Biology subjects

Yamamoto, N.

Publications and source records attributed to Yamamoto, N..

43 records · Page 3Linked to original sources

bioRxiv2019

Suppression of DSB Formation by Polβ in Active DNA Demethylation is Required for Postnatal Hippocampal Development

Genome stability is essential for brain development and function. However, the contribution of DNA repair to genome stability in neurons remains elusive. Here, we demonstrate that the base excision repair protein Pol{beta} is involved in hippocampal neuronal differentiation via a TET-mediated active DNA demethylation during early postnatal stages. Pol{beta} deficiency induced extensive DNA double-strand breaks (DSBs) in hippocampal neurons, and a lesser extent in cortical neurons, during a period in which decreased levels of 5-methylcytosine were observed in genomic DNA. Inhibition of the hydroxylation of 5-methylcytosine by microRNAs miR29a/b-1 expression diminished DSB formation. Conversely, its induction by TET1 overexpression increased DSBs. The damaged hippocampal neurons exhibited aberrant neuronal gene expression profiles and dendrite formation. Behavioral analyses revealed impaired spatial learning and memory in adulthood. Thus, Pol{beta} maintains genome stability in the active DNA demethylation that occurs during postnatal neuronal development, thereby contributing to differentiation and subsequent behavior.

neuroscience↗

bioRxiv2019

Silicon Nanowires for Intracellular Optical Interrogation with Sub-Cellular Resolution

Current techniques for intracellular electrical interrogation are substrate bound and are technically demanding, or lack high spatial resolution. In this work, we use silicon nanowires, which are spontaneously internalized by many cell types, to achieve photo-stimulation with sub-cellular resolution. Myofibroblasts loaded with silicon nanowires remain viable and can undergo cell division. Stimulation of silicon nanowires at separate intracellular locations results in local calcium fluxes. We also show that nanowire-containing myofibroblasts can electrically couple to cardiomyocytes in co-culture and that photo-stimulation of the nanowires increases the spontaneous activation rate in neighboring cardiomyocytes. Finally, we demonstrate that this methodology can be extended to the interrogation of signaling in neuron-glia interactions using nanowire-containing oligodendrocytes.

bioengineering↗

bioRxiv2019

Evaluation of the impact of seasonal variations in photoperiod on the hepatic metabolism of medaka (Oryzias latipes)

Organisms living in temperate regions are sensitive to seasonal variations in the environment; they are known to accumulate energy as fat in their livers during the winter when days are shorter, temperatures are lower, and food is scarce. However, the impact of variations in photoperiod alone on hepatic lipid metabolism has not been well-studied. Therefore, in this study, we analyzed lipid metabolism in the liver of medaka, Oryzias latipes, while varying the length of days at constant temperature. Larger amounts of fatty acids accumulated in the liver after 14 days under short-day conditions than under long-day conditions. Metabolome analysis showed no accumulation of the long-chain unsaturated fatty acids required at low temperatures, but showed a significant accumulation of long-chain saturated fatty acids. Short-day conditions induced decreased levels of succinate, fumarate, and malate in the tricarboxylic acid cycle, decreased expression of PPAR, and decreased accumulation of acylcarnitine, which suggested inhibition of lipolysis. In addition, when a high-fat diet was administered to transparent medaka under short-day conditions, larger amounts of fat accumulated and medaka with fatty liver were efficiently produced. Detailed analysis of the relationship between seasonal changes and hepatic steatosis will be important in the future as hepatic diseases become more prevalent in modern society; the findings obtained in our study will be useful for research studies pertaining to the relationship between photoperiod and disorders such as hepatic steatosis and non-alcoholic steatohepatitis.

physiology↗

bioRxiv2019

An Event-Related Potential Study of Onset Primacy in Visual Change Detection

Onset primacy is a behavioural phenomenon whereby humans identify the appearance of an object (onset) with greater efficiency than other kinds of visual change, such as the disappearance of an object (offset). The default mode hypothesis explains this phenomenon by postulating that the attentional system is optimised for onset detection in its initial state. The present study extended this hypothesis by combining a change detection task and measurement of the P300 event-related potential, which was thought to index the amount of processing resources available to detecting onsets and offsets. In an experiment, while brain activity was monitored by electroencephalography, participants indicated the locations of onsets and offsets under the condition in which they occurred equally often in the same locations across trials. Although there was no reason to prioritise detecting one type of change over the other, onsets were detected more quickly and they evoked a larger P300 than offsets. These results suggest that processing resources are preferentially allocated to onset detection. This biased allocation may be a basis on which the attentional system defaults to the onset detection mode.

neuroscience↗

bioRxiv2019

Targeting of RBM10 to S1-1 Nuclear Bodies: Targeting Sequences and its Biological Significance

RBM10 is an RNA-binding protein that regulates alternative splicing (AS). It localizes to the extra-nucleolar nucleoplasm and S1-1 nuclear bodies (NBs) in the nucleus. We investigated the biological significance of this localization in relation to its molecular function. Our analyses, employing deletion mutants, revealed that RBM10 possesses two S1-1 NB-targeting sequences (NBTSs), one in the KEKE motif region and another in the C2H2 Zn finger (ZnF). These NBTSs act synergistically to localize RBM10 to S1-1 NBs. The C2H2 ZnF not only acts as an NBTS, but is also essential for AS regulation by RBM10. Moreover, RBM10 does not participate in S1-1 NB formation, and without alterations of RBM10 protein levels, its NB-localization changes, increasing as cellular transcriptional activity declines, and vice versa. These results indicate that RBM10 is a transient component of S1-1 NBs and is sequestered in NBs via its NBTSs when cellular transcription decreases. We propose that the C2H2 ZnF exerts its NB-targeting activity when RBM10 is unbound by pre-mRNAs, and that NB-localization of RBM10 is a mechanism to control its AS activity in the nucleus. Note that the previous title of this manuscript was Targeting of RBM10 to S1-1 Nuclear Bodies: Targeting Sequences and its Biological Significance.

molecular biology↗

bioRxiv2018

Effects of Orientation Change during Environmental Learning on Age-Related Difference in Spatial Memory

It has been suggested that older adults suffer a greater degree of decline in environmental learning when navigating in an environment than when reading a map of the environment. However, the two types of spatial learning differ not only in perspectives (i.e., navigation is done with a ground-level perspective; a map is read from an aerial perspective) but also in orientations (i.e., orientations vary during navigation; spatial information is drawn from a single orientation in a map), making it unclear which factor critically affects older adults spatial learning. The present study addressed this issue by having younger and older participants learn the layout of a large-scale environment through an aerial movie that contained changes in orientations from which the environment was depicted. Results showed that older participants memories for the environmental layout were as distorted as those created through a ground-level movie (which involved the same orientation changes), whereas they formed more accurate memories through another aerial movie in which an orientation was fixed. By contrast, younger participants learned the environment equally well from the three movies. Taken together, these findings suggest that there is age-related alteration specifically in the ability to process multiple orientations of an environment while encoding its layout in memory. It is inferred that this alteration stems from functional deterioration of the medial temporal lobe, and possibly that of posterior cingulate areas as well (e.g., the retrosplenial cortex), in late adulthood.

neuroscience↗

bioRxiv2018

A survey of public attitudes towards third-party reproduction in Japan in 2014

Objective: The objective of this study was to examine public attitudes towards third-party reproduction and the disclosure of conception through third-party reproduction.\n\nMethods: We conducted the web-based survey for the public attitude towards third-party reproduction in February 2014. Twenty-five hundred people were recruited with equal segregation of age (20s, 30s, 40s, and 50s) and gender. We analyzed the association between gender, age, infertility, and ethical view using a questionnaire regarding donor sperm, donor oocyte, donor embryo, gestational surrogacy, and disclosure to offspring.\n\nResults: Of the respondents, 36.2% approved and 26.6% disapproved with gamete or embryo donation. The frequency of those who approved was the lowest in females in the 50-59 years age group, and was significantly higher in males or females with infertility. Secondly, 40.9% approved and 21.8% disapproved with gestational surrogacy. The frequency of those who approved gestational surrogacy was higher in males or females with infertility. Thirdly, 46.3% of respondents agreed and 20.4% disagreed with \"offspring have the right to know their origin\". Those who disagreed were primarily in the 50-59 age group of both genders, and disagreement was significantly higher in the infertility group compared with non-infertility group.\n\nConclusion: In this study, public attitudes were affected by gender, age, and experience of infertility. These study findings are important in understanding the attitude towards third-party reproduction and disclosure to the offspring. Respondents having indecisive attitudes were >30%, which might indicate an increased requirement for information and education to enhance the discussion on the ethical consensus on third-party reproduction in Japan.

scientific communication and education↗