Immunohistochemical localization of transcription factors, Pax6 and Nurr1, in the adult echinoderm nervous system

Abstract

Studies of the echinoderm nervous system have been advanced recently with the unraveling of the sea urchin Strongylocentrotus purpuratus genome. The identification of gene sequences similar to those of other animals has made possible the study specific of genes and gene products in the echinoderm nervous system. Here we have focused on the transcription factors, Pax6 and Nurr1. Bioinformatic analysis of Pax6 revealed that its coding sequence and characteristic domains are conserved in the echinoderms. Similarly, sequence analyses of the echinoderm predicted protein similar to Nurr1, revealed that the C‐terminus, which contains the ligand‐binding domain of the nuclear receptor, is the most conserved segment, while the N‐terminus is poorly conserved. Immunohistochemistry experiments showed that anti‐Nurr1 and anti‐Pax6 labeled cells and fibers within the echinoderm nervous system. The neural specificity of these transcription factors was verified by co‐labeling with the neural‐specific marker RN1. Our results suggest that Pax6 may have a yet unknown function in the adult echinoderm and that Nurr1 is present in the deuterostomes, rather than just in vertebrates as was previously thought. Additionally, our findings underscore the importance of studying the role and distribution of transcription factors in the echinoderm nervous system as these are responsible for the development of the nervous system.