Necl2/3-mediated mechanism for tripartite synapse formation.

Ramified, polarized protoplasmic astrocytes interact with synapses via perisynaptic astrocyte processes (PAPs) to form tripartite synapses. These astrocyte-synapse interactions mutually regulate their structures and functions. However, molecular mechanisms for tripartite synapse formation remain elusive. We developed an in vitro co-culture system for mouse astrocytes and neurons that induced astrocyte ramifications and PAP formation. Co-cultured neurons were required for astrocyte ramifications in a neuronal activity-dependent manner, and synaptically-released glutamate and activation of astrocytic mGluR5 metabotropic glutamate receptor were likely involved in astrocyte ramifications. Astrocytic Necl2 trans-interacted with axonal Necl3, inducing astrocyte-synapse interactions and astrocyte functional polarization by recruiting EAAT1/2 glutamate transporters and Kir4.1 K+ channel to the PAPs, without affecting astrocyte ramifications. This Necl2/3 trans-interaction increased functional synapse number. Thus, astrocytic Necl2, synaptically-released glutamate and axonal Necl3 cooperatively formed tripartite glutamatergic synapses in vitro. Studies on hippocampal mossy fiber synapses in Necl3 knockout and Necl2/3 double knockout mice confirmed these previously unreported mechanisms for astrocyte-synapse interactions and astrocyte functional polarization in vivo.

Severe cardiac involvement with preserved truncated dystrophin expression in Becker muscular dystrophy by +1G>A DMD splice-site mutation: a case report.

Becker muscular dystrophy (BMD) is caused by specific mutations in the DMD gene that causes progressive muscle weakness and primarily affects skeletal and cardiac muscle. Although cardiac involvement is a significant cause of mortality in BMD, the genetic-phenotype correlation for skeletal and cardiac muscles has not been elucidated. Here, we described a 39-year-old man with BMD, who presented with subtle skeletal muscle weakness in the right leg in his 20s and underwent left ventricular restoration for severe dilated cardiomyopathy at the age of 29. He had difficulty climbing stairs after the age of 35. Neither duplication nor deletion of exons was detected by multiplex ligation-dependent probe amplification. A hemizygous c.264 + 1G>A mutation in intron 4 of the DMD was identified by next-generation sequencing. Furthermore, exon 4 skipping of the DMD was confirmed in both skeletal and cardiac muscles evaluated by reverse transcriptase PCR. Endomyocardial and skeletal muscle biopsies revealed dystrophic pathology characterized by muscle fiber atrophy and hypertrophy with a mild degree of interstitial fibrosis. Interestingly, dystrophin immunohistochemistry demonstrated patchy and faint staining of the skeletal muscle membranes but almost normal staining of the cardiac muscle membranes. Western blot analysis revealed a decreased amount of truncated dystrophin in skeletal muscle but surprisingly almost normal amount in cardiac muscle. This case indicates that BMD patients may have severe cardiac dysfunction despite preserved cardiac truncated dystrophin expression.

Biclonal Gammopathy as a Misleading Indicator to Diagnose POEMS Syndrome: An Autopsy Case Report and a Review of the Literature.

A 76-year-old man presented with a four-month history of progressive bilateral lower limb muscle weakness and dysesthesia. The patient had extravascular volume overload, and laboratory findings confirmed hypothyroidism, renal dysfunction, and chronic inflammation. Serum protein and immunofixation electrophoresis revealed biclonality of immunoglobulin A (IgA)-kappa and IgA-lambda, which was attributed to chronic inflammation. Subsequently, we detected the proliferation of monoclonal plasma cells in the bone marrow, which led to a diagnosis of POEMS syndrome. Despite the initiation of chemotherapy, the patient died of aspiration pneumonia. In this case, biclonal gammopathy in peripheral blood delayed a diagnosis of POEMS syndrome.

Distant metastasis of hepatocellular carcinoma to Meckel's cave and cranial nerves: A case report and review of literature.

BACKGROUND: Metastasis occurs as a late event in the natural history of hepatocellular carcinoma (HCC), and most patients die of liver failure attributed to the tumor supplanting the liver. Conversely, the brain is a less common metastatic site. CASE SUMMARY: We describe a rare case of hepatitis C virus-related multiple HCC metastasizing to the cavernous sinus, Meckel's cave, and the petrous bone involving multiple cranial nerves in an 82-year-old woman. At admission imaging studies including Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (MRI) revealed multiple HCC nodules in both right and left lobes. Ultrasound guided biopsy of the left lobe revealed moderately differentiated HCC. Molecular targeted therapy with Lenvatinib (8 mg/d for 94 d, per os) and Ramucirumab (340 mg/d and 320 mg/d, two times by intravenous injection) were administered for 4 mo, resulting in progression of the disease. Three months after the start of molecular target therapy, the patient presented with symptoms of hyperalgesia of the right face and limited abduction of the right eye, indicating disturbances in the right trigeminal and abducens nerves. Brain MRI disclosed a mass involving the cavernous sinus, Meckel's cave and the petrous bone. Contrast-enhanced MRI with gadolinium-chelated contrast medium revealed a well-defined mass with abnormal enhancement around the right cavernous sinus and the right Meckel's cave. CONCLUSION: The diagnosis of metastatic HCC to the cavernous sinus, Meckel's cave, and the petrous bone was made based on neurological findings and imaging studies including MRI, but not on histological examinations. Further studies may provide insights into various methods for diagnosing HCC metastasizing to the craniospinal area.

[Retinal vasculopathy with cerebral leukoencephalopathy carrying TREX1 mutation diagnosed by the intracranial calcification: a case report].

A 40-year-old woman with renal dysfunction for 2 years was admitted to our hospital suffering from a headache. Family history revealed that her mother had a headache, renal dysfunction, and brain infarction in younger age. She had a retinal hemorrhage, a retinal atrophy, pitting edema in her lower extremities. Her neurological findings were unremarkable. Brain imaging showed multiple white matter lesions accompanied with calcifications and slightly enhancement. Kidney biopsy showed the thrombotic microangiopathy, Gene analysis demonstrated a causative mutation in three-prime repair exonuclease-1 (TREX1) gene, c.703_704insG (p.Val235GlyfsX6), thereby we diagnosed her as retinal vasculopathy with cerebral leukoencephalopathy (RVCL). RVCL is an autosomal dominant condition caused by C-terminal frame-shift mutation in TREX1. TREX1 protein is a major 3' to 5' DNA exonuclease, which are important in DNA repair. While TREX1 mutations identified in Aicardi-Goutieres syndrome patients lead to a reduction of enzyme activity, it is suggested that mutations in RVCL alter an intracellular location of TREX1 protein. There are no treatments based evidences in RVCL. We administered cilostazol to protect endothelial function, and her brain lesions and renal function have not become worse for 10 months after. It is necessary to consider RVCL associated with TREX1 mutation if a patient has retinal lesions, white matter lesions accompanied with calcifications, and multiple organ dysfunction.

Regulation of dendritic filopodial interactions by ZO-1 and implications for dendrite morphogenesis.

Neuronal dendrites dynamically protrude many fine filopodia in the early stages of neuronal development and gradually establish complex structures. The importance of the dendritic filopodia in the formation of axo-dendritic connections is established, but their role in dendrite morphogenesis remains unknown. Using time-lapse imaging of cultured rat hippocampal neurons, we revealed here that many filopodia dynamically protruded from dendrites and transiently interacted with each other to form dendritic filopodia-filopodia contacts in the early stages of neuronal development. The MAGUK family member, Zonula Occludens-1 (ZO-1), which is known to be associated with the nectin and cadherin cell adhesion systems, was concentrated at these dendritic filopodia-filopodia contact sites and also at the tips of free dendritic filopodia. Overexpression of ZO-1 increased the formation of dendritic filopodia and their interactions, and induced abnormal dendrite morphology. Conversely, knockdown of ZO-1 decreased the formation of dendritic filopodia and their interactions, and induced abnormal dendrite morphology which was different from that induced by the overexpression of ZO-1. The components of the nectin and cadherin systems were co-localized with ZO-1 at the dendritic filopodia-filopodia contact sites, but not at the tips of free dendritic filopodia. Overexpression of ZO-1 increased the accumulation of these cell adhesive components at the dendritic filopodia-filopodia contact sites and stabilized their interactions, whereas knockdown of ZO-1 reduced their accumulation at the dendritic filopodia-filopodia contact sites. These results indicate that ZO-1 regulates dendritic filopodial dynamics, which is implicated in dendrite morphogenesis cooperatively with the nectin and cadherin systems in cultured neurons.