Biology subjects

Egawa, S.

Publications and source records attributed to Egawa, S..

4 recordsLinked to original sources

bioRxiv2026

Neural populations in the dorsal and ventral cervical spinal cord share temporal dynamics during reach

Neural population dynamics provide a popular framework for studying motor cortex function. However, whether such dynamics reflect stage-specific computations or are shared across the input and output stages of a sensorimotor circuit is unknown. In the spinal cord, afferent inputs and motor outputs are segregated by anatomical depth. Here we developed depth-resolved Neuropixels recordings from the rat cervical spinal cord during targeted reaching behavior. Across our recordings, population activity was low-dimensional and organized into transient, rotational and target-specific dynamical motifs. Despite differences in single-neuron activity by depth, dorsal and ventral populations expressed nearly identical dynamics across targets and animals. The dominant target-invariant component was strikingly synchronized across depths, whereas other components, including the target-specific component, showed condition-dependent ventral-to-dorsal delays with timing consistent with movement-related feedback. Thus, cervical spinal population dynamics span sensory and motor territories, and may reflect shared coordination of activity rather than purely state-specific local processing.

neuroscience↗

bioRxiv2025

Spinal interneuronal populations encode static hindlimb posture in the cat

Proprioceptive signals from primary afferents reflect changes in single-joint angles, whereas neuronal population in the cerebral cortex represent whole-limb postures. Where and how this transformation emerges along the somatosensory axis from peripheral proprioceptive receptors remains unclear. We simultaneously recorded many lumbosacral spinal neurons in two decerebrate, immobilized cats while a robotic device held the hindlimb at 16 static endpoint positions spanning hip-knee configurations. Using high-density multielectrode recordings, we asked how spinal populations encode static limb state. At the single-neuronal level, activities in a majority of neurons covaried with a single joints angle (hip or knee), a smaller subset showed combined modulation by both joints, and a distinct subset ( single-endpoint neurons) fired selectively at one unique hip-knee configuration near the sampled joint-range limits and was quiescent in adjacent postures. Population analyses revealed a low-dimensional structure: the first two principal components tracked knee and hip angles, respectively, whereas a third component isolated a boundary-aligned, posture-specific pattern, with loadings peaking at the same extreme configurations preferred by single-endpoint neurons. Decoders trained on ensemble activity reconstructed both joint angles and the limbs endpoint position in body-centered coordinates, indicating that the recorded spinal-interneuron populations contain sufficient information to reconstruct whole-limb kinematics. Together, these findings are consistent with a hierarchical organization whereby joint-based representations within spinal-interneuron populations could contribute to the emergence of limb-centered representations in the ascending proprioceptive pathways. The boundary preference of single-endpoint neurons supports a possible categorical coding scheme at workspace limits that may provide spinal "landmarks" for switching control modes, enhancing stability near kinematic extremes, and supporting recalibration of proprioceptive population codes. Key PointsO_LIWe simultaneously recorded many lumbar spinal neurons in two decerebrate, immobilized cats while a robot held the hindlimb at 16 static positions to test how spinal populations encode posture. C_LIO_LIMany neurons varied with a single joint angle (hip or knee), a smaller subset showed combined hip-knee modulation, and a distinct subset was active only at one specific endpoint posture. C_LIO_LIPopulation analyses revealed a low-dimensional structure: the first two principal components tracked knee and hip angles, while a third captured a posture-specific pattern aligned with single-endpoint neurons. C_LIO_LIDecoders trained on ensemble activity reconstructed joint angles and the limbs endpoint, indicating that spinal interneuronal populations contain sufficient information for whole-limb kinematics. C_LIO_LIThese findings are consistent with a hierarchical organization whereby joint-based representations within spinal-interneuron populations could contribute to the emergence of limb-centered representations in the ascending proprioceptive pathways. C_LI

neuroscience↗

bioRxiv2025

The heterochronic activation of TGF-β signaling drives the diversity of the avian sterna

Adaptive evolution has driven the diversification of vertebrate skeletal morphology, enabling a wide array of locomotor modes and lifestyles. In volant birds (carinates), the sternum develops a ventral keel that provides an attachment site for massive pectoral muscles essential for powered flight. In contrast, flightless ratites have lost both flight capability and the keel, resulting in a striking morphological contrast between their sterna. Here, we interrogated the cellular and molecular basis underlying this morphological divergence by using chicken embryos as a carinate model and emu embryos as a ratite model. Through a series of analyses including spatiotemporal transcriptomics and a spheroid culture system, we found that TGF-{beta} signaling, which promotes proliferation of ventral sternal chondroprogenitors, is activated in both species until the stage when the left and right sternal progenitors meet; however, in chicken this activation persists beyond this stage, driving ventral extension of the keel primordium, whereas in emu it shuts off early, culminating in the absence of a protruding keel. Together, our findings suggest that skeletal morphological changes associated with behavioral transitions can arise from heterochrony in developmental signaling, thereby deepening our understanding of the evolutionary logic shaping skeletal diversification.

developmental biology↗

bioRxiv2019

miR-26a regulates extracellular vesicle secretion from prostate cancer cells via targeting SHC4, PFDN4 and CHORDC1

Extracellular vesicles (EVs) are known to be involved in intercellular communication during cancer progression; thus, elucidating the detailed mechanism will contribute to the development of a novel strategy for EV-targeted cancer treatment. However, the biogenesis of EVs in cancer cells is not completely understood. MicroRNAs (miRNAs) regulate a variety of physiological and pathological phenomena; thus, miRNAs could regulate EV secretion. Here, we performed high-throughput miRNA-based screening to identify the regulators of EV secretion using an ExoScreen assay. By using this miRNA-based screening, we identified miR-26a, which was reported as a tumor suppressive miRNA, as a miRNA involved in EV secretion from prostate cancer (PCa) cells. In addition, we found that the SHC4, PFDN4, and CHORDC1 genes regulate EV secretion in PCa cells. Suppression of these genes by siRNAs significantly inhibited the secretion of EVs in PCa cells. Furthermore, the progression of PCa cells was inhibited in an in vivo study. On the other hand, injection of EVs isolated from PCa cells partially rescued this suppressive effect on tumor growth. Taken together, our findings suggest that miR-26a regulates EV secretion via targeting SHC4, PFDN4, and CHORDC1 in PCa cells, resulting in the suppression of PCa progression.

cancer biology↗