Eye Color And Genetics

Eye color is determined by the pigmentation of the iris, with variations ranging from light blue to dark brown. Genes associated with melanin production, transport, and storage influence eye color. The OCA2 and HERC2 genes on chromosome 15 play pivotal roles. The OCA2 gene produces the P protein that affects melanin levels in the iris, while the HERC2 gene controls the expression of OCA2. Other genes like ASIP, IRF4, and TYR also contribute to eye color variation. The inheritance of eye color is more complex than previously believed, as multiple genes are involved. Disorders such as ocular albinism, oculocutaneous albinism, and heterochromia affect eye color due to genetic mutations or developmental issues.

Discovery of a Blindness Gene

 Within the past two decades, scientists have successfully identified and isolated a revolutionary gene--a gene that contributes to blindness. This defective gene, known as RP3, resides on the X chromosome, and the blindness trait is mostly expressed in young men. The normal function of this gene is not yet fully known; however, mutations in RP3 are known to result in retinitis pigmentosa disease and blindness. Retinitis pigmentosa is defined as a hereditary eye disease that causes degeneration of the retinal cells. 70% of all cases of retinitis pigmentosa are linked back to the mutated RP3 gene.

RP3 affects mostly men, causing them to become blind by the age of thirty. Symptoms develop in early childhood. If a boy has trouble seeing anything at night or begins to see with tunnel vision, this indicates a possibility the individual contains a defected RP3 gene. Keep an eye on your young male children.

I am amazed at the discovery of RP3. An average of 1 in 2000 people suffer from blindness; and since the gene, a major cause, has been discovered, a treatment may be devised within the upcoming years. For now, scientists can only genetically determine an individual's susceptibility.


Link to article: Gene Linked to Blindness

Other Article: Diseases and Conditions

Gene Therapy May Help Restore Sight in People With Eye Disease

A new type of gene therapy has been found to reverse some vision loss in people with certain degenerative eye diseases. The goal is to start treatment as early as possible in order to save as many light-sensing cells as possible. There is a window of time that gene therapy needs to be applied before vision damage is beyond repair. The earlier treatment is applied, the better the prognosis.

The surgical procedure used is risky since it involves detaching delicate retina tissue, but no complications have been reported. In fact, most participants report the ability to detect more light, read more letters and numbers, and see the stars at night. All of these things are major improvements for people who are used to very little vision, like Jonathan Wyatt in this article who was one of six people to receive treatment for choroideremia.

Choroideremia is the main condition studied in this work. It is an eye disease linked to a gene on the X chromosome. It is a rare disease that affects an estimated one in 50,00 people. Because it is X-linked, it primarily affects males. The disease usually begins in childhood and causes the progressive narrowing of vision and loss of the rods and cones and usually ends in blindness.

The treatment adds a working copy of the associated gene to the retinal cells of patients with the disease. This can be done by lifting the retina and injecting the gene therapy into the space created.

Other groups are working on developing gene therapies for retinal diseases as well. It is too soon to know for sure if this treatment will be appropriate for use in more patients and if it can stop the loss of retina tissue. It may take a few years, but researchers are hopeful.

Though this was a small trial and there is still a lot to learn from the experimental trials, this could be promising for patients with choroideremia. If it is successful, similar therapies could be applied for other genetic eye diseases for which there is not current treatment or cure. Hopefully more research will be done so that we can learn more about gene therapy use in eye disease.

Article: http://www.technologyreview.com/news/519426/gene-therapy-tested-as-a-way-to-stop-blindness/