Search This Blog

Loading...

Friday, May 18, 2012

The Fourth Symptom

By Mark Dunning

When someone is diagnosed with Usher syndrome, there are a lot of services offered to address the physical symptoms associated with the disorder. There are hearing aids and cochlear implants, speech therapy and ASL, FMs and loops and closed captioning for hearing loss. There is mobility training and tactile sign and braille and canes and guide dogs for vision loss. There’s physical therapy, and occupational therapy, and even hippotherapy for balance issues.

But the most debilitating aspect of the disorder, the psychological impact of living with Usher, is usually left for the family to address on their own.

There are two main psychological issues that people with Usher face. One is anxiety. The other is depression. I’ll talk about anxiety in a later post. Today, we’ll talk about depression. As always, let me state that I’m no expert on depression. But one thing I do know is that there is a stigma attached to it. Mental illness of any type is something that’s kept quiet everywhere and in some countries is so taboo that it’s not even spoken of within families. Depression is seen as weakness. You’re supposed to be able to handle it by yourself. Pull yourself up by your bootstraps. Get over it and get on with it.

Many with Usher do just that after they are first diagnosed. They deal with the emotions on their own. They get back on their feet and get on with their lives. The problem is that Usher is a degenerative disease. You don’t just get it and get over it. You are constantly dealing with loss. You can drive then you can’t. You don’t need a cane then you do. You can do your job then you can’t. You can read a book without magnification then you can’t. It’s just one thing after another. Sure you get over one thing and move on, but then there’s another issue lurking on the horizon. It is exhausting.

That constant loss is what makes it so hard to talk about. People with Usher are just like everyone else. They are just as positive and enjoy life just as much. No one wants to be the person that discusses their new ailment at every party. When people ask how you’re doing, they expect you to answer ‘good’. If you elaborate, they avoid talking to you the next time. People with Usher know that. They don’t want to burden their friends with their problems. So they keep them inside until the weight becomes too much.

The best way to deal with this is to see a therapist. Strong family supports help, too, but it has actually been found that spending too much time talking about it with friends can actually increase depression. But here, again, is that stigma. I have friends with Usher that see therapists. They whisper it, though, or allude to it. They say they see a doctor every week at the same time. Then they raise their eyebrows. Understand? They are confiding in me, sharing a secret we can’t acknowledge in public.

Well, why not?

Look, imagine someone worked as a chimney builder. Every day, day after day, for years on end this person carried a heavy burden of bricks up a ladder to build chimney upon chimney. Then one day the builder’s knee gives out. It’s not permanently broken. It can be fixed. Would anyone think it’s taboo to see a doctor for that knee? Would anyone tell him to get over it and get on with it, to deal with it himself, in quiet, and please don’t tell me about it? No, we’d marvel at the man’s stamina and talk about how it’s understandable and how he’ll be back as good as new soon enough because he’s so strong.

The people I know with Usher syndrome are some of the emotionally and psychologically strongest people I’ve ever met. So why don’t we treat depression the same way we’d treat the knee of the chimney builder? The chimney builder hurting his knee would be expected given the load he carried. The same is true for people with Usher. They shouldn’t have to be embarrassed about it.

I have my own experiences with depression. When Bella was first diagnosed with Usher syndrome, for a long time I could not see anything but the worst. Bella is vibrant and alive. She bubbles with enthusiasm for life. She’s always been that way. But the future Bella I saw was living with an elderly me, sitting in a rocking chair, alone and lonely, cut off from the world. She was rotting, waiting for time to turn her to dust.

I could see it all playing out. She would have to give up horse riding if she couldn’t see so she’d spend time at home. She wouldn’t be able to get around so she wouldn’t have any friends. She wouldn’t be able to read so she wouldn’t be able to graduate from school. She wouldn’t be able to get a job so she would have to live with us. And she wouldn’t be able to meet a man who would fall in love with her so she’d be lonely.

I spent weeks and weeks soaking in that vision of my daughter. It infected everything I did. My work suffered. I gained weight. The walk from the couch to the bed was too difficult, so I stayed up late. Once in bed, I didn’t want to get up. The world was dull and opaque. The sun wasn’t as warm. Food had no taste. I was watching my daughter die one breath at a time. What was the point?

I never considered seeing a therapist. Crazy people see therapists. I wasn’t crazy. I was just depressed. Looking back, I wish I had seen someone. It was months of agony. I’m not really sure how I pulled myself out of that hole. It was like crawling out of a pit of loose sand. Ever so slowly I gained purchase. Once I was out and looked back, it seemed like I should have been able to deal with it sooner. I felt like I had spent months dealing with something that could have gone by faster had I just sought the right help.

I was lucky, really, because the consequences of not seeking help can be dire. I have a friend. His sister had Usher syndrome and she lived my nightmare. She lived on the other side of the world, back in his home country, back where mental illness is taboo. She was older so her vision loss was advanced. She never married, never left home. She was lonely and aging. One day she gave up. She didn’t get out of bed. She stopped eating. My friend flew to see her and begged her to come back to them, but she couldn’t see them any longer, couldn’t hear his words. She just gave up on life and died.

And so I write this post today in her memory. I hope that her story inspires those readers dealing with depression to seek counseling. I am heartened every day by scientific discoveries. Treatments are coming and the future will be brighter. In the meantime, don’t give up on living with Usher. You can still accomplish pretty much anything. You could be a speed skater, a sky diver, a mountain climber, or a classical pianist. I understand that you might not be able to see that right now but believe me, it’s true. Once you climb out of that hole, you’ll see a long and happy life ahead of you.

Go get help. There is no shame in it.

You can start here and here. Good luck.

Monday, May 14, 2012

ARVO Day 4: Miles to go before we sleep

by Jennifer Phillips, Ph.D.

The bulk of the presentations I took in today were reports from clinicians treating Usher patients. I don’t get to interact with clinicians on a regular basis, so it is hugely instructive for me to get their perspective on diagnosis and monitoring of the progressive retinal degeneration seen in Usher syndrome. I’m keenly interested hearing about what they do and how they do it, because in some ways it seems like we’re looking at the same biological phenomenon through opposite ends of a telescope. I see the tissues, the cells, the proteins underlying the disorder. They see the whole person with the disorder.

It’s a perspective I value deeply, as it underscores the importance of building bridges toward one another: compressing the telescope so that our parallel efforts can be combined to help the people we are, through our different approaches, wholly focused on.

I spoke with clinicians who see Usher patients in five different countries. I asked them lots of na├»ve questions from my basic research-oriented perspective and had some extremely interesting conversations, some of which I’ll discuss below.

All the clinicians I spoke with were presenting different combinations of patients with certain USH subtypes or mutations, they are all using essentially the same tools to detect and follow the vision loss in Ush patients. As such, all are facing very similar limitations and frustrations. The common theme I heard was: it is quite hard to find any kind pattern in the variable clinical presentations of Usher syndrome, or even, to some extent, in the genes that cause Usher.

Clinical researchers from the Children’s Hospital Boston presented clinical test data from 18 young patients, aged 2 months to 17 years, with Usher syndrome: 12 with some sort of Ush type 1, 5 with Ush2a, and one Ush3a. One of their advantages was that they had long-term data on many of these subjects, an accumulation of years’ worth of test results to try to follow the disease progression. These clinicians reported a variety of retinal function tests, showing that most of the 18 patients had stable retinal function, although most or all were below the normal range, depending on the particular test. This makes sense given their ages, as severe drop-off in retinal function is most often seen later in life. Even within this small group, however, the representative Ush2a patient and one of the Ush1b patients showed precipitous declines in visual function over the time they were followed—showing that even in this age group there is variation in disease progression. One of the more positive findings presented was that visual acuity within the central retina—the part that usually lasts the longest in Usher patients, as degeneration most often proceeds from the peripheral retina inward—was within “normal limits” in the majority of these 18 patients. On the low end of “normal”, but still reassuring. The take home message from this group was that early defects can be detected in young Ush patients with these retinal tests, and as such, early assessment of retinal function in children with hearing problems is critical. I asked the presenter how she envisioned such early diagnosis becoming a standard of care and she replied that they were working with the Otolaryngology Department at their hospital to develop a comprehensive way to communicate the need for this screening to the local practitioners.

Another poster presented data accumulated from Usher type 1b patients at several London hospitals and one in Slovenia. The idea behind this particular research was to focus on the various mutations found in the MYO7A gene in these Ush1b patients and see if they could find a correlation between the particular location of the mutation (that would affect a particular domain of the encoded protein) and the severity of the disease phenotype. The median age of the participants in the study was 34 years, with data collected from 29 patients between ages 3 to 65. The median age of symptom onset was 9 years, and this too ranged from age 5 to 35. A few patients in the study were young enough not to have complained of vision loss yet. As with the previous report from the Boston study, the best news was that 50% of these Ush1b patients retained good visual acuity, albeit with the predictable visual field limitations, up to 40 years of age. Even with just looking at this one Usher type, however, huge variations were observed in the rate of decline and the severity of the vision loss. Moreover, no correlation was found between the location of the mutation and the specific vision loss symptoms. This should give you some idea of the incredible complexity we—and by ‘we’ I mean both the clinicians and the basic researchers—are dealing with in studying this genetic disease. The progression is predictable to a point, but with very large margins of error. It’s frustrating for me to have to think around these problems in a lab, knowing that I can’t predict what will happen when I disrupt a particular part of the coding region of a gene. It must be incalculably more frustrating for a clinician not to be able to say with any confidence what a young patient might expect. Of course they can explain that most patients with the same disease type experience certain things, but can’t deny that every case has the potential to be unique.

Other clinical results I saw presented dealt with genotyping: analyzing the genes of patients with clinical diagnoses of Usher along with those of living family members to try and identify the causative mutations. Some of these presentations dealt with comparing the different methods of sequencing available, and the bottom line on these is that the most accurate method is very slow and expensive, but there are faster, more cost-effective methods that can be used to generate a ‘first look’ at a family’s genetic variation. Other genotyping presentations revealed, yet again, the profoundly complex variation seen in Usher syndrome and, specifically, the difficulty in correlating the clinical symptoms with a particular genetic problem. One such study looked at a small subset of Ush patients in whom the causative genes were not known, and reveled the difficulties in figuring out which DNA changes in any given gene might be pathogenic, i.e. result in disease symptoms. Our genomes are full of differences—if you compared even a small genetic region, let’s say the sequence of a gene known to cause Usher syndrome when mutated, between two healthy people you would find an abundance of differences in the specific code. If you compared that same region between an Usher patient and a healthy person, you would find differences as well. The question is, which one of those differences, if any, is causing the Usher syndrome? Genetic comparisons between family members usually show fewer differences than comparisons of two unrelated humans, but there’s still a lot of variation to comb through, and while new sequencing techniques and software designed to read high volumes of DNA code and predict differences that could be pathogenic are widely available, it’s still a really tough and often inconclusive problem.

Another presentation by clinicians from Denmark really highlighted the need for better gene identification techniques. In their study, they looked at children aged 0-17 years with clinically diagnosed retinal dystrophies, including Usher syndrome, to establish the prevalence of this type of disease in Denmark and get a handle on how well the specific genetic cause could be identified. Their findings revealed that the prevalence of retinal dystrophies in this age group was 13 per 100,000 children, and, again most frustratingly, in more than half of these cases the causative gene was not identified. This is lamentable indeed, because while other research presented at this meeting makes it clear that we are really close to some sight-saving gene therapies, having access to these therapies, even in clinical trials, requires that the gene causing the vision loss is known.
___________________________________

The last set of presentations I visited described a widespread technique for analyzing progressive RP, where retinal images are taken under specific, restricted wavelengths of light, similar to those wavelengths used in fluorescent imaging. In many RP patients, this lighting reveals a ring-like pattern in the retina that fluoresces in the absence of any dyes or other chemical fluorescent markers. The source of this so called “auto-fluorescence”, or AF, is the accumulation of various shiny pigments in the retina, a hallmark of photoreceptor dysfunction that often precedes cell degeneration. One clinically interesting thing about these AF rings is that they often appear before other visible changes to the retinal architecture. The cells can still look ‘normal’ by other tests, but the presence of AF in these regions indicate that cell function is abnormal.

In Usher patients as well as those with other types of RP, this AF ring constricts over time, slowly closing in on the central retina. The cells within the ring are normally the cells still functioning well. Cells on the outside of the ring are often the ones already degenerated or severely impaired. The cells constituting the ring itself are on the border between the two. It’s a simple yet powerful way to take a look inside of an eye and assess how things are working, and, as many clinicians shared with me, one of the clearest visual ways to explain to a patient and his or her family how the disease is progressing. Below are some images that should help explain the diagnostic potential of this type of test:

Figure 1: image taken from Robson et al., Br J Ophthalmol 2006;90:472-479
Figure 1 shows a normal or ‘control’ eye from a healthy patient. The top panel is the picture taken with fluorescent lighting to show how the retina looks with no specific regions of AF, although the peripheral areas of the retina seem a little ‘glowier’ than the central region. The dark patch off to the right there is the optic nerve, by the way. The bottom panel is a representation of what’s called a multifocal electroretinogram, or ERG. In a standard ERG, electrical responses from all the retinal cells are combined into a single oscillating line or ‘trace’ that looks something like this:

Figure 2: image taken from http://www.thebalticeye.com/ZURICH.html
You can tell a lot about what the different cell populations in the retina (note the different peaks and valleys on the trace are labeled with the names of different cell types and functions) are doing, collectively, with this analysis, but you can’t assess whether all the cells in these various populations are performing at the same rate. In the multifocal ERG shown in the bottom panel of Figure 1, the cell responses from all the different regions of the eye aren’t pooled. So what you see is a series of little traces that in this control eye have essentially the same shape as each other and the same basic shape as the standard ‘pooled’ ERG shown in Figure 2. Another thing you can note is that the traces in the central region of the eye appear taller. This is due to the higher density of photoreceptors—mostly cones—in that region of the retina. There are simply more cells present there to give electrical responses, so the peaks appear larger. Lastly, the traces in the middle region of the far right of this mfERG are a bit flat. Note that this corresponds to the region of the optic nerve, often called the ‘blind spot’, where there’s a bit of a gap in the retinal cells for all those nerve fibers to pass through. Thus, it makes total sense that you’d get a diminished response from this particular region of the retina.

A standard ERG from an RP patient, depending on how advanced the degeneration is, is markedly abnormal. The peaks and valleys sort of flatten out, indicating that the overall response from the eye is reduced. But as we know, Usher syndrome doesn’t affect all areas of the eye equally, so maybe looking at one trace representing the entire retina isn’t telling the whole story. Enter the multifocal ERG. You’ve seen in figure 1 how it looks in a healthy eye. Let’s take a look at an eye with progressive retinal degeneration, as indicated by that AF ring we discussed earlier, and compare it to the control I showed in Figure 1 above:

Figure 3, from Robson et al.
The first thing to note is the AF ring, which appears white in the top panel image. The second thing to note is the differences in the sizes (what we call ‘amplitude’ in the trade) of the traces in the lower panel compared to the control. Again, these traces represent different, local responses from various regions of the retina. As with the control up in figure 1, you can see that the traces in the middle of the field, representing the central retina, are taller than the ones in the periphery, but unlike the traces in figure 1, they are not all the same shape. The traces in the periphery are much flatter and less organized squiggles compared to the smaller yet still well formed traces in the comparable regions of the control eye. Notice how the shape of the traces seems to degrade the farther out from the center they are.

The third and final thing to notice is that the part of the retina producing traces of more normal looking size and shape is pretty much aligned with the region that lies inside the AF ring. Without knowing how many cells actually remain alive in those peripheral regions, we can tell from the combination of these two analyses that cells at or outside of the limits of that bright autofluorescent ring are having problems. And, because this is correlation between AF ring position and retinal cell function is quite well established, a clinician can show a patient a picture of the AF ring in his or her retina and it will be fairly representative of where the remaining vision is. It certainly seems much easier to look at than those squiggly electrical output images!
____________________________
So, the good news is that there are clearly some very fine-tuned clinical tools in use worldwide that can diagnose and track retinal diseases and syndromes like Usher. The more challenging news is that all we can currently do is track it, rather than fix it, or even slow it down. And even though some patients might be helped in the near future by the emerging gene and cell therapies, there is a tremendous amount of work left to do before such therapies are available to all, or even most, of the sufferers of these diseases. We have far to go before these projects are completed. Miles to go before we sleep, to paraphrase Robert Frost.

Although the ARVO meeting will continue for a 5th day, this will be my last installment of the meeting updates this year. Because I came to Florida two days early for the Ciliopathy meeting, I’m skipping out early to make the long trek back home, so I have miles to go before I sleep literally as well as metaphorically.

I’m returning home inspired and a little overwhelmed as usual. Impressed with the wealth of quality data and quality people who are working so hard to improve vision in the world, a little frustrated at the limitations we all face, but motivated to continue pursuing my research and adding pieces to the puzzle. And of course I’ll be back this time next year, reporting on ARVO 2013.

I hope these posts have been informative, and as always I welcome any questions or comments from our readers.

Wednesday, May 9, 2012

Dispatches from ARVO Day 3: Making a Difference

by Jennifer Phillips, Ph.D.

"Something must be done beyond giving them a dog, a cane, or a Braille book. We must give those who need it the hope that science is actively probing the affliction robbing them of their sight."—Mildred Weisenfeld

Here at ARVO the last events of the day are the award lectures. Each year, several of the most impacting clinicians and scientists in the international Ophthalmology and vision research community are chosen to receive various awards and deliver a plenary lecture. One of the awards given last night was the Weisenfield award, named for Mildred Weisenfield. I’d never heard of her before, so I was delighted when both the introducer and the award recipient took some time to give the audience a little history about this remarkable woman.

Mildred was born in Brooklyn in 1921, and at age 15 was diagnosed with Retinitis Pigmentosa. She was blind by age 23. Frustrated that no vision funding went into research for treatments for blindness, she founded the National Council to Combat Blindness. She established this organization on her own, with $8, and worked tirelessly to raise awareness of and funds for vision research. The National Council to Combat Blindness later became known as Fight for Sight. Mildred had no scientific training, but she nonetheless testified on eye research at the United States Congress in 1946, which led to the creation of a National Institute of Neurological Disease and Blindness and, shortly thereafter, The National Eye Institute. You can read a bit more about her here.

The recipient of this year’s Weisenfeld Award was John Forrester, an ophthalmologist from Aberdeen, Scotland. He gave a fascinating talk about the trajectory of his career as a clinician-scientist, and stressed the importance of translational research—the union of basic science and clinical applications—as integral to developing therapies for ocular diseases. Dr. Forrester has made absolutely amazing contributions to vision research as well as to the state of vision care in his native Scotland. Sitting with several thousand other attendees listening to his achievements, it was hard not to feel a little inadequate. I’m a contributor to the big picture, you know, but unless something really remarkable happens, I’m never going to be lauded as one of the great scientists of my generation. But then I remembered Mildred and her $8. It’s a valuable reminder that small contributions coupled with a passion for change can make a huge difference. She didn’t know how it was all going to turn out when she started the NCCB, but she took the plunge and did something she was passionate about. Just as Mark and other parents of Usher kids have come together to organize support and information for families worldwide. Just as I and many other scientists continue to work at discovering things that might lead to a treatment for Usher patients. If we all stay involved and committed, there’s no limit to what we can accomplish.

Final ARVO 2012 report coming tomorrow.

Tuesday, May 8, 2012

Dispatches from ARVO, day 2.

by Jennifer Phillips, Ph.D.

Today was an 11-hour maelstrom* of really good science. Of all the great research stories I heard, there are several that will likely be of interest to our readers:

1. There were two posters there with updated information on the UshStat story. First, from the authors of the mouse studies I reported on previously, the continuation of the animal trials of this gene therapy: In this study, shaker1 mice treated with UshStat were subjected to all kinds of light conditions ranging from normal day/night illumination over several weeks to extremely bright light for a few hours. The retinas of these mice were compared with those of other shaker1 mice receiving a control injection, and in all cases, the UshStat protected the treated mice from the level of retinal degeneration experienced by controls. The researchers then applied the UshStat treatment to non-human primates in order to conduct safety studies. The determined that the treatment was tolerated well by the macaques and did many experiments to try and detect whether UshStat was detectable in body tissues other than the eye. An important safety consideration for gene therapy is that the DNA you are introducing won’t go ‘rogue’ and migrate to other tissues where it might have an effect you don’t intend. Encouragingly, no UshStat was detected in any of the numerous other body tissues or blood that were tested.

Another poster was presented by the researchers at the Casey Eye Institute who are conducting the clinical trials on UshStat and a similar gene therapy for Stargardt’s Macular Degeneration. No results of the treatment to report yet beyond the fact that the first patients have received their injections without incident. One of the images on the poster was a fundus photograph of an USH1B patient’s retina showing the site of injection that was administered two weeks ago. It’s very exciting to think that this trial is really happening, at last.

2. Another poster featured an alternate gene replacement therapy that’s being developed for USH1B patients, this one using a modified viral vector to deliver the genetic payload. The viral vector in question is called AAV (for adeno-associated virus) which, through natural talent augmented by human tinkering is extremely efficient at docking with and delivering its DNA content into human cells. The downside is that there’s a size limit to the DNA that can be packaged inside of it, so most of the Usher genes are just too big to fit. However, researchers from the Ophthalmology Department at the University of Florida were able to devise a way to deliver the whole Myo7a gene in two parts, which would be carried in separately by their respective vectors and then assemble into the complete gene once inside the cell. This has only been tested in cultured cells so far—no animal models yet—but it’s success thus far is promising indeed.

3. Following the trend of promising treatment directions for Usher syndrome, a fantastic story from one of my former collaborators, Jennifer Lentz, and her colleagues at Louisiana State University Health Sciences Center. They’re the ones who created the Ush1c mutant mouse containing a human ush1c mutation common to the Acadian population—a mutation that leads to improper splicing of the gene, thus producing a flawed protein that leads to Usher Syndrome Type 1C. Last year at ARVO, I reported some on some research that showed this improper splicing could be inhibited by the introduction of a small molecule designed to block the splicing machinery from reaching this mutated splice site. Over the past year, Lentz and colleagues have been testing out this molecule (an antisense oligonucleotide, if you’re trying to fill your science geek Bingo card) on the Ush1c ‘knock-in’ mice. They started by asking the very basic question, ‘will this molecule harm the mice?’ and as such didn’t go for great precision in their pilot experiments but instead injected a quantity of the molecule into the bellies of newborn mutant mice. They were then able to assess the development of the auditory and vestibular systems in these mice over the next few weeks. The first remarkable discovery was that the mice did not exhibit the strong circling behavior common to Usher 1 mice. They also performed much better on a variety of balance tests, indicating that the splice blocking treatment was actually working, and that normal Ush1c protein was being produced at significant levels over the mutant protein. Just as exciting, the young mice performed within normal limits on their hearing tests as well.

Tests on the retinal cell condition or function aren’t complete yet--recall that unlike many other Ush1 mice, these Ush1c ‘knock in’ mice do exhibit some retinal degeneration and loss of function, but not until later in life. However, this is an extremely encouraging beginning. In addition to the forthcoming vision tests, follow-up experiments in which the treatment is delivered into specific tissues (eyes and ears) are also planned.

4. Finally, an interesting treatment option that could forestall photoreceptor death was presented in one of the lectures I attended by an Ophthalmologist from UCSF. In this study, tiny capsules filled with cultured RPE cells were inserted into the retinas of several RP patients, one them an USH2A patient. As usual, in these types of trials, the other eye was left unimplanted to serve as a control. The RPE cells were engineered to excrete a molecule known to promote photoreceptor survival, and were encased in a special material that allowed small molecules to pass through—the photoreceptor survival factor could freely go out into the retina, while metabolic factors required for the continued happiness of the RPE cells could get into the capsule. This is a truly clever delivery system, as an adequate supply of the desired molecule (Ciliary Neurotrophic Factor, for you Bingo players) will continue to be produced for an extended period as long as the RPE cells inside the capsule remain viable. The end result? Over the course of a couple of years, the density of healthy cone photoreceptors was monitored in these patients. In the unoperated eyes, the number of cones decreased by 20-25%, but in the eyes implanted with the growth factor capsule, the numbers of healthy cones remained stable. While no reports of actual vision improvement were forthcoming, the fact that photoreceptors were apparently prevented from dying by this treatment is of clear benefit in the long term. Remember that the vast majority of the up and coming gene therapies will require for them to be some viable photoreceptors left in order to have an effect. Retinas that are too degenerated will likely have a very limited response to any kind of gene replacement if the cells in which those genes are required have already died. So preserving the cells, perhaps as a precursor to or in conjunction with a replacement therapy of some sort, could be a very promising option.

Oh, there’s so much more, but I’ll stop there with the hope that you will find these updates as encouraging as I do.

*I originally wrote ‘juggernaut’ here. Then I looked back at last year’s ARVO dispatches and discovered that I described ARVO Day 2 of 2011 as a juggernaut, so I came up with a new word. Basically, Day 2 is very intense.

Monday, May 7, 2012

Dispatches from (pre-)ARVO, Day 1

by Jennifer Phillips, Ph.D.

Hello once again from sunny Ft. Lauderdale, host of the 2012 ARVO meeting.
Ft. Lauderdale sunrise on Friday 5/4/12
The ARVO meeting started on Sunday, but I’ve actually been here since last Thursday to attend a pre-ARVO meeting on the topic of Retina Ciliopathies. That was an intensely focused two days, indeed. I have talked about the connecting cilium of the photoreceptor quite a bit on the blog, most recently in reviewing what we know about the molecular causes of USH1B. As you may recall, many of the Ush proteins tend to hang out around the cilia of sensory cells, and in the case of the photoreceptor it’s likely they have some role in the long, complicated process of transporting molecular cargo to the right location via the cilium. Because of the evidence of association between Ush proteins and the sensory cilia, at least some researchers classify Usher syndrome as a ciliopathy—a disease that affects the development or function of ciliated cells. But there are far more than just the Ush proteins at that particular cellular region. Scores of other factors involved in packaging, activating and shipping that molecular cargo are in that tiny little region of these very important cells. This, of course, is why ciliopathies have so many different causes. There is a LONG list of genes whose protein products have some role related to cilia growth or operation. I learned an amazing amount of new information in the two full days of the ciliopathy meeting—most of it highly technical, only a fraction of it directly related to Usher, but all of it highlighting the importance of figuring out everything we can about how this part of the cell works.

We all know how devastating a diagnosis of Usher can be. However, as far as ciliopathies go, it’s definitely on the mild end of the spectrum. The things that go wrong in Ush happen in two cell types—retinal cells and auditory hair cells. But there are so many other ciliated cells in the human body—in the brain, in the kidneys, in the lungs…the list goes on. Fundamental problems with cilia formation or function that affect all these cell types can lead to some severely debilitating and often fatal diseases. The good news is that there are a LOT of really smart people working on understanding ciliopathies. Around 200 people were at this meeting, all of us with detailed knowledge of some aspect of cilia development or function. Hundreds more people around the world who didn’t appear at this particular meeting are also working hard to unravel these mysteries. Listening to controversies brew over exactly which molecule does what thing when was a great way to get the scientific juices flowing for when the big meeting started.

Another great way to kick off meeting was with the keynote speaker on the first official day of ARVO: Craig Vetner. For most of you, this name probably won’t ring a bell, but he’s like the biologist’s version of Steve Jobs. He’s made astonishing contributions to the field of molecular biology and genetics, being one of the team that sequenced the human genome in the ‘90s and, more recently, lead the effort to create a synthetic organism by transplanting a genome that he and his team created into a bacterial cell. And by ‘created’, I mean ‘wrote themselves’, and by ‘wrote themselves’, I mean they decided the sequence of all 100,000 bases—the DNA alphabet—to the extent that they were able to embed the names of all 45 members of the team and some inspirational quotes IN THE GENETIC CODE OF THIS SYNTHETIC ORGANISM. Moreover, it works. The human-written code is sufficient for the organism to synthesize the materials it needs for normal life functions, including self-propagation.

Vetner and his team have spent the past several years sampling the genetic variation in various places all around the world, contributing in a truly global sense to the understanding of how we and every other living thing on the planet are related. In short, he’s one of the most significant innovators of the current era, and his storied career makes the impossible seem plausible. I’ll be hitting the ground running tomorrow, looking for inspiration, thinking more creatively, and searching that innovation that’s going to help me take my research to the next milestone.

Thursday, May 3, 2012

Are we there yet? A clinical trial to test a potential gene therapy for Usher 1B

by Jennifer Phillips, Ph.D.

In my last post, I summarized over a decade of research on the putative functions of the USH1B protein, MYO7A, in retinal cells. I did this in hopes that the forthcoming descriptions of the preclinical and clinical trials for this therapy would have a bit more relevance, so do let me know how that works out for you. Here goes:

At last year’s ARVO conference there was a presentation reporting successful animal testing for a gene therapy product called “UshStat”*. While this work has not yet appeared in a peer-reviewed publication the ARVO abstract can be found here. The poster presentation at the meeting described the use of a non-pathogenic viral vector to deliver a normal copy of the gene affected in Usher Type 1B (MYO7A) into the retina.

I’ve described the procedure for this type of viral delivery system previously, but briefly, these are virus strains that have been altered in a lab to disable whatever disease-causing effects they might have and to incorporate the genetic code for a functional copy of the gene of interest into the viral DNA. Once the virus has been modified to carry this ‘payload’, a solution is prepared containing many copies of this virus, which is then injected into the space behind the eye. Although the pathogenic nature of the virus has been altered, it still retains the ability of wild viruses to ‘dock’ with and insert viral DNA into an animal cell for the purpose of propagating itself. So, once injected adjacent to the retina, the virus enters the retinal cells and delivers the payload—a healthy version of a gene these cells require for normal function.

The researchers conducting the preclinical trial with UshStat used the shaker1 mouse I described in the last post, with the light-sensitive genetic background, to test the effects of this gene replacement therapy.

Recall that in these sensitized shaker1 mice, the myo7a mutation caused problems with transporting proteins within the photoreceptors. When mice are adapted to a dark environment, in which the fast-acting rod photoreceptors are primed to detect any tiny scrap of light that happens along, a protein called transducin inhabits the outer segment—the light receiving region—of the rods. When shifted to a more brightly lit environment, in which cone photoreceptors take on more of the light-sensing responsibility, this protein migrates down into lower regions of the photoreceptors. This light-dependent protein relocation can be seen in Panels A and B of the figure below:

From Peng et al, 2011
Panel A shows transducin protein, labeled orange, in a normal, ‘wild-type’, retina from a mouse that was dark adapted before being sacrificed for this experiment. Panel B shows a retina from a wild-type mouse that was dark adapted for several hours, just like the mouse in panel A and then shifted to a lighter environment for 1 hour before its demise.

Panels C and D are taken from sensitized shaker1 mice treated to the same light conditions as their wild-type brethren in A and B. C shows the dark adapted shaker1 mouse retina, which looks pretty similar to the normal retina in panel A. But as you can see in panel D, the protein migration after 1 hour of light exposure is no where near as robust as what we saw in panel B from the wild-type mouse. The shaker1 just can’t move things as efficiently as it seems, and although there is no experiment so far that has shown a direct connection between failure to efficiently move transducin and the subsequent retinal degeneration exacerbated by bright light conditions in sensitized shaker1 mice, it certainly seems plausible that such damage could result from having an accumulation of a light-reactive molecule like transducin in the wrong place. The authors showed that factors other than transducin also accumulate inappropriately in the sensitized shaker1 mouse retinas, so cell death may result from accumulation of some other protein, or the combination of some or all of these ‘traffic-jams’.

So, enter the preclinical trials of UshStat. No pictures to show here, but the abstract linked to earlier in this piece describes two major results when the sensitized shaker1 mice were treated with this gene replacement therapy:
  1. Transducin relocation in response to bright light became more efficient
  2. Light induced photoreceptor degeneration was rescued.
Again, it’s not known whether restoration of proper trafficking of transducin in particular is saving the photoreceptors from death, or some other factor, but it is probably fair to think of transducin as a ‘reporter’ of efficient trafficking from the outer segment in these experiments. At any rate, it’s a powerful finding, and, probably along with other studies that haven’t been made public yet, sufficiently convincing to the review board who approved the clinical trials that are just getting underway.

Obviously we won’t be able to view protein trafficking in the eyes of the Ush1B patients undergoing the trial, but in time we should know whether the treatment is forestalling their progressive retinal degeneration and preserving their vision over what the typical Ush1B disease progression would be. I wish them all the very best, and thank them for volunteering for this milestone study. Watch this space for further updates on this trial as they become available.

*UshStat is a registered trademark but I don't know how to put the little R in a circle next to the name throughout the post.  So just know it's a trademark when you see the name.

Reference: Peng, Y-W., Zallocchi, M., Wang W-M., Delimont, D and Cosgrove, D. (2011) Moderate light-induced degeneration of rod photoreceptors with delayed transducin translocation in shaker1 mice. IOVS 52 (9): 6421-6427.