The action “Degradation_ID” was implemented at the initial host institution University Hospital Erlangen, Germany (UKER) for the first 18 months and due to the relocation of the supervisor, continued for the final six months at the second host institution University of Bern, Switzerland (UBERN). The first objective of the action was to study mechanisms of FBXO11 deficiency in a human cell based model. Effects of different FBXO11 variants were studied in more detail and found to affect localization and expression of FBXO11. These results were recently published in the journal Human Molecular Genetics (open access). As a tool, I successfully generated FBXO11 knockout induced pluripotent stem cells (IPSCs) and differentiated them to neural precursor cells (NPCS). Those were then further differentiated into neurons. From these cells, transcriptomic analyses were performed and used to identify deregulated gene groups and pathways. Additionally, transcriptomic analysis was performed on heads of Drosophila melanogaster with an Fbxo11 deficiency as a cross comparison and validation. Interestingly, genes deregulated were enriched for genes involved in neuronal differentiation and differentiation programs seem to be slowed in FBXO11 deficient cells. Using mass-spectrometry approaches, I could identify a key regulator of cell fate decisions and stemness factor as a potential target of FBXO11. This interaction was validated using co-immunoprecipitation experiments. This lead me to the working hypothesis that FBXO11 deficiency leads to a persistent presence of this stemness factor, which in turn lead to impaired or delayed activation of differentiation programs in neural precursor cells. Those results are currently still followed up on and will then be published in a peer-reviewed journal upon completion of experiments.
The second objective of the project was to study Fbxo11 deficiency in the model organism Drosophila melanogaster to identify phenotypes and to test potential chemical interventions to alter phenotypes. Here I could identify a defect in dendritic development using a larval sensory neuron model in Fbxo11 deficient flies. Substance tests could identify two proteasome activating substances that led to an improvement of dendritic phenotypes in Fbxo11 deficient flies. Those convincing data have already led to the expansion of this line of research to more genes associated with NDDs and involved in proteasomal degradation. Results of this study will be published together with the expanded research data in a peer reviewed journal.