histology, Faculty of Biology, to confer the Honoris Causa Degree on Dr. Zon. This agreement recognizes Len’s brilliant teaching, outstanding research track record and his renown as a leading pediatrician. He is one of the world leading figures in the field of stem cells transplantation, a researcher specialized in blood diseases and, quite importantly, founder of a new avenue of hematological research and drug screening to cure cancers, among many other diseases, using the zebrafish as a vertebrate animal model. After the agreement was pronounced, the Rector kindly asked for the presence of the Laureate. Len entered accompanied by his promoter Dr. Mulero and the Dean of the Faculty of Biology, Dr. Jose Meseguer, to the tune of Concerto for Two Trumpets in C Major (RV537). After everyone took their seat, Professor Mulero gave his Laudatio of Len in which he offered an extensive overview of his outstanding and brilliant academic career. Then, the Rector awarded Len with a Doctor Honoris Causa, thus becoming a member of the University’s Senate of Doctors. The last part of the act included the new Doctor’s speech of acceptance, following the rendering.

Len acknowledged the award, by immediately telling a funny phrase which made everyone in the audience lose the solemnity of the act with a big laugh: “I have had the opportunity of being twice in each of the three most important cities in Spain, twice in Madrid, twice in Barcelona and of course, twice in Murcia” (Murcia is a quite small town without touristic recognition). He continued by speaking a bit about his daily work. He presented himself as a hematologist by training, a medical doctor who takes care of children presenting blood diseases or cancer, and a researcher keen to learn and decipher the biology of stem cells to produce effective drugs to treat mortal human diseases.

In his speech, he stressed the several advantages displayed by the zebrafish as a vertebrate animal model. He then introduced his particular and interesting research focus by using a graphical video which he produced. The video showed a transgenic zebrafish embryo expressing fluorescence in the blood cells and he described how it was used to dissect the formation of these important cells in vertebrates. The impressive video came to a climax when he introduced how blood stem cells go into the circulation and eventually, to the intermediate cell mass at the tail where the blood cells are formed, following the process known as homing, which is accomplished through the interaction with endothelial and stromal cells in the vascular hematopoietic niche. After dividing again, they then go back into circulation and eventually will colonize the kidney. Some will go further to the thymus, allowing the animal to have blood for its entire lifetime. Len highlighted the functional importance of this process, where he transplanted stem blood cells allowing sick people to live an entire life-time. Proud of his findings he mentioned “I’ve done this procedure in a broad number of patients. Although we know how to make bone marrow transplantation, we don’t really understand how it works”.

To end his acceptance speech, Len mentioned that now his laboratory is interested in knowing more about the mechanism and pathways, using the zebrafish as a feasible live vertebrate model. So far, using thousands of small zebrafish embryos and a high-throughput chemical genetic screening, he has identified prostaglandins as stimulators of blood stem cell production both during embryogenesis and in adulthood. His studies may support a deeper comprehension of how human blood stem cells home to the marrow, engraft and self-renew, and suggest new therapeutic approaches for hematological disorders.

Duke Study Uncovers Foundations of Heart Regeneration

Duke Study Uncovers Foundations of Heart Regeneration

duke

The outer layer of the zebrafish heart (shown in green) is regenerated rapidly after damage, covering the heart like a wave from the base of one chamber to the tip of the other. Researchers have discovered properties of this mysterious outer layer — known as the epicardium — that could help explain the aquarium denizen’s remarkable ability to regrow cardiac tissue.
Photo credit: Jingli Cao

While the human heart can’t heal itself, the zebrafish heart can easily replace cells lost by damage or disease. Now, researchers have discovered properties of a mysterious outer layer of the heart known as the epicardium that could help explain the fish’s remarkable ability to regrow cardiac tissue.

After an injury, the cells in the zebrafish epicardium dive into action — generating new cells to cover the wound, secreting chemicals that prompt muscle cells to grow and divide, and supporting the production of blood vessels to carry oxygen to new tissues.

A study appearing May 4 in the journal Nature found that when this critical layer of the heart is damaged, the whole repair process is delayed as the epicardium undergoes a round of self-healing before tending to the rest of the heart. The new research showed that the process requires signaling through a protein called sonic hedgehog, and demonstrated that adding this molecule to the surface of the heart can drive the epicardial response to injury.

The finding points to a possible target for repairing the damage caused by a heart attack, a major cause of death and disability in the United States. More than five million Americans are currently experiencing heart failure, and over 900,000 suffer from a heart attack each year.

“The best way to understand how an organ regenerates is to deconstruct it. So for the heart, the muscle usually gets all the attention because it seems to do all the work,” said Kenneth D. Poss, Ph.D., senior author of the study and professor of cell biology at Duke University School of Medicine. “But we also need to look at the other components and study how they respond to injury. Clearly, there is something special about the epicardium in zebrafish that makes it possible for them to regenerate so easily.”

Poss has been studying heart regeneration in zebrafish for the last 13 years. As a postdoctoral fellow he was the first to show that the puny, striped fish could regrow severed pieces of heart tissue, like a lizard growing back a pinched tail. Since then, his group has found that this regeneration involves the input of the epicardium, a thin layer of cells that cover the surface of the heart.

“The epicardium is underappreciated, but we think it is important because similar tissues wrap up most of our organs and line our organ cavities,” Poss said. “Some people think of it as a stem cell because it can make more of its own, and can contribute all different cell types and factors when there is an injury. The truth is we know surprisingly little about this single layer of cells or how it works. It is a mystery.”

In this study, Poss and his colleagues were determined to identify the properties of the epicardium that make it such a regenerative powerhouse. First, Duke postdoctoral fellow Jinhu Wang performed open-heart surgery on live zebrafish, removing approximately one fifth of the vital organ. Afterwards he used a set of sophisticated genetic tools to kill 90 percent of the epicardial cells and then measured how well the heart healed at various time points. He found that removing this outer layer created a clear lag in regeneration, but that eventually the healing process caught up to that of zebrafish with an intact epicardium.

The results suggested that the 10 percent of epicardial cells left behind were able to rebuild the epicardial layer before moving on to heart muscle. Intrigued by the finding, Poss decided to focus the next series of experiments on the epicardium and its ability to regenerate itself. Jingli Cao, another postdoctoral fellow in his laboratory, figured out a way to remove hearts from zebrafish and grow them in dishes in the laboratory, where the tiny two-chambered organs continued to beat and behave as if they were still tucked inside the organism.

As they had before, the researchers destroyed most of the heart’s epicardial layer, but this time they put the “explanted” organs under the microscope every day to capture the regeneration in action. They showed that the epicardium regenerated rapidly, covering the heart like a wave from the base of one chamber to the tip of the other in just a week or two.

The researchers then used this model to search for small molecule compounds or drugs that would affect the ability to regenerate. They screened molecules known to be involved in development of embryos, like fibroblast growth factors and sonic hedgehog, and found that the latter was critical for the regeneration process. The researchers now plan to perform larger screens for molecules that could enhance heart repair in zebrafish, and perhaps one day provide a new treatment for humans with heart conditions.

In a second paper appearing April 1, 2015, in the journal eLife, Poss and colleagues found that the epicardium produces a molecule called neuregulin1 that makes heart muscle cells divide in response to injury. When they artificially boosted levels of neuregulin1, even without injury, the heart started building more and more muscle cells. The finding further underscores the role of this tissue in heart health.

“Studies of the epicardium in various organisms have shown that this tissue is strikingly similar between fish and mammals, indicating that what we learn in zebrafish models has great potential to reveal methods to stimulate heart regeneration in humans,” said Poss.

The Nature study was supported by postdoctoral fellowships from the American Heart Association and grants from the National Institutes of Health (HL081674) and the American Federation for Aging Research.

Read original article here https://today.duke.edu/2015/05/heartlayer

A new role for zebrafish: Larger scale gene function studies

A new role for zebrafish: Larger scale gene function studies

new role

NHGRI scientists are homing in on specific genes in zebrafish to help them better understand the function of genes in people.

Read full article here

A relatively new method of targeting specific DNA sequences in zebrafish could dramatically accelerate the discovery of gene function and the identification of disease genes in humans, according to scientists at the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health.
In a study posted online on June 5, 2015, and to be published in the July 2015 issue of Genome Research, the researchers reported that the gene-editing technology known as CRISPR/Cas9 is six times more effective than other techniques at homing in on target genes and inserting or deleting specific sequences. The study also demonstrated that the CRISPR/Cas9 method can be used in a “multiplexed” fashion – that is, targeting and mutating multiple genes at the same time to determine their functions.
It was shown about a year ago that CRISPR can knock out a gene quickly,” said Shawn Burgess, Ph.D., a senior investigator with NHGRI’s Translational and Functional Genomics Branch and head of the Developmental Genomics Section. “What we have done is to establish an entire pipeline for knocking out many genes and testing their function quickly in a vertebrate model.” Researchers often try to determine the role of a gene by knocking it out — turning it off or removing it — and watching the potential effects on an organism lacking it.
Such larger scale — termed high-throughput — gene targeting in an animal model could be particularly useful for human genomic research. Only 10 to 20 percent of recognized human genes have been subjected to such rigorous testing, Dr. Burgess said. The functions of many other genes have been inferred based on analyzing proteins or have been identified as possible disease genes, but the functions of those genes have not been confirmed by knocking them out in animal models and seeing what happens.
This is a way to do that on a more cost-efficient and large scale,” Dr. Burgess said.
The study of zebrafish has already led to advances in our understanding of cancer and other human diseases,” said NHGRI Director Eric Green, M.D., Ph.D. “We anticipate that the techniques developed by NHGRI researchers will accelerate understanding the biological function of specific genes and the role they play in human genetic diseases.”
The CRISPR/Cas9 method of gene editing is one of the two essential components in the NHGRI team’s high-throughput method. Modeled on a defense mechanism evolved by bacteria against viruses, CRISPR/Cas9 activity was first described in 2012. Since then, its use has spread quickly in genomic research labs in the United States and abroad.
The acronym CRISPR stands for “clustered, regularly interspaced, short palindromic repeat,” referring to a pattern of DNA sequences that appears frequently in bacterial DNA. Scientists believe the CRISPR sequences reflect evolutionary responses to past viral attacks.

 

“We’ve shown that with relatively moderate resources, you can analyze hundreds of genes”
—Dr. Shawn Burgess
Senior Investigator, Translational and Functional Genomics Branch, NHGRI

The Cas9 protein is a nuclease, an enzyme that snips a stretch of DNA in two places, in effect cutting out a piece. Bound together, CRISPR/Cas9 becomes a powerful research tool that permits researchers to target and delete a particular sequence or to insert a new sequence into the DNA of animal-model embryos.
The other essential component of the NHGRI team’s method is the zebrafish. The zebrafish and the mouse are the most commonly studied vertebrate laboratory animals whose genomes have been completely sequenced. The zebrafish is better suited to larger scale gene editing because about 70 percent of zebrafish genes appear to have human counterparts and the fish are far less costly to maintain than are mice. They multiply astonishingly quickly; a female may produce as many as 200 eggs at one time. And the embryos are fertilized externally and are transparent, making them readily accessible to researchers.
To demonstrate the feasibility of high throughput editing, the researchers targeted 162 locations in 83 zebrafish genes – about 50 of which are similar to human genes involved in deafness. (Hearing is one of the other interests of Dr. Burgess’s lab.) This produced mutations in 82 of the 83 genes.
In screening embryos by fluorescent polymerase chain reaction (a technology that allows researchers to produce millions of copies of a specific DNA sequence) and high-throughput DNA sequencing, the researchers determined that overall, mutations were passed on to the next generation in 28 percent of cases. The transmission rate was higher for some genes than for others, but in most cases, screening offspring from parent fish should be enough to spot most mutations, the researchers reported.
The results demonstrated that using the CRISPR/Cas9 technique in zebrafish will make it possible to both generate mutants for all genes in the zebrafish genome and carry out large-scale phenotyping, they noted in the Genome Research paper.
The CRISPR/Cas9 methodology works in mice, too, but it is more costly and takes far longer. Although mice actually reach sexual maturity earlier than zebrafish, they produce far fewer offspring.
Ultimately, Dr. Burgess hopes that his lab will use the new method to knock out about 10 percent of the zebrafish’s roughly 25,000 genes, and he would like to see an even broader effort. “We’ve shown that with relatively moderate resources, you can analyze hundreds of genes,” Dr. Burgess said. “On the scale of big science, you could target every gene in the genome with what would be a relatively modest scientific investment in the low tens of millions of dollars.”
Coauthors of the Genome Research paper with Dr. Burgess were: Gaurav Varshney, Ph.D., Wuhong Pei, Ph.D., Matthew LaFave, Ph.D., Lisha Xu, M.S., Viviana Gallardo Mendieta, Ph.D., Blake Carrington, M.S., Kevin Bishop, M.S, Mary Pat Jones, M.S, Ursula Harper, M.S, and Raman Sood, Ph.D, all of NHGRI; Mingyu Li , Ph.D, and Wenbiao Chen, Ph.D, both of Vanderbilt University School of Medicine in Nashville; Sunny Huang, B.S, formerly of NHGRI, now of the University of Iowa in Iowa City; Jennifer Idol, M.S., formerly of NHGRI, now of the Jackson Laboratory in Bar Harbor, Maine; and Johan Ledin, Ph.D., of Uppsala University in Uppsala, Sweden.