Blindness from some eye diseases could be caused by gut bacteria

The human gut has trillions of bacteria and many of them play an important role in healthy digestion. At the same time, they can also be potentially harmful. The researchers were looking at the impact of the Crumbs homolog or CRB1 gene, which expresses in the eye’s retina and is essential for the blood-retina barrier that regulates what goes into and out of the eye.

CRB1 is also associated with inherited eye diseases, most commonly either Leber congenital amaurosis (LCA) or retinitis pigmentosa (RP). This gene is the cause of 10 per cent of LCA cases and 7 per cent of RP cases worldwide.

They used mouse models to discover that CRB1 plays an important role in controlling the integrity of the lower gastrointestinal tract. Over there, it fights pathogens and harmful bacteria by regulating what passes between the gut and the rest of the body.

When the gene has a particular mutation, its effect can be reduced and these barriers between the retina and the gut can be compromised, allowing bacteria in the gut to move through the body and into the eye. This can cause lesions in the retina that can lead to sight loss. Interestingly, treating these bacteria with antibiotics helped prevent sight loss in mice. But it did not undo the damage to the cell barriers in the eye.