背景资料：This gene encodes an abundant protein present in the small intestinal epithelium. It is thought to participate in the uptake and/or intracellular metabolism of vitamin A. Vitamin A is a fat-soluble vitamin necessary for growth, reproduction, differentiation of epithelial tissues, and vision. This protein may also modulate the supply of retinoic acid to the nuclei of endometrial cells during the menstrual cycle.