Basal Processes Research Articles

Two new species of Cerapanorpa (Mecoptera, Panorpidae) from the Qinling and Minshan mountains.

Two new species of Cerapanorpa Gao, Ma & Hua, 2016 are described from the Qinling and Minshan mountains, respectively. Cerapanorpa qinlingensissp. nov. can be readily distinguished from its congeners by the elongate hypovalves and the extremely developed basal process of gonostylus in male genitalia. Cerapanorpa minshanasp. nov. is characterized by its bifurcated parameres and a cluster of long black bristles on the inner apex of the gonocoxite. The number of species of Cerapanorpa is raised to 21. An updated key to species of Cerapanorpa is presented.

Photoreceptor progenitor dynamics in the zebrafish embryo retina and its modulation by primary cilia and N-cadherin.

Photoreceptor cells of the vertebrate neural retina originate in the neuroepithelium, and like other neurons, must undergo cell body translocation and polarity transitions to acquire their final functional morphology, which includes features of neuronal and epithelial cells. We analyzed this process in detail in zebrafish embryos using in vivo confocal microscopy and electron microscopy. Photoreceptor progenitors were labeled by the transgenic expression of enhanced green fluorescent protein under the regulation of the photoreceptor-specific promoter crx, and structures of interest were disrupted using morpholino oligomers to knock-down specific genes. Photoreceptor progenitors detached from the basal retina at pre-mitotic stages, rapidly retracting a short basal process as the cell body translocated apically. They remained at an apical position indefinitely to form the outer nuclear layer (ONL), initially extending and retracting highly dynamic neurite-like processes, tangential to the apical surface. Many photoreceptor progenitors presented a short apical primary cilium. The number and length of these cilia was gradually reduced until nearly disappearing around 60 hpf. Their disruption by knocking-down ift88 and elipsa caused a notorious defect on basal process retraction. To assess the role of cell adhesion in the organization of photoreceptor progenitors, we knocked-down cdh2/N-cadherin and observed the cell behavior by time-lapse microscopy. The ectopic photoreceptor progenitors initially migrated in an apparent random manner, profusely extending cell processes, until they encountered other cells to establish cell rosettes in which they stayed, acquiring photoreceptor-like polarity. Altogether, our observations indicate a complex regulation of photoreceptor progenitor dynamics to form the retinal ONL, previous to the post-mitotic maturation stages.

UPLC-MS metabolomics provides insights into the differences between black- and white-shelled Pacific oysters Crassostrea gigas

A variety of shell colors are one of the most fundamental characteristics of molluscs, which have importantly ecological and economic significance. The Pacific oyster Crassostrea gigas is distributed in many sea areas around the world and also an aquacultured mollusc with high nutritional value. In this study, the whole soft body and the mantle tissue of black-shelled Pacific oyster (BSO) and white-shelled Pacific oyster (WSO) with starkly different melanin contents were compared, and the differences in physiology and metabolism between BSO and WSO were analyzed. The results of physiological indicators suggested BSO show more melanin, more dry matter, more crude lipid content, and stronger ability to scavenge free radicals than WSO. The altered metabolites of glycerophospholipids, fatty acyls, and steroids revealed different regulatory mechanisms of lipids. The correlation analysis of metabolomics and previously published RNAseq data suggested that BSO and WSO mainly differed in the basal metabolic processes, such as lipid, amino acid and purine metabolisms. This study provides insights into the changes in the physiological indictors and the metabolites of oysters with varying melanin content.

Neurogenesis of medium spiny neurons in the nucleus accumbens continues into adulthood and is enhanced by pathological pain

In mammals, most adult neural stem cells (NSCs) are located in the ventricular–subventricular zone (V-SVZ) along the wall of the lateral ventricles and they are the source of olfactory bulb interneurons. Adult NSCs exhibit an apico-basal polarity; they harbor a short apical process and a long basal process, reminiscent of radial glia morphology. In the adult mouse brain, we detected extremely long radial glia-like fibers that originate from the anterior–ventral V-SVZ and that are directed to the ventral striatum. Interestingly, a fraction of adult V-SVZ-derived neuroblasts dispersed in close association with the radial glia-like fibers in the nucleus accumbens (NAc). Using several in vivo mouse models, we show that newborn neurons integrate into preexisting circuits in the NAc where they mature as medium spiny neurons (MSNs), i.e., a type of projection neurons formerly believed to be generated only during embryonic development. Moreover, we found that the number of newborn neurons in the NAc is dynamically regulated by persistent pain, suggesting that adult neurogenesis of MSNs is an experience-modulated process.

Compensating for changes in heart muscle resting heat production in a microcalorimeter.

The heat production of cardiac muscle, determined by calorimetry, can be used as a measure of cardiac metabolism. However, heat produced while a muscle is actively-shortening, thereby performing force-length work, comprises both active and basal metabolic processes. In this paper, we present a method for post-experimental processing of calorimetric measurements of muscle heat production, that uncovers and compensates for the measured basal heat rate during work. In this method, the relationships between muscle length, velocity of length change and muscle heat output are coupled with a simulation of the measurement instrument, providing a model-based estimate of change of measured basal heat while the muscle is performing work. We demonstrate the use of this technique in an experiment conducted on a working cardiac muscle sample. The ability to identify the various components of heat release in these muscles provides useful insight into their mechanical and energetic capabilities.

Adiposity covaries with signatures of asymmetric feedback learning during adaptive decisions.

Unhealthy weight gain relates, in part, to how people make decisions based on prior experience. Here we conducted post hoc analysis on an archival data set to evaluate whether individual differences in adiposity, an anthropometric construct encompassing a spectrum of body types, from lean to obese, associate with signatures of asymmetric feedback learning during value-based decision-making. In a sample of neurologically healthy adults (N = 433), ventral striatal responses to rewards, measured using fMRI, were not directly associated with adiposity, but rather moderated its relationship with feedback-driven learning in the Iowa gambling task, tested outside the scanner. Using a biologically inspired model of basal ganglia-dependent decision processes, we found this moderating effect of reward reactivity to be explained by an asymmetrical use of feedback to drive learning; that is, with more plasticity for gains than for losses, stronger reward reactivity leads to decisions that minimize exploration for maximizing long-term outcomes. Follow-up analysis confirmed that individual differences in adiposity correlated with signatures of asymmetric use of feedback cues during learning, suggesting that reward reactivity may especially relate to adiposity, and possibly obesity risk, when gains impact future decisions more than losses.

Revision of monogeneans parasitising Lythrurus (Cypriniformes: Leuciscidae) in eastern U.S.A., with description of Dactylogyrus lythruri sp. n. and new records of Dactylogyrus crucis Rogers, 1967 (Monogenoidea: Dactylogyridae).

A revisionary study revealed two species of monogeneans, Dactylogyrus crucis Rogers, 1967 and Dactylogyrus lythruri sp. n., parasitising Lythrurus Jordan (formerly a subgenus of Notropis Rafinesque, 1818). New records and updated taxonomy of seven of 12 known minnows of the genus of Lythrurus are provided for D. crucis. A record of Dactylogyrus attenuatus Mizelle et Klucka, 1953 (syn. Dactylogyrus umbratilus [Kimpel, 1939], nomen nudum) on Lythrurus umbratilis (Girard) is referrable to D. crucis. Dactylogyrus lythruri is described from eight species of Lythrurus. It most closely resembles Dactylogyrus beckeri Cloutman, 1987, but is distinguished by having a smaller base of the male copulatory organ (MCO) and lacking a ventral enlargement of the distal end of the basal process. Previous reports of Dactylogyrus banghami Mizelle et Donahue, 1944 and Dactylogyrus cf. beckeri Cloutman, 1987 from Lythrurus atrapiculus (Snelson) and Lythrurus bellus (Hay) from Alabama, and Dactylogyrus confusus Mueller, 1938 from L. umbratilis in Illinois are herein relegated to D. lythruri. Four species of Lythrurus appeared not to be infected with Dactylogyrus.

Habitat patchiness, ecological connectivity and the uneven recovery of boreal stream ecosystems from an experimental drought.

Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post-drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (a) algal biomass accrual; (b) microbial respiration; and (c) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An 8-day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal dieback began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short-term droughts can have extended consequences for stream ecosystems in the world's vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms.

Expression Analysis of Cnidarian-Specific Neuropeptides in a Sea Anemone Unveils an Apical-Organ-Associated Nerve Net That Disintegrates at Metamorphosis.

Neuropeptides are ancient neuronal signaling molecules that have diversified across Cnidaria (e.g., jellyfish, corals, and sea anemones) and its sister group Bilateria (e.g., vertebrates, insects, and worms). Over the course of neuropeptide evolution emerged lineage-specific neuropeptides, but their roles in the evolution and diversification of nervous system function remain enigmatic. As a step toward filling in this knowledge gap, we investigated the expression pattern of a cnidarian-specific neuropeptide—RPamide—during the development of the starlet sea anemone Nematostella vectensis, using in situ hybridization and immunohistochemistry. We show that RPamide precursor transcripts first occur during gastrulation in scattered epithelial cells of the aboral ectoderm. These RPamide-positive epithelial cells exhibit a spindle-shaped, sensory-cell-like morphology, and extend basal neuronal processes that form a nerve net in the aboral ectoderm of the free-swimming planula larva. At the aboral end, RPamide-positive sensory cells become integrated into the developing apical organ that forms a bundle of long cilia referred to as the apical tuft. Later during planula development, RPamide expression becomes evident in sensory cells in the oral ectoderm of the body column and pharynx, and in the developing endodermal nervous system. At metamorphosis into a polyp, the RPamide-positive sensory nerve net in the aboral ectoderm degenerates by apoptosis, and RPamide expression begins in ectodermal sensory cells of growing oral tentacles. In addition, we find that the expression pattern of RPamide in planulae differs from that of conserved neuropeptides that are shared across Cnidaria and Bilateria, indicative of distinct functions. Our results not only provide the anatomical framework necessary to analyze the function of the cnidarian-specific neuropeptides in future studies, but also reveal previously unrecognized features of the sea anemone nervous system—the apical organ neurons of the planula larva, and metamorphosis-associated reorganization of the ectodermal nervous system.

Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM) – Part 1: Boundary conditions and climatic forcing

Abstract. Simulations of the glacial–interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice sheet and the bedrock. Also climatic forcing covering the last glacial cycles is uncertain, as it is based on sparse proxy data. We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data, e.g., for modern basal heat flux or reconstructions of past changes of sea level and surface temperature. As computational resources are limited, glacial-cycle simulations are performed using a comparably coarse model grid of 16 km and various parameterizations, e.g., for basal sliding, iceberg calving, or for past variations in precipitation and ocean temperatures. In this study we evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also discuss isolated and combined effects of climate and sea-level forcing. Hence, this study serves as a “cookbook” for the growing community of PISM users and paleo-ice sheet modelers in general. For each of the different model uncertainties with regard to climatic forcing, ice and Earth dynamics, and basal processes, we select one representative model parameter that captures relevant uncertainties and motivates corresponding parameter ranges that bound the observed ice volume at present. The four selected parameters are systematically varied in a parameter ensemble analysis, which is described in a companion paper.

Sensitivity of the Northeast Greenland Ice Stream to Geothermal Heat

Recent observations of ice flow surface velocities have helped improve our understanding of basal processes on Greenland and Antarctica, though these processes still constitute some of the largest uncertainties driving ice flow change today. The Northeast Greenland Ice Stream is driven largely by basal sliding, believed to be related to subglacial hydrology and the availability of heat. Characterization of the uncertainties associated with Northeast Greenland Ice Stream is crucial for constraining Greenland's potential contribution to sea level rise in the upcoming centuries. Here, we expand upon past work using the Ice Sheet System Model to quantify the uncertainties in models of the ice flow in the Northeast Greenland Ice Stream by perturbing the geothermal heat flux. Utilizing a subglacial hydrology model simulating sliding beneath the Greenland Ice Sheet, we investigate the sensitivity of the Northeast Greenland Ice Stream ice flow to various estimates of geothermal heat flux, and implications of basal heat flux uncertainties on modeling the hydrological processes beneath Greenland's major ice stream. We find that the uncertainty due to sliding at the bed is 10 times greater than the uncertainty associated with internal ice viscosity. Geothermal heat flux dictates the size of the area of the subglacial drainage system and its efficiency. The uncertainty of ice discharge from the Northeast Greenland Ice Stream to the ocean due to uncertainties in the geothermal heat flux is estimated at 2.10 Gt/yr. This highlights the urgency in obtaining better constraints on the highly uncertain subglacial hydrology parameters.

Copulatory mechanics in the wolf spider Agalenocosa pirity reveals a hidden diversity of locking systems in Lycosidae (Araneae).

Genital traits are among the fastest to evolve, and the processes that drive their evolution are intensively studied. Spiders are characterized by complex genitalia, but the functional role of the different structures during genital coupling is largely unknown. Members of one of the largest spider groups, the retrolateral tibial apophysis (RTA) clade, are characterized by a RTA on the male palp, which is thought to play a crucial role during genital coupling. However, the RTA was lost in several families including the species-rich wolf spiders (Lycosidae) leading to the hypothesis that the genital coupling is achieved by alternative mechanisms. Here, we investigate the genital interactions during copulation in the wolf spider Agalenocosa pirity (Zoicinae) on cryofixed mating pairs using electron, optical and X-ray microscopy and compare our findings with other lycosids and entelegyne spiders. We found an unprecedented coupling mechanism for lycosid spiders involving the palea and a membranous cuticle folding adjacent to the epigynal plate. Additionally, we show an uncommon coupling between the median apophysis and the contralateral genital opening, and confirmed that the terminal apophysis acts as functional conductor, as previously hypothesized for males of Zoicinae. Phylogenetic mapping of RTA indicated that the basal tibial process found in Agalenocosa is a secondary acquisition rather than a modified RTA.

Neuromyelitis optica spectrum disorder with massive basal ganglia involvement: a case report

BackgroundOccurrence of basal ganglia involvement in neuromyelitis optica spectrum disorders (NMOSD) has rarely been reported and none documented pathologically.Case presentationA 73-year-old female was clinically diagnosed with a NMOSD based on the clinical and radiological features and positive serum autoantibodies to AQP4. One month before her death, she became acutely ill with disturbed consciousness and right hemiparesis, and was diagnosed and treated as having basal ganglia infarction based on the brain CT. She made a partial recovery but later died from heart failure. At autopsy, the corresponding basal ganglia process revealed a large fresh area of necrosis. Histologically, several pathological signatures of NMOSD could be recognized in the lesion, including inflammatory cell infiltrations by B and T lymphocytes, perivascular complement and fibrinogen deposition, and the appearance of numerous phagocytosed corpora amylacea within the infiltrating macrophages.ConclusionsThe present case illustrates that basal ganglia may be directly involved in the pathological processes of NMOSD, although the possibility of modification of the lesions by superimposed regional ischemia could not be excluded.

A negative bias in decoding positive social cues characterizes emotion processing in patients with symptom-remitted Borderline Personality Disorder

BackgroundImpairments in the domain of interpersonal functioning such as the feeling of loneliness and fear of abandonment have been associated with a negative bias during processing of social cues in Borderline Personality Disorder (BPD). Since these symptoms show low rates of remission, high rates of recurrence and are relatively resistant to treatment, in the present study we investigated whether a negative bias during social cognitive processing exists in BPD even after symptomatic remission. We focused on facial emotion recognition since it is one of the basal social-cognitive processes required for successful social interactions and building relationships.MethodsNinety-eight female participants (46 symptom-remitted BPD [r-BPD]), 52 healthy controls [HC]) rated the intensity of anger and happiness in ambiguous (anger/happiness blends) and unambiguous (emotion/neutral blends) emotional facial expressions. Additionally, participants assessed the confidence they experienced in their own judgments.ResultsR-BPD participants assessed ambiguous expressions as less happy and as more angry when the faces displayed predominantly happiness. Confidence in these judgments did not differ between groups, but confidence in judging happiness in predominantly happy faces was lower in BPD patients with a higher level of BPD psychopathology.ConclusionsEvaluating social cues that signal the willingness to affiliate is characterized by a negative bias that seems to be a trait-like feature of social cognition in BPD. In contrast, confidence in judging positive social signals seems to be a state-like feature of emotion recognition in BPD that improves with attenuation in the level of acute BPD symptoms.

Nuptial feeding and genital coupling of Neopanorpa scorpionflies (Insecta: Mecoptera: Panorpidae) with notal organs of various lengths

Neopanorpa, the second largest genus in Panorpidae, is mainly characterized by the well-developed notal organ on male tergum III. However, it remains largely unknown how the length of the notal organ influences the nuptial feeding behaviour of Neopanorpa. Here, we investigated the nuptial feeding by comparing the morphology of mating-related structures and the genital coupling of a) Neopanorpa lui Chou & Ran, 1981 with a weakly-developed notal organ, b) N. carpenteri Cheng, 1957 with a medium-sized notal organ, and c) N. longiprocessa Hua & Chou, 1997 with an extremely elongated notal organ. The couples of N. lui and N. carpenteri maintain an intermittent mouth-to-mouth mode but do not exchange any edible food. After that the males secrete a salivary mass onto the surface as a nuptial gift, which is distinctly larger in N. carpenteri than in N. lui. Correspondingly, the male salivary glands are more developed in N. carpenteri than in N. lui. Males of N. longiprocessa bear very short salivary glands corresponding to a coercive mating tactic. The genital couplings are similar among the three species of Neopanorpa. The paired hypovalves of males are used to control the cerci of females. The prominent basal processes of male gonostyli grasp the posterior portion of the female medigynium across the intersegmental membrane. The male aedeagus physically couples with the female medigynium to ensure the male phallotreme to connect to the female copulatory pore. The influence of the notal organ length on the nuptial feeding behaviour of Neopanorpa is briefly discussed.

Description of a new species of the Lissochlora albociliaria species group(Lepidoptera: Geometridae, Geometrinae).

The genus Lissochlora was described by Warren (1900) and revised by Pitkin (1993) with respect to the fauna of Costa Rica. Lissochlora has a small spur or kink to its aedeagus and is distinguished from related genera by the absence of basal costal process of the valva in the male genitalia, which is present in Nemoria Hübner, Rhodochlora Warren and Paromphacodes Warren (Pitkin 1993, 1996). Paromphacodes, Lissochlora and Nemoria cluster together, sharing a bilobed eighth sternite and the presence of a costal sclerite or ornamentation on the valva (Viidalepp 2017). Usually species of Lissochlora have a shorter uncus in the male genitalia than that of related genera, and the last abdominal sternite of the male is usually shorter than the corresponding tergite (Viidalepp 2017).

Expression of the RNA methyltransferase Nsun5 is essential for developing cerebral cortex

Nsun5 gene, encoding a cytosine-5 RNA methyltransferase, is deleted in about 95% patients with Williams-Beuren syndrome (WBS). WBS is a neurodevelopmental disorder and characterized by cognitive disorder. We generated single-gene Nsun5 knockout (Nsun5-KO) mice and reported that the Nsun5 deletion leads to deficit in spatial cognition. This study focused on investigating the influence of Nsun5 deficiency in the development of cerebral cortex. In comparison with wild-type littermates, the cortical thickness in postnatal day 10 Nsun5-KO mice was obviously reduced with an abnormal laminar organization, and the processes of pyramidal cells were shorter and finer. Nsun5 was selectively expressed in radial glial cells (RGCs) of cerebral cortex from embryonic day (E) 12.5 to E16.5, but not in intermediate progenitor cells (IPCs) or neocortical neurons. The Nsun5 deletion did not alter proliferation of RGCs or differentiation of RGCs into IPCs. Notably, the ablation of Nsun5 disrupted the growth of radial glial scaffolds, thus numerous basal processes of RGCs failed to reach pial basement membrane. Level of cell polarity regulator Cdc42 protein in radial glial scaffolds of E14.5 Nsun5-KO mice was reduced, but the level of Cdc42 mRNA was unchanged. The dysfunction of glial scaffolds impeded the radial migration of upper-layer and deeper-layer neurons to cause their subcortical accumulation and apoptosis, resulting in an obvious thinness of the cortical plate in E18.5 Nsun5-KO mice. These findings establish a critical role of Nsun5 in development of cerebral cortex through regulating radial glial scaffolds of RGCs to control migration of neocortical neurons.

Genes and Mechanisms Involved in the Generation and Amplification of Basal Radial Glial Cells.

The development of the cerebral cortex relies on different types of progenitor cell. Among them, the recently described basal radial glial cell (bRG) is suggested to be of critical importance for the development of the brain in gyrencephalic species. These cells are highly numerous in primate and ferret brains, compared to lissencephalic species such as the mouse in which they are few in number. Their somata are located in basal subventricular zones in gyrencephalic brains and they generally possess a basal process extending to the pial surface. They sometimes also have an apical process directed toward the ventricular surface, similar to apical radial glial cells (aRGs) from which they are derived, and whose somata are found more apically in the ventricular zone. bRGs share similarities with aRGs in terms of gene expression (SOX2, PAX6, and NESTIN), whilst also expressing a range of more specific genes (such as HOPX). In primate brains, bRGs can divide multiple times, self-renewing and/or generating intermediate progenitors and neurons. They display a highly specific cytokinesis behavior termed mitotic somal translocation. We focus here on recently identified molecular mechanisms associated with the generation and amplification of bRGs, including bRG-like cells in the rodent. These include signaling pathways such as the FGF-MAPK cascade, SHH, PTEN/AKT, PDGF pathways, and proteins such as INSM, GPSM2, ASPM, TRNP1, ARHGAP11B, PAX6, and HIF1α. A number of these proteins were identified through transcriptome comparisons in human aRGs vs. bRGs, and validated by modifying their activities or expression levels in the mouse. This latter experiment often revealed enhanced bRG-like cell production, even in some cases generating folds (gyri) on the surface of the mouse cortex. We compare the features of the identified cells and methods used to characterize them in each model. These important data converge to indicate pathways essential for the production and expansion of bRGs, which may help us understand cortical development in health and disease.

Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica

ABSTRACTWe derive the surface and basal radar reflectance and backscatter coefficients of the southern McMurdo Ice Shelf (SMIS) and part of the nearby Ross Ice Shelf (RIS), Antarctica, from radar statistical reconnaissance using a 60-MHZ airborne survey. The surface coefficients are further inverted in terms of snow density and roughness, providing a spatial distribution of the processes contributing to the surface boundary conditions. We disentangle the basal coefficients from surface transmission losses, and we provide the basal coherent content, an indicator of the boundary geometric disorder that is also self-corrected from englacial attenuation. The basal radar properties exhibit sharp gradients along specific iso-depths, suggesting an abrupt modification of the ice composition and geometric structure. We interpret this behavior as locations where the pressure-melting point is reached, outlining fields of freezing and melting ice. Basal steps are observed at both SMIS and RIS, suggesting a common geometric expression of widespread basal processes. This technique offers a simultaneous view of both the surface and basal boundary conditions to help investigate the ice-shelf stability, while its application to airborne data significantly improves coverage of the difficult-to-observe ice–ocean boundary. It also provides constraints on thermohaline circulation in ice shelves cavities, which are analogs for ice-covered ocean worlds.

Memo1-Mediated Tiling of Radial Glial Cells Facilitates Cerebral Cortical Development

Polarized, non-overlapping, regularly spaced, tiled organization of radial glial cells (RGCs) serves as a framework to generate and organize cortical neuronal columns, layers, and circuitry. Here, we show that mediator of cell motility 1 (Memo1) is a critical determinant of radial glial tiling during neocortical development. Memo1 deletion or knockdown leads to hyperbranching of RGC basal processes and disrupted RGC tiling, resulting in aberrant radial unit assembly and neuronal layering. Memo1 regulates microtubule (MT) stability necessary for RGC tiling. Memo1 deficiency leads to disrupted MT minus-end CAMSAP2 distribution, initiation of aberrant MT branching, and altered polarized trafficking of key basal domain proteins such as GPR56, and thus aberrant RGC tiling. These findings identify Memo1 as a mediator of RGC scaffold tiling, necessary to generate and organize neurons into functional ensembles in the developing cerebral cortex.