The eye as therapeutic model for genetic disease

Question 1

Describe how light can be perceived (i.e. what happens when light enters the eye).

Answer 1

• Light entering the eye triggers a photochemical reaction in rods and cones at the back of the retina.
• This chemical reactio in turn activation bipolar cells.
• Via bipolar cells, the information is send to ganglion cells that have axons that extend to the optic nerve.
• From there on, information is sent to the visual cortex via the thalamus.

Question 2

Describe the optic pathway.

Answer 2

Retina → optic nerve → optic chiasma → optic tract → lateral geniculate nucleus (LGN) → optic radiation (extending fibers of the LGN) → visual cortex.

Question 3

Name functions of the retinal pigment epithelium.

Answer 3

• Light absorption
• Epithelial transport
• Glia
• Visual cycle
• Phagocytosis
• Secretion

Question 4

What is the blood-retina barrier?

Answer 4

The blood–retinal barrier is part of the blood–ocular barrier that consists of cells that are joined tightly together to prevent certain substances from entering the tissue of the retina. It consists of two components: the retinal vascular endothelium and the retinal pigment epithelilum.

Question 5

What is an organoid?

Answer 5

A miniaturized and simplified version of an organ produced in vitro in three dimensions that shows realistic micro-anatomy.

Question 6

How can skin or blood cells be used to form an retinal pigment epithelium (RPE) model?

Answer 6

• Patient donates skin or blood cells.
• Cells are reprogrammed to induced pluripotent stemcells (iPSCs).
• iPSCs are differentiated towards retinal organoids.
• From here on out, e.g. the development of the retinal organoids can be researched.

Question 6

For what can organoids be used?

Answer 6

Isolation of different retinal cells from the organoid.

Question 7

What is Gyrate Atrophy of the Choroid and Retina (GACR)?

Answer 7

An extremely rare metabolic disorder, which is caused by an ornithine aminotransferase (OAT) deficiency. It mostly affects vision by the progressive degeneration of he chorioretina, early cataract formation and myopia.

Question 8

OAT deficiency affects multipe metabolic pathways. Name some of these pathways.

Answer 8

• Creatine biosynthesis
• Urea cycle
• Polyamine synthesis
• Proline synthesis

Question 9

So Gyrate Atrophy is caused by an ornithine aminotransferase (OAT) deficiency. What function has OAT normally and what happens when OAT is deficient?

Answer 9

• OAT convert ornithine to GSA/P5C (for proline synthesis).
• If OAT is deficient, ornithine is no longer coverted to GSA/P5C, which causes a build-up of ornithine serum concentration. With this, multiple pathways are affected.

Question 10

Name an example how Gyrate Atrophy of the choroid and retina (GACR) can be studied with the use of retinal models.

Answer 10

• Donation of patient and control skin or blood cells for the generation of iPSCs (2 control and 2 patients).
• After culturing the iPSCs, ornithine can be added to the medium.
• After x days, use of MTT assay to assess the effects of ornithine on cell viability for each cell line

Question 11

Name another example how Gyrate Atrophy of the choroid and retina (GACR) can be studied with the use of retinal models.

Answer 11

• Donation of patient and control skin or blood cells for the generation of iPSCs (2 control and 2 patients).
• Differentiating iPSCs into Retinal Pigment Epitelium (RPE).
• After culturing the RPEs, ornithine can be added to the medium.
• After x days, use of MTT assay to assess the effects of ornithine on cell viability for each cell line