Biology subjects

Alonso, C. R.

Publications and source records attributed to Alonso, C. R..

6 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

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↗

bioRxiv2024

A microRNA that controls the emergence of embryonic movement

Movement is a key feature of animal systems, yet its embryonic origins are not fully understood. Here we investigate the genetic basis underlying the embryonic onset of movement in Drosophila focusing on the role played by small non-coding RNAs (microRNAs, miRNAs). To this end, we first develop a quantitative behavioural pipeline capable of tracking embryonic movement in large populations of fly embryos, and using this system, discover that the Drosophila miRNA miR-2b-1 plays a role in the emergence of movement. Through the combination of spectral analysis of embryonic motor patterns, cell sorting and RNA in situs, genetic reconstitution tests, and neural optical imaging we define that miR-2b-1 influences the emergence of embryonic movement by exerting actions in the developing nervous system. Furthermore, through the combination of bioinformatics coupled to genetic manipulation of miRNA expression and phenocopy tests we identify a previously uncharacterised (but evolutionarily conserved) chloride channel encoding gene - which we term Movement Modulator (Motor) - as a genetic target that mechanistically links miR-2b-1 to the onset of movement. Cell-specific genetic reconstitution of miR-2b-1 expression in a null miRNA mutant background, followed by behavioural assays and target gene analyses, suggest that miR-2b-1 affects the emergence of movement through effects in sensory elements of the embryonic circuitry, rather than in the motor domain. Our work thus reports the first miRNA system capable of regulating embryonic movement, suggesting that other miRNAs are likely to play a role in this key developmental process in Drosophila as well as in other species.

developmental biology↗

bioRxiv2021

A novel post-developmental role of the Hox genes underlies normal adult behaviour

The molecular mechanisms underlying the stability of mature neurons and neural circuits are poorly understood. Here we explore this problem and discover that the Hox genes are a component of the genetic programme that maintains normal neural function in adult Drosophila. We show that post-developmental downregulation of the Hox gene Ultrabithorax (Ubx) in adult neurons leads to substantial anomalies in flight. Mapping the cellular basis of these effects reveals that Ubx is required within a subset of dopaminergic neurons, and cell circuitry analyses and optogenetics allow us to link these dopaminergic neurons to flight control. Functional imaging experiments show that Ubx is necessary for normal dopaminergic activity, and neuron-specific RNA-sequencing defines two previously uncharacterised ion channel-encoding genes as potential mediators of Ubx behavioural roles. Our study thus reveals a novel role of the Hox system in controlling adult behaviour and neural function.

neuroscience↗

bioRxiv2020

microRNA-dependent control of sensory neuron function regulates posture behaviour in Drosophila

All what we see, touch, hear, taste or smell must first be detected by the sensory elements in our nervous system. Sensory neurons, therefore, represent a critical component in all neural circuits and their correct function is essential for the generation of behaviour and adaptation to the environment. Here we report that a gene encoding the evolutionarily conserved microRNA (miRNA) miR-263b, plays a key behavioural role in Drosophila through effects on the function of larval sensory neurons. Several independent experiments support this finding. First, miRNA expression analysis by means of a miR-263b reporter line, and fluorescent-activated cell sorting coupled to quantitative PCR, both demonstrate expression of miR-263b in Drosophila larval sensory neurons. Second, behavioural tests in miR-263b null mutants show defects in self-righting: an innate and evolutionarily conserved posture control behaviour that allows the larva to return to its normal position if turned upside-down. Third, competitive inhibition of miR-263b in sensory neurons using a miR-263b sponge leads to self-righting defects. Fourth, systematic analysis of sensory neurons in miR-263b mutants shows no detectable morphological defects in their stereotypic pattern. Fifth, genetically-encoded calcium sensors expressed in the sensory domain reveal a reduction in neural activity in miR-263b null mutants. Sixth, miR-263b null mutants show a reduced touch-response behaviour and a compromised response to sound, both characteristic of larval sensory deficits. Furthermore, bioinformatic miRNA target analysis, gene expression assays, and behavioural phenocopy experiments suggest that miR-263b might exert its effects - at least in part - through repression of the bHLH transcription factor atonal. Altogether, our study suggests a model in which miRNA-dependent control of transcription factor expression affects sensory function and behaviour. Building on the evolutionary conservation of miR-263b, we propose that similar processes may modulate sensory function in other animals, including mammals.

neuroscience↗

bioRxiv2019

A single microRNA system controls complex movement in morphologically distinct forms of Drosophila

Movement is the main output of the nervous system. It emerges during development to become a highly coordinated physiological process essential to the survival and adaptation of the organism to the environment. Similar movements can be observed in morphologically-distinct developmental stages of an organism, but it is currently unclear whether these movements have a common or diverse molecular basis. Here we explore this problem in Drosophila focusing on the roles played by the microRNA (miRNA) locus miR-iab4/8 which was previously shown to be essential for the fruit fly larva to correct its orientation if turned upside down (self-righting) (Picao-Osorio et al., 2015). Our study shows that miR-iab4 is required for normal self-righting across all three Drosophila larval stages. Unexpectedly, we also discover that this miRNA is essential for normal self-righting behaviour in the Drosophila adult, an organism with radically different morphological and neural constitution. Through the combination of gene-expression, optical imaging and quantitative behavioural approaches we provide evidence that miR-iab4 exerts its effects on adult self-righting behaviour through repression of the Hox gene Ultrabithorax (Ubx) (Morgan, 1923; Sanchez-Herrero et al., 1985) in a specific set of motor neurons that innervate the adult Drosophila leg. Our results show that this miRNA-Hox module affects the function, rather than the morphology of motor neurons and indicate that post-developmental changes in Hox gene expression can modulate behavioural outputs in the adult. Altogether our work reveals that a common miRNA-Hox genetic module can control complex movement in morphologically-distinct organisms and describes a novel post-developmental role of the Hox genes in adult neural function.

neuroscience↗