Untangling the gordian knot: The intertwining interactions between developmental hormone signaling and epigenetic mechanisms in insects

Hormones control developmental and physiological processes, often by regulating the expression of multiple genes simultaneously or sequentially. Crosstalk between hormones and epigenetics is pivotal to dynamically coordinate this process. Hormonal signals can guide the addition and removal of epigenetic marks, steering gene expression. Conversely, DNA methylation, histone modifications and non-coding RNAs can modulate regional chromatin structure and accessibility and regulate the expression of numerous (hormone-related) genes. Here, we provide a review of the interplay between the classical insect hormones, ecdysteroids and juvenile hormones, and epigenetics. We summarize the mode-of-action and roles of these hormones in post-embryonic development, and provide a general overview of epigenetic mechanisms. We then highlight recent advances on the interactions between these hormonal pathways and epigenetics, and their involvement in development. Furthermore, we give an overview of several 'omics techniques employed in the field. Finally, we discuss which questions remain unanswered and possible avenues for future research.

Genetic and epigenetic determinants of reactivation of Mecp2 and the inactive X chromosome in neural stem cells

Rett syndrome may be treated by reactivating the silent copy of Mecp2 from the inactive X chromosome in female cells. Most studies that model Mecp2 reactivation have used mouse fibroblasts rather than neural cells, which would be critical for phenotypic reversal, and rely on fluorescent reporters that lack adequate sensitivity. Here, we present a mouse model based on a dual bioluminescent and fluorescent reporter to assess the level of reactivation of Mecp2 and the inactive X chromosome by treating neural stem cells with 5-azacytidine and Xist knockdown. We show that reactivation of Mecp2 and other X-linked genes correlates with CpG density, with distance from escapees, and, very strongly, with the presence of short interspersed nuclear elements. In addition, X-linked genes reactivated in neural stem cells overlap substantially with early reactivating genes by induced pluripotent stem cell reprogramming of fibroblasts or neuronal progenitors, indicating that X chromosome reactivation follows similar paths regardless of the technique or cell type used.

Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu

The gravity field of a small body provides insight into its internal mass distribution. We used two approaches to measure the gravity field of the rubble-pile asteroid (101955) Bennu: (i) tracking and modeling the spacecraft in orbit about the asteroid and (ii) tracking and modeling pebble-sized particles naturally ejected from Bennu's surface into sustained orbits. These approaches yield statistically consistent results up to degree and order 3, with the particle-based field being statistically significant up to degree and order 9. Comparisons with a constant-density shape model show that Bennu has a heterogeneous mass distribution. These deviations can be modeled with lower densities at Bennu's equatorial bulge and center. The lower-density equator is consistent with recent migration and redistribution of material. The lower-density center is consistent with a past period of rapid rotation, either from a previous Yarkovsky-O'Keefe-Radzievskii-Paddack cycle or arising during Bennu's accretion following the disruption of its parent body.

Graphene-Quantum Dot Hybrid Photodetectors with Low Dark-Current Readout

Graphene-based photodetectors have shown responsivities up to 10⁸ A/W and photoconductive gains up to 10⁸ electrons per photon. These photodetectors rely on a highly absorbing layer in close proximity to graphene, which induces a shift of the graphene chemical potential upon absorption, hence modifying its channel resistance. However, due to the semimetallic nature of graphene, the readout requires dark currents of hundreds of microamperes up to milliamperes, leading to high power consumption needed for the device operation. Here, we propose a different approach for highly responsive graphene-based photodetectors with orders of magnitude lower dark-current levels. A shift of the graphene chemical potential caused by light absorption in a layer of colloidal quantum dots induces a variation of the current flowing across a metal-insulator-graphene diode structure. Owing to the low density of states of graphene near the neutrality point, the light-induced shift in chemical potential can be relatively large, dramatically changing the amount of current flowing across the insulating barrier and giving rise to an alternative gain mechanism. This readout requires dark currents of hundreds of nanoamperes up to a few microamperes, orders of magnitude lower than that of other graphene-based photodetectors, while keeping responsivities of ∼70 A/W in the infrared, almost 2 orders of magnitude higher than that of established germanium on silicon and indium gallium arsenide infrared photodetectors. This makes the device appealing for applications where high responsivity and low power consumption are required.

Flexible graphene photodetectors for wearable fitness monitoring

Wearable health and wellness trackers based on optical detection are promising candidates for public health uses due to their noninvasive tracking of vital health signs. However, so far, the use of rigid technologies hindered the ultimate performance and form factor of the wearable. Here, we demonstrate a new class of flexible and transparent wearables based on graphene sensitized with semiconducting quantum dots (GQD). We show several prototype wearable devices that are able to monitor vital health signs noninvasively, including heart rate, arterial oxygen saturation (SpO2), and respiratory rate. Operation with ambient light is demonstrated, offering low-power consumption. Moreover, using heterogeneous integration of a flexible ultraviolet (UV)-sensitive photodetector with a near-field communication circuit board allows wireless communication and power transfer between the photodetectors and a smartphone, offering battery-free operation. This technology paves the way toward seamlessly integrated wearables, and empowers the user through wireless probing of the UV index.

High-Mobility, Wet-Transferred Graphene Grown by Chemical Vapor Deposition

We report high room-temperature mobility in single-layer graphene grown by chemical vapor deposition (CVD) after wet transfer on SiO₂ and hexagonal boron nitride (hBN) encapsulation. By removing contaminations, trapped at the interfaces between single-crystal graphene and hBN, we achieve mobilities up to ∼70000 cm² V^-1 s^-1 at room temperature and ∼120 000 cm² V^-1 s^-1 at 9K. These are more than twice those of previous wet-transferred graphene and comparable to samples prepared by dry transfer. We also investigate the combined approach of thermal annealing and encapsulation in polycrystalline graphene, achieving room-temperature mobilities of ∼30 000 cm² V^-1 s^-1. These results show that, with appropriate encapsulation and cleaning, room-temperature mobilities well above 10 000 cm² V^-1 s^-1 can be obtained in samples grown by CVD and transferred using a conventional, easily scalable PMMA-based wet approach.

Small-scale density variations in the lunar crust revealed by GRAIL

Data from the Gravity Recovery and Interior Laboratory (GRAIL) mission have revealed that ~98% of the power of the gravity signal of the Moon at high spherical harmonic degrees correlates with the topography. The remaining 2% of the signal, which cannot be explained by topography, contains information about density variations within the crust. These high-degree Bouguer gravity anomalies are likely caused by small-scale (10's of km) shallow density variations. Here we use gravity inversions to model the small-scale three-dimensional variations in the density of the lunar crust. Inversion results from three non-descript areas yield shallow density variations in the range of 100-200 kg/m3. Three end-member scenarios of variations in porosity, intrusions into the crust, and variations in bulk crustal composition were tested as possible sources of the density variations. We find that the density anomalies can be caused entirely by changes in porosity. Characteristics of density anomalies in the South Pole-Aitken basin also support porosity as a primary source of these variations. Mafic intrusions into the crust could explain many, but not all of the anomalies. Additionally, variations in crustal composition revealed by spectral data could only explain a small fraction of the density anomalies. Nevertheless, all three sources of density variations likely contribute. Collectively, results from this study of GRAIL gravity data, combined with other studies of remote sensing data and lunar samples, show that the lunar crust exhibits variations in density by ±10% over scales ranging from centimeters to 100's of kilometers.

Integrating an electrically active colloidal quantum dot photodiode with a graphene phototransistor

The realization of low-cost photodetectors with high sensitivity, high quantum efficiency, high gain and fast photoresponse in the visible and short-wave infrared remains one of the challenges in optoelectronics. Two classes of photodetectors that have been developed are photodiodes and phototransistors, each of them with specific drawbacks. Here we merge both types into a hybrid photodetector device by integrating a colloidal quantum dot photodiode atop a graphene phototransistor. Our hybrid detector overcomes the limitations of a phototransistor in terms of speed, quantum efficiency and linear dynamic range. We report quantum efficiencies in excess of 70%, gain of 10⁵ and linear dynamic range of 110 dB and 3 dB bandwidth of 1.5 kHz. This constitutes a demonstration of an optoelectronically active device integrated directly atop graphene and paves the way towards a generation of flexible highly performing hybrid two-dimensional (2D)/0D optoelectronics.

The combination of fast photo-response and high gain plays a pivotal role in photodetector devices. Here the authors combine a colloidal quantum dot photodiode with a graphene phototransistor to overcome the speed, quantum efficiency and linear dynamic range limitations of available phototransistors.

Immunohistological Description of Nongestational Ovarian Choriocarcinoma in Two Female Mice With Conditional Loss of Trp53 Driven by the Tie2 Promoter

Nongestational ovarian choriocarcinoma (NGCO) is a tumor of germ cell origin seldom described in nonhuman species. Few spontaneous cases are reported in macaques and mice, with the B6C3F1 strain overrepresented. This report describes 2 cases of ovarian choriocarcinoma in nulliparous female mice with conditional loss of Trp53 under the Tie2 promoter. The mouse line was maintained on a mixed genetic background including Crl: CD1(ICR) and 129X1/SvJ strains. In both cases, affected ovary was partially replaced by blood-filled lacunae lined by neoplastic trophoblast-like giant cells. Immunohistochemically, neoplastic cells expressed folate-binding protein and prolactin and were invariably negative for p53. To the authors’ knowledge, this is the first report characterizing this entity in a genetically engineered mouse (GEM) line. Considering that germ cells (the cell population from which NGCO originates) constitutively express Tie2 receptor, it can be speculated that Tie2-driven deletion of Trp53 may have played a role in the development of these tumors.

Tissue-wide overexpression of alpha-T-catenin results in aberrant trophoblast invasion but does not cause embryonic mortality in mice

Transcriptional activation of CTNNA3, encoding αT-catenin, by the Y153H mutated form of the human STOX1 transcription factor was proposed to be responsible for altered fetal trophoblast invasion into the maternal endometrium during placentation in pre-eclampsia. Here we have generated a mouse model to investigate the in vivo effects of ectopic αT-catenin expression on trophoblast invasion. Histological analysis was used to determine the invasive capacities of trophoblasts from transgenic embryos, as well as proliferation rates of spongiotrophoblasts in the junctional zone. Augmented expression of αT-catenin reduced the number of invading trophoblasts but did not cause embryonic mortality. The, αT-catenin positive cells could still invade into the decidual layer and migrated as deeply as wild-type trophoblasts. Furthermore, the junctional zone is enlarged in placentas of mice overexpressing αT-catenin due to hyperproliferation of the residing spongiotrophoblasts, suggesting a pivotal role of αT-catenin levels in the control of the proliferative versus invasive state of trophoblasts during placentation. Our study provides, for the first time, in vivo data on the effects of increased levels of αT-catenin in the placenta.

Predicting the wetting dynamics of a two-liquid system

We propose a new theoretical model of dynamic wetting for systems comprising two immiscible liquids, in which one liquid displaces another from the surface of a solid. Such systems are important in many industrial processes and the natural world. The new model is an extension of the molecular-kinetic theory of wetting and offers a way to predict the dynamics of a two-liquid system from the individual wetting dynamics of its parent liquids. We also present the results of large-scale molecular dynamics simulations for one- and two-liquid systems and show them to be in good agreement with the new model. Finally, we show that the new model is consistent with the limited data currently available from experiment.

Can we predict the spreading of a two-liquid system from the spreading of the corresponding liquid-air systems?

We present new data obtained from the spreading of a series of oil droplets, on top of a hydrophobic grafted silicon substrate, in air and immersed in water. We follow the contact angle and radius dynamics of hexane, dodecane, hexadecane, dibutyl phthalate, and squalane from the first milliseconds to approximately 1 s. Analysis of the images allows us to make several hundred contact angle and droplet radius measurements with great accuracy. The G-Dyna (Seveno et al. Langmuir 2010, 25, 13034) software is then used to fit the data with one of the wetting theories, the molecular-kinetic theory (MKT) (Blake et al. J. Colloid Interface Sci.1969, 30, 421), which takes into account the dissipation at the three-phase zone at the contact line. This theory allows us to extract the coefficient of friction of the contact line, which expresses the relationship between the driving force, that is, the unbalanced Young force, and the contact-line velocity V. It is first shown that the MKT is appropriate to describe the experimental data and then that the contact-line friction is a linear function of the viscosity as theoretically predicted. This is checked for oil-air and oil-water systems. A linear relation between the contact-line friction measured in oil-water systems and the contact-line frictions of the parent single liquid system seems plausible. To the best of our knowledge, this is the first trial to establish a link between the dynamics of wetting in liquid-liquid and in liquid-air systems.

αT-Catenin: a novel tissue-specific β-catenin-binding protein mediating strong cell-cell adhesion

Cadherins are major cell-cell adhesion proteins whose cytoplasmic domains bind to catenin proteins. Strong intercellular adhesion depends on linkage of the cadherin/catenin complex to the actin cytoskeleton via α-catenin. To date, it is not clear how different cell types achieve the variable strength of cell-cell adhesion clearly needed in a multicellular organism. Here, we report the cloning and molecular characterization of αT(testis)-catenin, a novel human cDNA encoding a protein with homology to both human αE(epithelial)-catenin and αN(neural)-catenin. Although originally discovered in testis, αT-catenin is expressed in other tissues, the highest levels being observed in heart. Immunohistochemical analysis showed human αT-catenin localization at intercalated discs of cardiomyocytes and in peritubular myoid cells of testis. In cells transfected with αT-catenin cDNA, interaction with β-catenin was demonstrated by co-immunoprecipitation. Transfection of α-catenin-deficient colon carcinoma cells recruited E-cadherin and β-catenin to cell-cell contacts and functional cadherin-mediated cell-cell adhesion was restored in this way. Moreover, compaction of these cells was at least as prominent as in the case of cells expressing endogenous αE-catenin. We propose that αT-catenin is necessary for the formation of stretch-resistant cell-cell adhesion complexes, in particular, muscle cells.

Evaluation of the effects of mivacurium chloride on hemodynamics and left ventricular function in patients with coronary artery disease undergoing abdominal aortic surgery

OBJECTIVE

To determine the effects of two doses of mivacurium chloride on hemodynamics and left ventricular function in patients with documented coronary artery disease undergoing aortic surgery.

DESIGN

A prospective study with the dose of mivacurium determined by randomization.

SETTING

Induction area at a university hospital.

PARTICIPANTS

Twenty consecutive patients undergoing aortic surgery with clinically and/or angiographically documented coronary artery disease.

INTERVENTIONS

Intravenous administration of mivacurium chloride.

MEASUREMENTS AND MAIN RESULTS

Induction of anesthesia was performed with midazolam and fentanyl. Two different doses of mivacurium chloride, 0.15 mg/kg (n = 10) and 0.2 mg/kg (n = 10; 2 and 2.5 ED95; respectively), were administered as a single bolus injection over a 60-second period in the absence of any surgical stimulation. In addition to standard hemodynamic monitoring, pulmonary artery catheterization and transesophageal echocardiography were used. The occurrence of myocardial ischemia was monitored using both a computerized three-lead ST-segment analysis system and the echocardiographic assessment of regional wall motion. No change in heart rate, mean arterial pressure, pulmonary capillary wedge pressure, cardiac output, and global left ventricular function was noted after administration of mivacurium with the two doses studied. No ST-segment change or new segmental wall motion abnormality was noted in either group.

CONCLUSION

Mivacurium chloride, when injected over a 60-second period, preserves global and regional myocardial function in patients with documented coronary artery disease undergoing noncardiac surgery.