Expression patterns of nonvisual opsins during zebrafish development

In most animals, detection of light depends on G-protein-coupled receptors termed opsins. Accordingly, opsins can be found expressed in the retina of many animals. However, opsins constitute a relatively large phylogenetic group of proteins with several members that are not involved in image-forming vision or light sensing at all, while the functions of others remain unknown. The transcriptome of zebrafish includes over 30 nonvisual opsins distributed over all major opsin families. Several of these sequences have been found and phylogenetically analyzed only recently. Most analyses of opsin expression and function in zebrafish focused on adult eye tissue. The goal of this study was to provide an expression catalog for nonvisual opsins in developing zebrafish larvae at three developmental stages: 24, 72 and 120 hpf. Using in situ hybridization, we observe that, early in development, nonvisual opsins exhibit dynamic expression patterns that narrow as development proceeds. We also observe commonality in expression patterns within functional opsin groups and document potential novel expression in ear and neuromast tissues. Our observations suggest that based on expression patterns, nonvisual opsin function during early development may be widely distributed before they become restricted in fully differentiated adult tissues.