This is the chief cause of the blindness so often suffered by severely malnourished children in parts of the world. In addition to causing visual problems, vitamin A deficiency can also weaken the immune system and make people more susceptible to infections. Supplementation, however, will pick them up right away. In another research project, Noy is studying the effects of retinoic acid on gene transcription. She says that, in addition to vision, vitamin A, though its metabolite retinoic acid, affects multiple processes in the body, such as embryonic development, cellular proliferation, differentiation of tissues, tissue remodeling, and tissue integrity.
Proteins are responsible for mediating the effects of retinoic acid on gene transcription.
Noy says these transcription factors are called retinoid receptors. They belong to a large family of transcription factors that are known to be activated by small hydrophobic compounds. Members of this family include transcription factors that regulate gene transcription in response to steroid hormones such as estrogen, thyroid hormone, and metabolites of vitamin A, vitamin D, and long-chain fatty acids. One of the retinoid receptors, called RXR, can interact with other members of this family. So now you have a complex-half of which responds to vitamin A and the other half of which responds to vitamin D, and together they regulate gene transcription.