Biology subjects

Coculla, A.

Publications and source records attributed to Coculla, A..

4 recordsLinked to original sources

bioRxiv2026

An HSP90-released reduced-eye phenotype alters light-dependent behaviour in Tribolium castaneum

Heat Shock Protein 90 (HSP90) functions as an evolutionary capacitor, allowing populations to store cryptic genetic variation that can be released under stress. While former studies have described the release of morphological variation, its behavioural consequences remain unexplored. In the red flour beetle, Tribolium castaneum, HSP90 inhibition released a phenotype with much smaller, less defined eyes that confers fitness benefits in continuous light and was subsequently assimilated. We hypothesized that altered eye morphology affects light perception and thereby changes light-dependent behaviours. To test whether phenotypes released via evolutionary capacitance can beneficially alter behaviour, we examined locomotor activity rhythm entrainment to light-dark cycles as well as individual and group light choice behaviour. Males of the reduced-eye phenotype exhibited a diminished startle response to sudden light exposure in locomotor activity assays. We also found reduced negative phototaxis in groups of beetles with reduced eyes. This modified behaviour, indicating reduced light sensitivity, may stem from impaired light perception caused by altered eye morphology. Lower light sensitivity could be beneficial under stressful environmental conditions by promoting the exploration of alternative niches. Therefore, this study provides the first evidence for potentially beneficial behavioural changes in a HSP90-released phenotype, reinforcing HSP90s role as an evolutionary capacitor.

evolutionary biology↗

bioRxiv2025

Hsp90 buffers behavioral plasticity by regulating Pdf transcription in clock neurons of Drosophila melanogaster

Circadian rhythms are prevalent on Earth and temporally organize behaviour and physiology of organisms to occur in species-specific temporal niches. However, species differ in how strictly individuals are controlled by their circadian clock, suggesting that it may offer a selective advantage for an individual to extend its temporal niche under certain circumstances, for example during stressful environmental conditions. A potential mechanism controlling temporal niche adherence involves the evolutionary capacitor and chaperon protein HSP90, known to assist the proper folding of important signalling molecules. If HSP90 becomes rate limiting (e.g., under environmental stress) hidden genetic variation will be expressed, producing novel and potentially beneficial phenotypes for the individual. While this role of HSP90 is well established for morphological traits, we show here that it extends to regulation of temporal behavioural patterns. We show that within a small subset of clock neurons in the fly brain, HSP83, the fly homologue of HSP90, mitigates inter-individual behavioural plasticity. We provide evidence for the requirement of HSP83 for efficient transcription of the gene encoding the circadian neuropeptide Pigment Dispersing Factor (PDF), and for correct PDF accumulation in central clock neurons. Strikingly, Hsp83 mutants affect synchronized oscillations of the clock protein PERIOD (PER) in subsets of circadian clock neurons in the same way as flies without PDF, further supporting a role of Hsp83 in regulating Pdf. Our findings therefore provide a mechanistic explanation for HSP83 function in regulation of behavioural plasticity, and offer an explanation for how to restrict temporal niche extension to stressful environmental conditions.

neuroscience↗

bioRxiv2025

Fruit flies actively restart their circadian clock by proactively shaping their environment

Circadian clocks are prevalent on Earth and are generally believed to provide adaptive advantage to organisms. Functional circadian clocks, and their synchronization with the outside world, has also been implicated to provide health benefits for humans. However, experimental evidence for the benefits of possessing a circadian clock is sparse and largely restricted to prokaryotic organisms. Here, we provide evidence for the benefits of circadian clocks and temporally organized life in the fruit fly Drosophila melanogaster. We demonstrate that flies prefer and actively choose to live under circadian clock regulation: Exposure to constant light breaks down the circadian clock and leads to arrhythmic locomotor activity patterns. When given the choice to move between dark and illuminated areas in a constant light environment, flies were able to maintain, or even re-gain, rhythmic behavioural patterns. These rhythms were mirrored by regular positional changes between the two areas, demonstrating that flies actively contribute to creating an environment allowing circadian clock function and temporal organisation. The self-inflicted rhythms were accompanied by molecular rhythms in the majority of the clock neurons known to drive behavioural rhythms in flies, showing that they are indeed controlled by the circadian clock. Finally, behavioural rhythmicity was correlated with restoration of rhythmic sleep patterns and less-fragmented sleep compared to arrhythmic flies. While life is possible without a circadian clock, we show that if given the choice, animals prefer to live in a temporally organized manner and actively contribute to make this possible. This provides strong arguments for the benefits of possessing and using a circadian clock, for example by ensuring a better quality of sleep.

neuroscience↗

bioRxiv2022

A role for thalamic projection GABAergic neurons in circadian responses to light

The thalamus is an important hub for sensory information and participates in sensory perception, regulation of attention, arousal and sleep. These functions are executed primarily by glutamatergic thalamocortical neurons that extend axons to the cortex and initiate cortico-thalamocortical connectional loops. However, the thalamus also contains projection GABAergic neurons that do not engage in direct communication with the cortex. Here, we have harnessed recent insight into the development of the intergeniculate (IGL), the ventrolateral geniculate (LGv) and the perihabenula (pHB) to specifically target and manipulate thalamic projection GABAergic neurons in female and male mice. Our results show that thalamic GABAergic neurons of the IGL and LGv receive retinal input from diverse classes of ipRGCs, but not from the M1 ipRGC type, while those in the pHB lack direct retinal input. We describe the synergistic role of the photoreceptor melanopsin and the thalamic neurons of the IGL/LGv in circadian entrainment to dim light. We identify a requirement for the thalamic IGL/LGv in the rapid changes in vigilance states associated with circadian light transitions. Furthermore, we map a previously undescribed thalamic network of developmentally related GABAergic neurons in the IGL/LGv complex and the pHB potentially involved in light-dependent mood regulation. Significance statementThe intergeniculate leaflet and ventral geniculate nucleus are part of the extended circadian system and mediate some non-image-forming visual functions. Here we show that each of these structures has a thalamic (dorsal) as well as prethalamic (ventral) developmental origin. We map the retinal input to thalamus-derived cells in the IGL/LGv complex and discover that while ipRGC input is dominant, this is not likely to originate from M1-ipRGCs. We describe the extent of similarity in synaptic input to developmentally related cells in the IGL/LGv and in the perihabenula nucleus (pHB). We implicate thalamic cells in the IGL/LGv in vigilance state transitions at circadian light changes and in overt behavioural entrainment to dim light, the latter exacerbated by concomitant loss of melanopsin expression.

neuroscience↗