Expression of CaBP transcripts in retinal bipolar cells of developing and adult zebrafish

Abstract

Ca2+-binding proteins play important roles in neuronal function by transducing Ca2+ signals and thereby regulating crucial processes like synaptic signaling and neuronal development, growth and survival. The Ca2+-binding protein (CaBP) subfamily is part of the vast EF-hand containing calmodulin superfamily. Eight genes encoding CaBPs have been identified in zebrafish, and many of them are expressed in specific subpopulations of retinal neurons during development. Among them, cabp2a and cabp5b have been shown to be expressed in the retinal inner nuclear layer (INL). Here, we demonstrate that their paralogues, cabp2b and cabp5a, are also specifically expressed in the INL of the developing retina. By extending expression analysis of cabp2a, cabp2b, cabp5a and cabp5b to the adult retina, we reveal exclusive expression of all four genes in the INL after retinal development is completed. Thus, our findings suggest functions of cabp2a, cabp2b, cabp5a and cabp5b in Ca2+ signaling in mature retinal neurons, besides a role in the developing retina.