In 1990 the Human Genome Project started. It was a massive scientific undertaking that aimed to identify and map out the body's complete set of DNA. This research has paved the way for new genetic discoveries; one of those has allowed scientists to study how to fix bad chromosomes.
Our bodies contain 23 pairs of them, 46 total. But if chromosomes are damaged, they can cause birth defects, disabilities, growth problems, even death.
Case Western scientist Anthony Wynshaw-Boris is studying how to repair damaged chromosomes with the help of a recent discovery. He's taking skin cells and reprogramming them to work like embryonic stem cells, which can grow into different cell types.
"You're taking adult or a child's skin cells. You're not causing any loss of an embryo, and you're taking those skin cells to make a stem cell." Anthony Wynshaw-Boris, M.D., PhD, of Case Western Reserve University, School of Medicine told Ivanhoe.
Scientists studied patients with a specific defective chromosome that was shaped like a ring. They took the patients' skin cells and reprogrammed them into embryonic-like cells in the lab. They found this process caused the damaged "ring" chromosomes to be replaced by normal chromosomes.
"It at least raises the possibility that ring chromosomes will be lost in stem cells," said Dr. Wynshaw-Boris.
While this research was only conducted in lab cultures on the rare ring-shaped chromosomes, scientists hope it will work in patients with common abnormalities like Down syndrome.
"What we're hoping happens is we might be able to use, modify, what we did, to rescue cell lines from any patient that has any severe chromosome defect," Dr. Wynshaw-Boris explained.
It's research that could one day repair faulty chromosomes and stop genetic diseases in their tracks.
The reprogramming technique that transforms skin cells to stem cells was so ground-breaking that a Japanese physician won the Nobel Prize in medicine in 2012 for developing it.
BACKGROUND: Gene mutations are what cause genetic disorders. They can either be an inherited trait from parents, or can occur during a persons' lifetime. There are three types of genetic disorders: single-gene disorders, such as sickle cell anemia, chromosomal disorders, such as Down syndrome, and complex disorders, such as colon cancer. Knowing a families' health history can help pre-screen patients who are concerned about genetic disorders. Common diseases that run in families are heart disease, cancer, asthma, and diabetes. More rare diseases can include hemophilia, and cystic fibrosis. The U.S. Surgeon General's Family History Initiative is a national public health campaign to motivate Americans to learn more about their family health history.
(Source: http://www.nlm.nih.gov/medlineplus/geneticdisorders.html, http://www.genome.gov/19016938)
TREATMENT: Genetic makeup determines how your body breaks down certain medicines; genetic testing studies the liver enzymes of an individual and how they break down and remove medicines from the body. The testing can be applied to finding the right dosage of a certain medicine to administer for an illness. Treating genetic disorders have some setbacks. Custom medications may be more costly, and not accessible to everyone who may need that treatment. Each genetic disease requires specific and usually personalized treatment – for a comprehensive list of disorders and their respective treatments, visit http://ghr.nlm.nih.gov/BrowseConditions.
(Source: http://www.genome.gov/19016938)
NEW DISCOVERY: A new way to correct a defective "ring chromosome" through cellular reprogramming has the promise to eliminate abnormalities that cause genetic disorders. An international team of geneticists from Ohio, California and Japan, led by Anthony Wynshaw-Boris, MD, PhD, researched and discovered how to reprogram a patient's skin cells into induced pluripotent stem cells (iPSCs). The technique was developed by Shinya Yamanaka, MD, PhD, co-author of the research study, at Kyoto University. The reprogramming technique has only been applied to cells in cultures, not people. Correcting structurally abnormal chromosomes is the next step for the research team, which would cover a broader variety of severe birth defects. The hope is to form a ring chromosome from the abnormal chromosome and applying the reprogramming technique.
(Source: http://casemed.case.edu/newscenter/news-release/newsrelease.cfm?news_id=193, http://case.edu/think/spring2014/fixing-defective-chromosomes.html#.VDaqlfldU1I)
FOR MORE INFORMATION ON THIS REPORT, PLEASE CONTACT:
Jeannette Spalding
Scientific Writer/Editor
Case Western Reserve University School of Medicine
(216) 368-3004
If this story or any other Ivanhoe story has impacted your life or prompted you or someone you know to seek or change treatments, please let us know by contacting Marjorie Bekaert Thomas at mthomas@ivanhoe.com
Anthony Wynshaw-Boris, M.D., Chair of the Department of Genetics and Genome Sciences at Case Western Reserve University, talks about reprogramming skin cells into embryonic cells that can replace damaged chromosomes that can cause severe health problems.
Interview conducted by Ivanhoe Broadcast News in September 2014.
Are you a member of any associations?
Dr. Wynshaw-Boris: Yes. I'm in the American Society for Human Genetics which is probably the main one. I'm also a member of the American College of Medical Genetics and Genomics, Boarded in Medical Genetics and then I belong to a number of scientific organizations.
We're going to talk about stem cells and how they've changed the game, they really have changed it for you, correct?
Dr. Wynshaw-Boris: Sure. Most of my career I've been interested in looking at models of human genetic diseases because I'm a geneticist. Particularly I'm interested in models of brain disease. We've been using mice for most of my career. The mouse has been a great model to understand how things work and how they don't work. But, several years ago Shinya Yamanaka developed the technology to take human and mouse skin cells and turn them in to embryonic cells, called induced pluripotent stem cells. Shinya won the Nobel Prize for that in 2012. That's how important it was. It gives researchers and opportunity to make cellular models, human cellular models of human genetic diseases. So we have changed a lot of what we do, I was virtually a one hundred percent mouse genetic lab studying human genetic diseases; now I'm about an eighty percent stem cell lab using induced pluripotent stem cells to study human neurogenetic diseases in these stem cell models.
About ten years ago there was a huge controversy on embryonic stem cells. They're not an endless supply right? It's endless but there is a certain number and here it seems like the Holy Grail, and the answer was skin cells.
Dr. Wynshaw-Boris: There were two things that were really remarkable about the discovery. Of course there are ethical issues with using embryonic stem cells and different people feel very differently about it. I myself think it's quite fine to use them. This alleviates that problem because you are taking an adult or a child's skin cells, you're not causing any loss of an embryo, and you're taking those skin cells to make a stem cell. The other thing is it has exactly the same genetic information that the patient that you want to study has; they have the disease gene, they have their own background that causes them to have whatever disease that they have. You're studying that patient's cells to which make it really an additional advantage.
With the skin cells, and we're talking about repairing damaged chromosomes, does that skin cell carry the damaged chromosome information as well?
Dr. Wynshaw-Boris: Correct. The chromosome abnormality that we were studying, it wasn't really that abnormality we were studying, it was a disease where the brains of individuals were smooth, and the surface was smooth. It's called, lissencephaly that means smooth brain. It's caused by a loss of part of a chromosome, chromosome 17, the tip of the short arm, AND about two million base payers or more are deleted on one of the chromosomes to cause the disease of lissencephaly, it's a special type called Miller Dieker syndrome.
What happens to people with that?
Dr. Wynshaw-Boris: They are born with a smooth brain, sometimes they are detected at birth, and they don't develop normally. Often they'll have seizures and that then brings them to medical attention and then it's discovered that they have a lissencephalic brain, and that's a severe brain malformation that causes mental retardation, seizures and often early death from the complications of not having normal brain development. We were studying that disease-- we studied it in mice for many years-- and then we started using the stem cells. And we just happened to use a cell line where the patient had a ring chromosome. The ring chromosome patient was the first patient where any genetic problem was discovered from lissencephaly because they found a ring chromosome on chromosome 17. The investigators then said oh, well maybe this Miller Dieker Syndrome is caused by loss of the chromosome when the ring chromosome forms. Because usually a chromosome is linear so it has two ends and those ends are protected by what are called telomeres. But if those telomeres are lost then you can take a linear chromosome and form a ring. And if during that formation of a ring you also lose genetic material then that can cause a disease. In this case the ring formed and the patient also lost two million or so base pairs at the tip of the chromosome that caused that patient to have Miller Dieker syndrome. That was the first patient that was identified. Then the investigators studying this at the time went and looked at other patients with Miller Dieker syndrome and found that it was in fact the tip of one of the arms of the chromosome that was responsible. The other patients didn't have a ring chromosome they just had a deletion, a loss of that tip. So we wanted to study the disorder and one of the patients had a ring and two of the patients had just the deletion. We reprogrammed them, in fact we reprogrammed them with Shinya Yamanaka's group because we were at UCSF at the time and we did it with the Master which was really good.
You reprogrammed it into skin cells?
Dr. Wynshaw-Boris: It was with skin cells from each of these three different patients, one with a ring chromosome and two with more typical deletions on one of the two chromosomes. That means the other chromosome is normal, so the patients have one normal 17 and one patient had a ring chromosome, other patients had one normal 17 and a deletion on one of their chromosomes.
What happens when you treat the skin cells?
Dr. Wynshaw-Boris: We had the skin cells and we reprogrammed them, but what that means is we take four to six different genes, they're mostly transcription factors that change the expression of genes and that causes the reprogramming of those skin cells into embryonic cells. It starts to change the whole program of the skin cells. What happens is then you can select cells that are embryonic cells, embryonic-like cells, you test them and make sure they act just like embryonic cells so they form all different types of tissue when you allow them to differentiate. Our goal was that we wanted to take those embryonic cells, make them into brain cells or neurons so we could study the neurons. But in the course of doing the experiment we tested their chromosomes after we made the IPS cells, the induced potent stem cells. And the two patients that had the typical deletion still had the typical deletion, so we can model the disease but the patient that had a ring chromosome his IPS lines had lost the ring chromosome and instead had two normal chromosome 17's. It was puzzling but it was perhaps kind of an interesting finding. My postdoctoral fellow whose name is Marina Bershsteyn started looking into it a little bit further. How was it lost and it seems like it takes about, what we call twenty passages to establish an IPS line. A passage means that you take cells and put them on a tissue culture dish and let them grow until they're pretty full and pretty close together on the dish, and then you remove them and separate them so they're pretty much individual cells and re-plate them in a smaller number of cells so that they can grow again. Each one of those changes is called a passage. We say that it's an induced pluripotent stem cell when it gets to about twenty of those passages because that means it is pretty much a stem cell. During about the eighth or the ninth passage we think that's when the ring chromosome is somehow lost and when it gets lost in some of those cells then it can get replaced by re-copying their normal chromosome and duplicating it. So now the cell has two normal copies of chromosomes, but both of them are identical and are copies of the normal one that they had.
What would this mean for the patient?
Dr. Wynshaw-Boris: All of this is in cell culture so it doesn't mean anything for the patient that had that but what it means is it at least raises the possibility that ring chromosomes will be lost in stem cells and if you happen to have a child with a ring chromosome and you wanted to make a normal cell for them. Let's say they had a problem with their bone marrow that they didn't grow blood cells, or they had leukemia, or something was wrong with their blood cells. And you wanted to transplant that child with the ring chromosome you could, theoretically (we haven't done this yet), theoretically take the child's skin cells that have the ring, reprogram it, lose the ring, and duplicate the normal chromosome. Now we have induced pluripotent stem cells. Then the next step would be making the bone marrow stem cells and giving the child the bone marrow back. All of what I just said is theoretical, none of that has been done but that's the potential.
Some of these things that you're talking about are things that develop later, not at birth. We were talking about Downs before and then you can talk about something like sickle cell. Is it a cure for both if you know that you are pregnant with a child with Down's?
Dr. Wynshaw-Boris: It will take a long time before you could ever get to the point where you could do something for a child, that's not to say it couldn't happen. But we don't really have any way of doing that now once you detect a fetus of rescuing all their cells. So it's probably more at this point the way that I think it would have any potential to help somebody today would be the example I gave you of a bone marrow transplant. But let's face it, a lot of people are studying regenerative medicine and they're trying to develop methods to make livers and hearts and skin or any sort of tissue muscle. When somebody develops such a method to take stem cells, and make and replace somebody's muscle or somebody's liver, then if we are successful in using this method to rescue these chromosome abnormalities, then it could possibly be used under those circumstances. And I think that's the most likely way that it would be used now.
How are they used in those kinds of circumstances? Is someone in a lab growing a lung that can be transplanted?
Dr. Wynshaw-Boris: No. If they can figure out a way to take stem cells and grow a lung and we wanted to transplant a lung using our technology then we would use the patient's own skin cells, to then make an IPS cell and then make a lung, that's how we'd do it.
There's no more rejection?
Dr. Wynshaw-Boris: That would be the goal if that would happen. Now I have to take one step back. We're talking about ring chromosomes, so ring chromosomes are rare, one in fifty thousand, one in a hundred thousand people in the population. It wouldn't have very much use because it's not something that happens often. And these ring chromosomes just happen randomly, they can happen to any one of the chromosomes. What we're hoping happens is we might be able to modify what we did to rescue cell lines from any patient that has any severe chromosome defect. You mentioned trisomy twenty-one or Downs's syndrome. They have an extra copy of chromosome 21. But there are a lot of patients that have either large deletions, similar to what we had for the Miller Dieker syndrome patient that I was talking about or large duplications and their chromosome has a big change on it that you can't really modify by any known genetic engineering techniques. So were hoping we could take the extra chromosome or the abnormal chromosome and force it to form a ring and then lose it during reprogramming then we can do that for any patient that has a chromosome defect. And that's more in the range of about one in every two hundred, two hundred and fifty patients.
It has to do with some cancers you said?
Dr. Wynshaw-Boris: Some individuals that have chromosome abnormalities, yes, may be predisposed to cancer. Some may have you know loss of big genes that could cause muscle problems. Others might have problems that cause a malformation of the heart or of their larynx. So again we can't do this today, but if other researchers develop ways to do replacement of a heart or a larynx or a lung or a liver, then if a patient also has a chromosome abnormality then we might be able to use these ring chromosome techniques to make a ring, get rid of it and give the patient back a more normal cell.
It almost sounds like sci-fi; you're going to fix somebody's chromosome.
Dr. Wynshaw-Boris: Well it is at the moment it's fiction, but it's our hope that that's where it will go. We're nowhere close to fixing a person now. And right now we're just trying to see if we can force an abnormal chromosome into a ring. We don't even really know if we can do that yet. So maybe by December we'll have the answer to that question.
How exactly does the chromosome get fixed?
Dr. Wynshaw-Boris: If I understand what you're asking the cell just does it itself. If there's a ring chromosome is seems to do it itself. But this is an interesting point and it does puzzle me too. The patient that I was telling you about that had Miller Dieker syndrome and that had the ring chromosome that caused their smooth brain as far as we know every cell in that patient had a ring chromosome; every brain cell, every blood cell, every skin cell. The reason I can say that is because a skin biopsy was taken in order to test the chromosomes -- every chromosome had a ring. Blood was taken, and every white blood cell that they tested had a ring chromosome. And because of what we know about the disease, the whole brain was smooth, so we have to think that every one of those brain cells had a ring chromosome. So a patient could grow up, be born and live at least several years with the ring chromosome in every cell in his/her body. Yet when we take that patient's cells and reprogrammed them they lose the ring chromosome. We think what happens is that it is unstable in stem cells because stem cells really only divide in a clockwork pattern; they don't do anything else. They reproduce their DNA, they divide, they reproduce their DNA they divide, and it happens really in a very specific very uniform fashion. Any slowing down of that process causes a problem. That's why we think it gets lost in twenty passages in culture. Probably even though humans are a big organism they probably don't have that many passages of their stem cells. They just divide for maybe five or six passages and then they form another tissue. The patient can have a ring chromosome but the stem cells in the induced pluripotent stem cell they lose them.
It's broken?
Dr. Wynshaw-Boris: No, you can't fix it; it's just in the cell itself, in the cells in the culture itself.
Does that spread to the rest of the body then?
Dr. Wynshaw-Boris: No. We have no way of doing it just those cells. Like I said if someone figures out a way to take those cells and build an organ out of it and maybe even transplant it in a way that it fills out a tissue, yes it could be used that way but for now that's not the way. I should talk about one other possibility -- it's not complication but what we know from the genome project, the project where the entire genome has been sequenced of individuals we all contain in our genomes about twenty maybe thirty genes that we carry that are totally inactive. It's only inactive in one copy so it doesn't cause a problem for us because we have another normal copy so in most cases that's okay. If we happen to have a defective gene on the normal chromosome that we wanted to duplicate when the ring gets replaced that now that cell could be homozygous for that problem and so it could be an issue.
You could create two defective genes?
Dr. Wynshaw-Boris: The two so-called normal chromosomes will now have two defective genes so that cell could have a defect. If that's a problem we can actually probably know that problem is there from sequencing individual genome. If we find it we could probably fix those individual base pairs if that's the case because there are techniques to repair a single base pair change or a small change. But the ring chromosome is as far as we know the only way that you can rescue a whole chromosome that's defective. So we couldn't use those techniques to fix big deletions, duplications.