Regulation and expression of elrD1 and elrD2 transcripts during early Xenopus laevis development

The Xenopus laevis elrD (elav-like ribonucleoprotein D) gene is a member of the elav/Hu family which encodes RNA-binding proteins. Most of the elav/Hu genes are expressed in the nervous system, where they are implicated in the development and maintenance of neurons. The regulation of elrD gene expression involves two promoters, pD1 and pD2. In this study, we analyzed the neural specificity directed by both promoters. They were fused to the gene encoding green fluorescent protein, and their ability to drive neural expression in injected Xenopus embryos was examined. We show that both promoters direct neural expression and that whole promoter sequences are needed to induce neural specific expression. Finally, we analyzed the spatial and temporal localization of the two elrD transcripts, elrD1 and elrD2. We found that the two transcripts present the same tissue-specific pattern of expression, with distinct developmental regulation. Our results show a complex regulation of the elrD gene and suggest that different transcripts resulting from alternative splicing of the elrD gene probably define different neurons.