Yesterday user u/Marc_Bago posted a TIL about Fibrodysplasia Ossificans Progressiva. Since it generated a significant amount of attention, I figured I would do an AMA as a grad student in the lab.

I'm a 5th year graduate student at the University of Pennsylvania, and I work in the lab or Dr. Eileen Shore and Dr. Fred Kaplan. Our lab, part of the McKay Orthopaedic Research group, studies FOP and another related genetic disorder, POH.

Here's more proof of me.

The lab has been in existence for about 20 years, and in 2006 the group published the gene (and mutation) that causes FOP - sorry, behind Nature Medicine pay wall. The mutation is a R206H missense mutation at codon 206 in the gene ACVR1, also known as ALK2. ALK2 is a BMP signaling receptor, and while BMPs have been shown to be involved in many life processes, their original discovery was as a factor that induces bone growth, not surprisingly.

This is what FOP looks like in an adult.

There's much that has been learned about FOP since the gene/mutation discovery in 2006, but I'll let you direct the questions. AMA!

Comments: 44 • Responses: 20  • Date: 

river_rat311711 karma

Has there ever been a report of a female with FOP ever getting pregnant? What would happen to a woman if she did?

MRC198612 karma

Not to my knowledge. As you can imagine, if your movement is even moderately restricted by the time you are 15-18 years old, your "reproductive fitness" is basically zero.

There are cases of familial inheritance with a relatively mild case of FOP, but the affected parent was the father, so no issues with pregnancy there. Even for a mildly-affected female patient, pregnancy would likely be difficult, because if the hip joints fuse during the pregnancy, natural birth would not be possible. And given that most surgeries that go beyond skin level induce more bone, a C-section would not be great either.

ryanbtw9 karma

In the TIL's title, it says:

Sufferers are slowly imprisoned by their own skeleton.

So... how true is this?

MRC198615 karma

Sadly, this is very true. While there are varying levels of severity among patients, even with the same R206H mutation (which occurs in about 95% of patients), eventually all patients slowly lose mobility and are literally frozen in place.

Acute bouts of cartilage/bone (which we term as "flare ups") can happen literally overnight. You go to bed and your right elbow can bend, and when you wake up it the joint is locked in whatever position it was when you started sleeping.

Developing extra bone where your muscle tissue used to be is bad enough, but what's really disabling is when that extra bone slowly grows and attaches to your endogenous skeleton. For example, a ribbon of extra bone starting from your sternum and eventually attaching to your hip. This usually means the patient is permanently frozen in a crouched or leaning position because your spine movement is now restricted by that extra scaffold of bone. It truly is devastating.

But even so, our patients have a great spirit and are really uplifting to see when they and their families tour the lab. Keeps us motivated in our lab work.

I_Am_A_Pumpkin5 karma

For example, a ribbon of extra bone starting from your sternum and eventually attaching to your hip.

would it be possible to break or surgically remove the bone so that movement is restored?

MRC19868 karma

This is one of the worst aspects of FOP - if you surgically remove bone, more extra bone appears. It's like a Medusa head of bone formation. Because remember, inflammation is a trigger of the disease, and surgery induces a potent inflammatory response.

While you may temporarily restore some movement, in the long run it will only get worse.

MaleCra7 karma

Thank you for doing this AMA!

What, specifically, occurs during the ossification of tissue? Do osteoblasts simply build onto the tissue as a random mutation, or what?

MRC19867 karma

Thanks for your interest!

The underlying cause is a genetic mutation in the gene ACVR1, which encodes the ALK2 protein. ALK2 is a Bone Morphogenetic Protein (BMP) receptor, which among many developmental and post-natal functions, is key in bone formation - both the endogenous skeleton and any fracture repair and pathological bone as seen in FOP.

While the mutation arises sporadically, we see the exact same mutation (R206H) in about 95% of patients, which is quite remarkable for a genetic disease, which usually involves many mutations in the same gene. We do see atypical mutations also in the ACVR1 gene, but they are very low compared to the classic R206H mutation. The effect of the mutation is an overactive receptor, i.e. - enhanced signaling levels.

Here is a link showing the progression of disease. (Let me know if you can see it, since it's from a Nature Reviews article that is likely behind a pay wall, but I can see it fine here in lab with our university access).

There is first an inflammatory trigger (which is what my thesis project is on), immune cells invade the damaged tissue and clear it out. However, instead of regenerating your skeletal muscle, or at worst forming scar tissue, stem cells are recruited to the site of injury and as a result of the mutation form extra cartilage and bone. We think of the same mutation doing different things in different cell types across the entire disease natural history.

Osteoblasts are the bone building cells, so they are involved. But we aren't sure whether the mutation causes ostoblasts to also be over active, as we have shown with other cell types along the pathway from injury to extra bone. We are focusing on earlier stages of the disease because the earlier we can therapeutically intervene, the better quality of life our patients will have.

Waspus6 karma

What's the worst case of FOP you've ever seen?

MRC19866 karma

Personally, I've only met a few patients who have come to Philadelphia for a check-up and then do a tour of the lab. All except one was still able to walk, so that's pretty encouraging, all things considered.

There was one patient who was wheelchair bound, but in a semi-standing position (because that's how the patient's hip joints were fused), so that was probably the most advanced case. But that patient is almost done with a college degree, so with assistance it is possible to get out there and do some pretty amazing things.

The spirits of all our patients and their families is really fantastic, which helps keep us going when some of our lab experiments don't pan out as we had hoped. But we are making excellent progress in the lab - starting clinical trials with a small molecular inhibitor of cartilage/bone formation shortly, so that is really exciting.

Marc_Bago6 karma


MRC19867 karma

Thank you, us as well.

Starting a clinical trial for FOP is quite an achievement for two reasons.

1) The FDA strongly hesitates performing clinical trials in children, but they are the affected population in FOP, so there is no way around this.

2) Clinical trials require many patients in order to have statistical power. Since there are only about 800 known patients worldwide, this requires a very careful design of the trial to obtain statistical power with fewer enrollees.

But the lab has been able to make progress on this. The clinical trial is being headed by our M.D. lab members.

scottapez6 karma

Is there an benefit to yoga/stretching etc. in these people? I read that they should avoid things like falls to prevent skeletal growth, would exercise and regular stretching encourage or inhibit the growth of the extra skeletal muscles?

MRC19867 karma

The best answer is "I'm not sure". Patients are advised to avoid any hard contact, as even mild bruises can be the inflammatory trigger that leads to an incident of extra bone. Stretching induces mild stress (as in kPa pressure "felt" by the cells) in connective tissues, so that actually sounds like something to be avoided. But the best answer is that we don't really know.

Your_Certificate5 karma

Have angiogenesis inhibiting drugs been tested with success on any of the subjects?

MRC19864 karma

Really good question. A research associate has studied how the mutation impacts how cells experience hypoxia, and how an hypoxic state affects downstream BMP signaling. I don't want to give too much away since the results aren't published yet (though almost), but it's looking like something to consider in the future.

wormwood3665 karma

Is it a genetic disease? What is the most common age for them to be diagnosed?

MRC19863 karma

Yes, FOP is a genetic disease. It is caused by a missense mutation in the gene ACVR1, which encodes the BMP receptor ALK2. Individuals can get non-genetic extra bone formation, though this is separate from FOP - most often occurs following traumatic injuries (like a blast injury from war) or invasive surgeries, such as hip replacement.

Patients are most commonly diagnosed within the first 10 years of life. Some as early as 2 years old (for severe cases) and some around 9-10. There are a few case reports of patients that never had any extra bone formation until their late 20s and 30s, even though they do express the classic R206H mutation. Those patients are of great interest to us because they suggest there may be ways to modulate the resultant increased BMP signaling such that we can pause disease progression.

initial-friend5 karma

What exactly is your job/role in the lab regarding this disease?

MRC19863 karma

My thesis project is looking into the inflammatory trigger(s) for FOP initiation and progression.

A comprehensive body of work, both primary research and case studies, have revealed that inflammatory triggers precede initiation of an FOP "flare up". Not all flare ups require inflammation (we call those "spontaneous"), but if you have an inflammatory event, you will likely go through the disease natural history:

-Inflammatory cell invasion, connective tissue apoptosis, clearance of dead cells, recruitment of progenitor cells, cartilage formation, and then bone.

We know that inflammation also seems to be contraindicated with non-genetic forms of extra bone, such as after traumatic blast injuries in veterans and invasive surgeries, like a hip replacement. We think that inflammation is a key feature for bone development in general (at least post-natal formation, like fracture repair or pathological extra bone), so I'm using FOP as a genetic model to study this.

Obviously, I want to identify specific cell(s) and pathway(s) to treat our patients, but learning about generalized inflammation/bone mechanisms will have a higher academic impact.

anolyphant5 karma

What are the treatments for this disease? Will there ever be a cure? Is it possible to detect this disease prenatally and abort the fetus?

Considering how few people this disease effects, is it really worth spending research dollars on? Why or why not

MRC19868 karma

The R206H mutation is commonly a sporadic mutation; i.e. - it isn't something that is carried down through inheritance. Though this is mostly because patients, due to having very limited mobility, have low "reproductive fitness", if you will. In mild cases the disease inheritance pattern is autosomal dominant.

The only sign at birth is a malformed great toe in both feet. Though the disease commonly manifests in the first decade of life, until that first sign of swelling and bone is seen, the infant has totally normal mobility. Since the disease is so rare (1 in 2 million), it likely will won't be detected prenatally, though technically it is possible via ACVR1 sequencing.

I'm really glad you brought up your final question. We get this asked all the time - "why spend millions of dollars researching a disease that affects less than 1,000 known patients worldwide?" While we are very much interested in improving the quality of life for our patient community, understanding why bone forms when it is not supposed has major implications instances where we do want new bone formed - such as in regenerative medicine applications. Forget a synthetic prosthesis for your blast injury, how about let's grow a new femur by seeding FOP cells on a biomaterial. Other labs in our ortho core are working on the biomaterial side of things right now.

Everyone knows about statins and how they are great at lowering cholesterol. However, the researchers that discovered how LDLs and HDLs work did their research on a family with levels of cholesterol WAY higher than average (like in the 3,000 range). Yet, that large of a difference allows for stark comparisons to be made versus the normal biology, and is more informative for general mechanisms that can then be applied to people with higher cholesterol, but closer to the top of the bell curve (like in the 250-300 range).

kozmund5 karma

  • The Shore Labs webpage mentions animal models. Should I assume that just refers to a R206H knock-in mouse, or are there newer animal models for the disorder?

  • 5th year, eh? Feeling the looming dissertation-pressure yet, or are you still in the sweet spot before that? What's your PI's average years-before-defending for their PhD students?

  • And lastly, just to be a weirdo: What's a fellow have to do to get his hands on a fop-ish mouse skeleton?

MRC19864 karma

-We have several mouse models of the disease, including our highest fidelity model - a full heterozygous knock-in at the actual gene locus. No issues of extra copy number or anything like that. Via an inducible system (either doxycycline or tamoxifen, we have both lines) we can irreversibly turn on expression of the mutant R206H allele globally. We have some promoter-driven Cre lines as well, but they aren't published yet, so have to keep those under wraps for now.

A collaborating lab was working on a zebrafish model, but it's taking longer than initially expected to complete.

-My PI is a great mentor, she expects consistent progress of her students, but she's not intimidating or anything like that. Which is good because I think that fosters a much more open and collaborative lab setting. I'm working to get a manuscript draft finished by this summer - currently have two projects I'm working on that are sorta related, but independent enough to get two papers out of. It's going well. We have a 6 year student defending on Tuesday, and that's about the average of her lab and our overall program at Penn.

-haha, we have skeletal preps of mice in the lab (alcian blue and alizarin red stained skeletons). Some pictures sure to come in future publications. As far as hands on, well, that's pretty much lab only hehe.

kozmund4 karma

Damn, I was hoping you'd say "We've got boxes and boxes of stained and prepped skeletons, want one?" Ever since the first publication of the mouse model, I've thought that would be the ultimate science-gift.

What protocol does your lab generally use to sac mice? I'm assuming that cervical dislocation is obviously off the table.

Sounds like you've got a great mentor. Good luck with the papers, hope they end up the journals you want.

MRC19864 karma

ha, sorry don't think we can send off samples, even if we have used them for prior publications. Sometimes we have found interesting things using other mouse models, so we like to keep them around to see if we missed something previously.

All sacrificing is done via CO2 according to UPenn IACUC protocols, unless the lab has a reason for a quicker sac method. The lab I worked in during my undergrad years was looking at stress hormones, so we had to sac immediately because CO2 causes extreme stress (obviously...) and would mess up with real levels.

Penn actually just revamped their CO2 protocol, so I'll be attending one of the new training sessions in the next few weeks.

Thanks for the support.

DavidPuddy6664 karma

Do you feel the FOP funding model is a good model for other rare diseases? I am amazed a disease with only ~800 patients has received this much support and research!

MRC19861 karma

Can you elaborate? Our funding is a mixture of NIH grants from the U.S. government, plus a good amount from our patient community via the International FOP Association.

If you are asking whether relying on private donations as a funding source is a model for other rare diseases - I am 100% in favor of dramatically increasing federal research funding to the NIH and NSF. I was just in Washington, D.C. this past Wednesday as part of a major graduate student advocacy effort for this very subject.

However, we are extremely grateful for the funds that the FOP community raises, as that money has had a major impact on the types of experiments we are able to perform. Most of our new equipment purchases have been possible via private donations, so that frees up NIH grant money to fund a good sized lab.

Quite honestly, I think the fact that FOP is such an observable and devastating disease (compared to other diseases that are less visible to the general public) helps with raising awareness and funds. It's also a testament to the IFOPA founders, who worked extremely hard to raise initial awareness. I'm not sure that other rare/orphan diseases would generate as much general public curiosity as FOP, and as such I think expanding federal funds specifically for rare/orphan diseases is the best way to go.

-TheNarwhal4 karma

Are you guys studying the effects of Squalamine? Since has been seen to be effective.

MRC19862 karma

Can you repost some of this information from the TIL? I briefly saw that reference, and I was surprised since that has never come up in our lab discussions. We aren't using it cell culture experiments.

From the Wikipedia article, it says the research team is lead by Dr. Michael Zasloff, and his name is familiar to the lab as he has been a co-author on some previous studies. Though none recently, if I recall correctly. So not sure who's taking the lead on that.

thegreatgazoo3 karma

What is the lifespan of someone with this disease? I presume at some point the person can't breath and dies from asphyxiation...

MRC19862 karma

Depends on the severity, but average is probably sometime in the 30s. Lifespan has increased as our lab has built up a strong knowledge base of how best to avoid flare ups. There are patients currently in their 50s, but there also have been patients that have died by 20.

MRC19863 karma

Also, our lab was featured The Atlantic last May in a superb article written by science journalist Carl Zimmer.

Marc_Bago2 karma


MRC19862 karma

Thanks for reading!

Yes, you bring up a very important point. At birth, the only observable sign of FOP is what is called "hallux valgus", or a malformation of the great toe. This occurs on both feet and in every patient with the classic R206H mutation. There are no other nodules or bumps of bone, just the great toe malformations.

We are unsure why this occurs, but another graduate student in the lab is studying this (in additional to more fundamental questions about the development of the limbs and how ALK2 is involved in both hind limb and fore limb).

Chaggi2 karma

This is very cool. I did my senior proposal project at the University of Michigan on this disease.

MRC19861 karma

May I ask how you found out about it? Awareness of FOP has increase immensely over the past eight years (since the gene discovery), but there still are physicians that are not aware of it, which is understandable given how rare it actually is.

The medical community here in Philadelphia (Penn, Drexel, Jefferson) definitely know about it, but that's because Philly is the home base of our lab and clinic.

madmikewindows2 karma

My dad is a pediatric radiologist who helped a few weeks ago diagnose a child with this disease who had previously been thought to have cancer. He was talking to me about it and the poor kid still wanted to go to PE and stuff at school.

I'm currently in school to be a physical therapist so I guess my question is what (if anything) can PTs do to help treat this disease? It seems like any interventions we may perform may just cause more inflammation. Maybe help maintain available range of motion?

MRC19861 karma

To my knowledge, I'm not aware of any mobility regimen that we give to patients to maintain range of motion. But I'm on the research side of things rather than in the clinic, so not 100% sure there.

Overall, any type of cellular stress is probably a bad thing, so stretching may actually not be the best course of action for patients. We advise them to avoid any hard contacts, as even a mild bruise can lead to a flare up.