sign in sign up
<<
Home , Human Genome Project

GENE THERAPY AND THE TREATMENT OF MUSCULAR DYSTROPHY

by

Lindsay C. Allen

A SENIOR THESIS

in

GENERAL STUDIES

Submitted to the General Studies Council in the College of Arts and at Texas Tech University in Partial fulfillment of the Requirements for the Degree of

BACHELOR OF GENERAL STUDIES

Approved

DECEMBER 2001 w. • T3

.••/ -.- ACKNOWLEDGEMENTS

A lot of hard work was put into researching and writing this thesis. 1 could not

have done it on my ovm and would like to thank those who helped me through this.

Dr. Michael San Francisco, the chairperson of my committee, gave me insights

and leads on the research and the preparation of this work. I want to thank him for his

time, which he gave plenty of, and his guidance through out the project. His patience

was greatly appreciated. I would also like to thank Dr. Randy Allen for sending me in

the right direction. He was of great help in starting the research and narrowing down

my ideas. I thank Dr. Michael Schoenecke and Linda Gregston for in their guidance into

and through this project. TABLE OF CONTENTS

ACKNOWLEDGEMENTS ii

CHAPTER

I. INTRODUCTION 1

The Concept of 1

Molecular Genetics and Manipulation 2

Microbiology 4

II. IN THE BEGINNING 7

ni. 12

rv. 15

V. MUSCULAR DYSTROPHY 21

VI. CONCLUSION 27

BIBILOGRAPHY 30

111 CHAPTER I

INTRODUCTION

The Concept of Genetics

The idea of genetic improvement has been around for at least the past six thousand years; people have been breeding plants for specific characteristics for at least as long (Bryan 6). (1809-1882) was one of the first to conceptualize the way that handles genetic manipulation. Although Danvin's ideas were not readily accepted at the time, he had indeed stumbled onto a natural process that had been taking place for millions of years (Bryan 6). An Austrian monk named Gregor

Johann Mendel (1822-1884) is considered to be the father of genetics because he was the first to perform many experiments in gene function and elucidated some mechanisms of gene inheritance (Bryan 7).

There have been many people that have contributed a great deal to the enormous amount of information in genetics that has been collected over the years. Many milestones have been passed, and there are many more to come. Genetics is a very broad field that has many facets. The accomplishments that scientists have made have already helped us better understand the bases of , gene expression, and development, and have enabled us to look into the possibilities of cures for disease and the prevention of some of the aihnents of , animals, and plants. and Gene Manipulation

The is the basis of human life, and total understanding of it is imperative for research into genetic disorders. wrote "The total human sequence is the grail of ... an incomparable tool for the investigation of every aspect of human function" (qtd. in Davies 12). Gene manipulation is the platform from which gene therapy stems (Hesterlee 4). Gene therapy does, after all, include manipulation of the genome to achieve desired results. Already, many disorders and genes coding for specific characteristics have been isolated (Davies 119-40). There are hopes that someday we will be able to eradicate genetic-based illnesses and disorders such as , Alzheimer's, muscular dystrophy, and blood conditions, such as

Hemophilia, although this is not likely. Of course there are many issues that are still being discussed daily on the moral implications of the power that we may someday have over our own genetic future.

Many disorders are caused by flawed genes in the ; these disorders have, in the past, been incurable. Because the problem lies in the genetic code, until recent discoveries and advancements, there was no hope for these people. Some conditions that are genetic based are the many types of muscular dystrophy, amyotrophic lateral sclerosis (Lou Gehrig's disease), Tay-Sachs disease. Hemophilia, and many more. Our understanding of the human genome has allowed us to begin to undertake some of these problems. With the completion of the Human Genome project earlier this year, we now have a much clearer picture of which genes are important.

There are current treatments for afflictions such as hemophilia, , and

2 Alzheimer's, but there is no cure as of yet. We can suppress some symptoms of such disorders with drugs, but many people yearn for a cure. is constantly testing new drugs as well as old ones to see if anything can help to stop the progression of the disease or at least to alleviate some of the discomfort associated with some of them

("Research Updates" 2). However, doctors are having a difficult time finding drugs that will work on at least most patients, and without harmful side effects. The problem in the long run is that nothing beats a cure, and so research is moving as quickly as possible to eradicate the problem.

A subject that has been getting a lot of attention is viral infections. have wreaked havoc on the human body since the beginning. Since science has not been able to defeat them, research has been conducted on how they work. Viruses are not living beings; they are packaged DNA. Viruses have the ability to attach to living cells receptor sites and inject their own DNA into the for replication. The cell is taken over by the viral DNA and becomes a factory of sorts for new viral bodies. Sometimes the cells' DNA gets packaged into the viral bundles and thus gets transferred into other cells. Because of their hardiness and their ability to inject DNA, they have become primary gene transfer vectors for gene therapy (Whal 3).

Scientists have been able to take harmless viruses and incorporate desired human genes into their DNA. When the infects the human cells it unwittingly delivers the desired genes. Some gene therapy has been used and the results are promising, but most of the experiments done are not long term (Whal 4). If gene therapy continues to advance, doctors might someday be able to cure these problems and stop them from being passed on to future generations.

3 Viruses are being used as transporters of healthy genes into human patients. This means that a virus has to be introduced into the person, and people are still skeptical about doing this (Glasner 23). Viruses have a bad reputation because of the havoc they can induce on the human body. Viruses are responsible for such ailments as the flu, the common cold, and the much more serious HIV virus, which is responsible for AIDS.

Scientists are still working on perfecting the technique, but some of the public may not be as enthusiastic about embracing this kind of treatment because of the complications they can cause. Viruses seem to be one of the best means to an end and so research continues.

Microbiology

The field of microbiology has played a major role in the development of genetics.

Microbiologists are responsible for many discoveries and have made possible many more scientific achievements. Since microbiology is the study of the area of too small to see, microbiologists are needed to be able to do any work on structures so small such as cells, and, of course, DNA itself, that are impossible to see with the naked eye. They carry the knowledge of how the in the body are made, used, and the problems associated with dysfunctional ones. Proteins are responsible for so many things in the body, and it is important to have a good understanding of their role in the life cycle (Fairbaim 15).

Health professionals are the other aspect of the field. Microbiologists may discover ways of treatment and can isolate particular genes, but the doctors are the ones who will perform the operations and who oversee the actual treatment of the patients.

4 Doctors study the human body and can give insight on how it might react to different and treatments. The two fields must work closely to get real goals accomplished. The people that are affected by genetic disorders do not go to the scientists for answers; they go to their doctors, and the doctors must then be aware of the current work of the scientists and be able to relate information and discoveries to their patients.

Gene therapy has only recently been incorporated into the options that patients have in treating their illnesses. Gene therapy is the manipulation of genes in order to correct a disorder that has been inherited or has been expressed due to a gene or genes . The current gene therapy method that is in use today is Somatic gene therapy, which changes the genes in ordinary body cells, not reproductive cells (Bryan 44). In the future we may be able to do germ line therapy, which changes the genes in the human egg and sperm (Bryan 44). This form is more drastic, and the implications are not yet known.

As scientists better imderstand different human afflictions, they are discovering new avenues of treatment. When they have a firm grasp of all aspects of what they are studying and trying to alter, then their minds are more open to possibilities they may not have seen otherwise. Although there are areas of genetics that have yet to be explored, the people working in these fields have certainly been doing their best to accomplish what they can.

Genetics started out with farmers and ranchers breeding for certain traits.

Whether or not they realized it at the time, they were manipulating the genome of their crops and animals for their benefit. Scientists have already successfully cloned a sheep.

5 Passing of this milestone also raised a cautionary flag. Members of the scientific community as well as the general public have expressed concem on the growing events taking place in the study of genetics (Bryan 4). There have even been temporary bans placed on research in the past, and in the fiiture, regulations will probably become more

strict.

The Human is currently underway to decode the entire human

genome. This is a world-encompassing project that has produced some incredible

advances as well as setbacks. Although acquiring this information will be extremely

useful, it will not give a clear understanding of every aspect of humans. It is said that it

will be more like a dictionary, giving definitions, but not teaching the language (Davies

46). People must understand what the code means and what it is capable of doing

before even venturing into the prospects of tackling human afflictions and correcting

them. However, it is a daunting and boring task; it is even stated in a genetics textbook

"could such a collection of unbelievably dull reading ever be of any value other then as

a lending or insomniacs" (Davies 33)7

Many genes have already been pinpointed on the individual , but

just because scientists have found the problem, does not necessarily mean that they can

fix it. There is still so much research to be done before we can successfully put to use

the huge store of information that has accumulated. Although the future goal was to

understand the entire genome, we may never be able to control every aspect of the

human body. CHAPTER n

IN THE BEGINNING

The beginning of the study of genetics is traditionally thought to have originated around the time of Darwin and Mendel, which was in the early part of the 19* century.

However, the practice of breeding for certain characteristics, in plants and animals, dates back 6,000 years. Although some people may not consider this to be genetics, it is, in practice, the same thing that we are doing in the science today except at a different rate and with different methods. The farmers and ranchers of the past had no idea that they were breeding for certain genetic changes; they were simply taking the best of what they had and trying to make it better (Davies 4). The scientific community has come a long way since then, and through numerous discoveries have opened the doors to many possibilities.

The father of genetics is considered to be an Austrian monk named Gregor Johann

Mendel. In 1866 he determined that traits were inherited through pairs of factors, one from the mother and one fi-om the father, which are now known as genes. Mendel also

determined that different forms of these factors could be present. These different forms are called . His work was done on garden peas, learning that pea size and flower

color were linked to these inherited factors (Shannon 3). When combined with

Darwin's theories, Mendel's work became the groundwork for upcoming scientists and

their study of genetics.

There have been many important figures in the field of genetics and to include

each one would take a book in itself was a key figure in early genetic research. His goal was to identify the physical foundation of Mendel's hereditary factors. Morgan and his students conducted experiments using the fruit fly

Drosophila. He concluded that the white eyes of males were linked to the X (sex) . He later won the Nobel Prize for Physiology and for his discoveries relating to the hereditary functions of the chromosomes in 1933 (Davies

155-58). Herman Muller was a student of his who also won a Nobel Prize for his work with Drosophila in 1946. He was successful in mutating the genes using X-rays. James

Watson began working with him at Indiana University in 1951.

James Watson and are credited v^th the elucidation of the structure of DNA; they, however, were not alone. Erwin Chargaff and Emst Vischer were studying the chemical composition of DNA, and Chargaff was able to establish the four bases as adenine (A), cytosine (C), guanine (G), and thiamine (T). He also noticed that although the bases were not found in equal numbers throughout DNA, there was a 1:1 ratio of A to T and C to G. Chargaff was not aware at the time if this was just a coincidence or if it had a more significant meaning (Davies 20).

In November 1951, Watson sat in on a lecture given by .

Franklin was an authority on crystallography and was speaking about her DNA crystals.

Watson was, unfortunately, not as interested as he should have been, and the information that he gathered was not accurate. Watson took the information, and along with Crick, they built a model of DNA. When Franklin came to Cambridge to view the model, she brought Maurice Wilkins, who was her supervisor. Franklin's first response to the model was ridicule, for the model's water content was off by a factor often

(Davies 21). , who had already been awarded two Nobel prizes in

8 Chemistry and in Peace, was also in the race for the structure. Pauling's model had the bases on the outside of the chain, making it resemble Watson and Crick's first attempt.

In a matter of days, Watson was visiting Wilkins and was shown a new photograph that Franklin had of DNA. This photograph was Photograph 51. Watson saw in this photograph that the X-rays formed the familiar cross, meaning that it was a helical molecule (Davies 22). Watson quickly came to the conclusion that the molecule most likely had two chains instead of three. Watson and Crick knew that important biological objects always came in pairs. They promptly began work on a two-chain model with the bases on the inside. Using cardboard models of the bases, they ascertained that with the 1:1 ratio of A+T and C+G, the bases fit perfectly within the two chains. This model allowed for the sequence of one strand to be the template for replication of a new strand (Davies 23).

The discovery was published in the April 25, 1953, issue oiNature. Watson and

Crick initiated the era of . About five weeks later they wrote a more thorough paper describing in more detail, the structure of DNA as well as some suggestions. They predicted that "any sequence of the pairs of bases can fit into the structure ... the precise sequence of the bases is the code which carries the genetical information" (Davies 23). They also suggested that could be the modification of the sequencing of the bases. Watson, Crick, and Wilkins were awarded the Nobel Prize in Medicine in 1962. Unfortunately Rosalind Franklin did not get part of the prize, because she died in 1958 of cancer (Davies 24).

It was not until twenty years later that the fu-st picture of the structure was seen.

In 1973, Alexander Rich, a structural biologist at MIT, was able to produce an image,

9 using atomic-resolution crystal structures, of DNA (Bragg 307). In the 1960s Crick, along with were able to prove that the fundamentals of the genetic code were written in triplets of bases. These three bases code the 20 different amino acids and also held the information for the starting and stopping of synthesis. By the end of 1966, they had cracked the entire genetic code. There were 64 different ways to arrange the four bases in groups of three (Bragg 314).

Although we do not have the entire genome mapped there have been many discoveries of distinct genetic disorders, and with completion of the human genome, many more are forthcoming. Victor McKusick, who is considered the grandfather of at John Hopkins University, has made a great impact. He is responsible for getting researchers to catalog more than 5,000 distinct genetic disorders.

In more that 1,000 cases, they know the gene(s) and mutation(s) that are responsible for the diseases. This is a remarkable advance since DNA was discovered (Bock 47).

There are many different outcomes to genes mutating, and although this sounds daunting, most are harmless (Davies 42). It is usually the mutations on a larger scale that pose a problem. In the case of Down's syndrome, there is an entire extra ; this causes many problems; some more serious than others. In

Huntington's disease and other neurodegenerative disorders, there are large sections that are repetitive the same bases repeated over and over. A number of mutations never affect the organism, while others may impair the expression of a particular gene causing disease and other complications. Mutations carry a bad reputation because of the harm they can do; however, the very existence of life depends upon mutations, the basis of is mutations in the genome (Davies 42).

10 Easing the symptoms can only treat most of the genetic disorders that have been pinpointed. Since the problem lies in the genetic code, there is not much that can be done, but to change the code. This is where gene therapy comes in. Gene therapy is the treatment of the disease by attempting to insert a functional gene into cells or tissue so as to overcome a defect in its corresponding (Latchman 14). With gene therapy, doctors and scientists hope to be able to correct the problem before symptoms begin. If they can locate the defective gene, correct or replace it, then the possibility of curing the disease becomes attainable. Naturally with this course of action, many debates arise.

There are arguments that this kind of medicine is against what God intended. This is a touchy area because many scientists believe that there are lines that should not be crossed (Peterson 64).

In 1974, a temporary ban was placed on and testing experiments (Bryan 9). Government committees must approve all experiments, and the tests are highly regulated. The fears that moved the scientists to enact the ban were concerns that the public may be exposed to health hazards such as genetically altered viruses and bacteria (Bryan 9). Some may see this type of restriction unnecessary; however, others believe that without regulations, science could get out of hand.

11 CHAPTER III

MICROBIOLOGY

The field of microbiology is fairly large and covers many aspects of biology.

Microbiology is the study of microscopic life, entities that are too small to see with the unaided eye. Microbiology is comprised of many sub-disciplines, which could probably be considered subjects in their own right due to the amount of information that they contain. Immunology is the study of the and how it works to protect the body from harmful substances and organisms. is the study of the viruses that infect other living organisms and how these viruses fiinction inside cells. Pathogenic

Microbiology is the study of disease-causing organisms and the disease process. The one that bears the most importance for this topic is Microbial Genetics, which is the study of gene function, expression and regulation. Finally, Microbial Physiology is the study of biochemical systems within bacteria (Fairbaim 74).

Microbiology in general dates back to the mid 300s B.C., when believed that living organisms could develop from non-living materials. Nothing was really proved at this time due to the unavailability of instruments and fiirther information. In

1590, Hans and Zacharias Janssen mounted two lenses in a tube to create the first compound microscope ("Research Updates" I). It was almost a century later in 1660 that published , which contained detailed drawings and observations of microscopic beings, using the most advanced compound microscope of the time. Sixteen years later Anton van Leeuwenhoek observed microorganisms. In

1931, Emst Ruska invented the electron microscope ("Research Updates" 1).

12 Without microbiology, the study of genetics would be impossible. Part of the reason that it has taken so long for this field to expand is due to the difficulty in studying such small objects. Every time there is a leap in discoveries in microbiology, a leap in technology coincides with it. With the development of more powerful microscopes, our ability to observe microbial structure more clearly has expanded.

Scientists have known for a long time that life was made up of interactive molecules. In 1836 Theodor Schwann helped to develop the cell theory of living things, basically deriving that all living things are comprised of one or more cells and that these cells were the basic functional aspect of life (Shannon 47). was a very important figure in this field. His work concluded that microorganisms did not arise by as was previously thought. His work also led to sterilization techniques that are still used today ("Research Updates" 1).

The breakthroughs in microbiology have allowed humans to achieve great advancements. Before the 1860s, surgery was not sterile and was as potentially dangerous as what was being operated on. Because of lack of a clean environment, many patients died due to complications caused by infections that were obtained from the operation. Joseph Lister introduced antiseptics into surgery in 1867 and greatly decreased the mortality rate of the procedure due to the bacterial infections ("Research

Updates" 1).

Study in this field has allowed humans to leam more about the worid that we live

in. Although microorganisms generally have a bad reputation, most of them are either

harmless or even helpful to humans ("Research Updates" 1). Microorganisms comprise

the majority of life on this planet. Microbiologists are constantly at work to discover

13 how these organisms can help us better our lives. Microorganisms are responsible for many of our everyday life actions. The food we eat is sometimes the byproducts of bacteria and we would not be able to digest much of our food if it were not for the help of microorganisms ("Research Updates" 1).

Viruses are usually considered the enemy, but scientists have even found a way for them to be helpful. Viruses are used in gene therapy to introduce the new genes into the patient. Scientists use bacteria to produce much needed products like insulin for diabetics, and human growth hormones. Bacteria are responsible for cheese and yogurt production; microorganisms impact so much of our lives.

Scientists are working on creating habitable environments in space using

microbid life (M SU 1). Microbes can be used to recycle air, water, and waste.

Microorganisms can be found as high into the atmosphere as six miles, at the bottom of

oceans, in hydrothermal vents, and toxic waste sites. This indicates that microbes are

metabolically flexible. They can live within just about any environment, even toxic

waste and oil, which some are even able to break down. Many microbial pathogens can

evade the immune system and cause disease. This is important for genetics because if

they can survive those conditions then they wall not have a problem transporting genes

in the human body, while being attacked by our immune system. This is one of the

methods that is currently used today in gene therapy.

14 CHAPTER rv

GENE THERAPY

Gene therapy has the potential to be one of the greatest breakthroughs in medical practice since the discovery of the properties of penicillin. In the past, doctors have been able to treat illnesses that are linked to infections of the body but have been virtually helpless in defense against genetic disorders. Because the problem of inherited disorders lies in the genes, symptoms can be relieved to an extent, but a cure was out of reach. Since the understanding of the genome and the isolation of many genes, scientists and doctors have begun to enter into the fimdamental arena of gene manipulation (Feigner 5).

Gene therapy is the treatment of disorders and diseases that begins on the genetic level. People bom with aliments such as cystic fibrosis, muscular dystrophy,

Huntington's, and possibly Alzheimer's have mutations in their DNA. These mutations make genes proteins that are non-functional or enable to carry out appropriate cellular activities. Inability to carry out basic cellular functions results in abnormal accumulation of toxins, inappropriate developments, healing, and metabolism, resulting in disease. Replacement of a non-functional gene with a "normal" one is gene therapy.

With gene therapy, scientists and doctors hope to cure these disorders (Bock 12).

Currently specialists are able to manipulate individual cells using somatic gene therapy, but this method still allows the spread of the faulty gene into future generations (Bryan

44). Because somatic gene therapy only changes the genes in mature cells, the sex cells, which carry the code for life, are unaffected. Somatic gene therapy has been preformed

15 and so far has been successful; however, it is too soon to tell if this type of medicine is really beneficial and how the procedure will impact the future life of those that have been treated (Whal 4).

In somatic gene therapy, vimses are recmited to deliver the transplant genes into the body. Vimses are chosen because they inject their ovm DNA into cells, which are used as factories for making many copies of the viral gene, spread of the virus, via the blood stream, allows for infection of other cells. This is good because vimses reproduce quickly and so many copies of the new functional gene can spread rapidly (Kedes 953).

There are problems associated with this method, however; the immune system sometimes reacts to the vimses the way it should and kills the vims before it can deliver enough of the targeted gene (Marasco 176). Other reactions can include the effect of the vims on the body, especially adenovimses, which can cause respiratory infections, inflammation, swelling, and fever (Davies 221-25). Patients have even died due to complications from infections caused by the vimses that are injected to save their lives

(Davies 221-25). This is one reason some people are not sold on the idea of gene therapy. Viruses have long been human adversaries, and it is hard to see them as usefiil, even life saving entities. There have been successfiil gene therapy treatments on the other hand, in which the patients treated have returned home seemingly fiilly recovered

(Whal 3). Because of the problems with somatic gene therapy, there is another method that is probably the better choice; it is called germ line therapy.

Germ line therapy is the method for the future. This method involves changing the genes in the eggs and sperm cells, which would prevent the dysfunctional genes from being passed on by parents to their offspring (Bryan 44-5). More testing must be

16 done on this method to determine long-term effects. Problems that may arise fi-om this type of gene manipulation enter into the realm of ethics. Thus, if individuals have had their genetic code changed, are they still the same individual, or someone new

(Chadwick 14)7 There will need to be regulations and guidelines set up before germ- line therapy can used. There is still no guarantee that this form of treatment will even work. Our genes make up our heritage; if what genes we are intended to have are no longer a part of us, then it could be argued that relatedness could be questioned. Some people may have a problem with this form of treatment because it is not just curing the illness or disease but changing the human and their future generations. It could be argued that if we cure all that ails us, which will probably never happen, what will stop the population from growing too large for the earth. This is already a current problem happening today. There are many different aspects of troubles that can and probably will arise from gene therapy; however, for those that suffer, there may be no other alternative.

Although the concept of gene therapy is not new, the capabilities are fairly recent.

About 10 years ago, a little girl named Amy Harper was one of the first humans to undergo gene therapy. She was treated for a that gave her a weak immune system. She and others treated for the same disorder are doing very good; however, it is too soon to tell if the treatment has really been as beneficial as hoped

(Bryan 41). Unfortunately it takes a lot of time to be able to determme the outcome of this kind of treatment in humans. Since humans have a very long life cycle and generation time, it is difficult to harvest the amount of results needed for the satisfaction of knowing for sure that this treatment is going to work. 17 Traditional methods of treatment of genetic disorders include treating the symptoms and trying to make patients as comfortable as possible. These methods, however, do nothing to alleviate the ultimate outcome of the situation. Gene therapy is a long-term method, which means that traditional treatment would still be necessary to alleviate any symptoms the patient may experience while undergoing therapy. Many people may be discouraged because of this, but it is important to understand that gene therapy is meant to correct the problem at the source, and so it is not an immediate relief approach.

Since it can take a long time for the outcome to reveal itself, long-term effects are unknown. It is hard to tell if changing a person's genetic code will create another set of problems. In theory, fixing only the affected gene would only alter the behavior expressed by that one gene. However, genes work together to carry on life, so the question of whether or not any other genes will be affected by the procedure is very important. Perhaps because of the malfionction of one gene, others have changed their behavior to make up for the dysfunction of another. These reasons and more are why it is important to continue testing in this area.

Many options are now available because of genetic therapy. People can get genetic profiles done on themselves and theu unborn children (Bryan 34-5). Doctors can tell a mother who is a carrier for hemophilia, if her child has inherited the gene even before the child is bom. This of course raises some issues such as is it right to know and what to do with the information once it has been obtained. Some may wonder how far this information could go. Concerns of who would have access to the information is genuine, if people could have complete genetic profiles made, could insurance

18 companies require a copy before coverage would be granted (Peterson 63)7 Since there are many issues that still need to be resolved, regulations will have to be enacted to put restrictions on what can and cannot be done.

This also brings up the subject of whether or not this treatment will be covered by insurance plans. Commons sense says that it is beneficial and cost efficient to cure the illness instead of just treating the symptoms for a lifetime; however, insurance companies may not see it that way. Because of the difficulty of the procedure and the experience needed of the personal, the costs involved with gene therapy are most likely not something that most people could afford on their own, that is to say, without help from insurance. Of course the question of whether or not people with these types of disabilities will even be able to get coverage must be answered first. The cost of treatment is probably initially high, although the savings over a lifetime of doctor visits and medications is probably enormous.

The sensitive nature of gene therapy makes it difficult to move forward. Although treatments have been successful so far, there have been some setbacks, and it is hard to test theories and run experiments. It will take time for long-term effects to be observed and so some may become impatient which can make it difficult to get funding for the experiments.

With the ability to manipulate genes comes the possibility of manipulating people to have specific characteristics. Breeding animals has never been a problem, but breeding humans is another story. There is also the concem of the off chance of generating new mutations accidentally. People are already purchasing "designer genes"

(Bryan 26); some may wonder how far is too far. Couples can buy eggs fi-om women

19 with specific characteristics, making designer babies. This may not be that different from choosing a partner with certain qualities, but some may argue that it is less unethical to choose that route rather than buying eggs.

20 CHAPTER V

MUSCULAR DYSTROPHY

There are different types of neuromuscular diseases; the most well known is probably Duchenne Muscular Dystrophy (DMD), also known as Pseudohypertrophic. It got its first name, pseudohypertrophic, because of the characteristic swelling of the calf muscles. Duchenne became the popular name of the disease when Guillaume-

Benjamin-Amand Duchenne, a French neurologist, gave a detailed description of the disorder. There are also different types of muscular dystrophies, such as, Becker MD,

Limb Girdle MD, Spinal MD, Myotonic MD, and Congenital MD. These are certainly not the only forms of MD; however, they all share the same basic principle, muscle deterioration.

DMD is inherited and is X-linked recessive meaning that females are carriers of the problematic gene. Genetic disorders that are linked to the usually do not affect the women carriers (Whal 3). This is because women, who have two X chromosomes, can use the one that does not carry the faulty gene as a backup. For

DMD, females sometimes show symptoms, but they are so slight that the women do not suffer from the disease. The chances a carrier will have a son with the defective gene is

50/50. If her son does inherit the defective gene he will have muscular dystrophy and probably not see his 30th birthday.

Duchenne muscular dystrophy affects 1 in every 3500 boys (Brown 1). This figure is daunting, namely because this is not some rare, obscure affliction of the human body; it is a very real, and common disorder. The high number of people affected

21 makes testing and research is very important. If a cure can be found, the effect will be enormous.

Duchenne M.D. symptoms include generalized weakening of the trunk and limb muscles first and calves that are enlarged making walking or mnning difficult. The onset of the diseases is early in life, symptoms usually surfacing between the ages of 2 and 6. People who suffer from DMD do not normally live past their early twenties. The cause of the disorder is a faulty gene that is responsible for the muscle protein dystrophin. Without this protein, muscles are weak and slowly deteriorate (Porter 1).

Another complication that can result fi-om having DMD is heart trouble. Since the heart is made up of muscle, eventually the deterioration of this muscle can cause it to fail. The lungs can have problems as well. Boys with advanced DMD often need respirators to breathe because the muscles of the lungs are unable to perform the necessary function (Porter 1).

Genetic tests are useful tools in detecting certain genetic disorders, but are not as sensitive as they should be. They can detect diseases such as DMD or BMD (Becker muscular dystrophy) but have a failure rate of about 30% for these disorders (Brown 9)

These tests are not good for point mutation detection, making negative results unclear.

Positive results are a lot more helpful because they can show if a person is a carrier or if a person will develop a disorder later in life. This information can be very useful when planning a family: people can make decisions on whether or not to have children based on the probability of carrying on genetic disorders.

Some may see this as wrong, since the option to terminate a pregnancy may result fi-om such tests results, but if gene therapy is successful, then early detection may mean

22 the end of the disease before it starts. In addition, if germ line therapy is applied and successful, then the parents can correct the problem before they conceive. At any rate, improvements on should be applauded and recognized for their ability to provide information that was unattainable only a short time ago. Scientists are continually working on making the tests more sensitive to the more elusive gene point mutations.

Early pioneers in the study of DMD were able to ascertain that the disease was most likely inherited and predominantly affects boys. A defective nervous system and malnutrition were originally believed to cause DMD (Ivory 2). Although these theories were w^-ong they were on the right path with malnutrition, since the weakening of the muscles is due to the lack of a protein.

Duchenne Muscular Dystrophy is a very sad disorder; boys who have inherited this disease will die at a young age. In time, hopefully, science and medicine will be able to put an end to this affliction to the human body, but as of right now, people afflicted with the disease have no hope of survival. While the unfortunate ones who have inherited the dysfunctional gene will eventually die, they do not experience any pain (Porter 3). The muscles weaken leaving them dependent on other people and machines to live, which may be painful to one's pride; nevertheless, the person does not feel any physical pain or discomfort from this, ^^ensations and mental capacities are not affected by the disorder; these boys can feel everything that touches them as well as all emotions. They are, mentally, normal little boys whose bodies have failed them because of a bad copy of one gene^

Although this disorder affects mostly boys, girls are also known to suffer fi-om the

23 disease. The usual reason that girls experience the affects of their faulty gene is when their "backup" X chromosome is either not complete or for some reason or another is switched off. Each cell can only use one X chromosome at a time; if both are active then the cell cannot survive (Wahl 3) if the body becomes more reliant on the X chromosome with the faulty gene. Then the girl will get the disease; this is called X inactivation. If this happens it is usually when the human is just developing.

There are some doctors and other people who feel there is a need for more research into carriers that are affected; however, most believe that the focus needs to remain on the boys who are the ones that are affected the greatest (Whal 4). Most women carriers will never experience any symptoms so some feel that there is not a need to separate the research, because, after all, if they can successfully control the disease in boys then they will also be able to treat the rare cases of carriers with symptoms. The most common problems that carriers suffer are heart problems, but they are usually mild.

Since only the symptoms of the condition can be treated, gene therapy holds a promising future for these people. In the less common cause of DMD, which is called premature stop codon, children whose genes have mutated to mix up the spelling, of sorts, of the gene, the dmg gentamicn, which is discussed later, may help the gene to overtook the problem and facilitate the production of dystrophin (Wahl 2).

Unfortunately this procedure will not work for the more common cause, DNA deletion.

In the case of DNA deletion, entire sections are missing in the genome. This is problematic because if the information is not there, then it caimot be read and interpreted. Treatment for this type would need to include injecting tlie missing

24 section/s and ensuring that they attach at the right point/s. research, which is discussed later, is the preferred method for this cause.

Tests with new dmgs are ongoing but do not offer much help. Oxandrolone

(oxandrin), which is used to improve athletic abilities, was tested and found to be of no help for DMD sufferers. Some children may have corticosteroid medications, but the side effects are not desirable since they can include weight gain, weakening of bones, increased chances of infections, and a greater chance of developing diabetes and cataracts (Porter 3). Another dmg, an antibiotic called gentamicn, helps to "read through" the problematic gene, as in the case of premature stop codon.

Gene therapy sounds like the best way to attack DMD since it would be correcting the problem at the source. It is not that simple, however; there are current projects underway and some first steps have been taken in trying this form of treatment, but results take time to gather. Doctors must start out slow to minimize negative affects of gene therapy. In the past couple of years, experiments have been preformed where doctors have injected fiinctioning genes into a patients foot, but it is really too soon to know if they will be able to expand the procedure to larger muscles of the body (Whal

4).

Gene therapy includes many different methods; they all share the commonality of using vectors to deliver "fixed" or new genes. Scientists have found that using stem cells may be the best way to go for cell transfer. Using stem cells taken from bone marrow or muscles, doctors have found that they can rebuild muscle tissue in mice.

Stem cells are primitive cells that develop into many different types of tissue, including muscle tissue (Wahl 1).

25 Doctors can use stem cells from healthy donors or use cells fi-om the patient. In the case of using cells from the patient, the cells are only reintroduced into the body after they have undergone gene therapy and successfiilly altered the genetic code to include the healthy form of the needed gene (Wahl I). Doctors have successfully mn this experiment with mice and hope to expand to human subjects soon.

Current methods, as previously discussed, include using vimses as tools to deliver the needed genes into the human body; the vimses become vectors for transporting the genes. The most common vims that is used is an adeno-associated or AAV, which has been rendered incapable of replicating itself and causes no known human illnesses even in its natural state (Wahl 3). The reason that this vims is chosen is because it is able to enter the body and deposit the genes without alerting the natural immune response from the human body. This is important because if the immune system, which is responsible for destroying any foreign bodies that may enter our system, detects it then it will launch an attack and kill the vectors before they can accomplish what they were intended to do.

Different forms of muscular dystrophy affect numerous people on a daily basis, making this research imperative. The more science can understand about this disorder, the more we can understand about other types of genetic disorders. Research takes time, and sicknesses like the flu and even the common cold will continue to change and make a better treatment, instead of a cure, more plausible.

26 CHAPTER VI

CONCLUSION

Science and all its branches has been around for many years, and has continued to grow and improve. Humans are able to do things that better the quality of life for people all over the world. Continued research and experimentation is carried on by the finest minds in the field. Funding from federal agencies such as the NIH or National

Institute of Health and fundraising like the well-known telethon hosted by Jerry Lewis, science labs can continue to make progress on DMD and other genetic disorders.

The fiiture of gene therapy looks hopeful: the experiments that have been performed have been going smoothly and hopefully soon they will have some concrete results to work from. Although many more experiments are needed, as time progresses, more are being run and results recorded; it may take many more years before we can count on gene therapy to do what it is intended to do. If scientists and doctors can perfect the methods used and continue to improve on them, then I think it is safe to say that in the near fiiture we can use gene therapy as a very real approach to treat patients with gene-linked disorders.

The future for DMD gene therapy is a bright one; experiments have already been done injecting functional genes into patients with limb-girdle muscular dystrophy, and the procedure went as expected, if the long-term results come out positive then treatment will probably take off for this disorder (Whal 1). The success of this experiment is cmcial for gene therapy; if the experiment produces the desired results then it will open the door for similar treatments for other forms of muscular dystrophy

27 and possibly other genetic disorders.

Developments are occurring rapidly in gene therapy, but sadly, not fast enough to help many people afflicted today. For them it probably seems to move at a snail's pace.

The best that they can hope for is that future generations of their families will not have to go through what they are. There may be some comfort in the thought that their children will have a better chance at a normal life. Those who are bom with genetic disorders have a better life then those afflicted 100 years ago, but improvement has been slow up until fairiy recently. Once the stmcture of DNA began to be mapped, a very rapid chain of events occurred that has allowed science and medicine to help explain people's conditions, if not treat them more efficiently.

Stem cells have been making headlines lately, primarily because of their ability to migrate to different areas of the body to fix any problems. Scientists have found that they are versatile and because of their ability to rebuild tissues, the MDA, Muscular

Dystrophy Association, is making stem cell research their top priority (Wahl 2). It is my understanding that stem cells are being researched to see if they can play a role in many different types of disorders, ones that involve needing tissue regeneration. This may be the break that scientists have been waiting for.

I have not been personally affected by any such disorders, but many have, and 1 think that one of the best tools is public knowledge. It would be greatly beneficial for the public to have access to the information that the science and medical communities have uncovered. The reason that people are so into AIDS and cancer research, in my opinion, is because we are bombarded with images and information on these conditions.

There are diseases out there that kill thousands of people, but the general public is

28 unaware of them unless they or a family member has been afflicted with one.

29 BIBILOGRAPHY

"Research Updates." Quest. 8. 3 (June 2001) 1-4.

Bock, Gregory R, Dalia Cohn, Jamie A. Goodel. From Genome to Therapy: Integrating Technologies With Dmg Development. Chichester, NY: John Wiley, 2000.

Bragg, Melvyn, Ruth Gardiner. On Giants' Shoulders: Great Scientists and Their Discoveries from Archimedes to DNA. : Hodder & Stoughton, 1998.

Brock TD, Madigan MT, Martinko JM, Parker J. (Eds.). "A Brief History of Microbiology." Biology of Micro-Organisms. Prentice Hall International. 8th ed. 1996.

Brown, Susan C, Jack A. Lucy. Dystrophin: Gene, protein and cell biology. United Kingdom: Cambridge University Press, 1997.

Bryan, Jenny. Genetic Engineering. Austin, TX: Raintree Stack-Vaughn, 1995.

Chadwick, Ruth F. The Concise Encyclopedia of the Ethics of New Technologies. San Diego, CA: Academic Press, 2001.

Davies, Kevin. Cracking the Genome: Inside the Race to Unlock Human DNA. New York, NY: The Free Press, 2001.

Digital Learning Center for Microbial . "Microbe Zoo." Michigan State University: 1995, 1996,2000. 1-2.

Fairbaim, Leslie J., Nydia G. Testa. "Hematopoiesis and Gene Therapy." Blood Cell . New York, NY: Kluwer Academic/Plenum Publishers, 1999.

Feigner, Philip L., Michael J. Heller, Pierre Lehn, Jean Paul Behr, Francis C. Szoka, Jr. "Artificial Self-Assembling Systems for Gene Delivery." Conference Proceedings Series. Washington, D.C.: American Chemical Society, 1996.

Glasner, Peter, Harry Rothman. Genetic Imaginations: ethical, legal, and social issues in human genome research. Aldershot, Brockfield, USA: Ashgate Pub, 1998.

Hesterlee, Sharon. "The Promise of Gene Therapy." Quest. 6. 4 (August 1999): 1-5.

Ivory, Phil. "The Legacy of Guillaume Duchenne." Quest. 5. 5 (October 1999): 1-4.

30 Kedes, Laurence H., Frank E. Stockdale. "Cellular and Molecular Biology of Muscle Development." UCLA Symposia on Molecular and Cellular Biology New Series. New York, NY: Alan R. Liss, Inc, Vol. 93 1989.

Marasco, Wayne A. Intrabodies: Basic Research and Clinical Gene Therapy Applications. Georgetown, TX: Springer-Verlag Berlin Heidelberg and R.G. Landes Company, 1998.

Latchman, David S. From Genetics to Gene therapy: the Molecular Pathology of Human Disease. Oxford, UK: BIOS Scientific Publishers, Hadon, VA: Distributors, USA & Canada, books International, 1994.

Peterson, James C. Genetic Tuming Points: the Ethics of Human Genetic Intervention. Grand Rapids, MI: Wm. B. Eerdmans Publishing Co, 2001.

Porter, Patricia B., Hall, Colin D., Williams, Faye. "A Teacher's guide to Duchenne Muscular Dystrophy." Quest. (August 1999): 1-6.

Shannon, Thomas A. Genetic Engineering: A Documentary History. Westport, Conn.: Greenwood Press, 1999.

Whal, Margaret. "But girl don't get Duchenne~or do they." Quest. 5. 6 (December 1998): 1-5.

Whal, Margaret. "First Gene Transfer injection 'Went like clockwork'." Quest. 6. 5 (October 1999): 1-4.

Whal, Margaret. "MDA Research at year 2000: Moving From Lab to Clinic." Quest. 7. 1 (Febmary 2000): 1-4.

31