Identification of zebrafish magnetoreceptor and cryptochrome homologs

Magnetoreception is essential for magnetic orientation in animal migration. The molecular basis for magnetoreception has re- cently been elucidated in fruitfly as complexes between the magnetic receptor magnetoreceptor （MagR） and its ligand crypto- chrome （Cry）. MagR and Cry are present in the animal kingdom. However, it is unknown whether they perform a conserved role in diverse animals. Here we report the identification and expression of zebrafish MagR and Cry homologs towards under- standing their roles in lower vertebrates. A single rnagr gene and 7 cry genes are present in the zebrafish genome. Zebrafish has four cryl genes （crylaa, crylab, crylba and cry]bb） homologous to human CRY1 and a single ortholog of human CRY2 as well as 2 cry-like genes （cry4 and cryS）. By RT-PCR, magr exhibited a high level of ubiquitous RNA expression in embryos and adult organs, whereas cry genes displayed differential embryonic and adult expression. Importantly, magr depletion did not produce apparent abnormalities in organogenesis. Taken together, magr and cry2 exist as a single copy gene, whereas cryl exists as multiple gene duplicates in zebrafish. Our result suggests that magr may play a dispensable role in organogenesis and predicts a possibility to generate rnagr mutants for analyzing its role in zebrafish.