RNA transport for gene expression control
Gene transcription control and how much protein is produced in time and space can be regulated by messenger RNA (mRNA) transport. Especially important for functions such as neuron positioning and synaptic plasticity, varying quantities of neurotransmitters will modulate strength of synapses and form the basis of memory. Furthermore, loss of proteins involved in regulating RNA transport has been linked to hereditary mental retardation. The 'Molecular mechanisms of mRNA transport in neurons' (NEURORNATRANSPORT) project has looked into which mRNAs are differentially localised and their transport mechanisms. Researchers used the model fly Drosophila, relevant in particular as the overall mechanism of RNA transport is conserved from Drosophila to humans. As a measurement of post-transcriptional control, the researchers looked at mRNA–protein complexes (mRNPs) that dictate the fate of RNA — whether it is to be translated or degraded. To do this, they developed a sensitive method that detects mRNPs in the nervous system of Drosophila larvae. Screening more than 300 three prime untranslated regions (3'-UTRs), the researchers found that although low-level dendritic localisation is widespread and efficient, localisation into dendrites is a rare process. 3'-UTRs play a crucial role in gene expression by influencing the localisation, stability, export, and translation efficiency of an mRNA. Project researchers found a single 3'-UTR that harbours a strong localisation element for dendrites. Moreover, they mapped the region responsible and developed a genome engineering toolbox to test its functional significance. The CRISPR/Cas toolbox contains transgenic Cas9 fly strains and high-efficiency guide RNA. Cas9 can control transcriptional activation and repression. In this case, the kit can be used to study detailed dendritic mRNA localisation of a candidate gene. The new toolbox can orchestrate genome engineering with remarkably high efficiency, implementing precise modifications to the genome as required. NEURORNATRANSPORT deliverables promise to reveal new insights into the cell biology of neurons and have broad implications for neuronal development, plasticity and disease.
