Intracellular positional information is crucial for the precise control of biological phenomena, including cell division, polarity, and motility. Intracellular reaction-diffusion (iRD) waves are responsible for regulating positional information within cells as morphogens in multicellular tissues. However, iRD waves are explained by the coupling of biochemical reactions and molecular diffusion which indicates nonlinear systems under far from equilibrium conditions. Because of this complexity, experiments using defined elements rather than living cells containing endogenous factors are necessary to elucidate their pattern formation mechanisms. In this review, we summarize the effectiveness of artificial cell systems for investigating iRD waves derived from their high controllability and ability to emulate cell-size space effects. We describe how artificial cell systems reveal the characteristics of iRD waves, including the mechanisms of wave generation, mode selection, and period regulation. Furthermore, we introduce remaining open questions and discuss future challenges even in Min waves and in applying artificial cell systems to various iRD waves.

Tauopathy is a spectrum of diseases characterized by fibrillary tau aggregate formation in neurons and glial cells in the brain. Tau aggregation originates in the brainstem and entorhinal cortex and then spreads throughout the brain in Alzheimer’s disease (AD), which is the most prevalent type of tauopathy. Understanding the mechanism by which locally developed tau pathology propagates throughout the brain is crucial for comprehending AD pathogenesis. Therefore, a novel model of tau pathology that artificially induces tau aggregation in targeted cells at specific times is essential. This study describes a novel optogenetic module, OptoTau, which is a human tau with the P301L mutation fused with a photosensitive protein CRY2olig, inducing various forms of tau according to the temporal pattern of blue light illumination pattern. Continuous blue light illumination for 12 h to Neuro2a cells that stably express OptoTau (OptoTauKI cells) formed clusters along microtubules, many of which eventually accumulated in aggresomes.

Conversely, methanol-resistant tau aggregation was formed when alternating light exposure and darkness in 30-min cycles for 8 sets per day were repeated over 8 days. Methanol-resistant tau was induced more rapidly by repeating 5-min illumination followed by 25-min darkness over 24 h. These results indicate that OptoTau induced various tau aggregation stages based on the temporal pattern of blue light exposure. Thus, this technique exhibits potential as a novel approach to developing specific tau aggregation in targeted cells at desired time points.

JCVI-syn3B (syn3B), a minimal synthetic bacterium that only possesses essential genes, facilitates the examination of heterogeneous gene functions in minimal life. Conventionally, Escherichia coli is used to construct DNA fragments for gene transfer into the syn3B genome through Cre/loxP system. However, the construction process is challenging and time-consuming due to various issues, including the inhibition of E. coli growth and unexpected recombination, especially with AT-rich DNA sequences such as those found in Mycoplasma genes. Therefore, in this study, we aimed to develop a new transformation method to overcome these issues. We assembled the vector and target DNA fragments using an in vitro homologous recombination system and subsequently transferred the products into the syn3B genome. We obtained approximately 10³~10⁴ recombinant colonies per milliliter of the original culture in eight days, which is four days shorter than the conventional period, without any recombination issues, even for AT-rich DNA. This method may be applicable to other gene manipulation systems based on Cre/loxP system.

The action potential of cardiomyocytes is controlled by electrolytes in serum such as Na⁺, K⁺ and Ca²⁺. Hyperkalemia, which refers to an abnormally high concentration of K⁺ in the blood, can induce lethal arrythmia. In this study, the extracellular potentials on a sheet of chick embryonic cardiomyocytes were investigated at increasing K⁺ concentrations using a multielectrode array system. We observed that the interspike interval (ISI) was prolonged by approximately 3.5 times; dV/dt (the slope of a waveform) was decreased by more than five times; the field potential duration (FPD) was shortened by 20%, and the conduction velocity was about half at 12 mM K⁺ against the control (4 mM K⁺). In calcium therapy for hyperkalemia, although the prolongation of ISI under hyperkalemic conditions was restored, the slowing of conduction velocity, the decrease in dV/dt, and the shortening of FPD were not recovered by increasing the extracellular Ca²⁺ concentration. These findings provide a comprehensive understanding of cardiomyocytes in hyperkalemic conditions. Electrophysiological analysis by varying the extracellular concentrations of multiple types of electrolytes will be useful for the further discussion of the results of this study and for the interpretation of the waveforms obtained by measuring the extracellular potential.

Four medicinal plants C. quadrangulare, D. linearis, P. adenophylla, and G. schomburgkiana growing in the South of Vietnam were investigated for their alpha-glucosidase inhibition. The crude methanol extract of C. quadrangulare was determined to be the most active extract, then was selected for further in vivo assays including antidiabetic study and toxicity. In vitro alpha-glucosidase inhibition of four medicinal plants C. quadrangulare, D. linearis, P. adenophylla, and G. schomburgkiana was screened using standard procedures. In vivo antidiabetic activity, acute toxicity and subchronical toxicity of C. quadrangulare leaves was assessed on Swiss albino mice. Swiss albino mice were induced with diabetes by intraperitoneal injection of alloxan at a dose of 150 mg/kg body weight. High-performance liquid chromatography with evaporative light scattering detector (HPLC-ELSD) were used to detect the bioactive components of C. quadrangulare leaves. All crude extracts from the studied plants showed promising alpha-glucosidase inhibition, with IC₅₀ values ranging from 2.4 to 35.3 μg/mL. The methanol extract of C. quadrangulare leaves was determined to be the most active extract. This extract was then selected for antidiabetic assay using alloxan induced model of type 2 diabetes mellitus mice. The results indicated that the extract at a dose of 400 mg/kg can effectively decrease blood glucose levels that is comparable to that of glibenclamide 2 mg/kg. This compound showed moderate activity toward alpha-glucosidase. Therefore, our study indicated that C. quadrangulare, D. linearis, P. adenophylla, and G. schomburgkiana extract are potential materials for producing α-glucosidase inhibitor drugs.

Neurons have an ionic system with several types of ion pumps and ion channels on their membranes. Each ion pump creates a specific difference in ion concentration inside and outside the neuron, and the energy resulting from this difference in concentration is maintained inside the neuron as a resting potential. Each ion channel senses the necessary situation, opens the channel, and allows the corresponding ion to pass through to perform its corresponding role. This ionic system realizes important functions such as (i) fast conduction of action potentials, (ii) achieving synaptic integration in response to several inputs with a time lag, and (iii) the information processing functions by neural circuits. However, the mechanisms by which these functions are realized have remained unclear. Therefore, based on the reports on various highly polymeric ion pumps, ion channels, cell membranes, and other components that have been elucidated so far, author analyzed how this ionic system can realize the above important functions from an electrical circuit designer point of view. As a result of a series of analyses, it was found that neurons realize each function by making full use of high-density packaging technology based on basic electrical principles and making maximum use of the extremely high dielectric properties of the ionic fluid of neurons. In other words, neuron looks to equip well designed ionic system which is the collaboration by designers of proteins and membranes that perform advanced functions and designers of electrical circuits that utilize them to achieve important functions electrically.