Monte Westerfield, Ph.D., and his team at the University of Oregon Institute of Neuroscience is developing the first animal model of Usher Syndrome type 1F to display vision loss. We interviewed him to provide you information about his work.
Why is it important for us to have an animal model of the Usher 1F mutation?
“Potential therapies need to be tested pre-clinically before they are approved for patients. We can use human cells in some types of preclinical studies, but an animal model is better because we can measure whether a treatment actually prevents loss of vision.”
Multiple attempts to develop a mouse model of the Usher 1F mutation failed. Why is a zebrafish a better animal model than a mouse?
“Mice have been great models for understanding the basis of deafness in Usher syndrome. Unfortunately, however, mice with Usher gene mutations typically do not develop vision loss, and, in the cases where they do, the retinal defects appear slowly very late in life. Many of our zebrafish models, on the other hand, develop retinal defects and vision loss within the first few weeks of life. This allows us to test potential therapies much more rapidly.
What potential treatments can a zebrafish model be used to test?
“Almost any type of treatment can be tested on zebrafish. We are currently developing zebrafish models of Usher 1F that have the exact same Usher 1F DNA gene sequence as human patients. These animals can be used to test a wide variety of drugs and gene therapies.
Can you explain what exon skipping is? Currently, at what stage is your work on our zebrafish?
“The Usher 1F mutation is a change in the DNA sequence at a single spot in the Usher 1F gene. When the gene is translated into protein, the mutation halts the process so a short, dysfunctional protein is produced. With exon skipping we hope to skip over the bad spot in the DNA so that a nearly full-length and hopefully fully-functional protein is produced. To date, we have made the first models to test whether skipping this region of the gene still produces a functional protein. If so, we can move to the next step of designing drugs to induce skipping in human cells.
How did your lab come to be the best place in the U.S. for zebrafish models of Usher syndrome? Why is your facility the best and most comprehensive for this kind of work?
“The use of zebrafish in biomedical research began at the University of Oregon with the pioneering work of George Streisinger in the 1970s. I joined the University in 1981, and there are now more than 100 researchers here using zebrafish for molecular genetics. For more than 10 years, our laboratory has focused on Usher syndrome, funded primarily by the National Institutes of Health (NIH). Recently we obtained a new grant from the NIH to build a large, state-of-the-art animal facility for housing zebrafish. This new facility also just received a $10 million gift from a donor that will help provide endowed support for raising our zebrafish models.”
About how many zebrafish total will you generate for this project?
“We are producing several different zebrafish families carrying the normal Usher 1F gene or mutant forms of the gene. For each family, we raise 25-50 fish to adulthood. We breed these fish to generate individuals for our studies. When zebrafish breed, they produce many hundreds of eggs. So all told, we will generate several thousand animals in the course of this work.”
Is there anyone or anyplace else using zebrafish technology?
“Yes. Although zebrafish genetic studies started with a single laboratory here at the University of Oregon, there are now over 7,000 researchers in more than 40 countries using zebrafish technology. We are collaborating with several of these researchers who are developing technologies that may be applicable to our studies of Usher 1F.”
What are the stages that you go through to incorporate the Usher 1F gene within the zebrafish and how long from step A to step Z does it take to formulate a result or a response?
“The first step was to obtain the human gene sequence from normal individuals and from Usher 1F patients. We then cut out the corresponding part of the zebrafish gene and replaced it with the human sequence to generate the models. These experiments were conducted in newly fertilized zebrafish eggs. We then grew the embryos up to adulthood and bred them to produce offspring that have Usher syndrome. This part of the work has taken about a year and half. We are now testing these Usher 1F models to ensure that the gene replacement is correct. Then we will start testing various strategies to treat the models with therapies that can eventually be used in patients. At that point, we will partner with companies that specialize in gene therapies and that can eventually help move the project forward to clinical trials with patients.
What is the most challenging part in using zebrafish with Usher 1F?
“Although zebrafish have been widely used for molecular genetics, this is one of the first experiments to swap in part of a human gene. Along the way, we have run into a number of unanticipated surprises that have altered our strategy. But, this is, of course, part of the challenge and excitement of basic research.”