Isolation and expression of Napor/CUG-BP2 in embryo development.

The human neuroblastoma apoptosis-related RNA-binding protein NAPOR is an ELAV-like RNA-binding protein with three characteristic RNA recognition motifs (RRMs). We report here the cloning and characterization of a zebrafish Napor that has a high sequence homology to human NAPOR protein. Whole-mount in situ hybridization analysis revealed that zebrafish napor is dynamically expressed in early development. In addition to its maternal expression, napor transcripts were detected in adaxial mesoderm cells and lateral neural plate cells at early somite stages. By 10-somite stage, napor expression was restricted to the central nervous system, having a specific expression domain of rhombomere 5 in the hindbrain. In 24 hpf embryo, napor was expressed in subsets of differentiating neural cells in the forebrain and hindbrain as well as somitic muscle cells. The number of napor-expressing neural cells was greatly increased in the mind bomb mutant that has neurogenic phenotype resulting from deficits in the Notch signaling pathway. Furthermore, overexpression of napor by RNA microinjection resulted in severe defects in nervous system and gastrulation, suggesting the need for tight control of napor gene regulation during embryo development.