16 April 2018

Is it in your genes?

We inherit all our genetic information from our parents which is packaged into 46 chromosomes in a twisted structure called DNA- Deoxyribonucleic Acid.  These chromosomes contain over 20 000 bytes of instruction for the production of every cell in our bodies. Each bit of code is called a gene. We inherit a complete set of 23 chromosomes from each parent and these chromosomes often include mistakes, or mutations. Serious mutations can lead to genetic diseases and are being linked to Cancer, Asthma, Diabetes, mental health issues and even blindness.

Retina South Africa is using International DNA Day to highlight the genetic causes of retinal blindness. These retinal disorders affect old and young alike and more than 200 000 South Africans are going blind due to these conditions. Those that affect children or young adults include Retinitis Pigmentosa, Stargardt Disease or Usher Syndrome- deaf blindness. One of the most common causes of vision loss in older Caucasians is Age Related Macular Degeneration. Most of these conditions occur in families with no previous history of blindness.  This is due to the fact that in order for the disease to manifest a gene with a mutation needs to be inherited from both carrier parents, who are themselves un-affected.  This is the most common form of inheritance, called recessive inheritance.

It was on this day in 1953 that researchers, Watson and Crick announced that they had uncovered the structure of DNA. Also on this day in 2003 it was announced that the Human Genome project, to map all of the 20 000+ genes was near to completion. Since then genetic research has exploded and researchers are now able to identify the mutations hidden in our DNA and the first ever gene replacement therapy for blindness has just been registered in the U.S.A.  This therapy is to replace a defective gene, RPE65, in early onset Leber Congenital Amaurosis [LCA] or Retinitis Pigmentosa. This therapy is raising the hope that all forms of inherited retinal disorders will be treatable in the near future.  The greatest challenge facing Retina South Africa is ensuring that all patients have access to these therapies in the future.

Retina South Africa in partnership with the Human Genetics Division of the University of Cape Town facilitates genetic testing to identify patients who will be eligible for these clinical trials and the ensuing treatments. 

Retina South Africa estimates that there are around 10 million unsuspecting carriers in South Africa of a single gene mutation for various forms of retinal degeneration and welcomes the registration of this first ever gene therapy to treat these significant causes of blindness. “This gene therapy is merely the first” said Claudette Medefindt, Head of Science for Retina South Africa. “There are dozens of clinical trials effectively treating hundreds of patients internationally. With the help of caring South Africans, we can bring these successful trials in the areas of gene therapy and stem cells to South Africa. If we treat the estimated 17 000 young people losing their vision to genetic retinal blindness we can save 1 million blind years.” Medefindt concluded. 

South Africans can support this research via the website

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