Single-cell transcriptomic resolution of stem cells and their developmental trajectories in the hippocampus reveals epigenetic control of cell state perseverance

Despite conceptual research on hippocampus development and the application of single-cell-resolved technologies, the nature and maturation of its diverse progenitor populations are unexplored. The chromatin modifier DOT1L balances progenitor proliferation and differentiation, and conditional loss-of-function mice featured impaired hippocampus development. We applied single-cell RNA sequencing on DOT1L-mutant mice and explored cell trajectories in the E16.5 hippocampus. We resolved in our data five distinct neural stem cell populations with the developmental repertoire to specifically generate the cornu ammonis (CA) 1 field and the dentate gyrus (DG). Within the two developing CA1- and CA3-fields, we identified two distinct maturation states and we thus propose CA1- and CA3-differentiation along the radial axis. In the developing hippocampus, DOT1L is primarily involved in the proper development of CA3 and the DG, and it serves as a state-preserving epigenetic factor that orchestrates the expression of several important transcription factors that impact neuronal differentiation and maturation.

ERECTA family signaling constrains CLAVATA3 and WUSCHEL to the center of the shoot apical meristem

The shoot apical meristem (SAM) is a reservoir of stem cells that gives rise to all post-embryonic aboveground plant organs. The size of the SAM remains stable over time due to a precise balance of stem cell replenishment versus cell incorporation into organ primordia. The WUSCHEL (WUS)/CLAVATA (CLV) negative feedback loop is central to SAM size regulation. Its correct function depends on accurate spatial expression of WUS and CLV3. A signaling pathway, consisting of ERECTA family (ERf) receptors and EPIDERMAL PATTERNING FACTOR LIKE (EPFL) ligands, restricts SAM width and promotes leaf initiation. While ERf receptors are expressed throughout the SAM, EPFL ligands are expressed in its periphery. Our genetic analysis demonstrated that ERfs and CLV3 synergistically regulate the size of the SAM, and wus is epistatic to erfs. Furthermore, activation of ERf signaling with exogenous EPFLs resulted in a rapid decrease of CLV3 and WUS expression. ERf-EPFL signaling inhibits expression of WUS and CLV3 in the periphery of the SAM, confining them to the center. These findings establish the molecular mechanism for stem cell positioning along the radial axis.

New Insights into Development of Female Reproductive Tract—Hedgehog-Signal Response in Wolffian Tissues Directly Contributes to Uterus Development

The reproductive tract in mammals emerges from two ductal systems during embryogenesis: Wolffian ducts (WDs) and Mullerian ducts (MDs). Most of the female reproductive tract (FRT) including the oviducts, uterine horn and cervix, originate from MDs. It is widely accepted that the formation of MDs depends on the preformed WDs within the urogenital primordia. Here, we found that the WD mesenchyme under the regulation of Hedgehog (Hh) signaling is closely related to the developmental processes of the FRT during embryonic and postnatal periods. Deficiency of Sonic hedgehog (Shh), the only Hh ligand expressed exclusively in WDs, prevents the MD mesenchyme from affecting uterine growth along the radial axis. The in vivo cell tracking approach revealed that after WD regression, distinct cells responding to WD-derived Hh signal continue to exist in the developing FRT and gradually contribute to the formation of various tissues such as smooth muscle, endometrial stroma and vascular vessel, in the mouse uterus. Our study thus provides a novel developmental mechanism of FRT relying on WD.

Anisotropic Psychophysical Trends in the Discrimination of Tactile Direction in a Precision Grip

Tactile cues arising from interactions with objects have a sense of directionality which affects grasp. Low latency responses to varied grip perturbations indicate that grasp safety margins are exaggerated in certain directions and conditions. In a grip with the ulnar-radial axis vertical, evidence suggests that distal and downward directions are more sensitive to task parameters and have larger safety margins. This suggests that, for the purpose of applying forces with the fingers, reference frames with respect to the hand and gravity are both in operation. In this experiment, we examined human sensitivities to the direction of tactile movement in the context of precision grip in orientations either orthogonal to or parallel to gravity. Subjects performed a two-alternative-forced-choice task involving a textured cube which moved orthogonal to their grip axis. Subjects’ arms were placed in a brace that allowed for finger movement but minimized arm movement. Movement of thumb and index joints were monitored via PhaseSpace motion capture. The subject was presented with a textured cube and instructed to lightly grasp the cube, as if it were slipping. In each trial the object was first translated 1 cm in 0° (proximal), 90° (radial), 180° (distal), or 270° (ulnar) and returned to its origin. This primary stimulus was immediately followed by a 10 mm secondary stimulus at a random 5° interval between −30° and 30° of the primary stimulus. Response from the subject after each pair of stimuli indicated whether the test direction felt the same as or different from the primary stimulus. Traditional bias and sensitivity analyses did not provide conclusive results but suggested that performance is best in the ulnar-radial axis regardless of gravity. Modeling of the response curve generated a detection threshold for each primary stimulus. Lower thresholds, indicating improved detection, persisted in the ulnar-radial axis. Anisotropic thresholds of increased detection appear to coincide with digit displacement and appear to be independent of the grasp orientation.

Postsynaptic integrative properties of dorsal CA1 pyramidal neuron subpopulations

The population activity of CA1 pyramidal neurons (PNs) segregates along anatomical axes with different behaviors, suggesting that CA1 PNs are functionally subspecialized based on somatic location. In dorsal CA1, spatial encoding is biased toward CA2 (CA1c) and in deep layers of the radial axis. In contrast, nonspatial coding peaks toward subiculum (CA1a) and in superficial layers. While preferential innervation by spatial vs. nonspatial input from entorhinal cortex (EC) may contribute to this specialization, it cannot fully explain the range of in vivo responses. Differences in intrinsic properties thus may play a critical role in modulating such synaptic input differences. In this study we examined the postsynaptic integrative properties of dorsal CA1 PNs in six subpopulations along the transverse (CA1c, CA1b, CA1a) and radial (deep, superficial) axes. Our results suggest that active and passive properties of deep and superficial neurons evolve over the transverse axis to promote the functional specialization of CA1c vs. CA1a as dictated by their cortical input. We also find that CA1b is not merely an intermediate mix of its neighbors, but uniquely balances low excitability with superior input integration of its mixed input, as may be required for its proposed role in sequence encoding. Thus synaptic input and intrinsic properties combine to functionally compartmentalize CA1 processing into at least three transverse axis regions defined by the processing schemes of their composite radial axis subpopulations. NEW & NOTEWORTHY There is increasing interest in CA1 pyramidal neuron heterogeneity and the functional relevance of this diversity. We find that active and passive properties evolve over the transverse and radial axes in dorsal CA1 to promote the functional specialization of CA1c and CA1a for spatial and nonspatial memory, respectively. Furthermore, CA1b is not a mean of its neighbors, but features low excitability and superior integrative capabilities, relevant to its role in nonspatial sequence encoding.

ERECTA family signaling constrains CLAVATA3 and WUSCHEL to the center of the shoot apical meristem

The shoot apical meristem (SAM) is a reservoir of stem cells that gives rise to all post-embryonic aboveground plant organs. The size of the SAM remains stable over time due to a precise balance of stem cell replenishment versus cell incorporation into organ primordia. The WUSCHEL (WUS)/CLAVATA (CLV) negative feedback loop is central to SAM size regulation. Its correct function depends on accurate spatial expression of WUS and CLV3. A signaling pathway, consisting of ERECTA family (ERf) receptors and EPIDERMAL PATTERNING FACTOR LIKE (EPFL) ligands, restricts SAM width and promotes leaf initiation. While ERf receptors are expressed throughout the SAM, EPFL ligands are expressed in its periphery. Our genetic analysis demonstrated that ERfs and CLV3 synergistically regulate the size of the SAM, and wus is epistatic to erfs. Furthermore, activation of ERf signaling with exogenous EPFLs resulted in a rapid decrease of CLV3 and WUS expression. ERf-EPFL signaling inhibits expression of WUS and CLV3 in the periphery of the SAM, confining them to the center. These findings establish the molecular mechanism for stem cell positioning along the radial axis.Summary statementERf signaling restricts the width of the shoot apical meristem, a structure which generates aboveground plant organs, by inhibiting expression of two principal regulators, CLV3 and WUS, at its periphery.

Diagnostics of dusty plasma properties in planar magnetron sputtering device

The effect of Al dust particles on glow discharge regions, dischargevoltage, discharge current, plasma potential, floating potential,electron density and electron temperature in planar magnetronsputtering device has been studied experimentally. Four cylindricalLangmuir probes were employed to measure plasma parameters atdifferent point on the radial axis of plasma column. The resultsshows the present of Al dust causes to increase the discharge voltageand reduce the discharge current. There are two electron groups inthe present and absent of Al dust particles. The radial profiles ofplasma parameters in the present of dust are non- uniform. Thefloating potential of probe becomes more negatively while theplasma potential becomes positive when the dust immersed intoplasma region. The electron density increases in the present of dustparticle which lead to decreases the electron temperature.

Patterning the Axes: A Lesson from the Root

How the body plan is established and maintained in multicellular organisms is a central question in developmental biology. Thanks to its simple and symmetric structure, the root represents a powerful tool to study the molecular mechanisms underlying the establishment and maintenance of developmental axes. Plant roots show two main axes along which cells pass through different developmental stages and acquire different fates: the root proximodistal axis spans longitudinally from the hypocotyl junction (proximal) to the root tip (distal), whereas the radial axis spans transversely from the vasculature tissue (centre) to the epidermis (outer). Both axes are generated by stereotypical divisions occurring during embryogenesis and are maintained post-embryonically. Here, we review the latest scientific advances on how the correct formation of root proximodistal and radial axes is achieved.

Anatomical Study of Periosteal Vascularization of the Forearm: Design of Vascularized Periosteal Flaps

Introduction Vascularized periosteal flaps (VPFs) have proven to be a useful technique for the treatment of unfavorable biological situations in children, with excellent results due to their osteogenic potential. The objective of this work is to present a detailed anatomical description of the periosteal vascularization of the radius and ulna, as well as the design of the forearm VPFs. Methods Anatomical study with 10 fresh-frozen specimens with antegrade injection of green colored latex. Periosteal branches of the radius and ulna, septocutaneous branches, and muscular branches were dissected. The size of the pre and postdissection flaps was measured, as well as the length of the vascular pedicles. Results The four vascular axes studied were the anterior interosseous vascular axis (AIA), radial axis (RA), ulnar axis (UA), and posterior interosseous vascular axis (PIA). The AIA (volar-radial VPF): an average of 16.2 periosteal branches were obtained, with a mean distance of 6.6 mm between them. The mean size of the VPF was 41.3 cm2 pre-dissection and 32.4 cm2 post-dissection. The average pedicle length was 16.1 cm. Vascular RA (radial VPF): an average of 20.8 branches was found, with a mean VPF size of 54.8 cm2predissection, and 39.3 cm2 post-dissection. The average pedicle length was 20.2 cm. Vascular PIA (dorsal-ulnar VPF): an average of 12.8 periosteal branches were obtained, with the mean VPF size being 26.2 cm2 pre-dissection and 20.4 cm2 post-dissection. The average pedicle length 12.6 cm. Vascular UA (ulnar VPF): an average of 10.2 periosteal branches were obtained with a mean VPF size of 37.5 cm2 pre-dissection and 28.2 cm2 post-dissection. of the average pedicle length was 14.8 cm. Conclusions We have described four new VPFs, with the most useful and versatile being the dorsal-ulnar VPF, based on the PIA, and the volar-radial, based on the AIA. The main advantages of these flaps with respect to microsurgical techniques are the simplicity and speed of the technique, its elasticity and adaptability to the recipient bed, as well as its versatility.