Mi-Ryoung Song

Ion channels are essential for sensing somatic stimuli, and their dysregulation can cause chronic conditions such as neuropathic pain. Although the potassium channel Twik-1 has been linked to sensory processing, its specific roles in the somatosensory system under normal and disease conditions remain unclear. Here, we demonstrate that systemic deletion of Twik-1 selectively reduces innocuous tactile and noxious mechanosensation evoked by both static and dynamic mechanical stimuli and facilitates recovery from mechanical hypersensitivity after peripheral nerve injury. Conditional deletion of Twik-1 in spinal cord neurons, pan-inhibitory neurons, or spinal inhibitory interneurons consistently disrupts innocuous tactile and noxious mechanical sensitivity, while sparing responses to high-intensity mechanical stimulation as well as noxious heat and cold. Notably, these manipulations do not affect nerve injury-induced mechanical hypersensitivity. In contrast, selective deletion of Twik-1 in dorsal root ganglion (DRG) neurons preserves baseline somatosensory and nociceptive functions, including innocuous tactile and noxious mechanical sensitivity, but impairs the persistence of mechanical hypersensitivity after nerve injury. This reduction in hypersensitivity is accompanied by decreased aberrant excitability in injured DRG neurons and distinct transcriptional changes. Together, these results suggest that Twik-1 facilitates innocuous tactile and noxious mechanosensation through spinal inhibitory circuits under baseline conditions, while supporting the maintenance of neuropathic pain via its functions in primary sensory neurons.

Motor neurons (MNs), which control body movement, consist of distinct motor pools, that target specific muscles. The precise delineation of these motor pools necessitates an understanding of their specialized gene expression profiles. By integrating single-cell transcriptomics and epigenomics, using scATAC-seq, scRNA-seq and histone modification datasets, we identified cis-regulatory elements (CREs) specific to five MN-lineage clusters, which exhibit distinct gene ontology terms, transcription factor (TF) binding motifs, and disease-associated traits across them. Notably, LIM-homeodomain (LIM-HD) TF motifs and their footprints were differentially enriched in corresponding individual motor column CREs, including a combined Isl1 and Lhx3 motif consistent with their known role in MN identity specification. Within the genomic locus of Etv4, a gene essential for limb motor pools, we identified three enhancer candidates among CREs enriched in LMC neurons. Functional assays demonstrated that these enhancers exhibited robust and specific activity in ETV4-expressing motor pools when electroporated into chicken neural tubes. This study demonstrates that an integrated in silico analysis of epigenetic and transcriptomic data at the single-cell level can predict putative CREs governing the identity of distinct MN subgroups, providing insights into motor pool diversification and gene regulation.

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.

The fidelity of motor control requires the precise positional arrangement of motor pools and the establishment of synaptic connections between these pools. In the developing spinal cord, motor nerves project to specific target muscles and receive proprioceptive input from the muscles via the sensorimotor circuit. LIM-homeodomain transcription factors are known to successively restrict specific motor neuronal fates during neural development; however, it remains unclear to what extent they contribute to limb-based motor pools and locomotor circuits. Here, we showed in mice that deletion of Isl2 resulted in scattered motor pools, primarily in the median motor column and lateral LMC (LMCl) populations, and lacked Pea3 expression in the hindlimb motor pools, accompanied by reduced terminal axon branching and disorganized neuromuscular junctions. Transcriptomic analysis of Isl2 - deficient spinal cords revealed that a variety of genes involved in motor neuron differentiation, axon development, and synapse organization were downregulated in hindlimb motor pools. Moreover, the loss of Isl2 impaired sensorimotor connectivity and hindlimb locomotion. Together, our studies indicate that Isl2 plays a critical role in organizing motor pool position and sensorimotor circuits in hindlimb motor pools.

Oxidative stress triggers axon degeneration and cell death, leading to the development of neurodegenerative diseases. Spinal motor nerves project very long axons, increasing the burden on axonal transport and metabolism. As such, spinal motor nerves are expected to be susceptible to oxidative stress, but model systems for visualizing and investigating acutely degenerating motor axons are limited. In this study, we establish motor nerve organoids from human pluripotent stem cells (hPSCs) with properties similar to those of neuromesodermal progenitors (NMPs), a population of progenitor cells that comprise the caudal spinal cord. Three-dimensional differentiation of organoids efficiently gave rise to mature motor neurons within 18 days. Adherent organoids showed robust axon fascicles and active growth cones under normal conditions. In addition, more homogenous and efficient generation of motor neurons were achieved when organoids were dissociated into individual cells. Hydrogen peroxide-induced oxidative stress resulted in a broad range of signs of axon degeneration including the disappearance of growth cones and neurites, axon retraction, axon fragmentation and bleb formation, and apoptotic cell death, whose severity can be reliably quantifiable in our culture system. Remarkably, cytoskeletal drugs modulating actin or microtubule turnover differentially facilitated axon dynamics and increased axon regenerative potential. Taken together, our motor nerve organoid model could be potentially useful for drug screens evaluating the rearrangement of cytoskeletons in regenerating motor axons.

본 연구의 목적은 불확실한 미래사회에 대응하기 위하여 아동이 갖추어야 할 역량이 무엇인지 규명하고, 아동기 역량지표를 개발하며 타당도를 검증하고자 하였다. 이를 위해 국내외 선행연구 고찰을 통해 4개 영역의 역량을 최초 개발하였으며, 초등학교 2, 4, 6학년 289명을 대상으로 설문조사를 실시하여 탐색적 요인분석, 확인적 요인분석, 그리고 신뢰도 분석 등을 실시하여 지표의 타당성을 확보하였다. 연구 결과, 아동기 역량지표는 ‘사회관계’, ‘심미적 감성’, ‘자기주도성 및 표현’, ‘자기관리’, ‘여가 및 놀이’의 5개 영역, 30개 문항으로 확정되었다. 본 연구에서 개발된 아동기 역량지표는 성인의 관점에서 아동이 달성하고 지향해야 할 발달목표가 아닌, 아동이라면 누구나 아동기에 누리고 경험하고 갖추어야 할 행동과 태도 요소를 모두 포괄하였다는데 의의가 있다. 또한 여가와 놀이, 심미적 감성 등 미래사회를 살아가는 아동이 갖추어야 할 역량을 포함하였다는데 의의가 크다. 본 지표가 아동이 자신이 가지고 있는 능력을 최대한 펼치고 미래사회에 부응하는 성인으로 성장하기 위해 갖추어야 할 지원 방향을 설정하는데 기초자료가 될 수 있을 것이라 기대한다.

본 연구의 목적은 정서적 학대와 방임의 판단 과정에서 판단의 준거 범주를 마련하고자 한다. 정서적 학대와 방임의 판단 준거 범주를 구성하기 위해, 아동학대를 판단하기 요인에 대한 문헌고찰을 통해 정서학대와 방임의 판단준거 안을 구성하였고, 판단 준거 안에 관해 전문가 21명 대상으로 쌍대비교 설문조사를 실시하였다. AHP 분석을 이용하여 판단 준거의 상대적 중요도를 도출하였다. 정서적 학대와 방임의 판단 준거 8개에 대한 상대적 중요도를 분석한 결과는 다음과 같다. 정서적 학대의 판단 준거에 대한 상대적 중요도 결과는 ‘결과의 심각성’(0.230), ‘행위의 위험성’(0.192), ‘지속성’(0.134), ‘반복성’(0.130), ‘의도성’(0.125), ‘신고 이력’(0.078), ‘아동의 연령’(0.070), ‘행위 유형’(0.041) 순으로 나타났다. 방임의 판단 준거에 대한 상대적 중요도는 ‘결과의 심각성’(0.248), ‘행위의 위험성’(0.189), ‘지속성’(0.124), ‘반복성’(0.120), ‘의도성’(0.105), ‘아동의 연령’(0.091), ‘신고 이력’(0.066), ‘행위 유형’(0.058) 순으로 나타났다. 정서적 학대와 방임의 8개 판단 준거를 설정하여 준거에 따른 점수를 부여하는 방법을 제시하였다. 이를 통해 정서학대와 방임 판단 시, 하나의 근거 자료로 활용 할 수 있다.

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.

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). 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. 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. 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.