CRISPR/Cas9-based edition of frataxin gene in Dictyostelium discoideum for Friedreich's Ataxia disease modeling

Here we present the development of a new model system for Friedreich's Ataxia (FA) using D. discoideum (Dd). FA is a rare disease caused by disfunction of frataxin (FXN), a protein involved in Fe-S cluster assembly machinery. We firstly investigated the conservation of function between human and D. discoideum. In this work we show that DdFXN can substitute the human version in the interaction and activation of Fe-S assembly supercomplex. DdFXN can in vitro displace HsFXN in competition assays and also it can activate cysteine desulfurase activity in the context of human Fe-S assembly supercomplex. We then manage to edit fxn locus and isolated clone 8, a defective mutant with undetectable levels of frataxin. Clone 8 presents landmarks of frataxin deficiency such as decrease in Fe-S cluster dependent enzymatic functions, growth rate reduction and increase sensitivity to oxidative stress. Besides these phenotypes, shared with other FA models, clone 8 presents defects in the multicellular developmental program induced by starvation in this protist. We then assessed the rescuing capacity of DdFXN G122V, a version that mimics a human variant presented in some FA patients. While expression of DdFXN G122V rescues growth and enzymatic activities defects as well as DdFXN does, multicellular development defects were only partially rescued. This work opens the door to develop drug or treatment screenings that would help to design, and/or evaluate therapeutical strategies. Besides this biological model offers a wide range of possibilities to easily explore diverse phenotypes in FA. ### Competing Interest Statement The authors have declared no competing interest.