The RNA m6A reader YTHDC1 silences retrotransposons and guards ES cell identity.

The RNA modification N6-methyladenosine (m6A) has critical roles in many biological processes1,2. However, the function of m6A in the early phase of mammalian development remains poorly understood. Here we show that the m6A reader YT521-B homology-domain-containing protein 1 (YTHDC1) is required for the maintenance of mouse embryonic stem (ES) cells in an m6A-dependent manner, and that its deletion initiates cellular reprogramming to a 2C-like state. Mechanistically, YTHDC1 binds to the transcripts of retrotransposons (such as intracisternal A particles, ERVK and LINE1) in mouse ES cells and its depletion results in the reactivation of these silenced retrotransposons, accompanied by a global decrease in SETDB1-mediated trimethylation at lysine 9 of histone H3 (H3K9me3). We further demonstrate that YTHDC1 and its target m6A RNAs act upstream of SETDB1 to repress retrotransposons and Dux, the master inducer of the two-cell stage (2C)-like program. This study reveals an essential role for m6A RNA and YTHDC1 in chromatin modification and retrotransposon repression.

Resolving Cell Fate Decisions during Somatic Cell Reprogramming by Single-Cell RNA-Seq.

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs), which is a highly heterogeneous process. Here we report the cell fate continuum during somatic cell reprogramming at single-cell resolution. We first develop SOT to analyze cell fate continuum from Oct4/Sox2/Klf4- or OSK-mediated reprogramming and show that cells bifurcate into two categories, reprogramming potential (RP) or non-reprogramming (NR). We further show that Klf4 contributes to Cd34+/Fxyd5+/Psca+ keratinocyte-like NR fate and that IFN-γ impedes the final transition to chimera-competent pluripotency along the RP cells. We analyze more than 150,000 single cells from both OSK and chemical reprograming and identify additional NR/RP bifurcation points. Our work reveals a generic bifurcation model for cell fate decisions during somatic cell reprogramming that may be applicable to other systems and inspire further improvements for reprogramming.

Effect of RPL27 knockdown on the proliferation and apoptosis of human liver cancer cells.

RPL27 is linked to the development of various diseases including malignant tumors. RPL27 may play an oncogenic function in hepatocellular carcinoma (HCC), but this is unknown. So, the aim of this study was to investigate how the human liver cancer cell lines SNU449 and HepG2 responded to RPL27 knockdown in terms of proliferation and apoptosis. SNU449 and HepG2 were cultured and infected with shCon and shRPL27 lentiviral particles to induce RPL27 knockdown, and then RPL27 expression was detected using qPCR and Western blot. Cell proliferation was measured using CCK8, cell cloning, cell scraping, and transwell migration and invasion, while apoptosis was measured using flow cytometry (FCM). The qPCR revealed that mRNA expression of RPL27 decreased after knocking down RPL27 in cells. The CCK8 and cell cloning assay confirmed that knocking down RPL27 significantly reduced cell viability. The cell scratch assay and transwell assays showed that the proliferation rate decreased after knocking down RPL27. A substantial increase in apoptotic cells was discovered by FCM. According to WB, RPL27 knockdown increased the expression of Bax and Caspase-3 while decreasing the expression of bcl-2. The findings showed that RPL27 knockdown inhibited cell proliferation in SNU449 and HepG2 via inducing apoptosis, proving that RPL27 is a novel gene linked with HCC and is crucial for both proliferation and apoptosis. These outcomes imply that RPL27 may be a potential target for liver cancer diagnosis and therapy.

A glutathione S-transferase GhTT19 determines flower petal pigmentation via regulating anthocyanin accumulation in cotton.

Anthocyanin accumulations in the flowers can improve seed production of hybrid lines, and produce higher commodity value in cotton fibre. However, the genetic mechanism underlying the anthocyanin pigmentation in cotton petals is poorly understood. Here, we showed that the red petal phenotype was introgressed from Gossypium bickii through recombination with the segment containing the R3 bic region in the A07 chromosome of Gossypium hirsutum variety LR compared with the near-isogenic line of LW with white flower petals. The cyanidin-3-O-glucoside (Cy3G) was the major anthocyanin in red petals of cotton. A GhTT19 encoding a TT19-like GST was mapped to the R3 bic site associated with red petals via map-based cloning, but GhTT19 homologue gene from the D genome was not expressed in G. hirsutum. Intriguingly, allelic variations in the promoters between GhTT19LW and GhTT19LR , rather than genic regions, were found as genetic causal of petal colour variations. GhTT19-GFP was found localized in both the endoplasmic reticulum and tonoplast for facilitating anthocyanin transport. An additional MYB binding element found only in the promoter of GhTT19LR , but not in that of GhTT19LW , enhanced its transactivation by the MYB activator GhPAP1. The transgenic analysis confirmed the function of GhTT19 in regulating the red flower phenotype in cotton. The essential light signalling component GhHY5 bonded to and activated the promoter of GhPAP1, and the GhHY5-GhPAP1 module together regulated GhTT19 expression to mediate the light-activation of petal anthocyanin pigmentation in cotton. This study provides new insights into the molecular mechanisms for anthocyanin accumulation and may lay a foundation for faster genetic improvement of cotton.

Study on Spontaneous Reactivation and Aging of Acetylcholinesterase Inhibited by Paraoxon and Malaoxon in Ten Species.

Organophosphorus insecticides (OPs), acting as serine phosphorylating agents in acetylcholinesterase (AChE), are highly effective neurotoxic insecticides. In our previous research, we found that six herbivorous pests and four ladybirds howed significantly higher AChE LC50 values than seven parasitoids and a predator (Epistrophe balteate), and that there was a significant correlation with the corresponding bimolecular rate constant (Ki) value. The Ki value of pests was much smaller than that of natural enemies and had a higher LC50 value.Then, we speculated that the low sensitivity of the pest AChE to OPs may be associated with its higher recovery and lower aging ability. In this work, the I50 and I90 were calculated, to determine the sensibility of AChE in ten representative species, including Plutella xylostella, Prodenia litura, Musca domestica, and Cavia porcellus, to paraoxon and malaoxon. The enzyme activities were measured at various time points, and kinetic calculations were used to obtain their spontaneous reactivation (Ks) and aging (Ka) constants, which were comprehensively compared. We conclude that the Ka and Ks of the AChE inhibited by OPs showed primarily species-specific correlations, and little correlation with the sensitivity to OPs. The differences in the AChE sensitivity to paraoxon among the ten species were much greater than in the sensitivity to malaoxon. Compared to paraoxon, malaoxon was more selective for Cavia porcellus. Coleoptera insects showed a stronger dephosphorylation ability than other insect groups. The recovery ability of phospho-AChE was stronger in mammals than in insects, which could be related to the low sensitivity of the AChE site of action to OPs. The Ka of the AChE inhibited by malaoxon was larger than that inhibited by paraoxon with the corresponding biomaterials, indicating that the OP type had a substantial relationship with the Ka of the AChE. We further discovered that, when insects were inhibited by OP, the tendency of AChE to undergo aging was greater than that of dephosphorylation. Overall, the study provides valuable information on the action mechanism of various OPs on AChE in several species, which could be used to further research into AChE and the potential dangers that organophosphates pose to animals.

1645†nm coherent Doppler wind lidar with a single-frequency Er:YAG laser.

Solid-state single-frequency lasers around 1.6 µm are ideal sources for coherent Doppler wind lidars (CDWLs). A CDWL system with 1645 nm sing-frequency, injection-seeded Er:YAG ceramic laser is demonstrated. The Er:YAG laser based on an "M-shaped" ring resonator operates at pulse repetition frequencies (PRFs) of 300-1000 Hz at room temperature. The maximum single-frequency output energy is 10.1 mJ with a pulse width of 179 ns at 300 Hz. The 1645 nm Er:YAG laser is first used in a long-range CDWL system, and a line of sight (LOS) wind velocity up to 25 km is detected with 90 m range resolution in 0.5 s observation. To verify the reliability of the measurement results, the relationship between detection range, pulse energy, and accumulated numbers is also demonstrated.

Er:YAG MOPA system based on a polarization-multiplexing 4-pass structure.

A 4-pass structure Er:YAG MOPA system at 1645 nm is theoretically and experimentally investigated. In accordance with the theoretical analysis, the 4-pass structure significantly improved the amplification performance. The highest gain is about 4 with 1 mJ incident seed energy. The power fluctuation and beam quality are improved after the amplification.

Single-frequency Q-switched Er:YAG laser with high frequency and energy stability via the Pound-Drever-Hall locking method.

We present an injection-seeding Q-switched 1645 nm Er:YAG ceramic laser with high frequency stability and energy stability by combining the injection-seeding technique and Pound-Drever-Hall technique. 10.31 mJ single-frequency pulses with optimal frequency stability (525 kHz) and relative energy stability (0.52%) at a high pulse repetition rate of 1 kHz are obtained. To the best of our knowledge, this is the highest frequency stability and energy stability so far in a high pulse repetition frequency, large pulse energy, single-frequency Q-switched Er-doped solid laser. This single frequency laser with high stability provides an excellent light source for a coherent lidar system.

High-repetition rate, single-frequency laser with a double Er:YAG ceramics ring cavity.

A high pulse repetition frequency (PRF) single-frequency Er:YAG ceramic ring laser is demonstrated. A double-ceramics ring cavity both end-pumped by a 1532-nm fiber laser is also used to increase the pulse energy. The maximum single-frequency output energies are 21.0 mJ, 18.3 mJ, and 14.4 mJ at the PRF of 500 Hz, 750 Hz, and 1 kHz, respectively. Correspondingly, the pulse widths are 93.2 ns, 106.8 ns, and 130 ns. To the best of our knowledge, this is the highest energy at high PRFs obtained from a single-frequency injection-seeded Er:YAG ceramic laser.

High-energy, single-frequency, Q-switched Er:YAG laser with a double-crystals-end-pumping architecture.

A high-energy, single-frequency, injection-seeded, Q-switched Er:YAG laser oscillating at 1645 nm is demonstrated. For obtaining high output energy, a double-crystals-end-pumping architecture is utilized. The maximum output energies of single-frequency pulses are 12.84 mJ, 16.87 mJ, and 20.3 mJ at pulse repetition rates of 500 Hz, 300 Hz and 200 Hz, respectively. Correspondingly, the pulse widths are 162 ns, 125 ns, and 110 ns, respectively. The half-width of the pulse spectrum at the pulse repetition rate of 200 Hz is 4.59 MHz, measured by using the heterodyne technique, which is 1.14 times transform limited. To the best of our knowledge, 20.3 mJ is the highest energy obtained from a single-frequency, injection-seeded Er:YAG laser.

The mechanism difference between CO2 and pH stimuli for a dual responsive wormlike micellar system.

To indicate the difference between pH and CO2 stimuli mechanisms, a dual responsive system is constructed with the aid of N-[3-(dimethylamino)propyl]docosanamide (NDPD) and sodium salicylate (NaSal), which is responsive to pH and CO2. The dual responsive system is characterized by rheometry, cryo-TEM and 1H NMR spectroscopy. After bubbling CO2 or adjusting the pH, the rheological properties indicate the formation of wormlike micelles. The cyro-TEM images also confirmed wormlike micelles. The effect of temperature is also clarified. By comparing the rheological properties of the wormlike micelles with pH and CO2 stimuli conditions, combined with cryo-TEM and 1H NMR results, the stimuli mechanisms of pH and CO2 to the dual responsive system are shown. Through this work, we expect to deepen our understanding of the responsiveness of a self-assembled system.

High-repetition-rate single-frequency Ho:YAG MOPA system.

A stable, 2.09 µm single-frequency Ho:YAG master oscillator and power amplifier (MOPA) system at a pulse repetition frequency of 1.25 kHz is demonstrated. The maximum output energy of the single-frequency injection-seeded laser is 13.76 mJ, and the corresponding pulse width is 178.9 ns. The seed laser is a continuous-wave Ho:YAG non-planar ring oscillator laser. The half-width of the pulse spectrum is measured to be 2.65 MHz by using the heterodyne technique, which is about 1.06 times Fourier transform limited.

Investigation of Novel Triple-Responsive Wormlike Micelles.

Smart wormlike micelles with stimuli-tunable rheological properties may be useful in a variety of applications, such as in molecular devices and sensors. The formation of triplestimuli-responsive systems so far has been a challenging and important issue. In this work, a novel triplestimuli (photo-, pH-, and thermoresponsive) wormlike micelle is constructed with N-cetyl-N-methylmorpholinium bromide and trans-cinnamic acid (CA). The corresponding multiresponsive behaviors of wormlike micellar system were revealed using cryogenic transmission electron microscopy, a rheometer, and 1H NMR. The rheological properties of wormlike micellar system under different temperatures, pH conditions, and UV irradiation times are measured. As confirmed by 1H NMR, chemical structure of a CA molecule can be altered by the multiple stimulation from an exotic environment. We expect it to be a good model for triple-responsive wormlike micelles, which is helpful to understand the mechanism of triple-responsiveness and widen their applications.

1 kHz single-frequency 2.09 µm Ho:YAG ring laser.

In this paper, we report the experimental realization of a high-repetition-rate single-frequency Ho-doped yttrium aluminum garnet (Ho:YAG) ring laser at 2.09 µm. Single-frequency operation of the ring laser is achieved by injection-seeding with a continuous wave (CW) Ho:YAG non-planar ring oscillator (NPRO) laser. The output energy of the ring laser is 6.24 mJ with a pulse width of 172 ns and a repetition rate of 1 kHz. The beam quality M2-factor is measured to be ∼1.3 at the maximum output energy. The half-width of the pulse spectrum is measured to be 2.61 MHz by a heterodyne technique.

High-energy, stable single-frequency Ho:YAG ceramic amplifier system.

We demonstrate a 2090 nm single-frequency, high-energy, Q-switched Ho:YAG ceramic master oscillator and power amplifier system that contains two-stage amplifiers. The maximum single-frequency pulse energy is 55.64 mJ at a pulse repetition frequency of 200 Hz. The half-width of the pulse spectrum is measured to be 3.96 MHz by a heterodyne technique. To the best of our knowledge, 55.64 mJ is the highest single-frequency output energy obtained from the Ho:YAG laser.

44 mJ, 2.1 µm single-frequency Ho:YAG amplifier.

A single-frequency two-stage amplifier delivering up to 44 mJ at 2.1 µm is demonstrated. The first-stage amplifier is double-end-pumped by a 1.9 µm Tm:YLF laser, and is seeded with a 15 mJ single-frequency Ho:YAG laser operating at 200 Hz. The second-stage amplifier is end-pumped by another 1.9 µm Tm:YLF laser. The output pulse width from the second-stage amplifier is 113 ns, with a beam quality of M2∼1.32.

Stable high-power Er:YAG ceramic single-frequency laser at 1645 nm.

A stable high-power single-frequency laser at 1645 nm from a monolithic Er:YAG ceramic nonplanar ring oscillator (NPRO) was demonstrated. 10.7 W single-frequency laser output was obtained with a slope efficiency of 61.2% and an optical efficiency of 52.1% with respect to incident pump power. The laser always stably operated in single-frequency mode with the pump power increasing from threshold to maximum pump power. When the crystal's set temperature changed from 17.2°C to 26.6°C, the Er:YAG ceramic NPRO had stable single-frequency laser output, and the widest continuous tuning range without mode-hoping was 4.5 GHz. The linewidth of the single-frequency laser was 5.75 kHz. The beam quality M2 factors were 1.23 and 1.24 in x and y directions, respectively.

Single-frequency, injection-seeded Q-switched Ho:YAG ceramic laser pumped by a 1.91µm fiber-coupled LD.

A 2090 nm injection-seeded Q-switched Ho:YAG ceramic laser pumped by a 1.91 µm fiber-coupled LD is demonstrated in this paper. Single-frequency operation of Q-switched Ho:YAG ceramic laser is achieved by injection seeding technique. The maximum output energy of the single-frequency Q-switched Ho:YAG ceramic laser is 14.76 mJ, with a pulse width of 121.6 ns and a repetition rate of 200 Hz. The half-width of the pulse spectrum measured by heterodyne technique is 3.84 MHz. The fluctuation of the center frequency of the pulsed laser is 1.49 MHz (RMS) in 1 hour. As far as we know, this is the first time to report a single-frequency, injection-seeded Ho:YAG ceramic pulsed laser.

Synergistic effect of pH-responsive wormlike micelles based on a simple amphiphile.

Imagine a novel solution that can be switched reversibly from low viscosity to high viscosity with only one additive, upon different commands. To this end, we have developed a simple and effective route to form smart, multi-response wormlike micelles based on a synthesized surfactant, N-cetyl-N,N-diisopropanolammonium bromide (CDIAB). Moreover, we provide new insight into the effects of synergy on this smart wormlike micelle. Rheological measurements were used to study the morphology of the wormlike micelles; (1)H NMR spectroscopy and density functional theory (DFT) calculations were employed to investigate the molecular arrangements and mechanism of the synergy involved in the reversible reactions of pH-response and CO2-response of the micelles in solution. Based on the abovementioned results, it is encouraging to discover that binding energy and electrostatic interaction are the basic driving forces in the formation of wormlike micelles. Moreover, stable viscoelastic behavior was observed in the CDIAB system, with strong binding energy and electrostatic interactions. It is highly anticipated that the synergy observed in this surfactant will be of particular interest due to its novel mechanism and unique properties.

34 mJ Ho:YAG ceramic master oscillator and power amplifier laser at 2097 nm.

We demonstrated a 2097 nm Ho:YAG ceramic master oscillator and power amplifier system pumped by Tm:YLF lasers. Laser characteristics of 0.6 at.% and 0.4 at.% Ho:YAG ceramics were studied in CW and Q-switched modes. An output energy of 20.6 mJ at a pulse repetition frequency of 200 Hz was achieved from the master oscillator. The pulse energy was amplified to 34 mJ by the Ho:YAG ceramic amplifier with a pulse duration of 54 ns.