Tuesday, April 18, 2017

19/04/2017: Fish eyes to help understand human inherited blindness

The discovery of a gene in zebrafish that triggers congenital blindness could lead to a suitable cure for similar disease in humans

The following is a press release from the Okinawa Institute of Science and Technology(OIST) Graduate University 

From left to right: Professor Ichiro Massai, Dr Maria
Iribarne and Dr Yuko Nishiwaki from the
Development Neurobiology Unit in the
OIST zebrafish facility.
Credit: OIST

Newborn babies can be at risk of congenital blindness, presenting sight defects due to lesions or to genetic mutations in their genome. 

Among the latter, Leber Congenital Amaurosis, or LCA, is one of the most widespread causes of child blindness and accounts for nearly five percent of vision impairments overall.

The syndrome can be genetically transmitted to a child when both parents possess at least one dysfunctional copy of a gene involved in eye development.

However, the molecular mechanism behind the disease remains unclear.

Now OIST researchers in the Developmental Neurobiology Unit have exposed a similar syndrome in zebrafish, which are an excellent model for studying human diseases.

From this research published in Scientific Reports, scientists aim to unravel the causes behind the disease in zebrafish and therefore provide new leads for a treatment for human LCA.

LCA affect the retina, the thin layer of tissue at the back of the eye that detects light as well as differentiates colours and communicates the information to the brain via the optic nerve.

A healthy retina usually features light-sensitive cells, photoreceptors, called cones and rods. Cones are specialized in bright environment and detect colours while rods are used in dim light but are monochrome, which is why we see in black and white at night.

A person with LCA will display deformed or absent cones and rods, thus preventing the detection of light. A total of 24 genes including a gene called Aipl1, standing for aryl hydrocarbon receptor interacting protein like 1, have been linked to LCA in humans and mice.

The illness occurs when a DNA mutation within one of the genes affects the normal ocular development or induces photoreceptor, the cones and rods, degeneration.

OIST scientists selected the zebrafish as an animal model because its retina is rich in cones and its visual acuity can be measured with a simple device.

The researchers studied a genetically mutated zebrafish embryo that did not react to visual stimuli.

They discovered that zebrafish DNA contains two Aipl1 genes, namely Aipl1a and Aipl1b, which are respectively active in rods and cones. The mutant, called gold rush (gosh), presents a genetic mutation in the Aipl1b DNA sequence, losing Aipl1 activity in cone photoreceptors. 

Read the original press release HERE.

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