Gene that Causes Cystic Fibrosis Disease

About 1 out of 201 Caucasian people carries at least one of the fatal defective genes that cause cystic fibrosis, CF, or mucoviscidosis (in Europe) although carriers don’t show any signs of the disease. Therefore, 10 million2 people carry the defective gene and aren’t aware of it. Consequently, it makes it one of the most common genetic defect in the United States.

CF is a autosomal recessive gene. That means that it may, but doesn’t always skip generations. In order to get this disease, both parents must be carriers. If one parent has CF and the other one is not a carrier than there is a 100% chance that their child will be a carrier. If one parent has CF and the other is a carrier than the child has a 50% chance of having CF and a 50% chance of just being a carrier. If both parents are carriers than their child will have a 25% of having CF, a 50% chance of being a carrier and a 25% chance of not being affected. CF is common in both males and females, there is not a specific sex that it is more common in.

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How does a person know if they have CF? There are many symptoms to this deadly disease including: salty tasting skin, constant coughing, large amounts of mucus, trouble gaining weight, frequent greasy, foul smelling bowel, growths in the nose (nasal polyps) and clubbed or enlarged fingertips and toe tips is another symptom. Now there are many tests that can be done to find put if a person has CF.

One way which CF can be detected is to observe the symptoms. A person doesn’t need to have all the symptoms in order to have cystic fibrosis, but they usually show most of them. Another way are different genetic testing. Doctors can now do genetic testing for CF, but about 10 years ago they couldn’t. In 1989, the location where the of the defective gene on chromosome number 7 is was discovered by Francis S. Collins from University of Michigan. Tests can now be taken to see if an unborn child is infected with CF such tests are amniocentesis, chronic villus biopsy3 and a removal of cells from the embryo during invitro.

Many years ago, New York4 had a heat wave, and the hospitals became overwhelmed with dehydrated CF children. These children became dehydrated much quicker than children without the disorder. Thus eventually resulting in the formation of the sweat test which is now the standard test. Doctors place a pad or filter paper on a patients arm or back. A chemical called Pilocarpine, makes a burst of electricity to produce more sweat. Then the pad is wrapped in plastic and is sent to a lab to get analyzed. The doctors then would look for a high chloride content in the sweat. Another test is a blood test that is administered 3 days after a baby is born. It is called Immunoreactive Trypsinogen5 if that comes back positive it is then double checked with a sweat test.

Furthermore CF causes the sweat glands to release about 5 times6 as much salt as a normal person would. This is why the skin of a CF patients may taste salty. They don’t sweat more, but when they perspire more salt is excreted. This causes the person to dehydrate.

CF is a disorder that causes the body to produce larger amount of mucus than normal. In a normal person, mucus in the lungs helps get rid of germs and bacteria in the air. In a CF patients the lungs become covered with a sticky mucus that is hard to remove and promotes infection from bacteria. Over time infections cause the lungs to become extremely weak, therefore ending in respiratory failure.

Also CF affects the digestive tract. The overproduction of mucus causes the pancreatic ducts to be clogged. Therefore preventing necessary enzymes to digest fats and proteins. Without those enzymes CF patients can’t gain weight. The undigested proteins and fats pass right through the body creating smelly bowel. In some cases this malnutrition causes people to die when they are only children. Also it is more common for people with cystic fibrosis to develop digestive tract cancer7. High levels of the protein CFTR (which the gene makes) are found in the digestive tissues. Doctors explain this increased risk of cancer because CF induces change in the digestive tract organs that causes the cell turnover. Patients with gastrointestinal tract problem should get examined for such tumors.

Women with CF can have children, but it is not very common. Giving birth is a vigorous process and puts the mother’s health at risk. It may also be hard for a women to get pregnant though because the mucus blocks the sperm from entering the uterus the to the fallopian tubes. About 98% of men with CF are infertile8. Even though sperm are produced, they can’t get to the semen because the vas deferens is blocked. In some new research, it has been thought that men who are sterile have a different form of CF that doesn’t involve the digestive system and the lungs.

There are now many drugs that are in the market and many more that are in development. Treatments mainly depends on what organs are effected. The first new drug therapy in 30 years was approved by the Food and Drug Administration in December of 93′. It’s a mucus-thinning drug called Pulmozyme®. Pulmozyme® has reduced the number of respiratory infections and improved lung function. There is also postural drainage or thumps. This treatment is when the patient is hit on the back and chest with cupped hands to loosen the mucus so it can be coughed up easier. There are many antibiotics that help treat lung infections. Also medicated vapors are inhaled and open clogged airways. Since mucus in the intestines causes the food not to get digested, there are enzyme supplements to help. Those enzymes allow patients to go back to a normal diet. Due to the high concentration of the enzymes the end result is deterioration of the pancreas leading to diabetes. With the supplements CF patients can eat normal food.

There are now many studies that the medicine ibuprofen (Advil, Motrin IB, Nuprin) prevents serious damage to lungs in children who have CF. The trials involved 85 patients between the ages of 5 and 39 with FEV1 equal or greater than 60%9. In this study patients that took ibuprofen had a slower rate of decline of FEV1. Patients that took it for 4 years consistently had even better results and showed best in patients under the age of 13. The dose of ibuprofen was selected between 50 and 100up/mL because the anti-neutrophil effects of ibuprofen are only attained at these levels. There are some side effects, including conjunctivitis (unknown reason) and epistaxi (due to the anti-platelet action in the ibuprofen. Doctors say that it is not sure if stomach pains are due to the ibuprofen, but to stay on the medicine and to take antacids with magnesium and aluminum and not those containing calcium. In 1990 two teams of researchers were able to correct CF cells in a petri dish10. The next huge step happened in 199311, when the first experimental dose of gene therapy was administered to a human. These were milestones in finding a cure or a preventive treatment. They were huge steps because it marked the first time that scientists were able to test new technology in people with the disease. Also in October of 93’12 scientists at the University of Iowa made another big step, they determined that the CF gene treatment worked! It had repaired the defective CF cells. This too was the first time that the basic defect was corrected in people with the disease.

Doctors and scientists know that the gene number 7 is the gene that CF is found upon. They also know that gene’s protein product most likely induces the movement of chloride directly or indirectly. They named the protein ,cystic fibrosis transmembrane conductance regulator (CFTR). While scientists and doctors were looking for the gene, they also discovered that there is an abnormality in the DNA of 70%13 of cystic fibrosis cases. That abnormality often called AF508 mutation, is made of the deleting of 3 nucleotides from that gene, that then causes the protein product to be missing an amino acid named phenylalanine at position 508. Doctors are now trying to get to this gene mutation and fix it. Scientists are trying to think of a way to administer healthy CFTR genes to the patients through gene therapy. If all goes as planed the DNA injected will help the cells to make the normal CFTR protein and cystic fibrosis will then be terminated.

Doctors have many “delivery vans” that deliver the good genes. Doctors transport them in viruses, fat capsules and synthetic vectors14. They are put in the body through the nose or bronchial tubes. Nine human gene therapy research studies are in the works as of now. Six of these nine are using the “delivery vans” to deliver healthy genes to the lungs or the nose. In one study the patients are given repeated doses of the CF gene therapy treatment to the lungs. While other studies gives repeated doses of the gene therapy to the nasal tissue of the patients. The other studies are using the fat capsules for delivery, another is making the fat capsule in air form and are breathed in by the patients. Putting the good genes in AAV (adeno-associated virus) is another way of getting the genes in the body. In the last study, are also uses the AAV to get the healthy genes into the lungs. There are about ninety people with CF who have gone through some sort of gene therapy. “There is a long way still to go before we have a cure for cystic fibrosis, but we are moving in the right direction,” says David Porteous of the Medical Research Council’s Human Genetics Units at Edinburgh University. Recently a grant15 has just been given to a company named Aradigm that might get us closer to a better delivery vector. Dr. Igor Gonda, Aradigm’s Vice President of research and development says, “By combining gene therapy with the AERx delivery system, our research could ultimately lead to a broadly-applicable technology for delivery of genes and olignucleotides to the respiratory tract. Diseases which might be treated by such genetic therapies include respiratory infections, lung cancer, emphysema, asthma and cystic fibrosis.”16

Cystic fibrosis is a genetic disorder that affects not only it’s victims, but it’s victims family and friends. Thanks to modern medicine and new techniques, the median survival rate has gone from 8 years old in 50’s to 30 years old in the late 90’s17. Unfortunately, all this new medication and discoveries has come to late for many people. One such individual is Alex Deford. She died when she was only 8 years old. Her father, Frank, wrote a book based on her life and their many struggles, from ignorant doctors who wouldn’t believe a dying child about a collapsed lung and the disease itself. Many times with any genetic disorder, the parents blame themselves. After all it was their bad genes that caused it. Actually, when Alex first went into the hospital to get a sweat test, it came back negative, when in reality it was positive. That was back in the early 70’s though. Now sweat tests have few oversights.

Cystic fibrosis is a disease that doesn’t take any prisoners. All victims will eventually die from complication due to CF. There are approximately 30,00018 children and adults that are living with this disorder. Now that scientists have found the gene in which CF is located, new medicines and new therapies will hopefully be invented. Perhaps in the next century, we can say that cystic fibrosis is completely abolished. Maybe the new medications and therapies won’t have to be as painful as they are now. Why should these individuals with CF be made to suffer in order to get better. Frank Deford says about chest physiotherapy and the disease, “Two thousands times I had to beat my sick child, make her cry and plead…and in the end for what?”

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Gene that Causes Cystic Fibrosis Disease. (2018, Jun 14). Retrieved from