Skip to main content
. Author manuscript; available in PMC: 2022 Aug 1.
Published in final edited form as: Dev Biol. 2021 Mar 25;476:68–78. doi: 10.1016/j.ydbio.2021.03.013

Figure 4. Retinoic acid signaling controls vitamin A production in mammals.

Figure 4.

(A) Abundance of dietary β-carotene leads to the synthesis of retinoic acid that binds the RAR-RXR heterodimer and induces the expression of ISX. ISX is a repressor of SR-BI and BCO1 that are required for β-carotene uptake and processing, respectively. This retinoic acid based negative feedback mechanism limits vitamin A production.

(B) Vitamin A deprivation results in a lack of retinoic acid and thus a loss of activation of the repressor ISX. The lack of ISX leads to an increased expression of SR-BI and BCO1 and thus increased vitamin A production through increased β-carotene uptake and processing, respectively.