Rare Mutation Causes Vitamin A Deficiency, Eye Deformities
SACRAMENTO, Calif. – Scientists at the University of California and University of Michigan have identified protein mutations that result in birth defects in the eyes.
By mapping sequences of family DNA in unrelated families who have suffered from congenital eye malformations, they have been able to identify mutations in RBP4, a protein that transports a form of vitamin A called retinol, which is essential for eye development in embryos.
The mutated proteins also block the cell surface receptor, keeping healthy proteins from delivering nutritional components to the tissue, which results in birth defects.
The findings are published online in the April 23 edition of the journal Cell.
RBP4 is secreted by the liver, and because retinol is not water-soluble it has to be carried in the bloodstream to the STRA6 receptor – and must pass through the placenta to the baby.
This process plays a crucial role in how the defect is passed from one generation to the next.
Researchers have found that the mutated gene is dominant –- but skips generations and is only problematic when passed through the mother.
When the gene is inherited through the father, enough vitamin A gets through to prevent the defect.
The study concludes that the unusual maternal inheritance pattern may have implications for other families experiencing congenital diseases.