AP Biology class blog for discussing current research in Biology

Tag: Gene Therapy

CRISPR technology may be the key to treating Huntington’s Disease

Huntington’s disease is a well-known neurological disorder that is characterized by a loss of movement, coordination, and cognitive function. More than 200,000 people live with Huntington’s disease and more than a quarter million Americans are at risk of inheriting the diseases, but there is currently no cure. Scientists have recently been trying to develop a treatment using RNA-targeting CRISPR/Cas13d technology to eliminate toxic RNA that causes Huntington’s disease. CRISPR allows scientists to edit, add, and remove genetic material from specific places in the genome. This tool is based on a immune-defense mechanism from bacteria. Since there is a risk of editing a part of the genome unintentionally, studies have focused more on targeting RNA directly instead.

Huntington’s disease is caused by a mutation in a gene for the protein huntingtin. This mutation, known as a trinucleotide repeat expansion, causes cytosine, adenine, and guanine to be repeated many more times in the gene that normal. As a result, the protein that is produced can form toxic clumps in the part of the brain responsible for movement, which is called the striatum.

In AP Bio, we learned how genes are used to produce proteins that our bodies use. First, the RNA polymerase creates mRNA from transcribing DNA. A guanine nucleotide is added to the 5′ end, a poly-A tail is added to the 3′ end, and the introns are cut out. Then, the mRNA leaves the nucleus and goes to a ribosome for translation. The anticodon on the tRNA matches with the codon on the mRNA, which brings along the corresponding amino acid. The amino acid connects with the next amino acid to create a protein molecule. The additional CAG sequences in the huntingtin gene are transcribed onto the mRNA, which is then used to create a polypeptide. Since it is longer than normal, this protein’s shape will be deformed and will be toxic to the brain.

In neuronal cultures from patients with Huntington’s disease, scientists have used CRISPR to destroy mutant RNA molecules and clear out toxic protein buildup. Other genes were not affected by this treatment. When tested in mice, scientists found that the mice had better motor coordination and less toxic protein levels.CRISPR CAS9 technology

I chose this topic because I am very interested in how scientists can use mechanisms seen in other organisms to help treat human diseases.


Are Artificial Chromosomes the Key to Future Medicine?

Our DNA is packaged intricately by proteins in order to make up chromatin. If DNA were like a thread, these proteins are the spools that the DNA thread winds around to keep itself neat, organized, and compact inside of a microscopic cell. If a foreign, naked DNA thread with no spool is introduced into the environment, the cell is armed and ready to supply this new thread with its own self-made spools, allowing this naked DNA thread to be stably maintained in the cellular environment as part of the cell’s new collection. This process is known as artificial chromosome formation.

Prospects for the Use of Artificial Chromosomes include the potential to overcome problems in gene therapy protocols such as immunogenicity, insertional mutagenesis, oncogene activation, or limitations in capacity for transgene expression. One case where artificial chromosomes can be useful is found with someone dealing with Cystic Fibrosis. This fatal chronic lung disease is caused by a mutation in the CFTR gene and is currently a disease without a known cure. Scientists have been studying the use of bacterial and yeast artificial chromosomes as a transmitter to implement the normal functioning CFTR gene and overcome the defective CFTR gene in patient cells.

Almost two trillion cells divide every day in an average human body. This means that two trillion cells have to make a perfect copy of themselves every time. In our class, we’ve gone over the importance of cell division and have discussed the Mitochondria and Chloroplast’s ability to replicate independently within cells. The cost of cell division that comes short of flawlessness is undoubtedly humankind’s worst enemy yet: cancer, in which many are characterized by chromosome instability. One important player in ensuring the inheritance of our chromosomes during cell division is the centromere. The current studies of artificial chromosomes provide novel insights into the chromosomal processes required for de novo centromere formation and chromosome maintenance.

Ultimately, the results of these studies could help advance the synthetic biology field by exploring how some characteristics can be designed to optimize the establishment of an artificial chromosome by improving the efficiency of de novo centromere formation through accurate segregation to improve the applications of artificial chromosomes as large-capacity transmitters for cloning and gene therapies.


Inhale RNA, Exhale Your Worries

The focus of a recent study is inhalation genetic therapy to give patients with Cystic Fibrosis relief when they breathe. A defective gene in people with Cystic Fibrosis causes a mucus build-up in specific organs. The respiratory complications due to mucus build-up in the lungs are which infections, clogged airways, inflammation, and respiratory failure.

Recently, scientists developed a study that involves mice inhaling messenger RNA. The messenger ribonucleic acid is genetically manipulated so that it contains an oxidative enzyme called “luciferase”, which is known for causing bioluminescence. Scientists manipulated the mRNA by “packaging” or combining the enzyme with a polymer that would be inhaled into the lungs of the mice. The inhaled polymer would then travel through the respiratory system and be taken in by the lungs, where it would eventually be broken down by cells within the lungs. Scientists were able to distinguish if the experiment was successful as the light from the luciferase combined with the mRNA could be detected from within a lung cell.

Another experiment was conducted with similar circumstances in that it tested genetically modified mice cells that glowed red from the cell’s reception of mRNA. This offered the scientists the opportunity to test a range of mRNA-polymer dosages to quantify or count the resulting “red” mice cells.

As we continue this road down modern medicine, mRNA can be evolutionary for patients with Cystic Fibrosis because the messenger RNA can recreate functional copies of itself to produce CFTR protein (cystic fibrosis transmembrane conductance regulator protein), which is the protein that codes and determines the functionality of the CFTR gene. Could mRNA polymers possibly be a treatment for milder respiratory issues like asthma? This experiment might just be a breakthrough in the world of medicine, as strands of ribonucleic acid could be the answer to ending compromising respiratory complications.

Breakthrough in Type 1 Diabetes Treatments!

A new study demonstrates that a gene therapy approach can lead to long-term survival of functional beta cells as well as normal blood glucose levels for extended periods of time in mice with type 1 diabetes. Researchers used an adeno-associated viral (AAV) vector to deliver to the mouse pancreas two proteins, Pdx1 and MafA, which reprogrammed the alpha cells into functional, insulin-producing beta cells.

Beta-cell replacement therapy is likely to fail because adding new cells will fall victim to the same autoimmunity that destroyed the original cells. The solution is to reprogram other cell types to functional beta-like cells, which can produce insulin but are distinct from beta cells and therefore are not attacked by the immune system.

Researchers Gittes and first author Xiangwei Xiao of the University of Pittsburgh School of Medicine engineered an AAV vector to deliver proteins called Pdx1 and MafA, which support beta cell maturation, proliferation, and function, to the mouse pancreas. The reason why they picked alpha cells to reprogram is because they are plentiful, resemble beta cells, and are in the correct location, all of these factors facilitate reprogramming of cells.

Comparing the gene expression patterns of normal beta cells and insulin-producing cells derived from alpha cells, the researchers confirmed that it was nearly complete cellular reprogramming. The gene therapy produced normal blood glucose levels in diabetic mice, for typically four months. Also, the therapy was able to generate functional insulin-producing cells from human alpha cells.

Unfortunately, the mice did eventually return to the diabetic state, suggesting that it would not cure the disease. But viral vectors can be delivered directly to the human pancreas through a routinely performed non-surgical endoscopic procedure; however, this procedure can elicit pancreatic inflammation. Also, the longevity of the treatment is unknown considering that some studies suggest that processes in mice are highly accelerated. Therefore, four months could translate to several years for humans according to Gittes.

Currently, researchers are testing the therapy on non-human primates. If they are able to produce intended results, researchers will begin work with the FDA to get approval for use of this viral gene therapy for diabetic, type 1 and 2, patients. This could be the breakthrough that leads to the cure for diabetes!

Gene Therapy Saves the Life of Dying Boy with Genetic Skin Disease

A 7-year-old boy with a rare genetic skin disease is reported to have made significant progress after eighty percent of his skin has been replaced through gene therapy. The boy, Hassan, was diagnosed a severe genetic disease called Junctional Epidermolysis Bullosa (EB) that destroyed most of his skin. Caused by a mutation in a gene encoding part of the protein Laminin 332, EB causes fragile skin that blisters and tears even with the slightest touch and is prone to infections and skin cancer.

When Hassan contracted a bacterial infection and lost two-thirds of his skin, doctors struggled to find a way to save the boy. Trying antibiotics, bandages, special nutritional, skin transplant from his father, nothing seemed to work, and after two months, doctors were sure they could not save him and thought that “he would die”.

Doctors then reached out to Dr. Michele De Luca, the director of the Center for Regenerative Medicine Stefano Ferrari at the University of Modena and Reggio Emilia in Modena, Italy and who had treated smaller patches of skin on patients with EB. Dr. Michele De Luca and his team experimentally extracted a sample of approximately half a square inch of the boy’s skin, genetically engineered the cells by using a virus to replace the mutated gene with a normal version in the DNA. In the laboratory, the new skin cells were grown into sheets of skin, which was then grafted by surgeons back onto the boy’s body.

By the end of the procedure, the doctors had replaced nine square feet or eighty percent of Hassan’s skin– the greatest surface area covered in a patient with the genetic disorder. As the surgery was a success, Dr. De Luca notes about Hassan, “when he woke up, he realized he had a new skin.”

The success of the project and surgery is “one of these [studies] that can determine where the future of the field is going to go,” states physician Jakub Tolar. This study can also potentially help researchers use stem cells to treat other genetic skin conditions. As researchers continue to search for further advances in the field, Hassan is now happily able to play soccer and run!

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