Search

MYOD-induced microRNA-494-3p expression inhibits fast oxidative myotube formation by downregulating myosin heavy chain 2 (MYH2) in human induced pluripotent stem cells (hiPSCs) during skeletal myogenesis. However, the molecular mechanisms regulating MYH2 expression via miR-494-3p remain unknown. Here, using bioinformatic analyses, we show that miR-494-3p potentially targets the transcript of the E1A-binding protein p300 at its 3′-untranslated region (UTR). Myogenesis in hiPSCs with the Tet/ON-myogenic differentiation 1 (MYOD1) gene (MyoD-hiPSCs) was induced by culturing them in doxycycline-supplemented differentiation medium for 7 days. p300 protein expression decreased after transient induction of miR-494-3p during myogenesis. miR-494-3p mimics decreased the levels of p300 and its downstream targets MYOD and MYH2 and myotube formation efficiency. p300 knockdown decreased myotube formation efficiency, MYH2 expression, and basal oxygen consumption rate. The binding of miR-494-3p to the wild type p300 3′-UTR, but not the mutated site, was confirmed using luciferase assay. Overexpression of p300 rescued the miR-494-3p mimic-induced phenotype in MyoD-hiPSCs. Moreover, miR-494-3p mimic reduced the levels of p300, MYOD, and MYH2 in skeletal muscles in mice. Thus, miR-494-3p might modulate MYH2 expression and fast oxidative myotube formation by directly regulating p300 levels during skeletal myogenesis in MyoD-hiPSCs and murine skeletal muscle tissues. [ABSTRACT FROM AUTHOR]

Two types of high-energy events have been detected from thunderstorms. One is "terrestrial gamma-ray flashes" (TGFs), sub-millisecond emissions coinciding with lightning discharges. The other is minute-lasting "gamma-ray glows". Although both phenomena are thought to originate from relativistic runaway electron avalanches in strong electric fields, the connection between them is not well understood. Here we report unequivocal simultaneous detection of a gamma-ray glow termination and a downward TGF, observed from the ground. During a winter thunderstorm in Japan on 9 January 2018, our detectors caught a gamma-ray glow, which moved for ~100 s with ambient wind, and then abruptly ceased with a lightning discharge. Simultaneously, the detectors observed photonuclear reactions triggered by a downward TGF, whose radio pulse was located within ~1 km from where the glow ceased. It is suggested that the highly-electrified region producing the glow was related to the initiation of the downward TGF. Thunderstorms are thought to produce two types of high-energy emissions, terrestrial gamma-ray flashes and gamma-ray glows however due to the difficulty in their observation the exact relation between the two is still not well-understood. Here, the authors report the simultaneous detection of a gamma-ray glow and a downward terrestrial gamma-ray flash suggesting the origin of the two phenomena are related. [ABSTRACT FROM AUTHOR]

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that 'Electron Tracking Compton Camera' (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics. [ABSTRACT FROM AUTHOR]