Assessment of medical students' clinical performance using high-fidelity simulation: comparison of peer and instructor assessment.

BACKGROUND: High-fidelity simulators are highly useful in assessing clinical competency; they enable reliable and valid evaluation. Recently, the importance of peer assessment has been highlighted in healthcare education, and studies using peer assessment in healthcare, such as medicine, nursing, dentistry, and pharmacy, have examined the value of peer assessment. This study aimed to analyze inter-rater reliability between peers and instructors and examine differences in scores between peers and instructors in the assessment of high-fidelity-simulation-based clinical performance by medical students. METHODS: This study analyzed the results of two clinical performance assessments of 34 groups of fifth-year students at Ajou University School of Medicine in 2020. This study utilized a modified Queen's Simulation Assessment Tool to measure four categories: primary assessment, diagnostic actions, therapeutic actions, and communication. In order to estimate inter-rater reliability, this study calculated the intraclass correlation coefficient and used the Bland and Altman method to analyze agreement between raters. A t-test was conducted to analyze the differences in evaluation scores between colleagues and faculty members. Group differences in assessment scores between peers and instructors were analyzed using the independent t-test. RESULTS: Overall inter-rater reliability of clinical performance assessments was high. In addition, there were no significant differences in overall assessment scores between peers and instructors in the areas of primary assessment, diagnostic actions, therapeutic actions, and communication. CONCLUSIONS: The results indicated that peer assessment can be used as a reliable assessment method compared to instructor assessment when evaluating clinical competency using high-fidelity simulators. Efforts should be made to enable medical students to actively participate in the evaluation process as fellow assessors in high-fidelity-simulation-based assessment of clinical performance in situations similar to real clinical settings.

Reactive microglia and astrocytes in neonatal intraventricular hemorrhage model are blocked by mesenchymal stem cells.

Severe intraventricular hemorrhage (IVH) in premature infants triggers reactive gliosis, causing acute neuronal death and glial scar formation. Transplantation of mesenchymal stem cells (MSCs) has often showed improved CNS recovery in an IVH model, but whether this response is related to reactive glial cells is still unclear. Herein, we suggest that MSCs impede the response of reactive microglia rather than astrocytes, thereby blocking neuronal damage. Astrocytes alone showed mild reactiveness under hemorrhagic conditions mimicked by thrombin treatment, and this was not blocked by MSC-conditioned medium (MSC-CM) in vitro. In contrast, thrombin-induced microglial activation and release of proinflammatory cytokines were inhibited by MSC-CM. Interestingly, astrocytes showed greater reactive response when co-cultured with microglia, and this was abolished in the presence of MSC-CM. Gene expression profiles in microglia revealed that transcript levels of genes for immune response and proinflammatory cytokines were altered by thrombin treatment. This result coincided with the robust phosphorylation of STAT1 and p38 MAPK, which might be responsible for the production and release of proinflammatory cytokines. Furthermore, application of MSC-CM diminished thrombin-mediated phosphorylation of STAT1 and p38 MAPK, supporting the acute anti-inflammatory role of MSCs under hemorrhagic conditions. In line with this, activation of microglia and consequent cytokine release were impaired in Stat1-null mice. However, reactive response in Stat1-deficient astrocytes was maintained. Taken together, our results demonstrate that MSCs mainly block the activation of microglia involving STAT1-mediated cytokine release and subsequent reduction of reactive astrocytes.

Cereblon Maintains Synaptic and Cognitive Function by Regulating BK Channel.

Mutations in the cereblon (CRBN) gene cause human intellectual disability, one of the most common cognitive disorders. However, the molecular mechanisms of CRBN-related intellectual disability remain poorly understood. We investigated the role of CRBN in synaptic function and animal behavior using male mouse and Drosophila models. Crbn knock-out (KO) mice showed normal brain and spine morphology as well as intact synaptic plasticity; however, they also exhibited decreases in synaptic transmission and presynaptic release probability exclusively in excitatory synapses. Presynaptic function was impaired not only by loss of CRBN expression, but also by expression of pathogenic CRBN mutants (human R419X mutant and Drosophila G552X mutant). We found that the BK channel blockers paxilline and iberiotoxin reversed this decrease in presynaptic release probability in Crbn KO mice. In addition, paxilline treatment also restored normal cognitive behavior in Crbn KO mice. These results strongly suggest that increased BK channel activity is the pathological mechanism of intellectual disability in CRBN mutations.SIGNIFICANCE STATEMENTCereblon (CRBN), a well known target of the immunomodulatory drug thalidomide, was originally identified as a gene that causes human intellectual disability when mutated. However, the molecular mechanisms of CRBN-related intellectual disability remain poorly understood. Based on the idea that synaptic abnormalities are the most common factor in cognitive dysfunction, we monitored the synaptic structure and function of Crbn knock-out (KO) animals to identify the molecular mechanisms of intellectual disability. Here, we found that Crbn KO animals showed cognitive deficits caused by enhanced BK channel activity and reduced presynaptic glutamate release. Our findings suggest a physiological pathomechanism of the intellectual disability-related gene CRBN and will contribute to the development of therapeutic strategies for CRBN-related intellectual disability.

Cdk5 regulates N-cadherin-dependent neuronal migration during cortical development.

Cyclin-dependent kinase 5 (Cdk5) controls neuronal migration in the developing cortex when multipolar newborn neurons transform to become bipolar. However, by which mechanisms Cdk5 controls cell adhesion in migrating neurons are not fully understood. In this study, we examined the functional interaction between Cdk5 and N-cadherin (Ncad) in newborn neurons when they undergo the multipolar to bipolar transition in the intermediate zone (IZ). Detailed expression analysis revealed that both Cdk5 and Ncad were present in GFP-electroporated migrating neurons in the IZ. Misexpression of dominant negative Cdk5 into the embryonic brains stalled neuronal locomotion in the lower IZ in which arrested cells were round or multipolar. When Ncad was co-introduced with Cdk5DN, however, cells continue to migrate into the cortical plate (CP) and migrating neurons acquired typical bipolar morphology with a pia-directed leading process. Similarly, downregulation of CDK5 resulted in lesser aggregation ability, reversed by the expression of Ncad in vitro. Down-regulation of activity or protein level of CDK5 did not alter the total amount of NCAD proteins but lowered its surface expression in cells. Lastly, expression of CDK5 and NCAD overlapped in the IZ of the human fetal cortex, indicating that the role of Cdk5 and Ncad in neuronal migration is evolutionarily conserved.

Lysophosphatidic acid receptor 1 (LPA1) plays critical roles in microglial activation and brain damage after transient focal cerebral ischemia.

BACKGROUND: Lysophosphatidic acid receptor 1 (LPA1) is in the spotlight because its synthetic antagonist has been under clinical trials for lung fibrosis and psoriasis. Targeting LPA1 might also be a therapeutic strategy for cerebral ischemia because LPA1 triggers microglial activation, a core pathogenesis in cerebral ischemia. Here, we addressed this possibility using a mouse model of transient middle cerebral artery occlusion (tMCAO). METHODS: To address the role of LPA1 in the ischemic brain damage, we used AM095, a selective LPA1 antagonist, as a pharmacological tool and lentivirus bearing a specific LPA1 shRNA as a genetic tool. Brain injury after tMCAO challenge was accessed by determining brain infarction and neurological deficit score. Role of LPA1 in tMCAO-induced microglial activation was ascertained by immunohistochemical analysis. Proinflammatory responses in the ischemic brain were determined by qRT-PCR and immunohistochemical analyses, which were validated in vitro using mouse primary microglia. Activation of MAPKs and PI3K/Akt was determined by Western blot analysis. RESULTS: AM095 administration immediately after reperfusion attenuated brain damage such as brain infarction and neurological deficit at 1 day after tMCAO, which was reaffirmed by LPA1 shRNA lentivirus. AM095 administration also attenuated brain infarction and neurological deficit at 3 days after tMCAO. LPA1 antagonism attenuated microglial activation; it reduced numbers and soma size of activated microglia, reversed their morphology into less toxic one, and reduced microglial proliferation. Additionally, LPA1 antagonism reduced mRNA expression levels of proinflammatory cytokines and suppressed NF-κB activation, demonstrating its regulatory role of proinflammatory responses in the ischemic brain. Particularly, these LPA1-driven proinflammatory responses appeared to occur in activated microglia because NF-κB activation occurred mainly in activated microglia in the ischemic brain. Regulatory role of LPA1 in proinflammatory responses of microglia was further supported by in vitro findings using lipopolysaccharide-stimulated cultured microglia, showing that suppressing LPA1 activity reduced mRNA expression levels of proinflammatory cytokines. In the ischemic brain, LPA1 influenced PI3K/Akt and MAPKs; suppressing LPA1 activity decreased MAPK activation and increased Akt phosphorylation. CONCLUSION: This study demonstrates that LPA1 is a new etiological factor for cerebral ischemia, strongly indicating that its modulation can be a potential strategy to reduce ischemic brain damage.

Epigenetic regulation of Kcna3-encoding Kv1.3 potassium channel by cereblon contributes to regulation of CD4+ T-cell activation.

The role of cereblon (CRBN) in T cells is not well understood. We generated mice with a deletion in Crbn and found cereblon to be an important antagonist of T-cell activation. In mice lacking CRBN, CD4(+) T cells show increased activation and IL-2 production on T-cell receptor stimulation, ultimately resulting in increased potassium flux and calcium-mediated signaling. CRBN restricts T-cell activation via epigenetic modification of Kcna3, which encodes the Kv1.3 potassium channel required for robust calcium influx in T cells. CRBN binds directly to conserved DNA elements adjacent to Kcna3 via a previously uncharacterized DNA-binding motif. Consequently, in the absence of CRBN, the expression of Kv1.3 is derepressed, resulting in increased Kv1.3 expression, potassium flux, and CD4(+) T-cell hyperactivation. In addition, experimental autoimmune encephalomyelitis in T-cell-specific Crbn-deficient mice was exacerbated by increased T-cell activation via Kv1.3. Thus, CRBN limits CD4(+) T-cell activation via epigenetic regulation of Kv1.3 expression.

Sphingosine 1-phosphate receptor subtype 3 (S1P3) contributes to brain injury after transient focal cerebral ischemia via modulating microglial activation and their M1 polarization.

BACKGROUND: The pathogenic roles of receptor-mediated sphingosine 1-phosphate (S1P) signaling in cerebral ischemia have been evidenced mainly through the efficacy of FTY720 that binds non-selectively to four of the five S1P receptors (S1P1,3,4,5). Recently, S1P1 and S1P2 were identified as specific receptor subtypes that contribute to brain injury in cerebral ischemia; however, the possible involvement of other S1P receptors remains unknown. S1P3 can be the candidate because of its upregulation in the ischemic brain, which was addressed in this study, along with underlying pathogenic mechanisms. METHODS: We used transient middle cerebral artery occlusion/reperfusion (tMCAO), a mouse model of transient focal cerebral ischemia. To identify S1P3 as a pathogenic factor in cerebral ischemia, we employed a specific S1P3 antagonist, CAY10444. Brain damages were assessed by brain infarction, neurological score, and neurodegeneration. Histological assessment was carried out to determine microglial activation, morphological transformation, and proliferation. M1/M2 polarization and relevant signaling pathways were determined by biochemical and immunohistochemical analysis. RESULTS: Inhibiting S1P3 immediately after reperfusion with CAY10444 significantly reduced tMCAO-induced brain infarction, neurological deficit, and neurodegeneration. When S1P3 activity was inhibited, the number of activated microglia was markedly decreased in both the periischemic and ischemic core regions in the ischemic brain 1 and 3 days following tMCAO. Moreover, inhibiting S1P3 significantly restored the microglial shape from amoeboid to ramified microglia in the ischemic core region 3 days after tMCAO, and it attenuated microglial proliferation in the ischemic brain. In addition to these changes, S1P3 signaling influenced the proinflammatory M1 polarization, but not M2. The S1P3-dependent regulation of M1 polarization was clearly shown in activated microglia, which was affirmed by determining the in vivo activation of microglial NF-κB signaling that is responsible for M1 and in vitro expression levels of proinflammatory cytokines in activated microglia. As downstream effector pathways in an ischemic brain, S1P3 influenced phosphorylation of ERK1/2, p38 MAPK, and Akt. CONCLUSIONS: This study identified S1P3 as a pathogenic mediator in an ischemic brain along with underlying mechanisms, involving its modulation of microglial activation and M1 polarization, further suggesting that S1P3 can be a therapeutic target for cerebral ischemia.

Functional Diversification of Motor Neuron-specific Isl1 Enhancers during Evolution.

Functional diversification of motor neurons has occurred in order to selectively control the movements of different body parts including head, trunk and limbs. Here we report that transcription of Isl1, a major gene necessary for motor neuron identity, is controlled by two enhancers, CREST1 (E1) and CREST2 (E2) that allow selective gene expression of Isl1 in motor neurons. Introduction of GFP reporters into the chick neural tube revealed that E1 is active in hindbrain motor neurons and spinal cord motor neurons, whereas E2 is active in the lateral motor column (LMC) of the spinal cord, which controls the limb muscles. Genome-wide ChIP-Seq analysis combined with reporter assays showed that Phox2 and the Isl1-Lhx3 complex bind to E1 and drive hindbrain and spinal cord-specific expression of Isl1, respectively. Interestingly, Lhx3 alone was sufficient to activate E1, and this may contribute to the initiation of Isl1 expression when progenitors have just developed into motor neurons. E2 was induced by onecut 1 (OC-1) factor that permits Isl1 expression in LMCm neurons. Interestingly, the core region of E1 has been conserved in evolution, even in the lamprey, a jawless vertebrate with primitive motor neurons. All E1 sequences from lamprey to mouse responded equally well to Phox2a and the Isl1-Lhx3 complex. Conversely, E2, the enhancer for limb-innervating motor neurons, was only found in tetrapod animals. This suggests that evolutionarily-conserved enhancers permit the diversification of motor neurons.

Putative Cell Adhesion Membrane Protein Vstm5 Regulates Neuronal Morphology and Migration in the Central Nervous System.

UNLABELLED: During brain development, dynamic changes in neuronal membranes perform critical roles in neuronal morphogenesis and migration to create functional neural circuits. Among the proteins that induce membrane dynamics, cell adhesion molecules are important in neuronal membrane plasticity. Here, we report that V-set and transmembrane domain-containing protein 5 (Vstm5), a cell-adhesion-like molecule belonging to the Ig superfamily, was found in mouse brain. Knock-down of Vstm5 in cultured hippocampal neurons markedly reduced the complexity of dendritic structures, as well as the number of dendritic filopodia. Vstm5 also regulates neuronal morphology by promoting dendritic protrusions that later develop into dendritic spines. Using electroporation in utero, we found that Vstm5 overexpression delayed neuronal migration and induced multiple branches in leading processes during corticogenesis. These results indicate that Vstm5 is a new cell-adhesion-like molecule and is critically involved in synaptogenesis and corticogenesis by promoting neuronal membrane dynamics. SIGNIFICANCE STATEMENT: Neuronal migration and morphogenesis play critical roles in brain development and function. In this study, we demonstrate for the first time that V-set and transmembrane domain-containing protein 5 (Vstm5), a putative cell adhesion membrane protein, modulates both the position and complexity of central neurons by altering their membrane morphology and dynamics. Vstm5 is also one of the target genes responsible for variations in patient responses to treatments for major depressive disorder. Our results provide the first evidence that Vstm5 is a novel factor involved in the modulation of the neuronal membrane and a critical element in normal neural circuit formation during mammalian brain development.

Signal transducer and activator of transcription-3 maintains the stemness of radial glia at mid-neurogenesis.

Radial glial cells are stem cell-like populations of glial nature that supply neurons either directly or indirectly via basal progenitors that give rise to neurons. Here we show that signal transducer and activator of transcription-3 (STAT3) signaling, a cytokine signaling mediated by Janus tyrosine kinase (Jak), is active during neurogenesis in radial glia (RG) but not in basal progenitors. Enhanced STAT3 signaling in cortical progenitors caused more RG to persist rather than become neurons. Targeted deletion or RNAi-mediated knockdown of Stat3 resulted in fewer radial glial cells and more basal progenitors and led to premature neurogenesis. The neuronal populations affected in Stat3 mutant mice were the late-born neurons that constitute the upper cortical layers rather than early-born neurons, thus supporting the view that the role of STAT3 at mid-neurogenesis is layer specific. Analysis of dividing RG revealed that STAT3 selectively increased the proportion of dividing RG, whereas downregulation of STAT3 reduced the proportion. Consistent with this, STAT3 activity in dividing RG was associated frequently with vertical cleavage. Pair-cell analysis showed that elevated STAT3 activity correlated with symmetric division of RG, producing more RG, whereas elimination of STAT3 generated more neurogenic cells. Together, our results suggest that STAT3 maintains the stemness of RG and inhibits their transition to basal progenitors at mid-neurogenesis, so probably preserving a pool of RG for later neurogenesis or gliogenesis.

Light-induced Notch activity controls neurogenic and gliogenic potential of neural progenitors.

Oscillations in Notch signaling are essential for reserving neural progenitors for cellular diversity in developing brains. Thus, steady and prolonged overactivation of Notch signaling is not suitable for generating neurons. To acquire greater temporal control of Notch activity and mimic endogenous oscillating signals, here we adopted a light-inducible transgene system to induce active form of Notch NICD in neural progenitors. Alternating Notch activity saved more progenitors that are prone to produce neurons creating larger number of mixed clones with neurons and progenitors in vitro, compared to groups with no light or continuous light stimulus. Furthermore, more upper layer neurons and astrocytes arose upon intermittent Notch activity, indicating that dynamic Notch activity maintains neural progeny and fine-tune neuron-glia diversity.

The E3 ligase Mind bomb-1 (Mib1) modulates Delta-Notch signaling to control neurogenesis and gliogenesis in the developing spinal cord.

The Notch signaling pathway is essential for neuronal and glial specification during CNS development. Mind bomb-1 (Mib1) is an E3 ubiquitin ligase that ubiquitinates and promotes the endocytosis of Notch ligands. Although Mib1 is essential for transmitting the Notch signal, it is still unclear whether it is a primary regulator of Notch ligand activity in the developing spinal cord. In Mib1 conditional knock-out mice, we observed depletion of spinal progenitors, premature differentiation of neurons, and unbalanced specification of V2 interneurons, all of which mimic the conventional Notch phenotype. In agreement with this, the reduction of progenitors in the absence of Mib1 led to a loss of both astrocytes and oligodendrocytes. Late removal of Mib1 using a drug-inducible system suppressed glial differentiation, suggesting that Mib1 continues to play a role in the formation of late progenitors mainly designated for gliogenesis. Finally, misexpression of Mib1 or Mib1 deletion mutants revealed that the ring domain of Mib1 is required for the specification of V2 interneurons in the chick neural tube. Together, these findings suggest that Mib1 is a major component of the signal-sending cells required to provide Notch ligand activity for specifying neurons and glia in the spinal cord.

The complex morphology of reactive astrocytes controlled by fibroblast growth factor signaling.

Astrocytes are the most abundant cell-type of the human brain and play a variety of roles in brain homeostasis and synaptic maturation, under normal conditions. However, astrocytes undergo dramatic pathological changes in response to brain injury, such as reactive gliosis and glial scar formation. Although abnormal hypertrophy and massive proliferation of astrocytes are obvious, the molecular identity and cues that dictate the structural changes in reactive astrocytes remain unclear. This study proposes that fibroblast growth factor (FGF) signaling is responsible for making astrocyte morphology more complex and hypertrophic in response to an inflammatory stimulus such as lipopolysaccharide. Primary astrocytes isolated from perinatal brains developed more branches in the presence of FGF8 or lesser branches in the presence of FGF2. Introduction of the constitutively active form of the FGF receptor 3 (caFGFR3) into the brain increases the structural complexity, with greater glial fibrillary acidic protein level in astrocytes, while overexpression of a dominant-negative form of FGFR3 (dnFGFR3) reduces it. Treatment of FGF8 facilitated the wound-healing process of primary astrocytes in vitro by changing their morphology, indicating that the FGF signal may control the responsiveness of astrocytes in injury conditions. Finally, the blockade of FGF signaling by introducing dnFGFR3 at the site of reactive gliosis reduces astrocyte branch formation and minimizes hypertrophic responses during reactive gliosis. Taken together, these results indicate that FGF8-FGFR3 signaling controls structural changes in astrocytes during reactive gliosis, under pathogenic conditions.

Translational regulation of NeuroD1 expression by FMRP: involvement in glutamatergic neuronal differentiation of cultured rat primary neural progenitor cells.

Fragile X mental retardation protein (FMRP) is encoded by Fmr1 gene in which mutation is known to cause fragile X syndrome characterized by mental impairment and other psychiatric symptoms similar to autism spectrum disorders. FMRP plays important roles in cellular mRNA biology such as transport, stability, and translation as an RNA-binding protein. In the present study, we identified potential role of FMRP in the neural differentiation, using cortical neural progenitor cells from Sprague-Dawley rat. We newly found NeuroD1, an essential regulator of glutamatergic neuronal differentiation, as a new mRNA target interacting with FMRP in co-immunoprecipitation experiments. We also identified FMRP as a regulator of neuronal differentiation by modulating NeuroD1 expression. Down-regulation of FMRP by siRNA also increased NeuroD1 expression along with increased pre- and post-synaptic development of glutamatergic neuron, as evidenced by Western blot and immunocytochemistry. On the contrary, cells harboring FMRP over-expression construct showed decreased NeuroD1 expression. Treatment of cultured neural precursor cells with a histone deacetylase inhibitor, valproic acid known as an inducer of hyper-glutamatergic neuronal differentiation, down-regulated the expression of FMRP, and induced NeuroD1 expression. Our study suggests that modulation of FMRP expression regulates neuronal differentiation by interaction with its binding target mRNA, and provides an example of the gene and environmental interaction regulating glutamatergic neuronal differentiation.

CoMAGC: a corpus with multi-faceted annotations of gene-cancer relations.

BACKGROUND: In order to access the large amount of information in biomedical literature about genes implicated in various cancers both efficiently and accurately, the aid of text mining (TM) systems is invaluable. Current TM systems do target either gene-cancer relations or biological processes involving genes and cancers, but the former type produces information not comprehensive enough to explain how a gene affects a cancer, and the latter does not provide a concise summary of gene-cancer relations. RESULTS: In this paper, we present a corpus for the development of TM systems that are specifically targeting gene-cancer relations but are still able to capture complex information in biomedical sentences. We describe CoMAGC, a corpus with multi-faceted annotations of gene-cancer relations. In CoMAGC, a piece of annotation is composed of four semantically orthogonal concepts that together express 1) how a gene changes, 2) how a cancer changes and 3) the causality between the gene and the cancer. The multi-faceted annotations are shown to have high inter-annotator agreement. In addition, we show that the annotations in CoMAGC allow us to infer the prospective roles of genes in cancers and to classify the genes into three classes according to the inferred roles. We encode the mapping between multi-faceted annotations and gene classes into 10 inference rules. The inference rules produce results with high accuracy as measured against human annotations. CoMAGC consists of 821 sentences on prostate, breast and ovarian cancers. Currently, we deal with changes in gene expression levels among other types of gene changes. The corpus is available at http://biopathway.org/CoMAGCunder the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0). CONCLUSIONS: The corpus will be an important resource for the development of advanced TM systems on gene-cancer relations.

The mouse Wnt/PCP protein Vangl2 is necessary for migration of facial branchiomotor neurons, and functions independently of Dishevelled.

During development, facial branchiomotor (FBM) neurons, which innervate muscles in the vertebrate head, migrate caudally and radially within the brainstem to form a motor nucleus at the pial surface. Several components of the Wnt/planar cell polarity (PCP) pathway, including the transmembrane protein Vangl2, regulate caudal migration of FBM neurons in zebrafish, but their roles in neuronal migration in mouse have not been investigated in detail. Therefore, we analyzed FBM neuron migration in mouse looptail (Lp) mutants, in which Vangl2 is inactivated. In Vangl2(Lp/+) and Vangl2(Lp/Lp) embryos, FBM neurons failed to migrate caudally from rhombomere (r) 4 into r6. Although caudal migration was largely blocked, many FBM neurons underwent normal radial migration to the pial surface of the neural tube. In addition, hindbrain patterning and FBM progenitor specification were intact, and FBM neurons did not transfate into other non-migratory neuron types, indicating a specific effect on caudal migration. Since loss-of-function in some zebrafish Wnt/PCP genes does not affect caudal migration of FBM neurons, we tested whether this was also the case in mouse. Embryos null for Ptk7, a regulator of PCP signaling, had severe defects in caudal migration of FBM neurons. However, FBM neurons migrated normally in Dishevelled (Dvl) 1/2 double mutants, and in zebrafish embryos with disrupted Dvl signaling, suggesting that Dvl function is essentially dispensable for FBM neuron caudal migration. Consistent with this, loss of Dvl2 function in Vangl2(Lp/+) embryos did not exacerbate the Vangl2(Lp/+) neuronal migration phenotype. These data indicate that caudal migration of FBM neurons is regulated by multiple components of the Wnt/PCP pathway, but, importantly, may not require Dishevelled function. Interestingly, genetic-interaction experiments suggest that rostral FBM neuron migration, which is normally suppressed, depends upon Dvl function.

Axonal neuropathy-associated TRPV4 regulates neurotrophic factor-derived axonal growth.

Spinal muscular atrophy and hereditary motor and sensory neuropathies are characterized by muscle weakness and atrophy caused by the degenerations of peripheral motor and sensory nerves. Recent advances in genetics have resulted in the identification of missense mutations in TRPV4 in patients with these hereditary neuropathies. Neurodegeneration caused by Ca(2+) overload due to the gain-of-function mutation of TRPV4 was suggested as the molecular mechanism for the neuropathies. Despite the importance of TRPV4 mutations in causing neuropathies, the precise role of TRPV4 in the sensory/motor neurons is unknown. Here, we report that TRPV4 mediates neurotrophic factor-derived neuritogenesis in developing peripheral neurons. TRPV4 was found to be highly expressed in sensory and spinal motor neurons in early development as well as in the adult, and the overexpression or chemical activation of TRPV4 was found to promote neuritogenesis in sensory neurons as well as PC12 cells, whereas its knockdown and pharmacologic inhibition had the opposite effect. More importantly, nerve growth factor or cAMP treatment up-regulated the expression of phospholipase A(2) and TRPV4. Neurotrophic factor-derived neuritogenesis appears to be regulated by the phospholipase A(2)-mediated TRPV4 pathway. These findings show that TRPV4 mediates neurotrophic factor-induced neuritogenesis in developing peripheral nerves. Because neurotrophic factors are essential for the maintenance of peripheral nerves, these findings suggest that aberrant TRPV4 activity may lead to some types of pathology of sensory and motor nerves.

Factors in turnover intention of cardiothoracic surgery residents.

Increasing numbers of cardiothoracic surgery residents are resigning, without completing their training. This study analyzes how their turnover intention is related to the training environment, and individual psychological factors. Responses by 57 Korean cardiothoracic surgery residents were analyzed. Their levels of depression, anxiety, grit, and empathy, working conditions, the effect of someone's presence to discuss their concerns with, burnout, and turnover intention were identified as the research variables. Descriptive statistical analysis, correlation analysis, and structural equation modeling were used for data analysis. Burnout has the most significant relationship with turnover intention. It has a mediating effect on the influence of depression, grit (sustained interest), and working conditions, over turnover intention. Empathy, and the presence of someone to discuss concerns with, also affect turnover intention directly. The study also confirmed that grit and work satisfaction affect turnover intention indirectly, through burnout. The study identified both individual- and systemic-level factors for an effective training environment, to reduce cardiothoracic surgery residents' tendencies of leaving the residency program, and supporting them for greater satisfaction with their career choice. In order to resolve negative emotions such as burnout and depression, and foster empathy, a human resource development program for the residents' psychological support must be prepared. The program director should be adequately educated to take charge of the training program, oversee the residents' education and welfare, and perform the roles of role-model and mentor.

Transcriptional control of motor pool formation and motor circuit connectivity by the LIM-HD protein Isl2.

The fidelity of motor control requires the precise positional arrangement of motor pools and the establishment of synaptic connections between them. During neural development in the spinal cord, motor nerves project to specific target muscles and receive proprioceptive input from these muscles via the sensorimotor circuit. LIM-homeodomain transcription factors are known to play a crucial role in successively restricting specific motor neuronal fates. However, their exact contribution to limb-based motor pools and locomotor circuits has not been fully understood. To address this, we conducted an investigation into the role of Isl2, a LIM-homeodomain transcription factor, in motor pool organization. We found that deletion of Isl2 led to the dispersion of motor pools, primarily affecting the median motor column (MMC) and lateral motor column (LMC) populations. Additionally, hindlimb motor pools lacked Etv4 expression, and we observed reduced terminal axon branching and disorganized neuromuscular junctions in Isl2-deficient mice. Furthermore, we performed transcriptomic analysis on the spinal cords of Isl2-deficient mice and identified a variety of downregulated genes associated with motor neuron (MN) differentiation, axon development, and synapse organization in hindlimb motor pools. As a consequence of these disruptions, sensorimotor connectivity and hindlimb locomotion were impaired in Isl2-deficient mice. Taken together, our findings highlight the critical role of Isl2 in organizing motor pool position and sensorimotor circuits in hindlimb motor pools. This research provides valuable insights into the molecular mechanisms governing motor control and its potential implications for understanding motor-related disorders in humans.

Islet-to-LMO stoichiometries control the function of transcription complexes that specify motor neuron and V2a interneuron identity.

LIM transcription factors bind to nuclear LIM interactor (Ldb/NLI/Clim) in specific ratios to form higher-order complexes that regulate gene expression. Here we examined how the dosage of LIM homeodomain proteins Isl1 and Isl2 and LIM-only protein Lmo4 influences the assembly and function of complexes involved in the generation of spinal motor neurons (MNs) and V2a interneurons (INs). Reducing the levels of Islet proteins using a graded series of mutations favored V2a IN differentiation at the expense of MN formation. Although LIM-only proteins (LMOs) are predicted to antagonize the function of Islet proteins, we found that the presence or absence of Lmo4 had little influence on MN or V2a IN specification. We did find, however, that the loss of MNs resulting from reduced Islet levels was rescued by eliminating Lmo4, unmasking a functional interaction between these proteins. Our findings demonstrate that MN and V2a IN fates are specified by distinct complexes that are sensitive to the relative stoichiometries of the constituent factors and we present a model to explain how LIM domain proteins modulate these complexes and, thereby, this binary-cell-fate decision.