Biology subjects

Martin-Burgos, B.

Publications and source records attributed to Martin-Burgos, B..

4 recordsLinked to original sources

bioRxiv2026

Action potential waveforms are state-dependent

Action potentials are brief electrical impulses that form the mechanistic basis for how neurons communicate. While it is well known that the shape of action potentials can differ across neurons, one fundamental assumption is that the complex voltage waveforms of action potentials within a given neuron are reducible to binary spikes. This assumption has constrained our conception of possible neural codes to those amenable to binary signaling, such as rate, temporal, and population codes. Here, we show that action potential waveform variability is not random, but is, instead, state dependent. To show this, we parameterize action potential waveforms in a set of very high temporal resolution (200 kHz) intracellular action potential recordings. We show that an action potential is not a digital '1', but is instead a rich signal whose fine-scale features influence the shape and timing of the next action potential and whose waveform is systematically biased by input drive. We then show that intracellular action potential waveforms can vary as a function of the extracellular local field potential, but do so heterogeneously, as a function of the field potential amplitude and standard deviation. Our results have profound implications for systems and computational neuroscience, especially regarding the development of next-generation, biologically-inspired artificial neural networks that incorporate waveform dynamics. Non-binary action potentials point to a broader landscape of possible neural codes, whereby neurons communicate not just via binary spikes, but through their state-dependent waveform features.

neuroscience↗

bioRxiv2024

Graphene-polymer Nanofibers Enable Optically Induced Electrical Maturation in Stem Cell-Derived Cardiomyocytes and Brain Organoids

Human pluripotent stem cell (hPSC)-derived electrically excitable cells provide a unique window into development, but they remain electrically immature partially due to the lack of chronic stimulation. Here, we fabricated electrospun polymer nanofibers containing light-reactive reduced graphene oxide (rGO) as part of a new classes of on-demand, electrically active biomaterials to enhance cell function. Fiber size, stiffness, and electrical conductivity varied with rGO concentration, which impacted hPSC-derived cardiomyocyte and neuron responses; with acute light stimulation, cardiomyocytes exhibited increased, synchronous calcium handling, and neurons showed more calcium peaks with higher frequency. Chronic, repetitive nanofiber light stimulation caused brain organoids to become increasingly electrically active and to activate photoreceptor pathways. This work outlines a tunable method where electrical cell functions can be titrated with rGO fibers and light stimulation, and it suggests that repetitive light stimulation may provide a novel method for retinal differentiation. HIGHLIGHTSO_LIElectrospun graphene-polymer nanofibers electrically respond to light stimulation C_LIO_LILight reactive graphene nanofibers stimulate electrically excitable cells in real-time C_LIO_LIStem cell-derived cardiomyocytes and neurons on nanofibers functionally improve C_LIO_LILight-training of brain organoids induces retinal and excitable neuron maturation C_LI

bioengineering↗

bioRxiv2021

Cell-type specific circadian bioluminescence rhythms recorded from Dbp reporter mice reveal circadian oscillator misalignment

Circadian rhythms are endogenously generated physiological and molecular rhythms with a cycle length of about 24 h. Bioluminescent reporters have been exceptionally useful for studying circadian rhythms in numerous species. Here, we report development of a reporter mouse generated by modification of a widely expressed and highly rhythmic gene encoding D-site albumin promoter binding protein (Dbp). In this line of mice, firefly luciferase is expressed from the Dbp locus in a Cre-recombinase-dependent manner, allowing assessment of bioluminescence rhythms in specific cellular populations. A mouse line in which luciferase expression was Cre-independent was also generated. The Dbp reporter alleles do not alter Dbp gene expression rhythms in liver or circadian locomotor activity rhythms. In vivo and ex vivo studies show the utility of the reporter alleles for monitoring rhythmicity. Our studies reveal cell-type specific characteristics of rhythms among neuronal populations within the suprachiasmatic nuclei ex vivo. In vivo studies show Dbp-driven bioluminescence rhythms in the liver of Albumin-Cre;DbpKI/+ "liver reporter" mice. After a shift of the lighting schedule, locomotor activity achieved the proper phase relationship with the new lighting cycle more rapidly than hepatic bioluminescence did. As previously shown, restricting food access to the daytime altered the phase of hepatic rhythmicity. Our model allowed assessment of the rate of recovery from misalignment once animals were provided with food ad libitum. These studies confirm the previously demonstrated circadian misalignment following environmental perturbations and reveal the utility of this model for minimally invasive, longitudinal monitoring of rhythmicity from specific mouse tissues.

physiology↗

bioRxiv2020

Methods for detecting PER2::LUCIFERASE bioluminescence rhythms in freely moving mice

Circadian rhythms are driven by daily oscillations of gene expression. An important tool for studying cellular and tissue rhythms is the use of a gene reporter, such as bioluminescence from the reporter gene luciferase controlled by a rhythmically expressed gene of interest. Here we describe methods that allow measurement of bioluminescence from a freely-moving mouse housed in a standard cage. Using a LumiCycle In Vivo (Actimetrics), we determined conditions that allow detection of circadian rhythms of bioluminescence from the PER2 reporter, PER2::LUC, in freely behaving mice. We tested delivery of D-luciferin via a subcutaneous minipump and in the drinking water. Further, we demonstrate that a synthetic luciferase substrate, CycLuc1, can support circadian rhythms of bioluminescence, even when delivered at a lower concentration than D-luciferin. We share our analysis scripts and suggestions for further improvements in this method. This approach will be straightforward to apply to mice with tissue-specific reporters, allowing insights into responses of specific peripheral clocks to perturbations such as environmental or pharmacological manipulations.

systems biology↗