Biology subjects

Hasegawa, S.

Publications and source records attributed to Hasegawa, S..

6 recordsLinked to original sources

bioRxiv2024

T-scope V4: miniaturized microscope for optogenetic tagging in freely behaving animals

A miniaturized microscope (i.e., miniscope) enables the imaging of neuronal activity using calcium sensors while simultaneously manipulating that activity using opsins in freely moving animals. However, many miniscopes use light-emitting diodes with broadband emission, leading to unintentional opsin stimulation by light intended solely for calcium sensor activation (a phenomenon referred to as "biological crosstalk"). To address this issue, we previously developed a miniscope including a port for chosen light sources, such as lasers, by restructuring the open-source UCLA Miniscope v3. However, targeting the same neuronal soma for both excitable opsin stimulation and calcium sensor imaging remained a challenge. Here, we integrated features from the UCLA Miniscope v4 into our new T-scope V4 miniscope. In optogenetic tagging experiments, we demonstrated that a 445-nm blue laser can be used to image neuronal activity with the calcium sensor GCaMP6s without inadvertently stimulating the ChrimsonR opsin, allowing for simultaneous neuronal activity imaging and manipulation in freely moving mice. Thus, the T-scope V4 can serve as a powerful tool for probing causal relationships between neuronal activity and its function in living animals. HighlightsO_LIWe developed the T-scope V4 that integrates features of the UCLA Miniscope v4 C_LIO_LIThis miniscope prevents "biological crosstalk" between sensors and opsins C_LIO_LIThis tool can help probe causal brain-behavior relationships in living animals C_LI

neuroscience↗

bioRxiv2023

Imbalanced expression of clustered protocadherins in pre- and post-synaptic compartments of CA1 pyramidal cells during hippocampal development

Clustered protocadherins (cPcdhs) are candidates for the neural circuit formation; however, the localization of cPcdhs in pre- and post-synaptic compartments has not been well characterized. Here we examined the localization of cPcdh{gamma} proteins in the mouse hippocampal CA1 region using light and electron microscopy. From postnatal day 7 to 21, cPcdh{gamma} immunosignals were detected in approximately 40-60% of spines of pyramidal cells. SDS-digested freeze-fracture replica labelling revealed that cPcdh{gamma} immunolabeling was found in 50% of PSD 95-positive postsynaptic profiles but only in less than 10% of vGluT1-positive pre-synaptic terminals. Interestingly, cPcdh{gamma}-positive pre-synaptic terminal was exclusively accompanied by cPcdh{gamma}-positive postsynaptic counterpart. In addition, electrophysiological investigations revealed that the miniature excitatory postsynaptic current frequency in cPcdh{gamma} cKO mice was significantly higher than that in wild-type mice. These results suggest that cPcdh{gamma} proteins are unequally distributed in the pre- and post-synaptic membrane during neural circuit development and regulate the number of excitatory synapses.

neuroscience↗

bioRxiv2023

Role of acetoacetyl-CoA synthetase in glucose uptake by HepG2 cells

Accelerated glucose metabolism is a common feature of cancer cells and represents a potential therapeutic target. Recent studies have revealed that lipid metabolism is related to glucose me-tabolism, especially glucose uptake. Acetoacetyl-CoA synthetase (AACS) converts acetoacetate, a ketone body, to acetoacetyl-CoA, which is incorporated into cholesterol and fatty acids. The AACS gene is highly expressed in HepG2 cells but not in the human normal liver. These results suggest a correlation between AACS and glucose metabolism. Therefore, we examined the relationship between AACS and glucose uptake in hepatocellular carcinoma (HepG2) cells. The expression of AACS was significantly upregulated when HepG2 cells were exposed to high concentrations of glucose. Lentiviruses, which code for shRNA against AACS (shAACS), were used to determine whether AACS knockdown affects the glucose uptake in HepG2 cells. AACS knockdown signifi-cantly reduced glucose uptake and increased the concentration of ketone bodies in the media, and treatment with {beta}-hydroxybutyrate, a ketone body, attenuated glucose uptake. Moreover, the knockdown of AACS, i.e., the increased concentration of the intracellular ketone body, slightly attenuated cell proliferation and significantly increased the sensitivity to the anticancer agent sorafenib. These results suggest that AACS plays an important role in glucose uptake and cell proliferation and that ketone bodies may compete with glucose as an important energy source for cancer cells.

molecular biology↗

bioRxiv2021

An autonomous tail-beating cycle period expressed by a region-specific swimming pattern generator in the Ciona larva

Swimming locomotion in aquatic vertebrates, such as fish and tadpoles, is expressed through orchestrated operations of central pattern generators. These parallel neuronal circuits are ubiquitously distributed and mutually coupled along the spinal cord to express undulation patterns accommodated to efferent and afferent inputs. While such sets of schemes have been shown in vertebrates, the evolutionary origin of those mechanisms along the chordate phylogeny remains unclear. Ascidians, representing a sister group of vertebrates, give rise to tadpole larvae that freely swim in seawater. In this study, we tried to locate the swimming pattern generator in larvae of the ascidian Ciona by examining locomotor ability of segmented body fragments. Our experiments demonstrated necessary and sufficient pattern generator activity in a short region ([~]10% of the body length as the longest estimation) including the trunk-tail junction but excluding most of the trunk and tail with major sensory apparatuses therein. Moreover, we found that these "mid-piece" body fragments express periodic tail beating bursts with [~]20-s intervals without any exogenous stimuli. Comparisons among temporal patterns of tail beating bursts expressed by the mid-piece fragments and by whole larvae placed under different sensory conditions suggested that the presence of parts other than the critical mid-piece had effects to shorten swimming burst intervals, especially in the dark, and also to expand the variance in burst durations. We propose that Ciona larvae perform swimming as modified representations of autonomous and periodic pattern generator drives, which operate locally in the region of the trunk-tail junction. Summary statementMid-piece fragments of tadpole larvae of the ascidian Ciona, lacking most of the anterior trunk and posterior tail, autonomously and periodically express tail beating bursts.

zoology↗

bioRxiv2019

The fate of carbon in a mature forest under carbon dioxide enrichment

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1,2,3,4,5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. While evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3,4,5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7,8,9,10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving an open question about the fate of additional carbon fixed under eCO24, 5, 7,8,9,10,11. Here, using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responds to four years of eCO2 exposure. We show that, although the eCO2 treatment of ambient +150 ppm (+38%) induced a 12% (+247 gCm-2yr-1) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone contributing [~]50% of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on CO2 fertilization as a driver of increased carbon sinks in standing forests and afforestation projects.

ecology↗

bioRxiv2017

Aberrant cerebellar-default-mode functional connectivity underlying auditory verbal hallucinations in schizophrenia revealed by multi-voxel pattern analysis of resting-state functional connectivity MRI data

Past neuroimaging studies have reported that aberrant functional connectivity (FC) underlying auditory verbal hallucinations (AVHs) in schizophrenia is highly distributed over multiple functional networks. There is thus a need for exploratory approaches without limiting analysis to particular seed regions or functional networks, to identify FC alterations underlying AVH. We applied a multi-voxel pattern analysis (MVPA) of FC together with a series of post-hoc FC analyses to resting-state fMRI data acquired from 25 patients with schizophrenia and 25 matched healthy controls. First, the MVPA revealed multiple clusters exhibiting altered FC patterns in schizophrenia. Subsequent multiple linear regression analysis using scores of these clusters identified that FC alteration in the right cerebellum crus I was significantly associated with the severity of AVH. Furthermore, post-hoc FC analysis with the right crus I as a seed revealed significant FC alterations with regions distributed across multiple functional networks, including speech, default-mode, thalamus, and cerebellum. Subsequent linear regression analyses further demonstrated that, among these regions, only reduced FC in the left precuneus was significantly associated with the severity of AVH. Our unbiased exploratory analysis of FC data revealed a novel evidence for the crucial role of FC between cerebellar and default-mode networks in AVH. (198 words)

neuroscience↗