Post-transcriptional regulation in motor and cognitive disorders

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Healthy neurons are very long cells, taking local decisions far away from their cell body. They are in this respect different from any other cell of our body. For this reason, they have built mechanisms of local decision-making unique to them. They also need to take different decisions in different parts of their extensions (called axons, dendrites and synapses) and for this, express genes that are able to produce a complex series of proteins. These genes are making one immature messenger RNA that can be cut (splicing) into many different versions, themselves translated into different proteins. As they are expressing many mature messengers by splicing, the neurons crucially need to control these alternative splicing. Problems in achieving these events are giving severe problems to the neurons. In the past 10 years, human genetic discovered that mutations in genes producing the splicing machinery are causing neurodegenerative disorders. We recently discovered the essential nuclear and cytoplasmic roles of such splicing factor, called SFPQ in motor circuit development and degeneration and found a novel type of splicing regulation, the cryptic last exon (CLE), normally repressed by SFPQ. This aberrant splicing event, often achieved at the expense of the normal messenger RNAs, produces stable short transcripts able to make interfering proteins, perfect candidates to carry pathologies typical of neurodegenerative processes. Our initial study showed strong evidence for a key role of SFPQ in Amyotrophic Lateral Sclerosis/Fronto-temporal dementia (ALS/FTD) neurodegenerative processes. In the past months, unambiguous findings show that loss of SFPQ is an early hallmark across sporadic and familial ALS patient iPSC-derived motor neurons in culture, putting this protein at the centre of motor degenerative mechanisms. Our ongoing studies of newly identified "SFPQ patients" indicates that the protein is likely to be at the core of a wider variety of degenerative disorders, including neurodevelopmental syndromes.We therefore propose to use our unique models to understand how loss, or mutations, of SFPQ protein during neuronal maturation and in adult circuits generates these CLE transcripts and identify the molecular and cellular consequence of CLE short transcripts on developing and adult neurons. These are of direct importance to develop early therapeutic avenues against neurodegeneration, targeting key pathogenic CLEs. In addition, better understand the CLE-generating novel splicing regulation is likely to have implications on a wider set of splicing-dependent pathologies such as cancers.