False memories in cuttlefish.

Episodic memory is a reconstructive process per se: during an event, the features composing it are encoded and stored separately in the brain, then reconstructed when the event's memory is retrieved. Even with source monitoring processes (e.g., did I see or did I smell it?), some mistakes can occur. These mnemonic mistakes happen especially when different events share several features, producing overlaps difficult to discriminate, leading to the creation of false memories. The common cuttlefish has the ability to remember specific events about what happened where and when, namely episodic-like memory. In order to investigate whether this memory, such as human episodic memory, is based on reconstructive processes, we elaborated a protocol promoting false memory formation. Our results suggest that cuttlefish do form visual false memories, but not olfactory false memories. These memory errors might be the first indication of the presence of reconstructive processes in the memory of cephalopods.

Language is the missing link in action-perception coupling: an EEG study.

The paper reports an electrophysiological (EEG) study investigating how language is involved in perception-action relations in musically trained and untrained participants. Using an original backward priming paradigm, participants were exposed to muted point-light videos of violinists performing piano or forte nuances followed by a congruent vs. incongruent word. After the video presentation, participants were asked to decide whether the musician was playing a piano or forte musical nuance. EEG results showed a greater P200 event-related potential for trained participants at the occipital site, and a greater N400 effect for untrained participants at the central site. Musically untrained participants were more accurate when the word was semantically congruent with the gesture than when it was incongruent. Overall, language seems to influence the performance of untrained participants, for which perception-action couplings are less automatized.

Cuttlefish show flexible and future-dependent foraging cognition.

Some animals optimize their foraging activity by learning and memorizing food availability, in terms of quantity and quality, and adapt their feeding behaviour accordingly. Here, we investigated whether cuttlefish flexibly adapt their foraging behaviour according to the availability of their preferred prey. In Experiment 1, cuttlefish switched from a selective to an opportunistic foraging strategy (or vice versa) when the availability of their preferred prey at night was predictable versus unpredictable. In Experiment 2, cuttlefish exhibited day-to-day foraging flexibility, in response to experiencing changes in the proximate future (i.e. preferred prey available on alternate nights). In Experiment 1, the number of crabs eaten during the day decreased when shrimp (i.e. preferred food) were predictably available at night, while the consumption of crabs during the day was maintained when shrimp availability was unpredictable. Cuttlefish quickly shifted from one strategy to the other, when experimental conditions were reversed. In Experiment 2, cuttlefish only reduced their consumption of crabs during the daytime when shrimps were predictably available the following night. Their daytime foraging behaviour appeared dependent on shrimps' future availability. Overall, cuttlefish can adopt dynamic and flexible foraging behaviours including selective, opportunistic and future-dependent strategies, in response to changing foraging conditions.

The apoptosis inhibitor Bcl-xL controls breast cancer cell migration through mitochondria-dependent reactive oxygen species production.

The Bcl-xL apoptosis inhibitor plays a major role in vertebrate development. In addition to its effect on apoptosis, Bcl-xL is also involved in cell migration and mitochondrial metabolism. These effects may favour the onset and dissemination of metastasis. However, the underlying molecular mechanisms remain to be fully understood. Here we focus on the control of cell migration by Bcl-xL in the context of breast cancer cells. We show that Bcl-xL silencing led to migration defects in Hs578T and MDA-MB231 cells. These defects were rescued by re-expressing mitochondria-addressed, but not endoplasmic reticulum-addressed, Bcl-xL. The use of BH3 mimetics, such as ABT-737 and WEHI-539 confirmed that the effect of Bcl-xL on migration did not depend on interactions with BH3-containing death accelerators such as Bax or BH3-only proteins. In contrast, the use of a BH4 peptide that disrupts the Bcl-xL/VDAC1 complex supports that Bcl-xL by acting on VDAC1 permeability contributes to cell migration through the promotion of reactive oxygen species production by the electron transport chain. Collectively our data highlight the key role of Bcl-xL at the interface between cell metabolism, cell death, and cell migration, thus exposing the VDAC1/Bcl-xL interaction as a promising target for anti-tumour therapy in the context of metastatic breast cancer.

The level of activity of the alternative lengthening of telomeres correlates with patient age in IDH-mutant ATRX-loss-of-expression anaplastic astrocytomas.

All cancer cells need to maintain functional telomeres to sustain continuous cell division and proliferation. In human diffuse gliomas, functional telomeres are maintained due either to reactivation of telomerase expression, the main pathway in most cancer types, or to activation of a mechanism called the alternative lengthening of telomeres (ALT). The presence of IDH1/2 mutations (IDH-mutant) together with loss of ATRX expression (ATRX-lost) are frequently associated with ALT in diffuse gliomas. However, detection of ALT, and a fortiori its quantification, are rarely, if ever, measured in neuropathology laboratories. We measured the level of ALT activity using the previously described quantitative "C-circle" assay and analyzed it in a well characterized cohort of 104 IDH-mutant and ATRX-lost adult diffuse gliomas. We report that in IDH-mutant ATRX-lost anaplastic astrocytomas, the intensity of ALT was inversely correlated with age (p < 0.001), the younger the patient, the higher the intensity of ALT. Strikingly, glioblastomas having progressed from anaplastic astrocytomas did not exhibit this correlation. ALT activity level in the tumor did not depend on telomere length in healthy tissue cells from the same patient. In summary, we have uncovered the existence, in anaplastic astrocytomas but not in glioblastomas with the same IDH and ATRX mutations, of a correlation between patient age and the level of activity of ALT, a telomerase-independent pathway of telomere maintenance.

Replication Stress at Telomeric and Mitochondrial DNA: Common Origins and Consequences on Ageing.

Senescence is defined as a stress-induced durable cell cycle arrest. We herein revisit the origin of two of these stresses, namely mitochondrial metabolic compromise, associated with reactive oxygen species (ROS) production, and replicative senescence, activated by extreme telomere shortening. We discuss how replication stress-induced DNA damage of telomeric DNA (telDNA) and mitochondrial DNA (mtDNA) can be considered a common origin of senescence in vitro, with consequences on ageing in vivo. Unexpectedly, mtDNA and telDNA share common features indicative of a high degree of replicative stress, such as G-quadruplexes, D-loops, RNA:DNA heteroduplexes, epigenetic marks, or supercoiling. To avoid these stresses, both compartments use similar enzymatic strategies involving, for instance, endonucleases, topoisomerases, helicases, or primases. Surprisingly, many of these replication helpers are active at both telDNA and mtDNA (e.g., RNAse H1, FEN1, DNA2, RecQ helicases, Top2α, Top2ß, TOP3A, DNMT1/3a/3b, SIRT1). In addition, specialized telomeric proteins, such as TERT (telomerase reverse transcriptase) and TERC (telomerase RNA component), or TIN2 (shelterin complex), shuttle from telomeres to mitochondria, and, by doing so, modulate mitochondrial metabolism and the production of ROS, in a feedback manner. Hence, mitochondria and telomeres use common weapons and cooperate to resist/prevent replication stresses, otherwise producing common consequences, namely senescence and ageing.