BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: Mutation

Embryo Gene Editing can Ensure Offspring Do Not Inherit a Deafness Gene!

Denis Rebrikov, A scientist in Russia has done research regarding ways in which he can edit the genome sequence of an embryo in order to prevent the fetus from developing certain gene mutations, specifically in this case a hearing problem or possible complete deafness. His plans are very controversial to some, who believe the possible risks of very harmful mutations to DNA that would be passed onto direct and future offspring, outweigh the possible benefits. However, some people find this scientific possibility to be worth the risk, if it means not passing a potentially very harmful gene down to offspring. If these methods are done correctly, it should alter the genome sequence in the embryo so that future offspring off that embryo will not inherit the negative mutation.

One couple shared their story in detail, in which both parties have a hearing deficiency, the man with partial deafness, and the woman completely deaf. Their biggest hope is to have children who will not inherit hearing issues, because of the apparent challenges they have had to face themselves because of them. They would be the first couple to perform this gene editing on an IVF embryo, so they obviously have some reservations. One of those being publicity, but more importantly the potential risks of using the CRISPR genome editor. They already have a daughter with hearing loss, but they never chose to test her genes for mutations, nor did they get her a cochlear implant to aid her hearing, because of the potential risks of that. When they finally tested her genes, they learned that she had the same common hearing loss mutation called 35delG in both her copies of a gene called GJB2. The parents then tested themselves, realizing they were both 35delG homozygous, meaning their daughter’s mutations were not unique to her, they had been inherited.

If either the mother or father had a normal copy of the GJB2 gene, a fertility clinic could have more easily created embryos by IVF and tested a few cells in each one to select a heterozygote–with normal hearing–to implant. At this stage, Denis Rebrikov informed them that CRISPR genome editing would be their only option. However, the process presents possibly deal breaking risks, such as mosaicism, in which a gene edit might fail to fix the deafness mutation, which could create other possible dangerous mutations like genetic disorders or cancer. The couple has not decided to go through with the editing just yet, but it is something they are open to in the future as more possible new research or test subjects become available.

Explaining the CRISPR Method: “The CRISPR-Cas9 system works similarly in the lab. Researchers create a small piece of RNA with a short “guide” sequence that attaches (binds) to a specific target sequence of DNA in a genome. The RNA also binds to the Cas9 enzyme. The modified RNA is used to recognize the DNA sequence, and the Cas9 enzyme cuts the DNA at the targeted location… Once the DNA is cut, researchers use the cell’s own DNA repair machinery to add or delete pieces of genetic material, or to make changes to the DNA by replacing an existing segment with a customized DNA sequence.” -US National Library of Medicine Genetics Home Reference

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Woman with a hearing aid 

If you had the opportunity to alter something in the gene’s of your baby’s embryo, would you? Under what circumstances would you consider this, and what risks might stop you from deciding to do it? Comment down below.

 

 

A Gene Mutation that Keeps You Awake and Functioning for Longer

INTRODUCTION:

Could a gene mutation really allow someone to finish college in two and a half years? The answer is yes! We all wish we could get by a function perfectly, or even better than normal, on less sleep. This is a reality for some, specifically people with a rare gene mutation. I saw an article titled, “Why Do Some People Need Less Sleep? It’s in their DNA,” and I thought this was a rather interesting topic, because I have never heard of less sleep ever being a positive thing. I am interested to see more research on this, and the possibility of it being an added benefit for others. It prompted me to think about whether or not this is something I would want, considering some of the implications. 

People with this gene mutation can get significantly less sleep than recommended for function, as little as three to four hours—without suffering any health consequences and while actually performing on memory tests as well as, or better than, most people. There is now a new study correlating to a new genetic mutation found with these “powers,” after previous studies revealed other types of mutations that may impact sleep.

 

HOW DID IT START?: 

To understand this rare ability when presented to them, scientist Ying-Hui Fu and her team, at the University of California, San Francisco, in 2009, began this study on some individuals, but also on mice, to simulate a similar sleep equilibrium to humans. After a woman came in claiming she was functioning at a high level on very short sleep time, scientists needed to understand, as lack sleep is typically correlates with health issues such as risk of heart attack, cancer, or even Alzheimer’s. They initially found a small mutation in the DEC2 gene, a transcriptional repressor (hDEC2-P385R) that is associated with a human short sleep phenotype. According to UCSF, DEC2 helps regulate “circadian rhythms, the natural biological clock that dictates when hormones are released and influences behaviors such as eating and sleeping. This gene oscillates this particular c schedule: rising during the day, but falling at night.” The newer study reveals that the DEC2 gene lowers your level of alertness in the evening by binding to and blocking MyoD1, a gene that turns on orexin production, a hormone involved in maintaining wakefulness. Fu says the mutation seen in human short sleepers weakens DEC2’s ability to put the breaks on MyoD1, leading to more orexin production and causing the short sleepers to stay awake longer.

THE NEW GENE MUTATION: 

In a new study, released on October 16, 2019, by Science Translational Medicine brought on by a mother and daughter duo, mice were studied again to mimic the human sleep pattern. The mice again required less sleep, and were able to remember better. In the study, researchers identified a point mutation in the neuropeptide S receptor 1 (NPSR1) gene responsible for the short sleep phenotype. The mutation increased receptor sensitivity to the exterior ligand, and mice with the mutation displayed increased mobility time and reduced sleep duration. Even more interestingly, the animals were resistant to cognitive impairment induced by sleep deprivation. The results and findings in the study point to NPSR1 playing a major role in sleep-related memory consolidation. NSPR1 is a gene that codes for a brain receptor that controls functions in sleep behaviour and awakeness. In the new study, when mice were given this gene mutation, there were no obvious health, wellness, or memory issues over time. Although the family members did not appear to experience any of the negative effects of sleep deprivation, the researchers make sure to emphasize that longer term studies would be needed to confirm these findings.

WHAT DOES THE FUTURE HOLD?: 

In the future, a possible drug could be produced to synthesize a change in one of these genes, as a possible treatment for insomnia or other sleep disorders. We would need a lot more research about their functions, though, because of possible negative neurological side effects. 

If a medication with these powers were to exist, do you think it would cause social issues regarding some  possibly forcing certain individuals to take it to work longer hours/get more done? Do you think that it should be available to everyone, or only people with certain conditions? Comment about this below. 

 

Could CRISPR Cure Duchenne Muscular Dystrophy?

What is Duchenne Muscular Dystrophy?

https://www.flickr.com/photos/150276478@N03/34406844136

Duchenne muscular dystrophy, DMD, is an X-linked recessive disease caused by defects in the gene that makes the dystrophin protein. This particular gene is made of 79 exons, and the defects can occur on any of them. These defects lead to degeneration of skeletal and heart muscle, forcing patients to rely and wheelchairs and respirators. Without a cure, most people with the disease die by the age of 30. So, the question becomes, how can we find a cure?

What is Precision Editing?

http://www.njsta.org/news/crispr-in-the-classroom-by-simon-levien

CRISPR technology has advanced tremendously in the past several years, with each study building off the last. CRISPR technology has the capability to cut out segments of DNA, but with the risk of cutting out too much or the wrong parts. Thus, it is crucial that the cutting be as precise as possible. The CRISPR-Cas9 gene-editing tool, uses an RNA strand to guide the Cas9 enzyme along the DNA strand, skipping over important “healthy” DNA and leading the enzyme to cut a specific portion of DNA.

 How do DMD and Precision Editing Connect?

Dr. Olsen is Co-Director of the Wellstone Muscular Dystrophy Cooperative Research Center, a lab in which a team has been working to apply precision editing to DMD. The method uses one single cut of DNA along strategic points and is less intrusive than other methods. Scientists have developed guide RNAs with the purpose of finding mutation “hotspots” along the dystrophin gene. The RNA strand guides the Cas9 enzyme to 12 regions where most DMD mutations have been found. According to the article, “the new strategy can potentially correct a majority of the 3,000 types of mutations that cause DMD.” Wow! In a recent study using this method, these RNAs helped rescue cardiac function to near-normal levels in human heart muscle tissue.

Why is it Important?  

The new study demonstrates eliminating abnormal splice sites in human DNA can correct a wide range of mutation. In the case of DMD, the splice sites that were removed using CRISPR technology instruct the genetic machinery to build abnormal dystrophin molecules. Once these sites are removed, an improved dystrophin protein was observed. Even more fascinating, correcting only half of the damaged cells restored cardiac function to a healthy level. Does this sound fascinating? If you answered yes, click here to learn more!

What Does the Future Hold?

The strategy of single-cut editing may be useful for treating other single-gene diseases. News of such prospects has generated a great deal of hope for patients. Much more research is needed before CRISPRCas9 can be used on human patients. Labs and researchers around the world are working to perfect this method so that it can get federal government approval and move to the next stage – human trials. As research progresses, it will be faced with backlash from some who believe DNA should not be altered and that the technique is too risky and support from those who believe this new technique could save lives. Which side do you fall on?

New Research Sheds New Light on Cancer Preventing Proteins

Cells in the human body are constantly dividing. Whenever cells divide into two, the DNA within them must be copied as well. Most of the time this process works as planned, but some times the DNA can be copied incorrectly. Other factors such as UV rays and radiation can damage DNA and lead to problems like cancer. While these errors in DNA copying can cause significant mutations, they are usually corrected by certain proteins within the cell. New research at the University of Michigan is allowing scientists to get a better idea of how these proteins go about finding the damaged sites and repairing them.

Mutación ADN

Image Source

In this study, researchers at UM examined the MutS protein in bacteria. According to Lyle Simmons, associate professor of molecular, cellular, and developmental biology at UM, it has been known for a long time that the MutS protein could find and repair errors in DNA. “MutS is the first protein involved in DNA mismatch repair and is responsible for detecting rare errors that can predispose people to certain types of cancer, a hereditary condition called Lynch syndrome or cancer family syndrome. If a person’s mismatch repair system is hindered, the mutation rate increases 100-to-1,000 fold” says Simmons.  Despite knowing what these proteins do, it remained unclear as to how they perform these tasks.

To see how the protein works, researchers “fused the MutS protein to a fluorescent tag and activated fluorescence with a laser.” They then studied the protein’s actions inside of a bacterial cell. Tagging the proteins with fluorescence allowed researchers to track its movement through the cell. Scientists observed that MutS moved quickly through the nucleoid but slowed down at DNA replication sites. This indicates that the proteins look for sites of replication rather than individual mismatches. The protein then searched the new DNA being created for errors. Mismatches occur when the wrong nitrogenous bases are paired with each other. “The mismatched pair kinks the DNA at the replication fork where DNA is made. MutS positions itself at that fork so it’s ready to catch any mistakes. As an added bonus, this positioning likely tells MutS which side is correct and which side is the new, altered DNA.” says Julie Biteen, assistant professor of chemistry.

Despite the study being performed on bacteria, it is very likely that the same process occurs in human cells.  This discovery is very important because it provides information that will be essential to learning more about how the body responds to mutations.  Further advances in this area of study could possibly help researchers understand cancer better.

Original Article

The mutation and spread of Cancer caused by changes in Epigenetics

Epigenetics could be the key to understanding how cancer originates, when it mutates, and how it spreads. Researchers at the Boston University School of Medicine (BUSM) believe that different types of cancer are caused by an “on and off” switch in the epigenome. While many scientists believe  that many cancers originate in cells called progenitor cells, they cannot concoct a model that explains  how cancer spreads from the progenitor cell and mutates into many forms as it continues to grow in a person’s body.

One of the lead researchers, Sibaji Sarkar, posited “there should be a general mechanism that initiates cancer progression from predisposed progenitor cells, which likely involves epigenetic changes.” The researchers believe that the theory of an epigenetic switch is supported by the growth of tumors, which go through many different stages. The team believes that if cells can be altered to become cancerous and remain stuck in their stage of growth while they replicate out of control, then there must also be an off switch to this uncontrolled replication. They also suspect that epigenetic changes can determine the rapidity of growth and the mutability of the characteristics of the cancer and tumors.

Although Sarkar’s team has not yet found specific epigenetic code that causes these mutations and growth, he believes that their hypothesis will cause other scientists to focus their attention on the epigenome and find ways to prevent progenitor cells from spreading and mutating into malignant tumors.

This epigenetic research relates to our study of the relationship between the epigenome and cancer. Specifically the absence of an active p53 protein would prevent a certain part of the DNA from being  read and the cell would therefore lack a protein that inhibits the cell cycle. This would cause uninhibited cell division and the spread of cancer.

 

Methylation of DNA

640px-DNA_methylation

How the “guardian of the genome” falls:

 

 

 

p53 is a protein that plays a vital role in the G2 checkpoint phase before mitosis begins. This checkpoint “ serves to prevent the cell from entering mitosis (M-phase) with genomic DNA damage.” (http://www.cellsignal.com/reference/pathway/Cell_Cycle_G2M_DNA.html) The role of p53 is to trigger repair for damaged DNA if possible and to hold the cell in the G1/S checkpoint until it is repaired and if the repair of the DNA is not possible p53 triggers apoptosis. Therefore, p53 plays a large role is preventing cancer because a cancerous cell starts with a mutation in DNA.  However mutant p53 allows cells who have DNA damage and have “tranformed” to be cancerous to enter into M-phase and proliferate thus forming a tumor.

Biologists, chemists and computer scientists at UC bolder however have discovered a “an elusive binging pocket” in the quaternary structure of p53 which is open “5 percent of the time.” (http://www.sciencedaily.com/releases/2013/01/130131121312.htm) The reason the pocket is only open 5 percent of the time is because the p53 protein undulates, meaning it sways so this pocket was hard to find and target. Their team then screened almost 2,500 molecules and tested out 45 molecules to see if any of them could fit into this pocket and trigger the normal tumor-suppressing abilities found in p53 in a mutated p53 molecule. They found that stictic acid fit and triggered the tumor-suppressing abilities. Although stictic acid is not able to be used as a drug, they can now scan other molecules that have similar properties as stictic acid making this a large step in cancer research because mutated p53 is found in over 40 percent of diagnosed cancer cases. (http://www.sciencedaily.com/releases/2013/01/130131121312.htm)

 

Sources:

http://www.sciencedaily.com/releases/2013/01/130131121312.htm

http://www.cellsignal.com/reference/pathway/Cell_Cycle_G2M_DNA.html

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