Biology subjects

Roseby, W.

Publications and source records attributed to Roseby, W..

4 recordsLinked to original sources

bioRxiv2026

Connectomic analysis reveals the axial circuit for self-righting posture control in Drosophila

Postural control, the capacity of an animal to detect and correct an inappropriate body orientation, is a widespread and fundamental neurobiological function, yet the neural circuits that implement it remain poorly resolved in most species. The larva of Drosophila melanogaster performs a posture control stereotyped self-righting (SR) manoeuvre when turned upside-down, a behaviour previously shown to depend on a pair of segmentally repeated lateral transverse motor neurons (LT1/2-MNs) and on the normal expression of several Hox-targeting microRNAs. Here, we use a connectomics and a functional behavioural approach to trace and test the sensory, interneuronal and motor architecture of the SR circuit along the antero-posterior axis. Starting from the LT1/2-MNs, we identify a set of pre-motor interneurons, their principal upstream partners, and a population of class IV multidendritic sensory neurons as core components of the circuit, and show, through neuron-specific thermogenetic silencing, that inhibiting the great majority of these elements significantly impairs SR performance. We further find substantial overlap between the SR circuit and the previously described nociceptive rolling and touch crawling circuits, converging on shared interneurons including DnB, A02o (Wave-1) and TePn05. Network and axial connectivity analyses reveal a nested, hub-like organisation, a small number of integrator neurons bridging sensory and motor sub-networks, and a consistent decline in synapse number and density towards posterior segments. Together, these data yield the first axial wiring diagram for a postural control circuit in any animal and offer a set of structural principles including: hub organisation, shared sensory-motor structure, and antero-posterior connectivity gradients, which may extend to other segmentally organised nervous systems.

neuroscience↗

bioRxiv2025

Global organisation of structural covariance networks derived from parcellated cortical surface area in atypical populations.

Higher-order features of brain organisation are powerful measures for understanding the relationship between brain and experience. In particular, the global arrangement of structural features of the cortex provides insight into neurodevelopmental processes that underlie individual differences in perception and cognition. Structural covariance networks (SCNs), which capture regional coordination of brain morphometry, are an efficient method to derive global properties of the cortex. However, their interpretation relies on an array of methodological choices that are often inconsistent between studies. Using a hierarchically-clustered version of the Human Connectome Project (HCP) atlas, we constructed SCNs of regional cortical surface area for groups with four different conditions - synaesthesia, autism, early psychosis, and anxiety or depression - and compared global network properties with those of age- and sex-matched controls. SCNs for synaesthesia and autism showed globally stronger connectivity, with specific increases at moderate cortical distances, as well as lower network complexity. Conversely, the SCN for early psychosis showed a globally lower connectivity and a greater complexity, while depression and anxiety showed few differences compared to controls. The results for autism and depression were replicated across two datasets each. These findings support the notion that synaesthesia and autism share neurodevelopmental mechanisms, while psychosis may involve a diverging process. This study is also an important proof of principle for analysing diverse populations under one methodological framework.

neuroscience↗

bioRxiv2025

Region-specific mechanosensation in Drosophila postural control behaviour

The relation between regional morphological features derived from the bilaterian body plan and the behaviours necessary to extract utility from such structures is not well understood. Here we use the Drosophila larva to investigate this form-function problem focusing on the mapping of the regional stimuli that trigger an adaptive and evolutionarily conserved behaviour termed self-righting: a postural control system that allows the animal to restore its natural position if turned upside-down. Through the development of new methodologies that allow regionally-restricted mechanical stimulation and zonal-specific neuronal optogenetics, we find that multidendritic sensory neuron inhibition in anterior areas (thoracic/anterior abdominal) has a profound effect on self-righting performance, whilst inhibition of posterior sensory elements (mid and posterior abdomen) produces no effects. To gain insight into how regional neuronal inhibition affects the different subcomponents of the self-righting sequence we applied a deep neural network tracking method which revealed that reduction of neural activity in anterior sensory neurons primarily increases head casting behaviour, and that this, in turn, is strongly correlated with abnormally long self-righting times. Furthermore, to explore the mechanistic bases of our behavioural observations, we considered the hypothesis that the Hox genes - well known for their roles in axial developmental patterning - might play a role in the functional specification of multidendritic sensory neurons along the body axis. Molecular expression analysis of FACS-sorted neural populations, fluorescent immunolabelling and neuron-specific knock-down experiments demonstrate that normal sensory neuron expression of the Hox genes Antennapedia and Abdominal-b is necessary for self-righting in the Drosophila larva. Altogether, our work shows that region-specific mechanosensory processes mediated by multidendritic sensory neurons and instructed via Hox gene inputs are essential for self-righting, providing a link between regional structural features and an adaptive and widely evolutionarily conserved postural control behaviour.

neuroscience↗

bioRxiv2022

Impact of energy limitations on function and resilience in long-wavelength Photosystem II

Photosystem II (PSII) uses the energy from red light to split water and reduce quinone, an energy-demanding process based on chlorophyll a (Chl-a) photochemistry. Two kinds of cyanobacterial PSII can use Chl-d and Chl-f to perform the same reactions using lower energy, far-red light. PSII from Acaryochloris marina has Chl-d replacing all but one of its 35 Chl-a, while PSII from Chroococcidiopsis thermalis, a facultative far-red species, has just 4 Chl-f and 1 Chl-d and 30 Chl-a. From bioenergetic considerations, the far-red PSII were predicted to lose photochemical efficiency and/or resilience to photodamage. Here, we compare enzyme turnover efficiency, forward electron transfer, back-reactions and photodamage in Chl-f-PSII, Chl-d-PSII and Chl-a-PSII. We show that: i) all types of PSII have a comparable efficiency in enzyme turnover; ii) the modified energy gaps on the acceptor side of Chl-d-PSII favor recombination via PD1+Phe- repopulation, leading to increased singlet oxygen production and greater sensitivity to high-light damage compared to Chl-a-PSII and Chl-f-PSII; ii) the acceptor-side energy gaps in Chl-f-PSII are tuned to avoid harmful back reactions, favoring resilience to photodamage over efficiency of light usage. The results are explained by the differences in the redox tuning of the electron transfer cofactors Phe and QA and in the number and layout of the chlorophylls that share the excitation energy with the primary electron donor. PSII has adapted to lower energy in two distinct ways, each appropriate for its specific environment but with different functional penalties.

biochemistry↗