Absence of MMACHC in peripheral retinal cells does not lead to an ocular phenotype in mice

Combined methylmalonic aciduria with homocystinuria (cblC type) is a rare disease caused by mutations in the MMACHC gene. MMACHC encodes an enzyme crucial for intracellular vitamin B₁₂ metabolism, leading to the accumulation of toxic metabolites e.g. methylmalonic acid (MMA) and homocysteine (Hcy), and secondary disturbances in folate and one-carbon metabolism when not fully functional. Patients with cblC deficiency often present in the neonatal or early childhood period with a severe multisystem pathology, which comprises a broad spectrum of treatment-resistant ophthalmological phenotypes, including retinal degeneration, impaired vision, and vascular changes. To examine the potential function of MMACHC in the retina and how its loss may impact disease, we performed gene expression studies in human and mouse, which showed that local expression of MMACHC in the retina and retinal pigment epithelium is relatively stable over time. To study whether functional MMACHC is required for retinal function and tissue integrity, we generated a transgenic mouse lacking Mmachc expression in cells of the peripheral retina. Characterization of this mouse revealed accumulation of cblC disease related metabolites, including MMA and the folate-dependent purine synthesis intermediates AICA-riboside and SAICA-riboside in the retina. Nevertheless, fundus appearance, morphology, vasculature, and cellular composition of the retina, as well as ocular function, remained normal in mice up to 6 or 12 months of age. Our data indicates that peripheral retinal neurons do not require intrinsic expression of Mmachc for survival and function and questions whether a local MMACHC deficiency is responsible for the retinal phenotypes in patients.     

Elevated rates of positive selection drive the evolution of pestiferousness in the Colorado potato beetle (Leptinotarsa decemlineata,Say)

Contextualizing evolutionary history and identifying genomic features of an insect that might contribute to its pest status is important in developing early detection and control tactics. In order to understand the evolution of pestiferousness, which we define as the accumulation of traits that contribute to an insect population's success in an agroecosystem, we tested the importance of known genomic properties associated with rapid adaptation in the Colorado potato beetle (CPB), Leptinotarsa decemlineata Say. Within the leaf beetle genus Leptinotarsa, only CPB, and a few populations therein, has risen to pest status on cultivated nightshades, Solanum. Using whole genomes from ten closely related Leptinotarsa species native to the United States, we reconstructed a high‐quality species tree and used this phylogenetic framework to assess evolutionary patterns in four genomic features of rapid adaptation: standing genetic variation, gene family expansion and contraction, transposable element abundance and location, and positive selection at protein‐coding genes. Throughout approximately 20 million years of history, Leptinotarsa species show little evidence of gene family turnover and transposable element variation. However, there is a clear pattern of CPB experiencing higher rates of positive selection on protein‐coding genes. We determine that these rates are associated with greater standing genetic variation due to larger effective population size, which supports the theory that the demographic history contributes to rates of protein evolution. Furthermore, we identify a suite of coding genes under positive selection that are putatively associated with pestiferousness in the Colorado potato beetle lineage. They are involved in the biological processes of xenobiotic detoxification, chemosensation and hormone function.     

The physiological ups and downs of thermal variability in temperate freshwater ecosystems

Freshwater fish face a variety of spatiotemporal thermal challenges throughout their life. On a broad scale, temperature is an important driver of physiological, behavioural and ecological patterns and ultimately affects populations and overall distribution. These broad patterns are partly underpinned by the small-scale local effects of temperature on individuals within the population. Climate change is increasing the range of daily thermal variation in most freshwater ecosystems, altering behaviour and performance of resident fishes. The aim of this review is understanding how daily thermal variation in temperate rivers affects individual fish physiology, behaviour and overall performance. The following are highlighted in this study: (a) the physical characteristics of rivers that can either buffer or exacerbate thermal variability, (b) the effects of thermal variability on growth and metabolism, (c) the approaches for quantifying thermal variation and thermal stress and (d) how fish may acclimatize or adapt to our changing climate.     

Critical considerations for the development of potency tests for therapeutic applications of mesenchymal stromal cell-derived small extracellular vesicles

Mesenchymal stromal/stem cells (MSCs) have been widely tested against many diseases, with more than 1000 registered clinical trials worldwide. Despite many setbacks, MSCs have been approved for the treatment of graft-versus-host disease and Crohn disease. However, it is increasingly clear that MSCs exert their therapeutic functions in a paracrine manner through the secretion of small extracellular vesicles (sEVs) of 50–200 nm in diameter. Unlike living cells that can persist long-term, sEVs are non-living and non-replicative and have a transient presence in the body. Their small size also renders sEV preparations highly amenable to sterilization by filtration. Together, acellular MSC-sEV preparations are potentially safer and easier to translate into the clinic than cellular MSC products. Nevertheless, there are inherent challenges in the development of MSC-sEV drug products. MSC-sEVs are products of living cells, and living cells are sensitive to changes in the external microenvironment. Consequently, quality control metrics to measure key identity and potency features of MSC-sEV preparations have to be specified during development of MSC-sEV therapeutics. The authors have previously described quantifiable assays to define the identity of MSC-sEVs. Here the authors discuss requirements for prospective potency assays to predict the therapeutic effectiveness of the drug substance in accordance with International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines. Although potency assays should ideally reflect the mechanism of action (MoA), this is challenging because the MoA for the reported efficacy of MSC-sEV preparations against multiple diseases of diverse underlying pathology is likely to be complex and different for each disease and difficult to fully elucidate. Nevertheless, robust potency assays could be developed by identifying the EV attribute most relevant to the intended biological activity in EV-mediated therapy and quantifying the EV attribute. Specifically, the authors highlight challenges and mitigation measures to enhance the manufacture of consistent and reproducibly potent sEV preparations, to identify and select the appropriate EV attribute for potency assays despite a complex “work-in-progress” MoA and to develop assays likely to be compliant with regulatory guidance for assay validation.     

Exosomes from neuronal stem cells may protect the heart from ischaemia/reperfusion injury via JAK1/2 and gp130

Myocardial infarction requires urgent reperfusion to salvage viable heart tissue. However, reperfusion increases infarct size further by promoting mitochondrial damage in cardiomyocytes. Exosomes from a wide range of different cell sources have been shown to activate cardioprotective pathways in cardiomyocytes, thereby reducing infarct size. Yet, it is currently challenging to obtain highly pure exosomes in quantities enough for clinical studies. To overcome this problem, we used exosomes isolated from CTX0E03 neuronal stem cells, which are genetically stable, conditionally inducible and can be produced on an industrial scale. However, it is unknown whether exosomes from neuronal stem cells may reduce cardiac ischaemia/reperfusion injury. In this study, we demonstrate that exosomes from differentiating CTX0E03 cells can reduce infarct size in mice. In an in vitro assay, these exosomes delayed cardiomyocyte mitochondrial permeability transition pore opening, which is responsible for cardiomyocyte death after reperfusion. The mechanism of MPTP inhibition was via gp130 signalling and the downstream JAK/STAT pathway. Our results support previous findings that exosomes from non-cardiomyocyte-related cells produce exosomes capable of protecting cardiomyocytes from myocardial infarction. We anticipate our findings may encourage scientists to use exosomes obtained from reproducible clinical-grade stocks of cells for their ischaemia/reperfusion studies.     

Colliding fragment islands transport independent lineages of endemic rock-crawlers (Grylloblattodea: Grylloblattidae) in the Japanese archipelago

Fragment islands, viewed from the paradigm of island biogeographic theory, depend on continual immigration from continental sources to maintain levels of species diversity, or otherwise undergo a period of relaxation where species diversity declines to a lower equilibrium. Japan is a recently derived fragment island with a rich endemic flora and fauna. These endemic species have been described as paleoendemics, and conversely as recently derived Pleistocene colonists. Geological events in the Miocene period, notably the fragmentation and collision of islands, and the subsequent uplift of mountains in central Japan, provided opportunities for genetic isolation. More recently, cyclical climatic change during the Pliocene and Pleistocene periods led to intermittent land bridge connections to continental Asia. Here we investigate the pattern and timing of diversification in a diverse endemic lineage in order to test whether ongoing migration has sustained species diversity, whether there is evidence of relaxation, and how geological and climatic events are associated with lineage diversification. Using multi-locus genetic data, we test these hypotheses in a poorly dispersing, cold-adapted terrestrial insect lineage (Grylloblattodea: Grylloblattidae) sampled from Japan, Korea, and Russia. In phylogenetic analyses of concatenated data and a species tree approach, we find evidence of three deeply divergent lineages of rock-crawlers in Japan consistent with the pattern of island fragmentation from continental Asia. Tests of lineage diversification rates suggest that relaxation has not occurred and instead endemism has increased in the Japanese Grylloblattidae following mountain-building events in the Miocene. Although the importance of climate change in generating species diversity is a commonly held paradigm in Japanese biogeography, our analyses, including analyses of demographic change and phylogeographic range shifts in putative species, suggests that Pleistocene climatic change has had a limited effect on the diversification of rock-crawlers.     

Establishing Restoration Strategy of Eastern Oyster via a Coupled Biophysical Transport Model

For marine fish and invertebrates, larval dispersal plays a critical role in determining connections among source and sink habitats, and the lack of a predictive understanding of larval dispersal is a fundamental obstacle to the development of spatially explicit restoration plans for marine populations. We investigated larval dispersal patterns of eastern oyster in an estuary along the Northern Gulf of Mexico under different simulation scenarios of tidal amplitude and phase, river discharge, wind direction, and larval vertical migration, using a coupled biophysical transport model. We focused on the dispersal of larvae released from the commercially exploited (Cedar Point, CP) and non‐exploited (Bon Secour Bay, BSB) oyster populations. We found that high flushing rates through the dominant inlet prevented larval exchange between the commercially exploited and non‐exploited populations, resulting in negligible connectivity between them. Variations in tidal amplitude, river discharge and wind direction played a more important role in the amount of larvae retained in Mobile Bay when they are released from CP than from BSB. Under most of the scenarios, larvae from BSB were retained around the spawning area, while larvae from CP showed a predominant westward flow. Net sinking behavior of late‐stage larvae increased larval retention in the bay, but physical transport showed a higher impact in the amount of larvae retained. These findings have enhanced our understanding of larval dispersal of eastern oyster in a wide, shallow estuarine system, and been used to establish spatially explicit strategies for oyster restoration in the Mobile Bay system, Alabama.     

Is the edTPA the Right Choice for Evaluating Teacher Readiness?

The purpose of this article is to describe and analyze the edTPA, a performance assessment created by the Stanford Center for Assessment, Learning, and Equity (SCALE) and administered by Pearson, Inc., to assess the professional readiness of student teachers. We challenge claims made in support of using this assessment, specifically within the context of arts teacher preparation programs, and we address areas of immediate critical concern to make alternative recommendations.