Comparative analysis of neural related microRNAs during the development of amphioxus and ascidians

Micro RNAs are small non-coding RNAsthat act as postransciptional and translational regulators of gene expression. Recent studies suggested that increased morphological complexity in metazoans is correlated with the number and funcion of mirRNAs. We analyzed and compared the spatio-temporal expression of miRNAs in the ampioxus Branchiostoma floridae and in two ascidian species, Phallusia mammillata and Ciona intestinalis. We focused our attention on 6 conserved miRNA families known to be expressed exclusively or preferentially in the nervous system of invertebrates and vertebrates. Iterestingly, some of the analyzed miRNAs showed a conserved pattern of expression among the analyzed species,while others differ regarding the spatial (CNS vs PNS) or the temporal (early vs late) expression pattern. These data can help to elucidate the evolution of nervous system in chordates.