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

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.

Alternative splicing is essential for normal development and homeostasis and plays a critical part in neuronal circuit activity in animal models and humans. Yet, very little is known of the mechanisms by which this process is controlled.
The proposed research programme aims to fill a key gap in understanding the complex mechanisms of alternative splicing and RNA transport in developing and adult neurons, building on the applicants recent uncovering of a key novel cytoplasmic role of the splicing factor SFPQ and snRNP70 in motor circuit development. In particular, the axonal pool of SFPQ proteins has a fundamental role in developing and mature motor axons and synapses, controlling axonal morphology, synapse formation and connectivity.
Having developed unique genetic models, our project proposes a set of original cellular, molecular and genetic approaches to unveil the function of splicing factors outside of their traditional nuclear role. Its ambition is to understand RNA dynamics and interplay between splicing proteins and mature and immature transcripts in these structures, aiming to provide some key mechanisms driving local decisions in neuronal circuits, assessing the possibility of non-nuclear splicing in neurons. If verified, this concept has the potential to revolutionise our understanding of RNA processing.

1. Academic impact
The expected beneficiaries of this research proposal are mainly the scientists and clinicians in the fields of cell biology, developmental neurobiology and neurodevelopmental disorders.
2. From basic research to clinic
The beneficiaries are clinicians working on neurodisorders involving RNA processing in their pathology as this project will lead to identification of novel molecules and molecular mechanisms involved in these processes. We will engage with international clinicians specialized in these pathologies both by participating to clinical symposia and by collaborating extensively on SFPQ pathologies in human,
3. Application and exploitation:
Any commercial potential of our discoveries will be discussed with KCL enterprise. Potential commercial outcome may stem from this proposal but will require further research development before any commercial venture can be envisaged. However, development of research projects with the industry may well stem from the proposed research.
4. Communications and engagement:
The lead applicant is communicating her results through public lectures in school and public events organised by various organisations. She also teaches at and direct international courses and organises international workshops (eg. EMBO. MBL).
The IoPPN is in the process of developing a website for public communications of research output that will be used by the applicants.

The findings will be shared with the public (see beneficiaries). All peer-reviewed articles will be published in Open Access format and findings will be explained in the form of public lectures and illustrations/3D model made for public science exhibitions. The lead applicant has contacts with the BBC to explore possibilities of a new form of public communication of our results promoting at the same time the impact of basic research on Health and the involvement of women in research advances.