Finding undetected needles in large haystacks – the ABCA4 gene in juvenile macular dystrophy

    Andrew R Webster, Consultant OPhthalmologist, Moorfield   Eye Hospital. London.

The most common cause of macular disease affecting younger people is sequence change of the ABCA4 gene. This gene was first found to cause Stargardt’s disease and is essential for healthy retinal function. Given that the gene was discovered in 1997, why is a test not yet available to patients?

Imagine a large haystack in which there are two silver needles that represent the gene changes in the person concerned. In this case the haystack is unusually large (ABCA4 is very big), there are a number of non-silver, steel needles that confuse us (the normal gene has changes too) and some of the real silver needles just seem to escape our standard metal detectors. The MDS has generously agreed to fund a study to exploit two new technologies, one a DNA chip to search for 430 types of needle simultaneously, and another a novel DNA probe technique to find deletions/duplications (those needles that escape detection).

This will be the first such survey ever: it might find the missing needles and should sharpen our case to provide NHS testing for patients and families in the future.