A reverse genetics and genomics approach to gene paralog function and disease: Myokymia and the juxtaparanode.

The leucine-rich glioma-inactivated (LGI) family consists of four highly conserved paralogous genes, LGI1-4, that are highly expressed in mammalian central and/or peripheral nervous systems. LGI1 antibodies are detected in subjects with autoimmune limbic encephalitis and peripheral nerve hyperexcitability syndromes (PNHSs) such as Isaacs and Morvan syndromes. Pathogenic variations of LGI1 and LGI4 are associated with neurological disorders as disease traits including familial temporal lobe epilepsy and neurogenic arthrogryposis multiplex congenita 1 with myelin defects, respectively. No human disease has been reported associated with either LGI2 or LGI3. We implemented exome sequencing and family-based genomics to identify individuals with deleterious variants in LGI3 and utilized GeneMatcher to connect practitioners and researchers worldwide to investigate the clinical and electrophysiological phenotype in affected subjects. We also generated Lgi3-null mice and performed peripheral nerve dissection and immunohistochemistry to examine the juxtaparanode LGI3 microarchitecture. As a result, we identified 16 individuals from eight unrelated families with loss-of-function (LoF) bi-allelic variants in LGI3. Deep phenotypic characterization showed LGI3 LoF causes a potentially clinically recognizable PNHS trait characterized by global developmental delay, intellectual disability, distal deformities with diminished reflexes, visible facial myokymia, and distinctive electromyographic features suggestive of motor nerve instability. Lgi3-null mice showed reduced and mis-localized Kv1 channel complexes in myelinated peripheral axons. Our data demonstrate bi-allelic LoF variants in LGI3 cause a clinically distinguishable disease trait of PNHS, most likely caused by disturbed Kv1 channel distribution in the absence of LGI3.

Cellular senescence in progenitor cells contributes to diminished remyelination potential in progressive multiple sclerosis.

Cellular senescence is a form of adaptive cellular physiology associated with aging. Cellular senescence causes a proinflammatory cellular phenotype that impairs tissue regeneration, has been linked to stress, and is implicated in several human neurodegenerative diseases. We had previously determined that neural progenitor cells (NPCs) derived from induced pluripotent stem cell (iPSC) lines from patients with primary progressive multiple sclerosis (PPMS) failed to promote oligodendrocyte progenitor cell (OPC) maturation, whereas NPCs from age-matched control cell lines did so efficiently. Herein, we report that expression of hallmarks of cellular senescence were identified in SOX2+ progenitor cells within white matter lesions of human progressive MS (PMS) autopsy brain tissues and iPS-derived NPCs from patients with PPMS. Expression of cellular senescence genes in PPMS NPCs was found to be reversible by treatment with rapamycin, which then enhanced PPMS NPC support for oligodendrocyte (OL) differentiation. A proteomic analysis of the PPMS NPC secretome identified high-mobility group box-1 (HMGB1), which was found to be a senescence-associated inhibitor of OL differentiation. Transcriptome analysis of OPCs revealed that senescent NPCs induced expression of epigenetic regulators mediated by extracellular HMGB1. Lastly, we determined that progenitor cells are a source of elevated HMGB1 in human white matter lesions. Based on these data, we conclude that cellular senescence contributes to altered progenitor cell functions in demyelinated lesions in MS. Moreover, these data implicate cellular aging and senescence as a process that contributes to remyelination failure in PMS, which may impact how this disease is modeled and inform development of future myelin regeneration strategies.

Effect of transcranial direct current stimulation (tDCS) on food craving and eating when using a control method that minimizes guessing of the real vs. control condition.

PURPOSE: Validation of transcranial direct current stimulation (tDCS) to treat obesity is hampered by evidence that participants can distinguish real from the traditional-control condition. Correctly guessing the real condition precludes knowing if it is neuromodulation or expectation that suppresses food craving and eating. Therefore, this study tested the putative efficacy of tDCS to the dorsolateral prefrontal cortex (DLPFC) to reduce food craving and eating when an alternative control condition was used that would be difficult to distinguish from the real condition. METHODS: N = 28 adults with a 26-50 BMI range received a typical 20-min 2 mA current session of tDCS targeting the DLPFC as the real condition and a same duration/current tDCS session targeting the sensorimotor cortex (SMC), a region not expected to affect appetite, as the control. Food image craving ratings, in-lab food consumption, and momentary ratings of physical sensations were measured. RESULTS: DLPFC failed to reduce food craving and consumption compared to SMC stimulation. When interviewed, 71% of participants were unable to guess real from control conditions. Those who guessed DLPFC tDCS as real attributed their guess to increased number and frequency of sensations. However, their sensation ratings during tDCS did not differ between conditions. CONCLUSIONS: The results question if tDCS suppresses craving and eating at all, or if the DLPFC is the best target to do so. The results also indicate that alternate-site constant stimulation as the control method may strengthen the scientific evaluation of tDCS to treat obesity. LEVEL OF EVIDENCE: Level I, experimental study.

The effect of expectation on transcranial direct current stimulation (tDCS) to suppress food craving and eating in individuals with overweight and obesity.

Transcranial direct current stimulation (tDCS) is a neuromodulation technique with potential to treat eating disorders and obesity. As for any potential treatment, it is important to assess the degree to which expectation effects contribute to its reported efficacy. This study assessed the effect of tDCS on amount of food craving and eating while tightly controlling treatment expectation. N = 74 adults with overweight or obesity were informed of the known effects of tDCS to suppress craving and eating. Once electrodes were on the head, half of the participants were told they were receiving real, and the other half sham tDCS. Within these groups, approximately half actually received real and the other half sham tDCS. Stimulation parameters used were those previously found to reduce craving and eating, including in our lab: 2 mA, anode right/cathode left targeting the dorsolateral prefrontal cortex for 20 min (real), or only for the first and last minute (sham). Analyses controlled for demographics, hunger, trait impulsiveness, eating motives, dieting, binge eating, suggestibility, and baseline craving and eating. Participants told they were receiving real tDCS craved and ate less than participants told they were receiving sham tDCS (both p < 0.01), regardless of tDCS condition administered. There was no main effect of real vs. sham tDCS on craving or eating or an interaction between tDCS condition and expectation. The scientific validation of tDCS as a treatment for eating-related conditions hinges on controlling for the powerful effects of expectation. This can include the type of information provided on consent forms and participants' ability to guess real from sham conditions.

After Nerve Injury, Lineage Tracing Shows That Myelin and Remak Schwann Cells Elongate Extensively and Branch to Form Repair Schwann Cells, Which Shorten Radically on Remyelination.

There is consensus that, distal to peripheral nerve injury, myelin and Remak cells reorganize to form cellular columns, Bungner's bands, which are indispensable for regeneration. However, knowledge of the structure of these regeneration tracks has not advanced for decades and the structure of the cells that form them, denervated or repair Schwann cells, remains obscure. Furthermore, the origin of these cells from myelin and Remak cells and their ability to give rise to myelin cells after regeneration has not been demonstrated directly, although these conversions are believed to be central to nerve repair. Using genetic lineage-tracing and scanning-block face electron microscopy, we show that injury of sciatic nerves from mice of either sex triggers extensive and unexpected Schwann cell elongation and branching to form long, parallel processes. Repair cells are 2- to 3-fold longer than myelin and Remak cells and 7- to 10-fold longer than immature Schwann cells. Remarkably, when repair cells transit back to myelinating cells, they shorten ∼7-fold to generate the typically short internodes of regenerated nerves. The present experiments define novel morphological transitions in injured nerves and show that repair Schwann cells have a cell-type-specific structure that differentiates them from other cells in the Schwann cell lineage. They also provide the first direct evidence using genetic lineage tracing for two basic assumptions in Schwann cell biology: that myelin and Remak cells generate the elongated cells that build Bungner bands in injured nerves and that such cells can transform to myelin cells after regeneration.SIGNIFICANCE STATEMENT After injury to peripheral nerves, the myelin and Remak Schwann cells distal to the injury site reorganize and modify their properties to form cells that support the survival of injured neurons, promote axon growth, remove myelin-associated growth inhibitors, and guide regenerating axons to their targets. We show that the generation of these repair-supportive Schwann cells involves an extensive cellular elongation and branching, often to form long, parallel processes. This generates a distinctive repair cell morphology that is favorable for the formation of the regeneration tracks that are essential for nerve repair. Remyelination, conversely, involves a striking cell shortening to form the typical short myelin cells of regenerated nerves. We also provide evidence for direct lineage relationships between: (1) repair cells and myelin and Remak cells of uninjured nerves and (2) remyelinating cells in regenerated nerves.

Graded Elevation of c-Jun in Schwann Cells In Vivo: Gene Dosage Determines Effects on Development, Remyelination, Tumorigenesis, and Hypomyelination.

Schwann cell c-Jun is implicated in adaptive and maladaptive functions in peripheral nerves. In injured nerves, this transcription factor promotes the repair Schwann cell phenotype and regeneration and promotes Schwann-cell-mediated neurotrophic support in models of peripheral neuropathies. However, c-Jun is associated with tumor formation in some systems, potentially suppresses myelin genes, and has been implicated in demyelinating neuropathies. To clarify these issues and to determine how c-Jun levels determine its function, we have generated c-Jun OE/+ and c-Jun OE/OE mice with graded expression of c-Jun in Schwann cells and examined these lines during development, in adulthood, and after injury using RNA sequencing analysis, quantitative electron microscopic morphometry, Western blotting, and functional tests. Schwann cells are remarkably tolerant of elevated c-Jun because the nerves of c-Jun OE/+ mice, in which c-Jun is elevated ∼6-fold, are normal with the exception of modestly reduced myelin thickness. The stronger elevation of c-Jun in c-Jun OE/OE mice is, however, sufficient to induce significant hypomyelination pathology, implicating c-Jun as a potential player in demyelinating neuropathies. The tumor suppressor P19ARF is strongly activated in the nerves of these mice and, even in aged c-Jun OE/OE mice, there is no evidence of tumors. This is consistent with the fact that tumors do not form in injured nerves, although they contain proliferating Schwann cells with strikingly elevated c-Jun. Furthermore, in crushed nerves of c-Jun OE/+ mice, where c-Jun levels are overexpressed sufficiently to accelerate axonal regeneration, myelination and function are restored after injury.SIGNIFICANCE STATEMENT In injured and diseased nerves, the transcription factor c-Jun in Schwann cells is elevated and variously implicated in controlling beneficial or adverse functions, including trophic Schwann cell support for neurons, promotion of regeneration, tumorigenesis, and suppression of myelination. To analyze the functions of c-Jun, we have used transgenic mice with graded elevation of Schwann cell c-Jun. We show that high c-Jun elevation is a potential pathogenic mechanism because it inhibits myelination. Conversely, we did not find a link between c-Jun elevation and tumorigenesis. Modest c-Jun elevation, which is beneficial for regeneration, is well tolerated during Schwann cell development and in the adult and is compatible with restoration of myelination and nerve function after injury.

Metalloproteinase-dependent and -independent processes contribute to inhibition of breast cancer cell migration, angiogenesis and liver metastasis by a disintegrin and metalloproteinase with thrombospondin motifs-15.

The ADAMTS proteinases are a family of secreted, matrix-associated enzymes that have diverse roles in the regulation of tissue organization and vascular homeostasis. Several of the 19 human family members have been identified as having either tumor promoting or suppressing roles. We previously demonstrated that decreased ADAMTS15 expression correlated with a worse clinical outcome in mammary carcinoma (e.g., Porter et al., Int J Cancer 2006;118:1241-7). We have explored the effects of A Disintegrin and Metalloproteinase with Thrombospondin motifs-15 (ADAMTS-15) on the behavior of MDA-MB-231 and MCF-7 breast cancer cells by stable expression of either a wild-type (wt) or metalloproteinase-inactive (E362A) protein. No effects on mammary cancer cell proliferation or apoptosis were observed for either form of ADAMTS-15. However, both forms reduced cell migration on fibronectin or laminin matrices, though motility on a Type I collagen matrix was unimpaired. Knockdown of syndecan-4 attenuated the inhibitory effects of ADAMTS-15 on cell migration. In contrast to its effects on cell migration, wt ADAMTS-15 but not the E362A inactive mutant inhibited endothelial tubulogenesis in 3D collagen gels and angiogenesis in the aortic ring assay. In experimental metastasis assays in nude mice, MDA-MB-231 cells expressing either form of ADAMTS-15 showed reduced spread to the liver, though lung colonization was enhanced for cells expressing wt ADAMTS-15. These studies indicate that extracellular ADAMTS-15 has multiple actions on tumor pathophysiology. Via modulation of cell-ECM interactions, which likely involve syndecan-4, it attenuates mammary cancer cell migration independent of its metalloproteinase activity; however, its antiangiogenic action requires catalytic functionality, and its effects on metastasis in vivo are tissue niche-dependent.

c-Jun activation in Schwann cells protects against loss of sensory axons in inherited neuropathy.

Charcot-Marie-Tooth disease type 1A is the most frequent inherited peripheral neuropathy. It is generally due to heterozygous inheritance of a partial chromosomal duplication resulting in over-expression of PMP22. A key feature of Charcot-Marie-Tooth disease type 1A is secondary death of axons. Prevention of axonal loss is therefore an important target of clinical intervention. We have previously identified a signalling mechanism that promotes axon survival and prevents neuron death in mechanically injured peripheral nerves. This work suggested that Schwann cells respond to injury by activating/enhancing trophic support for axons through a mechanism that depends on upregulation of the transcription factor c-Jun in Schwann cells, resulting in the sparing of axons that would otherwise die. As c-Jun orchestrates Schwann cell support for distressed neurons after mechanical injury, we have now asked: do Schwann cells also activate a c-Jun dependent neuron-supportive programme in inherited demyelinating disease? We tested this by using the C3 mouse model of Charcot-Marie-Tooth disease type 1A. In line with our previous findings in humans with Charcot-Marie-Tooth disease type 1A, we found that Schwann cell c-Jun was elevated in (uninjured) nerves of C3 mice. We determined the impact of this c-Jun activation by comparing C3 mice with double mutant mice, namely C3 mice in which c-Jun had been conditionally inactivated in Schwann cells (C3/Schwann cell-c-Jun(-/-) mice), using sensory-motor tests and electrophysiological measurements, and by counting axons in proximal and distal nerves. The results indicate that c-Jun elevation in the Schwann cells of C3 nerves serves to prevent loss of myelinated sensory axons, particularly in distal nerves, improve behavioural symptoms, and preserve F-wave persistence. This suggests that Schwann cells have two contrasting functions in Charcot-Marie-Tooth disease type 1A: on the one hand they are the genetic source of the disease, on the other, they respond to it by mounting a c-Jun-dependent response that significantly reduces its impact. Because axonal death is a central feature of much nerve pathology it will be important to establish whether an axon-supportive Schwann cell response also takes place in other conditions. Amplification of this axon-supportive mechanism constitutes a novel target for clinical intervention that might be useful in Charcot-Marie-Tooth disease type 1A and other neuropathies that involve axon loss.

Alignment of Consumers' Expected Brain Benefits from Food and Supplements with Measurable Cognitive Performance Tests.

Consumers often cite cognitive improvements as reasons for making dietary changes or using dietary supplements, a motivation that if leveraged could greatly enhance public health. However, rarely is it considered whether standardized cognitive tests that are used in nutrition research are aligned to outcomes of interest to the consumer. This knowledge gap presents a challenge to the scientific substantiation of nutrition-based cognitive health benefits. Here we combined focus group transcript review using reflexive thematic analysis and a multidisciplinary expert panel exercise to evaluate the applicability of cognitive performance tools/tasks for substantiating the specific cognitive benefits articulated by consumers with the objectives to (1) understand how consumers comprehend the potential benefits of nutrition for brain health, and (2) determine the alignment between consumers desired brain benefits and validated tests and tools. We derived a 'Consumer Taxonomy of Cognitive and Affective Health in Nutrition Research' which describes the cognitive and affective structure from the consumers perspective. Experts agreed that validated tests exist for some consumer benefits including focused attention, sustained attention, episodic memory, energy levels, and anxiety. Prospective memory, flow, and presence represented novel benefits that require the development and validation of new tests and tools. Closing the gap between science and consumers and fostering co-creative approaches to nutrition research are critical to the development of products and dietary recommendations that support realizable cognitive benefits that benefit public health.

Assessment of Mental Health and Coping Disparities Among Racial and Ethnic Groups Amid COVID-19 From the "How Right Now" Campaign.

OBJECTIVES: How Right Now (HRN) is an evidence-based, culturally responsive communication campaign developed to facilitate coping and resilience among US groups disproportionately affected by the COVID-19 pandemic. To inform the development of this campaign, we examined patterns in emotional health, stress, and coping strategies among HRN's audiences, focusing on differences among racial and ethnic groups. METHODS: We used a national probability panel, AmeriSpeak, to collect survey data from HRN's priority audience members in English and Spanish at 2 time points (May 2020 and May 2021). We conducted statistical testing to examine differences between time points for each subgroup (Hispanic, non-Hispanic Black, and non-Hispanic White) and differences among subgroups at each time point. RESULTS: We found disparities in COVID-19-related mental health challenges and differences in coping strategies. Non-Hispanic Black respondents were more likely than non-Hispanic White respondents to report challenges related to the social determinants of health, such as affording food and housing (26.4% vs 9.4% in May 2020) and experiencing personal financial loss (46.6% vs 29.2% in May 2020). In May 2021, 30.6% of Hispanic respondents reported being unable to meet basic food or housing needs versus 8.2% of non-Hispanic White respondents, and 51.6% reported personal financial loss versus 26.5% of non-Hispanic White respondents. CONCLUSIONS: Our study further illuminates what is needed to build emotional well-being pathways for people who historically have been economically and socially marginalized. Our findings underscore the need for public health interventions to provide culturally responsive mental health support to populations disproportionately affected by COVID-19 during the pandemic and into the future, with a focus on racial and ethnic disparities.

Brain matters: unveiling the distinct contributions of region, age, and sex to glia diversity and CNS function.

The myelinated white matter tracts of the central nervous system (CNS) are essential for fast transmission of electrical impulses and are often differentially affected in human neurodegenerative diseases across CNS region, age and sex. We hypothesize that this selective vulnerability is underpinned by physiological variation in white matter glia. Using single nucleus RNA sequencing of human post-mortem white matter samples from the brain, cerebellum and spinal cord and subsequent tissue-based validation we found substantial glial heterogeneity with tissue region: we identified region-specific oligodendrocyte precursor cells (OPCs) that retain developmental origin markers into adulthood, distinguishing them from mouse OPCs. Region-specific OPCs give rise to similar oligodendrocyte populations, however spinal cord oligodendrocytes exhibit markers such as SKAP2 which are associated with increased myelin production and we found a spinal cord selective population particularly equipped for producing long and thick myelin sheaths based on the expression of genes/proteins such as HCN2. Spinal cord microglia exhibit a more activated phenotype compared to brain microglia, suggesting that the spinal cord is a more pro-inflammatory environment, a difference that intensifies with age. Astrocyte gene expression correlates strongly with CNS region, however, astrocytes do not show a more activated state with region or age. Across all glia, sex differences are subtle but the consistent increased expression of protein-folding genes in male donors hints at pathways that may contribute to sex differences in disease susceptibility. These findings are essential to consider for understanding selective CNS pathologies and developing tailored therapeutic strategies.

p53 directs leader cell behavior, migration, and clearance during epithelial repair.

Epithelial cells migrate across wounds to repair injured tissue. Leader cells at the front of migrating sheets often drive this process. However, it is unclear how leaders emerge from an apparently homogeneous epithelial cell population. We characterized leaders emerging from epithelial monolayers in cell culture and found that they activated the stress sensor p53, which was sufficient to initiate leader cell behavior. p53 activated the cell cycle inhibitor p21WAF1/CIP1, which in turn induced leader behavior through inhibition of cyclin-dependent kinase activity. p53 also induced crowding hypersensitivity in leader cells such that, upon epithelial closure, they were eliminated by cell competition. Thus, mechanically induced p53 directs emergence of a transient population of leader cells that drive migration and ensures their clearance upon epithelial repair.

Matrix metalloproteinases: protective roles in cancer.

The original notion that matrix metalloproteinases (MMPs) act as tumour and metastasis-promoting enzymes by clearing a path for tumour cells to invade and metastasize has been challenged in the last decade. It has become clear that MMPs are involved in numerous steps of tumour progression and metastasis, and hence are now considered to be multifaceted proteases. Moreover, more recent experimental evidence indicates that some members of the MMP family behave as tumour-suppressor enzymes and should therefore be regarded as anti-targets in cancer therapy. The complexity of the pro- and anti-tumorigenic and -metastatic functions might partly explain why broad-spectrum MMP inhibitors failed in phase III clinical trials. This review will provide a focussed overview of the published data on the tumour-suppressive behaviour of MMPs.

G-helix of maspin mediates effects on cell migration and adhesion.

Maspin is a member of the serine protease inhibitor (serpin) superfamily that lacks protease inhibitory ability, although displaying tumor metastasis-suppressing activity resulting from its influence on cell migration, invasion, proliferation, apoptosis, and adhesion. The molecular mechanisms of these actions of maspin are as yet undefined. Here, we sought to identify critical functional motifs by the expression of maspin with point mutations at sites potentially involved in protein-protein interactions: the G α-helix (G-helix), an internal salt bridge or the P1 position of the reactive center loop. Our findings indicate that only mutations in the G-helix attenuated inhibition of cell migration by maspin and that this structural element is also involved in the effect of maspin on cell adhesion. The action of maspin on cell migration could be mimicked by a 15-mer G-helix peptide, indicating that the G-helix is both essential and sufficient for this effect. In addition, we provide evidence that the effects of the G-helix of maspin are dependent on ß1 integrins. These data reveal that the major extracellular functions associated with the tumor suppressive action of maspin likely involve interactions in which the G-helix plays a key role.

Age-related loss of axonal regeneration is reflected by the level of local translation.

Regeneration capacity is reduced as CNS axons mature. Using laser-mediated axotomy, proteomics and puromycin-based tagging of newly-synthesized proteins in a human embryonic stem cell-derived neuron culture system that allows isolation of axons from cell bodies, we show here that efficient regeneration in younger axons (d45 in culture) is associated with local axonal protein synthesis (local translation). Enhanced regeneration, promoted by co-culture with human glial precursor cells, is associated with increased axonal synthesis of proteins, including those constituting the translation machinery itself. Reduced regeneration, as occurs with the maturation of these axons by d65 in culture, correlates with reduced levels of axonal proteins involved in translation and an inability to respond by increased translation of regeneration promoting axonal mRNAs released from stress granules. Together, our results provide evidence that, as in development and in the PNS, local translation contributes to CNS axon regeneration.

How Right Now? Supporting Mental Health and Resilience Amid COVID-19.

The How Right Now communication initiative (HRN) was developed to facilitate resilience amid the COVID-19 pandemic in the United States. HRN was designed as a conduit for promoting mental health and addressing feelings of grief, worry, and stress experienced during this time. This article provides an overview of the rapid, mixed-method, culturally responsive formative research process undertaken to inform the development of HRN. Specifically, it describes how HRN's disproportionately affected audiences (adults aged 65 and older and their caregivers, adults with preexisting physical and mental health conditions, adults experiencing violence, and adults experiencing economic distress) describe and discuss emotional resilience, what they need to be resilient, and what factors contribute to the perceptions of their ability to "bounce back" from the conditions caused by the COVID-19 pandemic. Data collection methods included an environmental scan (n ≥ 700 publications), social listening (n ≥ 1 million social media posts), partner needs-assessment calls (n = 16), partner-convened listening sessions with community members (n = 29), online focus groups (n = 58), and a national probability survey (n = 731), all in English and Spanish. Results revealed that HRN's audiences have diverse perceptions of what constitutes resilience. However, common factors were identified across populations to support resilience amid the COVID-19 pandemic, including informal and formal social support and access to services to meet basic needs, including food and housing resources. Stress, anxiety, depression, and experience with stigma and discrimination were also linked to resilience. Understanding the perspectives and experiences of disproportionately affected populations is vital to identifying supports and services, including the engagement of community stakeholders.

Failures of nerve regeneration caused by aging or chronic denervation are rescued by restoring Schwann cell c-Jun.

After nerve injury, myelin and Remak Schwann cells reprogram to repair cells specialized for regeneration. Normally providing strong regenerative support, these cells fail in aging animals, and during chronic denervation that results from slow axon growth. This impairs axonal regeneration and causes significant clinical problems. In mice, we find that repair cells express reduced c-Jun protein as regenerative support provided by these cells declines during aging and chronic denervation. In both cases, genetically restoring Schwann cell c-Jun levels restores regeneration to control levels. We identify potential gene candidates mediating this effect and implicate Shh in the control of Schwann cell c-Jun levels. This establishes that a common mechanism, reduced c-Jun in Schwann cells, regulates success and failure of nerve repair both during aging and chronic denervation. This provides a molecular framework for addressing important clinical problems, suggesting molecular pathways that can be targeted to promote repair in the PNS.

Binding of extracellular maspin to beta1 integrins inhibits vascular smooth muscle cell migration.

Maspin is a serpin that has multiple effects on cell behavior, including inhibition of migration. How maspin mediates these diverse effects remains unclear, as it is devoid of protease inhibitory activity. We have previously shown that maspin rapidly inhibits the migration of vascular smooth muscle cells (VSMC), suggesting the involvement of direct interactions with cell surface proteins. Here, using immunofluorescence microscopy, we demonstrate that maspin binds specifically to the surface of VSMC in the dedifferentiated, but not the differentiated, phenotype. Ligand blotting of VSMC lysates revealed the presence of several maspin-binding proteins, with a protein of 150 kDa differentially expressed between the two VSMC phenotypes. Western blotting suggested that this protein was the beta1 integrin subunit, and subsequently both alpha3beta1 and alpha5beta1, but not alphavbeta3, were shown to associate with maspin by coimmunoprecipitation. Specific binding of these integrins was also observed using maspin-affinity chromatography, using HT1080 cell lysates. Direct binding of maspin to alpha5beta1 was confirmed using a recombinant alpha5beta1-Fc fusion protein. Using conformation-dependent anti-beta1 antibodies, maspin binding to VSMC was found to lead to a decrease in the activation status of the integrin. The functional involvement of alpha5beta1 in mediating the effect of maspin was established by the inhibition of migration of CHO cells overexpressing human alpha5 integrin, but not those lacking alpha5 expression. Our observations suggest that maspin engages in specific interactions with a limited number of integrins on VSMC, leading to their inactivation, and that these interactions are responsible for the effects of maspin in the pericellular environment.

Reprogramming of Fibroblasts to Oligodendrocyte Progenitor-like Cells Using CRISPR/Cas9-Based Synthetic Transcription Factors.

Cell lineage reprogramming via transgene overexpression of key master regulatory transcription factors has been well documented. However, the poor efficiency and lack of fidelity of this approach is problematic. Synthetic transcription factors (sTFs)-built from the repurposed CRISPR/Cas9 system-can activate endogenous target genes to direct differentiation or trigger lineage reprogramming. Here we explored whether sTFs could be used to steer mouse neural stem cells and mouse embryonic fibroblasts toward the oligodendrocyte lineage. We developed a non-viral modular expression system to enable stable multiplex delivery of pools of sTFs capable of transcriptional activation of three key oligodendrocyte lineage master regulatory genes (Sox10, Olig2, and Nkx6-2). Delivery of these sTFs could enhance neural stem cell differentiation and initiated mouse embryonic fibroblast direct reprograming toward oligodendrocyte progenitor-like cells. Our findings demonstrate the value of sTFs as tools for activating endogenous genes and directing mammalian cell-type identity.

The migration of paraxial and lateral plate mesoderm cells emerging from the late primitive streak is controlled by different Wnt signals.

BACKGROUND: Co-ordinated cell movement is a fundamental feature of developing embryos. Massive cell movements occur during vertebrate gastrulation and during the subsequent extension of the embryonic body axis. These are controlled by cell-cell signalling and a number of pathways have been implicated. Here we use long-term video microscopy in chicken embryos to visualize the migration routes and movement behaviour of mesoderm progenitor cells as they emerge from the primitive streak (PS) between HH stages 7 and 10. RESULTS: We observed distinct cell movement behaviours along the length of the streak and determined that this is position dependent with cells responding to environmental cues. The behaviour of cells was altered by exposing embryos or primitive streak explants to cell pellets expressing Wnt3a and Wnt5a, without affecting cell fates, thus implicating these ligands in the regulation of cell movement behaviour. Interestingly younger embryos were not responsive, suggesting that Wnt3a and Wnt5a are specifically involved in the generation of posterior mesoderm, consistent with existing mouse and zebrafish mutants. To investigate which downstream components are involved mutant forms of dishevelled (dsh) and prickle1 (pk1) were electroporated into the primitive streak. These had differential effects on the behaviour of mesoderm progenitors emerging from anterior or posterior regions of the streak, suggesting that multiple Wnt pathways are involved in controlling cell migration during extension of the body axis in amniote embryos. CONCLUSION: We suggest that the distinct behaviours of paraxial and lateral mesoderm precursors are regulated by the opposing actions of Wnt5a and Wnt3a as they leave the primitive streak in neurula stage embryos. Our data suggests that Wnt5a acts via prickle to cause migration of cells from the posterior streak. In the anterior streak, this is antagonised by Wnt3a to generate non-migratory medial mesoderm.