Abstract
Abstract: :
Purpose: NRL (neural retina leucine zipper) is a rod and pineal-specific, basic motif leucine zipper transcription factor that is essential for rod photoreceptor differentiation. The aim of the present study was to examine whether candidate extrinsic factors can regulate NRL expression. Methods: Two different experimental in vitro models were used: Y79 cells and adult pig photoreceptor cultures, maintained under standard conditions and with or without serum. Following serum starvation for 24 hr, cultures were treated for 24 hr with either 15% fetal bovine serum, 9-cis, 11-cis or all-trans retinoic acid (10 µM each), or acidic or basic fibroblast growth factor (FGF1 (15 ng/ml) and FGF2 (25 ng/ml) respectively). Cultures were lysed and the cell extracts analyzed by SDS-PAGE followed by immunoblotting with specific anti-NRL antibody. NRL expression was quantified by densitometric scanning of the 29-35 kD bands of different isoforms of NRL in immunoblots. Results: NRL expression was greatly reduced within 8 hr of serum starvation. Addition of either fetal bovine serum or each retinoic acid completely restored NRL expression to its initial levels, whereas and FGF1 and FGF2 partially restored expression levels. Conclusions: Both retinoids and candidate polypeptide growth factors regulate NRL expression in vitro, and such data should help in delineating signaling pathways involved in photoreceptor differentiation and function. CI: None Support: NIH-EY11115, FFB, RPB
Keywords: photoreceptors • retinoids/retinoid binding proteins • growth factors/growth factor receptors