YAP (yes-associated protein), a key transcriptional co-factor that is negatively regulated by the Hippo pathway, is crucial for the development and size control of multiple organs, including the ...liver. However, its role in the brain remains unclear. Here, we provide evidence for YAP regulation of mouse neocortical astrocytic differentiation and proliferation. YAP was undetectable in neurons, but selectively expressed in neural stem cells (NSCs) and astrocytes. YAP in NSCs was required for neocortical astrocytic differentiation, with no apparent role in self-renewal or neural differentiation. However, YAP in astrocytes was necessary for astrocytic proliferation. Yap (Yap1) knockout, Yap(nestin) conditional knockout and Yap(GFAP) conditional knockout mice displayed fewer neocortical astrocytes and impaired astrocytic proliferation and, consequently, death of neocortical neurons. Mechanistically, YAP was activated by BMP2, and the active/nuclear YAP was crucial for BMP2 induction and stabilization of SMAD1 and astrocytic differentiation. Expression of SMAD1 in YAP-deficient NSCs partially rescued the astrocytic differentiation deficit in response to BMP2. Taken together, these results identify a novel function of YAP in neocortical astrocytic differentiation and proliferation, and reveal a BMP2-YAP-SMAD1 pathway underlying astrocytic differentiation in the developing mouse neocortex.
Yes-associated protein (Yap) is a major effector of the Hippo pathway that regulates cell proliferation and differentiation during development and restricts tissue growth in adult animals. However, ...its role in synapse formation remains poorly understood. In this study, we characterized Yap's role in the formation of the neuromuscular junction (NMJ). In
mice where Yap was mutated specifically in muscle cells, AChR clusters were smaller and were distributed in a broader region in the middle of muscle fibers, suggesting that muscle Yap is necessary for the size and location of AChR clusters. In addition,
mice also exhibited remarkable presynaptic deficits. Many AChR clusters were not or less covered by nerve terminals; miniature endplate potential frequency was reduced, which was associated with an increase in paired-pulse facilitation, indicating structural and functional defects. In addition, muscle Yap mutation prevented reinnervation of denervated muscle fibers. Together, these observations indicate a role of muscle Yap in NMJ formation and regeneration. We found that β-catenin was reduced in the cytoplasm and nucleus of mutant muscles, suggesting compromised β-catenin signaling. Both NMJ formation and regeneration deficits of
mice were ameliorated by inhibiting β-catenin degradation, further corroborating a role of β-catenin or Wnt-dependent signaling downstream of Yap to regulate NMJ formation and regeneration.
This paper explored the role of Yes-associated protein (Yap) in neuromuscular junction (NMJ) formation and regeneration. Yap is a major effector of the Hippo pathway that regulates cell proliferation and differentiation during development and restricts tissue growth in adult animals. However, its role in synapse formation remains poorly understood. We provide evidence that muscle Yap mutation impairs both postsynaptic and presynaptic differentiation and function and inhibits NMJ regeneration after nerve injury, indicating a role of muscle Yap in these events. Further studies suggest compromised β-catenin signaling as a potential mechanism. Both NMJ formation and regeneration deficits of
mice were ameliorated by inhibiting β-catenin degradation, corroborating a role of β-catenin or Wnt-dependent signaling downstream of Yap to regulate NMJ formation and regeneration.
Proprioception is sensed by muscle spindles for precise locomotion and body posture. Unlike the neuromuscular junction (NMJ) for muscle contraction which has been well studied, mechanisms of spindle ...formation are not well understood. Here we show that sensory nerve terminals are disrupted by the mutation of Lrp4, a gene required for NMJ formation; inducible knockout of Lrp4 in adult mice impairs sensory synapses and movement coordination, suggesting that LRP4 is required for spindle formation and maintenance. LRP4 is critical to the expression of Egr3 during development; in adult mice, it interacts in trans with APP and APLP2 on sensory terminals. Finally, spindle sensory endings and function are impaired in aged mice, deficits that could be diminished by LRP4 expression. These observations uncovered LRP4 as an unexpected regulator of muscle spindle formation and maintenance in adult and aged animals and shed light on potential pathological mechanisms of abnormal muscle proprioception.
ABSTRACT
Introduction: The prevalence and characteristics of agrin and low‐density lipoprotein–related receptor protein 4 (LRP4) antibody‐positive amyotrophic lateral sclerosis (ALS) patients were ...studied. Methods: We tested 82 ALS patients and 59 controls for agrin and LRP4 antibodies using enzyme‐linked immunoassay (ELISA). Results: We found that 13.8% of ALS patients had agrin antibodies, and 9.8% had LRP4 antibodies. Women with ALS are twice as likely as men to have antibodies. Agrin‐positive ALS patients are younger than agrin‐negative ALS patients. Conclusions: Antibodies to agrin and LRP4 are found in ALS patients. It must be determined whether these antibodies are pathogenic. Because antibody‐positive patients have upper as well as lower motor neuron findings, the antibodies' effects cannot be explained solely by their actions at the neuromuscular junction. A breakdown in interneuronal signaling may be the cause of ALS. Further research is needed to resolve this question. Muscle Nerve, 2016 Muscle Nerve 55: 430–432, 2017
During aging, acetylcholine receptor (AChR) clusters become fragmented and denervated at the neuromuscular junction (NMJ). Underpinning molecular mechanisms are not well understood. We showed that ...LRP4, a receptor for agrin and critical for NMJ formation and maintenance, was reduced at protein level in aged mice, which was associated with decreased MuSK tyrosine phosphorylation, suggesting compromised agrin-LRP4-MuSK signaling in aged muscles. Transgenic expression of LRP4 in muscles alleviated AChR fragmentation and denervation and improved neuromuscular transmission in aged mice. LRP4 ubiquitination was augmented in aged muscles, suggesting increased LRP4 degradation as a mechanism for reduced LRP4. We found that sarcoglycan α (SGα) interacted with LRP4 and delayed LRP4 degradation in cotransfected cells. AAV9-mediated expression of SGα in muscles mitigated AChR fragmentation and denervation and improved neuromuscular transmission in aged mice. These observations support a model where compromised agrin-LRP4-MuSK signaling serves as a pathological mechanism of age-related NMJ decline and identify a novel function of SGα in stabilizing LRP4 for NMJ stability in aged mice.
This study provides evidence that LRP4, a receptor of agrin that is critical for NMJ formation and maintenance, is reduced at protein level in aged muscles. Transgenic expression of LRP4 in muscles ameliorates AChR fragmentation and denervation and improves neuromuscular transmission in aged mice, demonstrating a critical role of the agrin-LRP4-MuSK signaling. Our study also reveals a novel function of SGα to prevent LRP4 degradation in aged muscles. Finally, we show that NMJ decline in aged mice can be mitigated by AAV9-mediated expression of SGα in muscles. These observations provide insight into pathological mechanisms of age-related NMJ decline and suggest that improved agrin-LRP4-MuSK signaling may be a target for potential therapeutic intervention.
Background Alzheimer's disease (AD) and osteoporosis are two distinct diseases but often occur in the same patient. Their relationship remains poorly understood. Studies using Tg2576 AD animal model ...demonstrate bone deficits, which precede the brain phenotypes by several months, arguing for the independence of bone deficits on brain degeneration and raising a question if the bone deficits contribute to the AD development. To address this question, we investigated the effects of PTH.sub.1-34, a peptide of parathyroid hormone analog and a well-recognized effective anabolic therapy drug for patients with osteoporosis, on 5XFAD animal model. Methods 5XFAD mice, an early onset beta-amyloid (Abeta)-based AD mouse model, were treated with PTH.sub.1-34 intermittently once daily injection of hPTH.sub.1-34 (50 mug/Kg), 5 days/week, starting at 2-month old (MO) for 2-3 month. Wild type mice (C57BL/6) were used as control. The bone phenotypes were examined by microCT and evaluated by measuring serum bone formation and resorption markers. The AD relevant brain pathology (e.g., Abeta and glial activation) and behaviors were assessed by a combination of immunohistochemical staining analysis, western blots, and behavior tests. Additionally, systemic and brain inflammation were evaluated by serum cytokine array, real-time PCR (qPCR), and RNAscope. Results A reduced trabecular, but not cortical, bone mass, accompanied with a decrease in bone formation and an increase in bone resorption, was detected in 5XFAD mice at age of 5/6-month old (MO). Upon PTH.sub.1-34 treatments, not only these bone deficits but also Abeta-associated brain pathologies, including Abeta and Abeta deposition levels, dystrophic neurites, glial cell activation, and brain inflammatory cytokines, were all diminished; and the cognitive function was improved. Further studies suggest that PTH.sub.1-34 acts on not only osteoblasts in the bone but also astrocytes in the brain, suppressing astrocyte senescence and expression of inflammatory cytokines in 5XFAD mice. Conclusions These results suggest that PTH.sub.1-34 may act as a senolytic-like drug, reducing systemic and brain inflammation and improving cognitive function, and implicate PTH.sub.1-34's therapeutic potential for patients with not only osteoporosis but also AD. Keywords: Alzheimer's disease, PTH, Abeta, Neuroinflammation, Astrocytes
Ozone concentrations have increased sharply since the implementation of the Clean Air Action plan in China, but the reasons for the increase are still unclear. Here, we analyzed the annual ozone ...trends at different altitudes from 2013 to 2018 based on ozonesonde observations in the southern suburb of Beijing. Large differences in ozone concentrations were observed among different years and were most significant within 2 km above the ground. Ozone in the lower boundary layer exhibited a strong increase before 2016 and a weak decrease after 2016, while ozone in the upper boundary layer exhibited a weak increase before 2016 and a strong decrease after 2016. The main factor responsible for these ozone trends was ozone precursors, which induced the transition of ozone production from being sensitive to VOC to being sensitive to NOx. This study indicated that a large amount of NOx reduction would be conducive to ozone pollution control in China.
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•The inter-annual variation of ozone is concentrated below 2 km above the ground.•Ozone precursors dominates the inter-annual change of ozone in Beijing.•Beijing has bypassed the NOx titration trap in ozone pollution control.•Continuous reduction of NOx would conducive to ozone pollution control in Beijing.
To determine whether human anti-LRP4/agrin antibodies are pathogenic in mice and to investigate underpinning pathogenic mechanisms.
Immunoglobulin (Ig) was purified from a patient with myasthenia ...gravis (MG) with anti-LRP4/agrin antibodies and transferred to mice. Mice were characterized for body weight, muscle strength, twitch and tetanic force, neuromuscular junction (NMJ) functions including compound muscle action potential (CMAP) and endplate potentials, and NMJ structure. Effects of the antibodies on agrin-elicited muscle-specific tyrosine kinase (MuSK) activation and AChR clustering were studied and the epitopes of these antibodies were identified.
Patient Ig-injected mice had MG symptoms, including weight loss and muscle weakness. Decreased CMAPs, reduced twitch and tetanus force, compromised neuromuscular transmission, and NMJ fragmentation and distortion were detected in patient Ig-injected mice. Patient Ig inhibited agrin-elicited MuSK activation and AChR clustering. The patient Ig recognized the β3 domain of LRP4 and the C-terminus of agrin and reduced agrin-enhanced LRP4-MuSK interaction.
Anti-LRP4/agrin antibodies in the patient with MG is pathogenic. It impairs the NMJ by interrupting agrin-dependent LRP4-MuSK interaction.
Fluoro-ruby was injected into the posterior funiculus of the spinal cord in the cervical （C5-T2） and lumbar （L3-6） segments of adult guinea pigs. The spinal cord was cut into serial frozen sections. ...The Fluoro-ruby labeling was clearly delineated from the surrounding structure. The labeling traversed the cervical, thoracic and lumbar segments, and was located on the ventral portion of the posterior funiculus on the injected side, proximal to the intermediate zone of the dorsal gray matter. The fluorescence area narrowed rostro-caudally. The spinal cord, spinal cord gray matter and corticospinal tract were reconstructed using 3D-DOCTOR 4.0 software, resulting in a robust three-dimensional profile. Using functionality provided by the reconstruction software, free multi-angle observation and sectioning could be conducted on the spinal cord and corticospinal tract. Our experimental findings indicate that the Fluoro-ruby retrograde fluorescent tracing technique can accurately display the anatomical location of corticospinal tract in the guinea pig and that three-dimensional reconstruction software can be used to provide a three-dimensional image of the corticospinal tract.
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