Disease models
Induced pluripotent stem cells (iPSCs)
In collaboration with the Stem Cell Institute Leuven (SCIL, directed by Prof. Catherine Verfaillie) we develop stem cell models for various forms of ALS-FTD. Patient-derived skin biopsies from the ALS-FTD clinic are reprogrammed with the 4 Yamanaka factors using a Sendai viral transduction. The cell lines are fully characterized for pluripotency, genetic integrity and their potential to differentiate into mature motor neurons and cortical neurons. Disease-specific phenotypes are studied and will be used to unravel disease mechanisms.
Zebrafish
The zebrafish, or Danio Rerio, is a frequently used model in research. Since it’s a vertebrate with high genetic homology to humans it can offer valuable and relevant insights into human diseases. Zebrafish have several practical advantages, including small size, easy housing and handling, high reproductive capacity and fast development. Since zebrafish embryos develop externally and are transparent during the first days of development, most experiments are conducted in this early developmental stage.
To obtain a zebrafish model for ALS, genetic material containing an ALS related mutation is injected into fertilized eggs. The day after, the axons of the motor neurons are examined in the developing embryo, searching for abnormalities of these axons. Hence, since these motor neurons are the cells which degenerate in patients with ALS this can be used as a model to investigate ALS. We have generated a zebrafish model for three major ALS mutations; SOD1, TDP43 and C9orf72.
Fruit flies
The fruitfly, or Drosophila melanogaster, is a well-known animal model that is often used in translational research. Besides comparable cellbiological mechanisms, 75% of the human disease-causing genes are present in the fruitfly. The full genome of Drosophila is annotated and contains only 4 chromosomes: one X/Y pair and 3 autosomes. Due to excellent working tools available and the fast generation time, the fruitfly is a very attractive animal model to work with.
This animal model is used in different projects to investigate the complex toxic mechanisms leading to motor neuron death. Different genetic causes of ALS and FTD are described, including mutations in the RNA-binding protein FUS. To obtain better insights into the pathobiological mechanism of FUS, our research group developed an ALS-FUS Drosophila model in which WT and mutant (R521G, R521H and P525L) human FUS is expressed using the UAS-GAL4 expression system. Flies with FUS overexpression in their motor neurons show severely reduced lifespan together with age-dependent, progressive motor performance defects. Our model thus shows ALS-like phenotypes.
Patients with ALS have a striking variability in disease presentation. Furthermore, variation in age of onset and disease progression are described. Therefore, the presence of unknown modifying genes is suggested. The identification of genetic modifiers will have a great impact for predicting the disease course of patients, but also for understanding pathways of motor neuron death and for developing novel therapeutic strategies. With the full genome of Drosophila being annotated and the availability of genetic tools, whole genome screens become very attractive to identify disease-modifying genes. We used commercially available chromosomal deletions, RNAi lines and null mutant lines to identify potential modifiers of FUS toxicity. Validation experiments in higher order mechanisms will be performed to understand the underlying mechanisms.
Mice
We use mouse models of genetically or surgically induced neuronal damage, such as the nerve crush, axotomy, stroke and spinal cord injury models. We have several techniques to investigate neurological phenotypes of these models, such as measuring the compound muscle action potential (CMAP) or sensory nerve action potential (SNAP) and/or performing rotarod, grip strength, hanging wire or von Frey experiments.
In addition, we established methods to introduce viruses, nanobodies or drugs into the central nervous system. Depending on the needed frequency of administration we can either choose for a single injection, multiple injections via cannula or continuous administration via osmotic pumps. The goal of these experiments is to influence the disease progression and to find new druggable targets for these incurable disorders.