Zebrafish mutants as models for studying receptors involved in the intestinal uptake of dietary vitamin A for vision

Abstract

Purpose: To elucidate the biological function of the novel retinol binding receptor, RBPR2, in the intestinal uptake of endogenous preformed vitamin A and whether loss of this receptor impacts embryonic retinoid metabolism for vision and also retinoic acid-dependent developmental processes in the zebrafish.

Methods: Whole-mount in-situ hybridization (WISH) staining was performed to evaluate RBPR2 mRNA expression patterns in staged zebrafish embryos. Biochemical and cell culture studies were performed to evaluate the retinol-binding capabilities of this receptor. Localization studies were performed by over-expressing recombinant zebrafish RBPR2 protein in NIH3T3 cultured cells.

Results: WISH staining for RBPR2 mRNA showed expression patterns at the 8 somite embryo stage in the yolk syncytium and mesendodermal cells, becoming more restricted to the intestine, liver and pancreas between 4-6 days post fertilization. Biochemical studies using HPLC analysis for retinoids showed that NIH3T3 cells constitutively expressing zebrafish RBPR2 are capable of retinol uptake from its bound form. Finally, localization studies showed a predicted plasma membrane pattern for the overexpressed zebrafish RBPR2 protein in NIH3T3 cells.

Conclusions: RBPR2 mRNA expression patterns and biochemical assessment in the zebrafish model suggest a functional role for this receptor in the intestinal uptake of retinol. By studying corresponding human homologous of proteins proposed in retinol uptake using animal models like the zebrafish we hope to obtain a more detailed molecular understanding of the regulatory principles of retinol uptake processes. This would aid in elucidating novel strategies for the prevention and therapy of blindness and retinopathies associated with vitamin A deficiency.

Keywords: 705 retinoids/retinoid binding proteins • 761 vitamin A deficiency • 583 lipids