BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: human gene editing

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.

 

 

The First “in vivo” CRISPR-Cas9 Gene Editing

At the start of the new year all of the scientists working in different fields being to create a schedule of perceived accomplishments that will occur in regard to their specific field of study. In the term of the people working with CRISPR, they speculate that the first in body injection in order to conduct real time genome editing will occur in 2020. Prior to this year, CRISPR has been used to edit and alter the DNA of red blood cells outside of the body, but the scientists working with this new form of biological technology belief that this year it will be used the way it is intended to be used.

CRISPR was originally found in 2012 inside bacteria in order to help stop viruses from infecting them. Scientists saw the possible benefit of this in humans and through years of research discovered that CRISPR can help place another enzyme Cas9, which snips out parts of DNA, in a correct spot on the genome to alter and edit a person’s DNA code. While over time some scientists have wondered about the ethics of this new discovery, most are excited by all of the possibilities that CRISPR has on curing diseases.

Currently, the reason that CRISPR-Cas9 has become a talking point recently was due to the fact and difference between gene editing “in vivo” versus gene editing “ex vivo”, meaning within the body or outside the body. Scientists working with CRISPR have been able to understand how editing “ex vivo” works. They are able to see the genes they want to edit and watch the process occur. This is also easier for the scientists because if the editing messes up, they do not need to reinsert the altered cell back into the body. On the other hand, “in vivo” gene editing is much more efficient and can be completed through a simple injection, but may cause dangerous consequences, such as cancer, if a mistake is made in both the scientists’ coding of the CRISPR or in the process done by the CRISPR itself.

Now that scientists are starting to attempt to move from “ex vivo” editing to “in vivo” editing, all of these questions and issues are being brought up. With lots of labs around the country working on moving into “in vivo” editing and an FDA approval for the procedure, the first CRISPR-Cas9 “in vivo” gene editing is bound to happen soon. Hopefully, this new biological technology does its job properly and gives hope to those who have various currently seemingly incurable disease. If successful, CRISPR could revolutionize medicine itself to make it more efficient and effective. Feel free to comment about how you think CRISPR will do in the first “in vivo” test and how it could effect life later on.

CRISPRi Antibiotics: Will Pathogens Cease to Exist?

Recently, a researcher at the University of Wisconsin-Madison and his collaborators at the University of California, San Francisco have discovered a way to repurpose CRISPR, a gene-editing tool, to develop new antibiotics.

What does this mean?

It is known that many disease-causing pathogens are resistant to current antibiotics. This new technique, Mobile-CRISPRi, is helping to change that. Mobile-CRISPRi allows scientists to “screen for antibiotic function in a wide range of pathogenic bacteria.” Scientists used of bacterial sex to transfer Mobile-CRISPRi from laboratory strains into any diverse bacteria. This easily transferred technique will now allow scientists to to study any bacteria that cause disease or help one’s health.

To break it down, Mobile-CRISPRi “reduces the production of protein, from targeted genes, allowing researchers to identify how antibiotics inhibit the growth of pathogens.” This will allow researchers to more thoroughly understand different bacterias’ resistance to current antibiotics.

Unlike CRISPR, which can split DNA into two halves, CRISPRi is a defanged form that is unable to cut DNA. Instead, it stays on top of the DNA, blocking other proteins from being able to turn on a specific gene.

Genes (DNA)

Why is this important?

It has been proved that a decrease in the amount of protein targeted by an antibiotic will make bacteria become more sensitive to lower amounts of that same antibiotic. This evidence association between “gene and drug” has allowed scientists to “screen thousands of genes at a time,” as they try to gain more knowledge about the mechanisms of how antibiotics work in organisms to improve those on the market now.

In order to study how antibiotics directly work in pathogens, researchers needed to make this CRISPRi mobile, or easily transferred onto different bacterias. There were two tests done to test CRISPRi’s mobility using conjugation. One involving a transfer of CRISPRi to the pathogens Pseudomonas, Salmonella, Staphylococcus, Listeria, and others, and another involving the bacteria that grows on cheese.

Science Daily describes the “landscapes of microbes cheese creates as it ages.” A bacteria called “Vibrio casei” was found on a French cheese in a lab back in 2010. With bacteria that have been taken out of their environment, it is hard to manipulate and study said pathogen’s genes, like “Vibrio casei.”

However, the mobile-CRISPRi was able to easily transfer onto the strain of  Vibrio casei that was discovered back in 2010. This has given scientists a new way of understanding how bacteria colonizes and ages cheese.

Peters, the head researcher of mobile-CRISPRi is generous enough to offer this system to other scientists who would like to study other germs. With this technology being available to others, scientists could potentially see first-hand how antibiotics work in pathogens, and use that information to improve those that currently exist, hopefully getting rid of these bacterias like pseudomonas, or listeria before they kill the human they are inside of.

CRISPR Cas9, too good to be true?

After its peak in popularity following its reveal as a possible “genetic modifier” in 2013, the CRISPR Cas-9 enzyme system has been the center of debate within the biology community. Thought to be the solution to all genetic and hereditary diseases by simply “cutting out” the fault gene, new research and studies have shown that a majority of people (65 to 79 percent) have antibodies that would fight cas-9 proteins.

“The study analyzed blood for antibodies to two bacteria from which Cas9 is derived: Streptococcus pyogenes and Staphylococcus aureus. The researchers’ concern stemmed from the fact that these bacteria frequently cause infections in humans, and so antibodies to them may be in our blood” states bigthink.com

While the overall effects are unclear, the study concludes that the result would be “significant toxicity” and an unsafe use of the gene editing tool.

What do you think? Is the current risk of using Cas-9 worth the reward?

Click here, here, and here for more information.

Cas9, photo by J LEVIN W

 

CRISPR, A Cure to Heart Disease?

Photo Source page: Flickr.com

     While CRISPR‘s full potential in the department of gene editing is still being researched, scientists have just successfully discovered CRISPR’s ability to correct a defective gene that causes a certain type of heart disease. Though scientists are unclear as to the type of gene corrected in order to cause this change, this discovery was made for the first time in the United States, by an experiment done on live human embryos. However the new information yielded from this experiment is extremely beneficial as it shows CRISPR’s potential in correcting genetic errors that cause disease, as well as in human embryos meant for pregnancy.

Another reason for which this study particularly stands out in its importance, is because it is much different from the other developments scientists have made in CRISPR’s abilities. Studies have been conducted worldwide using CRISPR to edit of somatic cell’s gnomes, however, this only affects individual people. This study (also done by researchers in China), has been done by editing germ line cells, which result in changes that are passed down through every following generation.

However since the changes made to cells do affect all generations that follow, scientists are unsure of the exact effects of this new technique. Although it seems that this technology will be very beneficial in stopping harmful genetic diseases, it can also be used for changing DNA to genetically determine the eye colors, height or even mental and physical abilities and intelligence. This new phenomenon is own as “designer babies”, and for many reasons, this is not something that the United States is trying to use CRISPR’s abilities for. For this reason, United States has recently created more severe guidelines regarding gene editing technology, as well as enforcing CRISPR’s use on embryos only for prevention of harmful genetic diseases, when other treatments were not successful – as a last resort – formed by the National Academies of Sciences, Engineering and Medicine.

In the study done, scientists edited out a mutant copy of MYBPC3, using CRISPR. MYBPC3 is a gene that encodes a protein that creates well maintained and structured heart muscles. Hypertrophic cardiomyopathy, known as HCM, are caused by mutations in that gene, and cause spontaneous cardiac arrest. This occurs in even the youngest and healthiest of athletes, affecting 1 in 500 humans.

In this study, the mother was carrying the normal version of a gene, while the father had the mutant gene. Using CRISPR, the scientists were able fix the mutant version, by cutting and replacing the DNA. Directly after they placed the fertilized egg in a petri dish, while introducing the genome editing parts at the same time. The results of this process proved to be very effective, as 75% of the embryos showed no mutant genome. Without the use of CRISPR when egg fertilization occurred, the chances of mutation would have been present in 50%!

From these results the researchers came to the conclusion that they have realized the potential for mosaicism. Mosaicism is when only some of the cells are edited and the rest are not affected, which results in some normal cells, as well as some mutant cells. The scientists have also gathered the effects of off-targets. Off targets are the CRISPR edited genes that appear to look like mutant genes, but are actually not. Within this study, one egg fertilized from 58 showed mosaicism, and there was no detection of effects from off-targets. Theseare very impressive results, due to the fact that both of these possible situations can cause limitations in effectiveness and safety.

Though researchers need to do over this experiment many times in order to soliditfy the effectiveness of this study for the future, if they want to use this on eggs intended for pregnancy, as the eggs fertilized in the study were not meant for pregnancy… However, the results have yielded nothing but good news for the future of CRISPR technology (besides, the risk in advancements in “designer babies”, which couldchange the future of conceiving, forever…). This article was extremely interesting for me to read, as I am very interested in studying Biology in the future, or even pursuing a track to medicine. Perhaps, I may get the chance to even experiment with CRISPR at some time in my life, as it becomes a growing presence throughout the science world!

Primary Source Article: U.S. researchershave used gene editing to combat heart disease in human embryos

HIV Adapts to CRISPR-Cas9 Treatment

There has been an abundance of research using CRISPR/Cas9 gene editing to search for a cure for HIV. The HIV virus enters immune cells and uses the host cell’s method of replication to replicate the viral genome. With CRISPR/Cas9, specific mutations can be introduced in order to make it more challenging for the HIV virus to enter Helper T-Cells. Guided by specific strands of RNA, the Cas9 enzyme can cut a particular piece of the viral genome out, rendering it useless.

When a team of researchers at McGill University attempted to use the CRISPR method to disable the HIV viral genome, they found a major roadblock. Two weeks after the CRISPR/Cas9 treatment, the host cells appeared to be creating copies of the virus. This may be attributed to an error in the enzymes that copy the viral DNA, causing a change in the genome, and a mutation that allows it to evade the CRISPR treatment. However, the McGill researchers believe that this mutation was a result of the CRISPR treatment itself.

After DNA is cut by the Cas9 enzyme, the host cell usually attempts to repair the damage. Occasionally, this results in the addition or deletion of a few nitrogenous bases. While these changes usually result in the inactivation of the cut gene, sometimes they don’t. The active cut DNA is no longer recognized by the machinery used to prevent HIV infection of the cell, and the mutated viral genome is resistant to the usual methods of disablement.

More researchers at the University of Amsterdam had similar results in their research. While it is not that surprising that HIV can overcome the CRISPR/Cas9 gene editing at some point, the leader of the research (Atze Das) said “What is surprising is the speed- how fast it goes”.

If CRISPR was used at the same time as HIV-attacking drugs (inhibitors of protease, reverse transcriptase, and integrase), perhaps the mutations would be less  detrimental. This roadblock does not mean that a CRISPR cure for HIV is impossible, but it does make it far more challenging to overcome.

The Grey Area of Human Gene Editing

The process of Human Gene Editing developed with the goal to prevent future generations from suffering from genetic diseases present in past generations, like our own. Human gene editing, provided it is done only to the correct disease, alters the DNA in embryos, eggs, and sperm to the when reproduction occurs, the gene for the disease or disability is not inherited. However, two weeks ago the National Academies of Sciences and Medicine issued a report stating that human gene editing is being used to enhance people’s health or abilities. This is considered unethical according to organizers of a Global Summit on human gene editing.

Human gene editing has been given a “yellow light” because the process is not yet approved to be done on people. There are high hopes that diseases caused by only 1 genetic mutation such cystic fibrosis and Huntington’s disease will be eliminated due to this process. Unfortunately diseases that are caused by more than one genetic mutation, such as autism or schizophrenia, are not curable by this process.

National Cancer Institute

Gene Editing on humans is such a controversial topic right now: is it ethical to change genes? should the practice be used to change physical appearances? Ultimately, if Human Gene Editing is approves, who decides when it becomes too much, or unethical. This grey area is presented to be somewhere between when it is appropriate to help aid the life of a human, ridding them of a disease, and when enhancements are made.

 

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