While the global incidence of ALS has increased over the years, the molecular mechanisms of the disease remain largely unknown. Our innovative approach has the potential to uncover the pathogenic mechanisms by which mutations in FUS, TDP-43 and C9orf72 result in ALS-associated aberrant protein aggregation and motorneuron degeneration. Thus, our project can lead to novel therapeutic strategies for ALS.
Amyotrophic Lateral Sclerosis (ALS) is caused by mutations in genes such as C9orf72 or the RNA-binding proteins FUS and TDP-43. While these proteins are ubiquitously expressed, their mutations selectively cause motorneuron degeneration. In the brain of ALS patients, FUS, TDP-43 and C9orf72 form cytoplasmic toxic aggregates, which also contain other RNA-binding proteins. Here we will use an innovative approach based on a combination of disease modelling using pluripotent stem cells derived from patients (ALS-iPSCs) with model organisms to uncover mechanisms for ALS intervention.
First, we will perform an integrated analysis to identify potential modulators of the protein aggregation phenotype induced by mutant FUS, TDP-43 and C9orf72 variants in motor neurons derived from ALS-iPSCs. Then, we will screen whether these factors modulate protein aggregation and neurotoxicity in ALS organismal models expressing the same human mutant FUS, TDP-43 and C9orf72 variants of our ALS-iPSC lines.
Once we identify modulators of ALS-related aggregation in these models, we will determine their impact in human motorneurons derived from ALS-iPSCs.
Defining changes induced by ALS-mutant related proteins
Screen in ALS disease models
Ameliorate protein aggregation in human motor neurons derived from ALS-iPSCs
David Vilchez’s laboratory has made important contributions to our understanding of how human pluripotent stem cells regulate protein quality control.
For instance, his lab found that pluripotent stem cells exhibit up-regulation of specific E3 ubiquitin ligase enzymes to modulate factors required for hESC/iPSC function and self-renewal (Saez et al, Scientific Reports 2018, Saez et al, FEBS Letters 2019). Among them, they found a novel pathway involved in the degradation and modification of histone H3 link with Huntington’s disease (Irmak et al, Human Molecular Genetics 2018, Fatima et al, In revision in Stem Cell Reports).
David’s lab also defined that the E3 ubiquitin ligase UBR5 prevents aggregation of mutant huntingtin in iPSCs derived from Huntington’s disease patients (Koyuncu et al, Nature Communications 2018). In these lines, his lab discovered that human pluripotent stem cells also have enhanced levels of other proteostasis mechanisms to suppress toxic protein aggregation (Noormohammadi et al, Nature Communications 2016). For instance, hESCs/iPSCs have endogenous mechanisms of post-transcriptional regulation and protein synthesis (Lee et al, Nature Communications 2017) as well as protein folding (Noormohammadi et al, Nature Communications 2016).
Importantly, mimicking these proteostasis mechanisms in somatic tissues was sufficient to prolong organismal healthspan and delay age-related diseases in C. elegans models (Koyuncu et al, Nature Communications 2018, Lee et al, Nature Communications 2017, Noormohammadi et al, Nature Communications 2016). Besides its work on proteostasis of stem cells, David’s laboratory has made significant advances on understanding the cell non-autonomous mechanisms by which germ stem cells regulate the fitness of the soma. Importantly, they discovered that germ stem cells communicate with somatic tissues by releasing prostaglandin signals to coordinate extended reproductive capacity with longevity under favourable conditions, without compromising either fertility or organismal healthspan (Lee et al, Nature Metabolism 2019, cover).