Gene Editing

Genome editing is a group of technologies that give scientists the ability to change an organism’s DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome. CRISPR-Cas9, which is short for “clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9”, is faster, cheaper, more accurate, and more efficient than other existing genome editing methods.

CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria. Researchers create a small piece of RNA with a short “guide” sequence that attaches 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.

The Food and Drug Administration has approved the first therapy to replace a faulty disease-causing gene with a healthy one. The injected gene therapy is designed to improve sight in people with an inherited

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Eye Study Perspectives

I recently visited the Scheie Eye Institute in Philadelphia, where I volunteered for “The MacTel
Study: A Natural History Observation and Registry Study of Macular Telangiectasia Type 2” under the
Principal Investigator, Dr. Alexander Brucker. The evaluation took about 4 hours to complete, and
involved a full eye examination – refraction, visual acuity, slit-lamp exam (to check the surface of the eye, eye mobility, pupils, angles, eye pressures, etc.), dilated eye exam (to examine the back of the
eye/retina), blood draw for genetic testing, medical history and family history.

Then the second half involved a whole roomful of different equipment for imaging. Those tests included:

  • Optical Coherence Tomography (OCT) scans (takes cross-section pictures of the back of the eye/retina to
    measure the thickness of each layer)
  • Fundus Photographs (color images of the retina)
  • Fluorescein Angiography (“the dye test” – fluorescein dye is injected into the arm and photographs are taken
    of the inside of the eye as the dye moves through the blood vessels). This dye turns your urine the color of a
    bright yellow highlighter for a day, but hey, now I can cross that off my bucket list, right? 😉
  • Fundus Autofluorescence (done on the OCT machine, just

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