Biology subjects

Jimenez-Lopez, C.

Publications and source records attributed to Jimenez-Lopez, C..

4 recordsLinked to original sources

bioRxiv2026

Brain inputs to the vestibular nuclei in lampreys

To avoid image blurring, the vestibulo-ocular (VOR) and the optokinetic (OKR) reflexes stabilize gaze. In all vertebrates, the VOR is mediated via direct projections from the vestibular nuclei to the motor nuclei that control the extraocular muscles. Lampreys show three vestibular nuclei that are well characterized in terms of their projections and sensory inputs, but much less is known about their inputs from other brain regions and the connectivity between them. Using tracer injections and electrophysiological recordings, we show that the lamprey vestibular nuclei are largely interconnected, while their inputs from other brain regions are scarce. The main rostral areas projecting to the vestibular nuclei are the pretectum and the ventral tier of the thalamus, which send ipsilateral inputs to the three vestibular nuclei.

neuroscience↗

bioRxiv2025

Disruption of Plasma Membrane Lipid Asymmetry Alters Cellular Energetics

Biological membranes often feature an unequal and actively maintained concentration gradients of lipids between bilayer leaflets, termed lipid asymmetry.1-3 Lipid asymmetry has been linked to many cellular processes4,5, but the mechanisms that connect lipid trans-bilayer concentration gradients to cellular functions are poorly understood. Here we systematically map the cellular processes affected by dysregulation of lipid asymmetry by knocking out flippases, floppases, and scramblases in mammalian cells. We identify broad alterations to core metabolic pathways including nutrient uptake, neutral lipid turnover, pentose phosphate pathway and glycolysis. Lipidomics, respirometry, lipid and metabolic imaging, and live-cell calorimetry revealed elevated neutral lipid and ATP consumption rates which are coupled with increased heat loss per unit of biomass synthesized despite slower growth. This suggests that compensatory maintenance of lipid asymmetry strains the cellular energy budget, inducing a shift from a growth-promoting anabolic to a more energy-using catabolic state. Our data indicate that lipid asymmetry and its active maintenance is key for proper cell energetics, highlighting its putative role as a cellular store of potential energy akin to proton and ion transmembrane gradients.

cell biology↗

bioRxiv2024

Direct retino-iridal projections and intrinsic iris contraction mediate the pupillary light reflex in early vertebrates

The pupillary light reflex (PLR) adapts the amount of light reaching the retina, protecting it and improving image formation. Two PLR mechanisms have been described in vertebrates. First, the pretectum receives retinal inputs and projects to the Edinger-Westphal nucleus (EWN), which targets the ciliary ganglion through the oculomotor nerve (nIII). Postganglionic fibers enter the eye-globe, travelling to the iris sphincter muscle. Additionally, some vertebrates exhibit an iris-intrinsic PLR mechanism mediated by sphincter muscle cells that express melanopsin inducing muscle contraction. Given the high degree of conservation of the lamprey visual system, we investigated the mechanisms underlying the PLR to shed light onto their evolutionary origins. Recently, a PLR mediated by melanopsin was demonstrated in lampreys, suggested to be brain mediated. Remarkably, we found that PLR is instead mediated by direct retino-iridal cholinergic projections, a mechanism not demonstrated before, although suggested to be present in mice. This retina-mediated PLR acts synergistically with the iris-intrinsic mechanism mediated by melanopsin, which has contribution of gap junctions, as in other vertebrates. In contrast, we show that lampreys lack the brain-mediated PLR. Our results suggest that two eye-intrinsic PLR mechanisms were present in early vertebrate evolution, whereas the brain-mediated PLR has a more recent origin.

neuroscience↗

bioRxiv2023

Functional development of eye movements and visuomotor circuits in lampreys

Animals constantly redirect their gaze away or towards relevant targets and, besides these goal-oriented responses, stabilizing movements clamp the visual scene avoiding image blurring. The vestibulo-ocular (VOR) and the optokinetic reflexes are the main contributors to gaze stabilization, whereas the optic tectum integrates multisensory information and generates orienting/evasive gaze movements in all vertebrates. Lampreys show a unique stepwise development of the visual system whose understanding provides important insights into the evolution and development of vertebrate vision. Although the developmental emergence of the visual components, and the retinofugal pathways have been described, the functional development of the visual system and the development of the downstream pathways controlling gaze are still unknown. Here, we show that VOR followed by light-evoked eye movements are the first to appear already in larvae, despite their burrowed lifestyle. However, the circuits controlling goal-oriented responses emerge later, in larvae in nonparasitic lampreys but during late metamorphosis in parasitic lampreys. The appearance of stabilizing responses earlier than goal-oriented likely reflects their evolution, and its stepwise emergence offers a unique opportunity to isolate the functioning of their underlying circuits.

neuroscience↗