BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: retina

The Quest to CRISPR Vision

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On April 17, 2024

In Student Post

Retinitis Pigmentosa is a genetic disorder that causes severe vision loss. The tunnel vision and narrow sight progressively damage the retina and as the condition progresses, daily life becomes more and more of a challenge. This condition affects over one million people worldwide and causes inherited blindness in 1 out of every 4,000 people. But what if this condition could be cured using gene editing?

Retinitis Pigmentosa is the progressive deterioration of photoreceptor cells that line the back of the eye and convert light into electrical impulses that are sent to the brain. The condition is caused by genetic mutations and it can be hereditary. At least 100 genes are associated with the disease, one being phosphodiesterase 6b. This protein-coding gene is a huge part of the phototransduction pathway as it converts light into an electrical signal that the brain interprets as vision. The mutation affects the cone photoreceptor cells and the loss of these cells leads to the irreversible deterioration of vision.

Consecutive OA in retinitis pigmentosa

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is gene editing technology that targets specific DNA sequences. It uses specialized cellular machinery to make precise cuts in the DNA strand which allows the removal of mutated genes, replacing them when non-mutated ones.

CRISPR Cas9

A study in China used CRISPR gene editing to restore the vision of mice with retinitis pigmentosa. The researchers used PESpRY to correct the mutation in the PDE6b gene through precise edits while not being limited by PAM interferences. This corrected the activity of the gene in the retinas of the mice, while also preventing the death of the cone photoreceptors and restoring their electrical responses to light. Tests proved the mice sustained good vision into old age and the photoreceptors were preserved.

This relates to what we have learned in AP Bio because of the relation to gene expression and genetic disorders. Gene expression is the process where DNA sequences are transcribed into messenger RNA and then translated into a protein. This process is tightly regulated but can be influenced by genetic mutations, such as retinitis pigmentosa. In this case, scientists are able to manipulate the DNA to fix specific genetic mutations which highlights the importance of understanding genetic mechanisms.

The use of CRISPR gene editing is a promising approach for treating genetic diseases in the retina, and with more testing could be used for humans as well. So, would you try this out if it could help fix your vision?

 

 

Can Your Eyes Save Your Brain?

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On February 16, 2022

In Student Post

Are Retinal Tests Able to Identify Early-Onset Alzheimer’s?

According to The Alzheimer’s Association, In 2021, 6.2 million Americans were living with Alzheimer’s Disease. 1 in every 9 people (11.3%) above the age of 65 has Alzheimer’s Disease, and these percentages only increase with age, leaving 35 percent of people above the age of 85 with Alzheimer’s or Dementia. For those who do not know, Dementia is a general term for the loss of memory and other thinking abilities, severe enough to interfere with daily life. Alzheimer’s is the most common type of Dementia, and it affects not just memory but behavior. Mainly recognized in adults above the age of 60, our current form of diagnosing Alzheimer’s is waiting until people become overly forgetful or begin to act out of character. Although early detection is occasionally possible through brain scans, this method is expensive and unsuitable for most. 

My uncle Steven was only 51 when he was diagnosed with Alzheimer’s. Although caught decently early, his changes in behavior and short-term memory loss were apparent. Often asking a question only minutes after he had previously been told the answer, my family was devastated. Before being diagnosed, my uncle was the CFO of a Fortune 500 company and was always seen as a mentally and physically strong man. Having no choice but to retire young and focus on his health was a hard truth for all of us to accept. 

Alzheimer's Disease

Sad and confused about how this had happened, I did extensive research on the causes of Alzheimer’s. Although there are multiple possible causes and factors that play into the development of Alzheimer’s disease, one way is through inheritance. Early-onset Alzheimer’s diseases, like my uncle’s, can be inherited genetically. Humans typically have 46 chromosomes in each cell of their body. Each of these chromosomes contains anywhere between 20,000 and 250,000 genes. Usually having two copies of each chromosome, one copy comes from the mother’s egg and the other from the father’s sperm. Each egg and the sperm are haploid, meaning they contain 23 chromosomes. When the sperm fertilizes the egg, two copies of each chromosome and gene are present. Although some genes are required from both parents to be passed onto their offspring, Alzheimer’s is inherited in an autosomal dominant pattern. This is one of the many ways that disorders can be passed down through families, and it means that only one parent needs to have the abnormal gene for you to get the disease. Thus people who inherit one copy of the APOE e4 allele have a significant chance of developing Alzheimer’s. However, those who inherit two copies of their allele are at even greater risk. It is important to note that not all people with the disease have the e4 allele, and not all people with the allele develop Alzheimer’s. Because in most cases, an infected person inherits the gene from an infected parent, it is not likely that my uncle developed Alzheimer’s genetically as no one else in my family tree ever had the disease.

Autosomal dominant inheritance

Moving forward with my research, I looked into possible treatments; unfortunately, most drugs are still in trial or only applicable to individuals diagnosed before any level of severe memory loss occurs. While this is a sign of good progress, I can’t help but feel there must be some better solution to diagnose Alzheimer’s before it becomes too late. Thankfully, Dr. Ashleigh Barrett-Young and her team agreed.

Working at Otago’s Dunedin Multidisciplinary Health and Development Research Unit, Barrett-Young and her team of researchers have investigated the retina’s potential to indicate Alzheimer’s earlier in life. As stated by Barrett-Young, “In the near future, it’s hoped that artificial intelligence will be able to take an image of a person’s retina and determine whether that person is at risk for Alzheimer’s long before they begin showing symptoms, and when there is a possibility of treatment to mitigate the symptoms.” The Dunedin study analyzed the retinal nerve fiber layer (RNFL) and Ganglion cell layer (GCL) of 865 people at the age of 45. Dr. Barret-Young and her team reported that thicker RNFL and GCL were associated with better cognitive performance, while a thinner RNFL was linked to a more significant decline in processing speed. Adding to their report, “These findings suggest that RNFL could be an indicator of overall brain health. This highlights the potential for optical scans to aid in the diagnosis of cognitive decline.” Since treatment for Alzheimer’s is yet to be discovered, the ability to identify the disease in preclinical stages could allow the possibility of aid before it’s too late. Although further studies are required to determine if retinal scans can predict precisely Alzheimer’s, or just the expected cognitive decline of the brain, researchers have hope. 

So, while this solution sadly offers no benefit to my uncle, I feel hopeful that this new diagnosis technique will be beneficial for the millions of people who would have had family members or friends combating Alzheimer’s disease but caught it early enough to intervene and do something about it. 

Big News for Retina Pigmentosa Patients

By

On March 10, 2013

In Student Post

 

Photo by luisar

In a recent article, it was revealed that patients with the rare disease retinitis pigmentosa, may be able to find treatment using the Argus II Retinal Prosthesis System. Retinitis Pigmentosa is a rare, only about 100,000 Americans have it, inherited retinal disease that “causes the breakdown of cells in the retina.”

Dr. Robert Greenberg, CEO of Second Sight (the company that created the Argus II Retinal Prosthesis System), stated that those with retinal pigmentosa are “looking down a tunnel that gradually narrows until it disappears entirely.”

The Argus II uses a “video camera and a transmitter mounted on a pair of glasses” to help the individual. “Images are then wirelessly transmitted to electrodes implanted into the patient’s retina.” While the Argus II will not restore vision completely, it will allow users to partially regain vision. Tests show that the Argus II helped patients perform daily activities with ease. These activities included “navigating sidewalks and curbs, matching different color socks, and recognizing large words in sentences.”

Personally, I think this is a great technological leap. This prosthesis system will hopefully reach out to those with retinal pigmentosa and others with macular degeneration.

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