Novel Function of Splicing factors in Establishment and Maintenance of Neuronal Connectivity

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Motor neuron disorders are a group of neurological pathologies that affects motor neurons, the cells that control essential voluntary muscle activity such as walking, breathing, and speaking. Normally, messages from neurons in the brain are transmitted to neurons in the brain stem and spinal cord where they inform muscles to contract. When there are disruptions in the signals between the motor neurons and the muscles, the latter progressively weaken, twitches abnormally and finally stop contracting. In the last decade, a lot of progress has been made in identifying genes in which mutations induce (or increase the chance of) pre- or post-natal motor neuron dysfunction. The identification of these genes lead to the unexpected finding that most motor pathologies arise from abnormalities in a restricted set of biological processes in the neurons. However, we don't yet understand the nature of the specific changes made in these processes and how these trigger neuronal abnormalities. One of these processes is mRNA processing and transport, the mechanism by which draft versions of transcripts are transformed into mature messenger RNA and transported into local areas of the neurons where they are translated into specific proteins. The lead applicant has very recently developed zebrafish genetic models to study the role of splicing factors in motor neuron development and maintenance during adult life. Through a set of particular zebrafish mutants, the applicants have identified a new mechanism required to distribute information locally in complex neurons. This key actors in this mechanism are proteins called splicing factors, that are transforming the pre-mRNA (draft version of a messenger RNA) into a mature messenger RNA. This group of molecules is known to be active in the nucleus. However, the applicants found that at least two of these (called SFPQ and snRNP70) are also active in the axon of motor neurons, the part of the motor neuron that transfer the information to the muscle.This research programme proposes - To use this new zebrafish models to image and understand the biological process driving motor dysfunction in absence of axonal splicing factors.- To understand what are SFPQ and snRNP70 doing with RNAs in the axon, and which are the proteins their interact with to achieve these roles.We expect that the proposed research will bring a novel understanding of the role of splicing factors outside of the cell nucleus. It will also identify a novel molecular network driving motor impairment and uncover a specific mechanism allowing very long and complex neurons to take very controlled local decisions.