Threatening stimuli elicit a sequential cardiac pattern in arthropods.

In order to cope with the challenges of living in dynamic environments, animals rapidly adjust their behaviors in coordination with different physiological responses. Here, we studied whether threatening visual stimuli evoke different heart rate patterns in arthropods and whether these patterns are related with defensive behaviors. We identified two sequential phases of crab's cardiac response that occur with a similar timescale to that of the motor arrest and later escape response. The first phase was modulated by low salience stimuli and persisted throughout spaced stimulus presentation. The second phase was modulated by high-contrast stimuli and reduced by repetitive stimulus presentation. The overall correspondence between cardiac and motor responses suggests that the first cardiac response phase might be related to motor arrest while the second to the escape response. We show that in the face of threat arthropods coordinate their behavior and cardiac activity in a rapid and flexible manner.

CRISPR/Cas9-based edition of frataxin gene in Dictyostelium discoideum.

In this paper, we describe the development of a Dictyostelium discoideum strain deficient in frataxin protein (FXN). We investigated the conservation of function between humans and D. discoideum and showed that DdFXN can substitute the human version in the interaction and activation of the Fe-S assembly supercomplex. We edited the D. discoideum fxn locus and isolated a defective mutant, clone 8, which presents landmarks of frataxin deficiency, such as a decrease in Fe-S cluster-dependent enzymatic functions, growth rate reduction, and increased sensitivity to oxidative stress. In addition, the multicellular development is affected as well as growing on bacterial lawn. We also assessed the rescuing capacity of DdFXN-G122V, a version that mimics a human variant present in some FA patients. While the expression of DdFXN-G122V rescues growth and enzymatic activity defects, as DdFXN does, multicellular development defects were only partially rescued. The results of the study suggest that this new D. discoideum strain offers a wide range of possibilities to easily explore diverse FA FXN variants. This can facilitate the development of straightforward drug screenings to look for new therapeutic strategies.