Language：English   Publishing type：Research paper (scientific journal)  

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by an expanded CAG repeat in the androgen receptor (AR) gene. To elucidate the cell type-specific temporal gene expression in SBMA, we performed single-nucleus RNA sequencing on the spinal cords of an SBMA mouse model (AR-97Q). Among all cell types, oligodendrocytes had the highest number of differentially expressed genes before disease onset. Analysis of oligodendrocyte clusters suggested that pathways associated with cation channels and synaptic function were activated before disease onset, with increased output from oligodendrocytes to neurons in AR-97Q mice compared with wild-type mice. These changes in the early stages were abrogated at the advanced stages. An oligodendrocyte model of SBMA showed phenotypes similar to those of AR-97Q mice at early stages, such as increased transcriptional changes in synapse organization, and Ca2+ imaging of oligodendrocytes in AR-97Q mice revealed the increased Ca2+ responses. A coculture system of primary rat oligodendrocytes and neurons revealed that the mutant AR in oligodendrocytes affected the activity and synchronization of neurons. These findings suggest that dysregulated cell-to-cell communication plays a critical role in early SBMA pathology and that synaptic or ion channel-related proteins, such as contactin associated protein 2 (Cntnap2) and NALCN channel auxiliary factor 1 (Fam155a), are potential therapeutic targets for SBMA.

DOI： 10.1172/jci.insight.182123

Open Access

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disorder caused by CAG trinucleotide expansion in the androgen receptor (AR) gene. To improve the quality of in vitro cell-based assays for the evaluation of potential drug candidates for SBMA, we developed a morphology-based phenotypic analysis for a muscle cell model of SBMA that involves multiparametric morphological profiling to quantitatively assess the therapeutic effects of drugs on muscle cell phenotype. The analysis was validated using dihydrotestosterone and pioglitazone, which have been shown to exacerbate and ameliorate the pathophysiology of SBMA, respectively. Gene expression analysis revealed activation of the JNK pathway in the SBMA cells compared to the control cells. Phenotypic analysis revealed the effect of naratriptan, a JNK inhibitor, on the phenotypic changes of SBMA cells, and the results were confirmed by LDH assays. We then trained a predictive machine learning model to classify the drug responses, and it successfully discriminated between pioglitazone-type and naratriptan-type morphological profiles based on their morphological characteristics. Our morphology-based phenotypic analysis provides a noninvasive and efficient screening method to accelerate the development of therapeutics for SBMA.

DOI： 10.1242/dmm.052220

Open Access

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: Spinal and bulbar muscular atrophy (SBMA) is a hereditary neuromuscular disorder caused by the expansion of trinucleotide cytosine-adenine-guanine (CAG) repeats, which encodes a polyglutamine (polyQ) tract in the androgen receptor (AR) gene. Recent evidence suggests that, in addition to motor neuron degeneration, defective skeletal muscles are also the primary contributors to the pathogenesis in SBMA. While benefits of physical exercise have been suggested in SBMA, underlying mechanism remains elusive. METHODS: We investigated the effect of running exercise in a transgenic mouse model of SBMA carrying human AR with 97 expanded CAGs (AR97Q). We assigned AR97Q mice to exercise and sedentary control groups, and mice in the exercise group received 1-h forced running wheel (5 m/min) 5 days a week for 4 weeks during the early stage of the disease. Motor function (grip strength and rotarod performance) and survival of each group were analysed, and histopathological and biological features in skeletal muscles and motor neurons were evaluated. RESULTS: AR97Q mice in the exercise group showed improvement in motor function (~40% and ~50% increase in grip strength and rotarod performance, respectively, P < 0.05) and survival (median survival 23.6 vs. 16.7 weeks, P < 0.05) with amelioration of neuronal and muscular histopathology (~1.4-fold and ~2.8-fold increase in motor neuron and muscle fibre size, respectively, P < 0.001) compared to those in the sedentary group. Nuclear accumulation of polyQ-expanded AR in skeletal muscles and motor neurons was suppressed in the mice with exercise compared to the sedentary mice (~50% and ~30% reduction in 1C2-positive cells in skeletal muscles and motor neurons, respectively, P < 0.05). We found that the exercise activated 5'-adenosine monophosphate-activated protein kinase (AMPK) signalling and inhibited mammalian target of rapamycin pathway that regulates protein synthesis in skeletal muscles of SBMA mice. Pharmacological activation of AMPK inhibited protein synthesis and reduced polyQ-expanded AR proteins in C2C12 muscle cells. CONCLUSIONS: Our findings suggest the therapeutic potential of exercise-induced effect via AMPK activation in SBMA.

DOI： 10.1002/jcsm.13344

Open Access

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

Lower motor neuron degeneration is the pathological hallmark of spinal muscular atrophy (SMA), a hereditary motor neuron disease caused by loss of the SMN1 gene and the resulting deficiency of ubiquitously expressed SMN protein. The molecular mechanisms underlying motor neuron degeneration, however, remain elusive. To clarify the cell-autonomous defect in developmental processes, we here performed transcriptome analyses of isolated embryonic motor neurons of SMA model mice to explore mechanisms of dysregulation of cell-type-specific gene expression. Of 12 identified genes that were differentially expressed between the SMA and control motor neurons, we focused on Aldh1a2, an essential gene for lower motor neuron development. In primary spinal motor neuron cultures, knockdown of Aldh1a2 led to the formation of axonal spheroids and neurodegeneration, reminiscent of the histopathological changes observed in human and animal cellular models. Conversely, Aldh1a2 rescued these pathological features in spinal motor neurons derived from SMA mouse embryos. Our findings suggest that developmental defects due to Aldh1a2 dysregulation enhances lower motor neuron vulnerability in SMA.

DOI： 10.1016/j.neures.2023.04.007

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: The α-Synuclein (α-Syn) V15A variant has been found in two Caucasian families with Parkinson's disease (PD). However, the significance of this missense variant remained unclear. OBJECTIVE: We sought to elucidate whether V15A could increase aggregation or change phospholipid affinity. METHODS: A sequencing analysis for the SNCA encoding α-Syn from 875 patients with PD and 324 control subjects was performed. Comparing with known pathogenic missense variants of α-Syn, A30P, and A53T, we analyzed the effects of V15A on binding to phospholipid membrane, self-aggregation, and seed-dependent aggregation in cultured cells. RESULTS: Genetic screening identified SNCA c.44 T>C (p.V15A) from two Japanese PD families. The missense variant V15A was extremely rare in several public databases and predicted as pathogenic using in silico tools. The amplification activity of α-Syn V15A fibrils was stronger than that of wild-type α-Syn fibrils. CONCLUSIONS: The discovery of the V15A variant from Japanese families reinforces the possibility that the V15A variant may be a causative variant for developing PD. V15A had a reduced affinity for phospholipids and increased propagation activity compared with wild-type. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

DOI： 10.1002/mds.29162

Open Access

PubMed

Language：Japanese   Publisher：(株)中外医学社  

Language：Japanese   Publisher：(株)中外医学社  

Language：Japanese   Publisher：日本内科学会  

CiNii Research

Applicant：アークトゥラス・セラピューティクス・インコーポレイテッド

Application no：特願2022-577758  Date applied：2021.6

Publication no：特表2023-530487  Date published：2023.7

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