The Retinol Binding Protein Receptor 2 (Rbpr2) is required for Photoreceptor Outer Segment Morphogenesis and Visual...

Area of Science:

• Developmental Biology
• Vision Science
• Molecular Biology

Background:

• Vitamin A (all-trans retinol) is crucial for development and vision.
• Specific mechanisms for tissue uptake and storage of dietary vitamin A are necessary.
• While Stra6 mediates ocular retinol uptake, the hepatic RBP4-retinol receptor was recently identified.

Purpose of the Study:

• To investigate the role of zebrafish retinol binding protein receptor 2 (Rbpr2) in RBP4-retinol uptake during embryonic development.
• To assess the impact of Rbpr2 deficiency on eye development and visual function in zebrafish.

Main Methods:

• Utilized cultured cells to examine Rbpr2 localization and function in RBP4-retinol uptake.
• Generated and analyzed two rbpr2 mutant zebrafish lines to study in vivo effects.
• Assessed ocular phenotypes, systemic malformations, photoreceptor integrity, visual pigment expression, and visual function in mutant zebrafish.

Main Results:

• Rbpr2 localized to membranes and enhanced RBP4-retinol uptake in cultured cells.
• Rbpr2 expression was observed in developing intestinal enterocytes and liver hepatocytes in larvae.
• Rbpr2 deficiency in zebrafish mutants led to small eyes, hydrocephaly, cardiac edema, shorter photoreceptor outer segments, visual pigment defects, and reduced visual function.

Conclusions:

• Rbpr2-mediated RBP4-retinol uptake in the developing liver and intestine is vital.
• Sufficient retinol supply is necessary for ocular retinoid production, photoreceptor maintenance, and visual function.
• Rbpr2 plays a critical role in ensuring adequate vitamin A availability for vision.