Dicer expression and localization in post-mitotic neurons

RNA-mediated gene silencing is recently emerged as a fundamental mechanism of regulation of gene expression in many organisms and tissues, with special emphasis with respect to the nervous system. With the aim to study the components of RNA silencing machinery, we have investigated the expression profile and localization of dicer protein RNase III endonuclease in cultures of post-mitotic neurons. Dicer catalyzes the processing of double-stranded RNAs (dsRNAs) into approximately 21-25 nucleotide-long small interfering (si)RNAs and micro (mi)RNAs, and it represents an essential step in the biogenesis of these small non-coding RNA molecules. We show that in rat primary neurons dicer is localized in the somatodendritic compartment, at the Golgi-reticulum area network level. This peculiar distribution was altered by brefeldin A treatment. Moreover the Golgi-reticulum dicer signal was observed also in primary astroglial cells. In addiction dicer was observed to be regulated during the embryogenesis and development in several tissues. In fact its expression is developmentally regulated in cultured cerebellar granule neurons. This is the first study in which dicer is shown preferentially distributed in the Golgi-reticulum area in post-mitotic terminally differentiated neuronal and glial cells and that its profile is modulated during maturation and development of in vitro cultured cerebellar granule neurons.