Abstract
BackgroundMicroRNAs are small noncoding RNAs regulating expression of protein coding genes at post-transcriptional level and controlling several biological processes. At present microRNAs have been identified in various metazoans and seem also to be involved in brain development, neuronal differentiation and subtypes specification. An approach to better understand the role of microRNAs in animal gene expression is to determine temporal and tissue-specific expression patterns of microRNAs in different model organisms. Therefore, we have investigated the expression of six neural related microRNAs in amphioxus, an organism having an important phylogenetic position in terms of understanding the origin and evolution of chordates.ResultsIn 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.ConclusionWe 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.
Highlights
MicroRNAs are small noncoding RNAs regulating expression of protein coding genes at posttranscriptional level and controlling several biological processes
Our results show that all six miRNAs are expressed in specific regions of the central nervous system (CNS) of amphioxus, many of which can be correlated with cell types identified by microanatomical studies [20,41,42,43]
We found that all six miRNAs are expressed in the amphioxus CNS, miR-7, miR-184 and miR-137 are present in a strikingly broad spectrum of developing tissues derived from mesoderm and endoderm, while miR-183 is expressed in some ectodermal sensory cells of the peripheral nervous system (PNS)
Summary
MicroRNAs are small noncoding RNAs regulating expression of protein coding genes at posttranscriptional level and controlling several biological processes. 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 [1,2,3,4]. Comparisons of gene expression and mapping of neurons and their connections have indicated that the amphioxus CNS consists of a diencephalic forebrain (the telencephalon is lacking), a small midbrain, a hindbrain and spinal cord [18,19]. In addition to the frontal eye, there are many other photoreceptors in the amphioxus CNS Those developing in the hindbrain and spinal cord, called the organs of Hesse, are rhabdomeric or microvillar photoreceptors, while those in the forebrain, except for the Joseph cells, are ciliary photoreceptors. The larvae are positively phototropic from the mid-neurula stage and begin muscular movements at the late neurula stage
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