A study of neural-related microRNAs in the developing amphioxus

In amphioxus, all the microRNAs we examined are expressed in specific regions of the CNS, and some of them are correlated with specific cell types. In addition, miR-7, miR-137 and miR-184 are also expressed in endodermal and mesodermal tissues. Several potential targets expressed in the nervous system of amphioxus have been identified by computational prediction and some of them are coexpressed with one or more miRNAs.We identified six miRNAs that are expressed in the nervous system of amphioxus in a variety of patterns. miR-124 is found in both differentiating and mature neurons, miR-9 in differentiated neurons, miR-7, miR-137 and miR-184 in restricted CNS regions, and miR-183 in cells of sensory organs. Therefore, such amphioxus miRNAs may play important roles in regional patterning and/or specification of neuronal cell types.MicroRNAs (miRNAs) are a large class of non-coding RNAs involved in post-transcriptional regulation. They were first discovered in nematodes and subsequently found to be widely distributed in plants and animals [1-4]. miRNAs are 18 to 24 nucleotides long and regulate translation by binding to the respective mRNA transcripts, either inducing mRNA degradation or directly inhibiting translation. In animals, miRNAs bind to specific bases in the 3' untranslated regions (UTR) of mRNA targets [5]. Each miRNA can regulate translation of several genes and modulate many biological processes such as developmental timing, cell proliferation, cell death, Hox gene expression and early embryogenesis [6]. miRNAs play also important roles in stem cell biology, furthermore altered miRNA functions have been implicated in a number of human disorders and cancers [7]. In particular, miRNAs are known to regulate translation of a number of genes involved in development of the central nervous system (CNS) [8-10].miRNAs are to a large extent evolutionarily conserved. The basal chordate amphioxus has 115 miRNA families, 55 of which are homologous to those of vertebrate