Transcriptome profile of subsynaptic myonuclei at the neuromuscular junction in embryogenesis

Skeletal muscle fiber is a large syncytium with multiple and evenly distributed nuclei. Adult subsynaptic myonuclei beneath the neuromuscular junction (NMJ) express specific genes, the products of which coordinately function in the maintenance of the pre- and post-synaptic regions. However, the gene expression profiles that promote the NMJ formation during embryogenesis remain largely unexplored. We performed single-nucleus RNA sequencing (snRNA-seq) analysis of embryonic and neonatal mouse diaphragms, and found that each myonucleus had a distinct transcriptome pattern during the NMJ formation. Among the previously reported NMJ-constituting genes, Dok7, Chrna1, and Chrnd are specifically expressed in subsynaptic myonuclei at E18.5. In the E18.5 diaphragm, ca. 10.7% of the myonuclei express genes for the NMJ formation (Dok7, Chrna1, and Chrnd) together with four representative β-catenin regulators (Amotl2, Ptprk, Fam53b, and Tcf7l2). Additionally, the temporal gene expression patterns of these seven genes are synchronized in differentiating C2C12 myoblasts. Amotl2 and Ptprk are expressed in the sarcoplasm, where β-catenin serves as a structural protein to organize the membrane-anchored NMJ structure. In contrast, Fam53b and Tcf7l2 are expressed in the myonucleus, where β-catenin serves as a transcriptional coactivator in Wnt/β-catenin signaling at the NMJ. In C2C12 myotubes, knockdown of Amotl2 or Ptprk markedly, and that of Fam53b and Tcf7l2 less efficiently, impair the clustering of acetylcholine receptors. In contrast, knockdown of Fam53b and Tcf7l2, but not of Amotl2 or Ptprk, impairs the gene expression of Slit2 encoding an axonal attractant for motor neurons, which is required for the maturation of motor nerve terminal. Thus, Amotl2 and Ptprk exert different roles at the NM compared to Fam53b and Tcf7l2. Additionally, Wnt ligands originating from the spinal motor neurons and the perichondrium/chondrocyte are likely to work remotely on the subsynaptic nuclei and the myotendinous junctional nuclei, respectively. We conclude that snRNA-seq analysis of embryonic/neonatal diaphragms reveal a novel coordinated expression profile especially in the Wnt/β-catenin signaling that regulate the formation of the embryonic NMJ.

Calcitriol ameliorates motor deficits and prolongs survival of Chrne-deficient mouse, a model for congenital myasthenic syndrome, by inducing Rspo2

Signal transduction at the neuromuscular junction (NMJ) is compromised in a diverse array of diseases including congenital myasthenic syndromes (CMS). Germline mutations in CHRNE encoding the acetylcholine receptor (AChR) ε subunit are the most common cause of CMS. An active form of vitamin D, calcitriol, binds to vitamin D receptor (VDR) and regulates gene expressions. We found that calcitriol enhanced MuSK phosphorylation, AChR clustering, and myotube twitching in co-cultured C2C12 myotubes and NSC34 motor neurons. RNA-seq analysis of co-cultured cells showed that calcitriol increased the expressions of Rspo2, Rapsn, and Dusp6. ChIP-seq of VDR revealed that VDR binds to a region approximately 15 ​kbp upstream to Rspo2. Biallelic deletion of the VDR-binding site of Rspo2 by CRISPR/Cas9 in C2C12 myoblasts/myotubes nullified the calcitriol-mediated induction of Rspo2 expression and MuSK phosphorylation. We generated Chrne knockout (Chrne KO) mouse by CRISPR/Cas9. Intraperitoneal administration of calcitriol markedly increased the number of AChR clusters, as well as the area, the intensity, and the number of synaptophysin-positive synaptic vesicles, in Chrne KO mice. In addition, calcitriol ameliorated motor deficits and prolonged survival of Chrne KO mice. In the skeletal muscle, calcitriol increased the gene expressions of Rspo2, Rapsn, and Dusp6. We propose that calcitriol is a potential therapeutic agent for CMS and other diseases with defective neuromuscular signal transmission.

Association between switching prescribed drugs for lower urinary tract symptoms and independence of urination in post-stroke patients: A retrospective cohort study

OBJECTIVES

Stroke patients frequently exhibit loss of independence of urination, and their lower urinary tract symptoms change with the phase of stroke. However, it is unclear whether switching prescribed drugs for lower urinary tract symptoms during hospitalization from acute care wards to convalescence rehabilitation wards affects patients' independence of urination at discharge. It is also unclear whether the impact of switching varies by stroke type. This retrospective cohort study aimed to examine these issues.

MATERIALS AND METHODS

We analyzed 990 patients registered in the Kaga Regional Cooperation Clinical Pathway for Stroke database during 2015-2019. Prescriptions for lower urinary tract symptoms from pre-onset to convalescence rehabilitation were surveyed. Logistic regression analysis was performed to examine the association between switching drugs and independence of urination based on bladder management and voiding location at discharge. Stroke types were also examined in subgroup analyses.

RESULTS

About 21 % of patients had their lower urinary tract symptoms prescriptions switched during hospitalization. Switching was positively associated with independence of bladder management (odds ratio 1.65, 95 % confidence interval 1.07 to 2.49) and voiding location (odds ratio 2.72, 95 % confidence interval 1.72 to 4.37). Similar associations were observed in different stroke types.

CONCLUSIONS

Approximately 20 % of patients had their lower urinary tract symptoms medications switched upon transfer from acute to convalescence rehabilitation wards. Switching was significantly associated with improved urinary independence at discharge. Consistent results were observed across different stroke types, suggesting that switching medications contributes to urinary independence after stroke, regardless of the etiology or severity of stroke.

Splicing regulation of GFPT1 muscle-specific isoform and its roles in glucose metabolisms and neuromuscular junction

Glutamine:fructose-6-phosphate transaminase 1 (GFPT1) is the rate-limiting enzyme of the hexosamine biosynthetic pathway (HBP). A 54-bp exon 9 of GFPT1 is specifically included in skeletal and cardiac muscles to generate a long isoform of GFPT1 (GFPT1-L). We showed that SRSF1 and Rbfox1/2 cooperatively enhance, and hnRNP H/F suppresses, the inclusion of human GFPT1 exon 9 by modulating recruitment of U1 snRNP. Knockout (KO) of GFPT1-L in skeletal muscle markedly increased the amounts of GFPT1 and UDP-HexNAc, which subsequently suppressed the glycolytic pathway. Aged KO mice showed impaired insulin-mediated glucose uptake, as well as muscle weakness and fatigue likely due to abnormal formation and maintenance of the neuromuscular junction. Taken together, GFPT1-L is likely to be acquired in evolution in mammalian striated muscles to attenuate the HBP for efficient glycolytic energy production, insulin-mediated glucose uptake, and the formation and maintenance of the neuromuscular junction.

Telemedicine for Pregnant Women on a Japanese Remote Island: A Two-year Report

Introduction

Remote antenatal checkups were conducted on the northernmost island of Japan to reduce the burden of hospital visits among pregnant women. This study aims to investigate the effectiveness and safety of remote antenatal checkups for pregnant women living on a remote island.

Methods

This observational study included singleton pregnancies on Rebun Island between October 2020 and September 2022. General surgeons conducted medical interviews and performed fetal sonography using an obstetrician videoconference system at the main central hospital. The primary outcomes were the degrees of physical, mental, and economic burdens of hospital visits and the levels of anxiety and satisfaction with remote antenatal checkups as assessed using a questionnaire survey. Moreover, we investigated the incidence of adverse perinatal events, including maternal death, fetal death, neonatal death, severe neonatal neurological disorders, and other obstetric complications.

Results

This study included 16 out of 22 pregnant women from Rebun Island who visited the central hospital. No adverse perinatal events occurred as a result of the remote antenatal checkups. One pregnant woman had gestational diabetes, whereas the others had no obstetric complications. The participants underwent a median of two remote antenatal checkups. According to a questionnaire survey, 90.0%, 80.0%, and 70.0% of the pregnant women perceived improvements in their physical, mental, and economic burdens, respectively. Although 70.0% of the participants experienced anxiety regarding remote antenatal checkups before the introduction, all were satisfied after delivery.

Conclusions

Remote antenatal checkups effectively reduced the burden of hospital visits for pregnant women, who reported high levels of satisfaction. Furthermore, antenatal checkups were safely conducted on remote islands.

FexSplice: A LightGBM-Based Model for Predicting the Splicing Effect of a Single Nucleotide Variant Affecting the First Nucleotide G of an Exon

Single nucleotide variants (SNVs) affecting the first nucleotide G of an exon (Fex-SNVs) identified in various diseases are mostly recognized as missense or nonsense variants. Their effect on pre-mRNA splicing has been seldom analyzed, and no curated database is available. We previously reported that Fex-SNVs affect splicing when the length of the polypyrimidine tract is short or degenerate. However, we cannot readily predict the splicing effects of Fex-SNVs. We here scrutinized the available literature and identified 106 splicing-affecting Fex-SNVs based on experimental evidence. We similarly identified 106 neutral Fex-SNVs in the dbSNP database with a global minor allele frequency (MAF) of more than 0.01 and less than 0.50. We extracted 115 features representing the strength of splicing cis-elements and developed machine-learning models with support vector machine, random forest, and gradient boosting to discriminate splicing-affecting and neutral Fex-SNVs. Gradient boosting-based LightGBM outperformed the other two models, and the length and nucleotide compositions of the polypyrimidine tract played critical roles in the discrimination. Recursive feature elimination showed that the LightGBM model using 15 features achieved the best performance with an accuracy of 0.80 ± 0.12 (mean and SD), a Matthews Correlation Coefficient (MCC) of 0.57 ± 0.15, an area under the curve of the receiver operating characteristics curve (AUROC) of 0.86 ± 0.08, and an area under the curve of the precision-recall curve (AUPRC) of 0.87 ± 0.09 using a 10-fold cross-validation. We developed a web service program, named FexSplice that accepts a genomic coordinate either on GRCh37/hg19 or GRCh38/hg38 and returns a predicted probability of aberrant splicing of A, C, and T variants.

Neural Isoforms of Agrin Are Generated by Reduced PTBP1-RNA Interaction Network Spanning the Neuron-Specific Splicing Regions in AGRN

Agrin is a heparan sulfate proteoglycan essential for the clustering of acetylcholine receptors at the neuromuscular junction. Neuron-specific isoforms of agrin are generated by alternative inclusion of three exons, called Y, Z8, and Z11 exons, although their processing mechanisms remain elusive. We found, by inspection of splicing cis-elements into the human AGRN gene, that binding sites for polypyrimidine tract binding protein 1 (PTBP1) were extensively enriched around Y and Z exons. PTBP1-silencing enhanced the coordinated inclusion of Y and Z exons in human SH-SY5Y neuronal cells, even though three constitutive exons are flanked by these alternative exons. Deletion analysis using minigenes identified five PTBP1-binding sites with remarkable splicing repression activities around Y and Z exons. Furthermore, artificial tethering experiments indicated that binding of a single PTBP1 molecule to any of these sites represses nearby Y or Z exons as well as the other distal exons. The RRM4 domain of PTBP1, which is required for looping out a target RNA segment, was likely to play a crucial role in the repression. Neuronal differentiation downregulates PTBP1 expression and promotes the coordinated inclusion of Y and Z exons. We propose that the reduction in the PTPB1-RNA network spanning these alternative exons is essential for the generation of the neuron-specific agrin isoforms.

Influence of using history of immune checkpoint inhibitor therapy for neutropenia caused by combination therapy of ramucirumab and docetaxel

Recently, pretreatment with immune checkpoint inhibitors (ICIs) has been shown to enhance the therapeutic effects of the combination therapy of ramucirumab (RAM) and docetaxel (DTX); however, its influence on the drug's side effects remains unclear. This study investigated the influence of pretreatment with ICIs on the incidence of neutropenia caused by RAM + DTX therapy in patients with non-small cell lung cancer (NSCLC). Patients with NSCLC who received RAM + DTX therapy at Gifu Prefectural General Medical Center between April 2016 and December 2020 were enrolled. Retrospective data regarding age, sex, performance status and detailed treatment history, among others, at treatment initiation were collected from the patients' electronic medical records. Additionally, data on the course number of RAM + DTX therapy, supportive therapy and blood biochemical parameters, including leukocyte and neutrocyte counts, during the treatment period were collected. We identified 41 patients receiving RAM + DTX therapy. Among the more than grade 3 adverse events caused by this therapy, neutropenia was the most common (78.1%). Despite the fact that all previous risk factors influencing this incidence rate had corresponded, the only factor influencing the incidence rate of neutropenia more than grade 3 was ICI treatment history. A difference in the incidence of neutropenia more than grade 3 in the Kaplan-Meier curve was observed between patients with and without ICI pretreatment history (p = 0.037). The pretreatment history of ICI therapy affects the incidence of neutropenia caused by RAM + DTX therapy in patients with NSCLC.

Coronary ostial angioplasty for juvenile Takayasu arteritis involving the coronary artery using external iliac artery grafts

Takayasu arteritis can affect the coronary ostia, leading to myocardial ischemia. Coronary ostial angioplasty effectively treats coronary artery ostial lesions associated with Takayasu arteritis. We present a case of juvenile Takayasu arteritis with bilateral subclavian artery occlusions treated with a novel coronary artery ostial angioplasty using the external iliac artery.

Extremely low-frequency pulses of faint magnetic field induce mitophagy to rejuvenate mitochondria

Humans are frequently exposed to time-varying and static weak magnetic fields (WMF). However, the effects of faint magnetic fields, weaker than the geomagnetic field, have been scarcely reported. Here we show that extremely low-frequency (ELF)-WMF, comprised of serial pulses of 10 µT intensity at 1–8 Hz, which is three or more times weaker than the geomagnetic field, reduces mitochondrial mass to 70% and the mitochondrial electron transport chain (ETC) complex II activity to 88%. Chemical inhibition of electron flux through the mitochondrial ETC complex II nullifies the effect of ELF-WMF. Suppression of ETC complex II subsequently induces mitophagy by translocating parkin and PINK1 to the mitochondria and by recruiting LC3-II. Thereafter, mitophagy induces PGC-1α-mediated mitochondrial biogenesis to rejuvenate mitochondria. The lack of PINK1 negates the effect of ELF-WMF. Thus, ELF-WMF may be applicable for the treatment of human diseases that exhibit compromised mitochondrial homeostasis, such as Parkinson’s disease.

The effect of extremely low-frequency pulses of faint magnetic field on mitochondria is investigated, where it led to reduced mitochondrial mass, membrane potential and electron transport chain activity, and induced mitophagy.

Meclozine ameliorates skeletal muscle pathology and increases muscle forces in mdx mice

We screened pre-approved drugs for the survival of the Hu5/KD3 human myogenic progenitors. We found that meclozine, an anti-histamine drug that has long been used for motion sickness, promoted the proliferation and survival of Hu5/KD3 cells. Meclozine increased expression of MyoD, but reduced expression of myosin heavy chain and suppressed myotube formation. Withdrawal of meclozine, however, resumed the ability of Hu5/KD3 cells to differentiate into myotubes. We examined the effects of meclozine on mdx mouse carrying a nonsense mutation in the dystrophin gene and modeling for Duchenne muscular dystrophy. Intragastric administration of meclozine in mdx mouse increased the body weight, the muscle mass in the lower limbs, the cross-sectional area of the paravertebral muscle, and improved exercise performances. Previous reports show that inhibition of phosphorylation of ERK1/2 improves muscle functions in mouse models for Emery-Dreifuss muscular dystrophy and cancer cachexia, as well as in mdx mice. We and others previously showed that meclozine blocks the phosphorylation of ERK1/2 in cultured cells. We currently showed that meclozine decreased phosphorylation of ERK1/2 in muscles in mdx mice but not in wild-type mice. This was likely to be one of the underlying mechanisms of the effects of meclozine on mdx mice.

Regulated splicing of large exons is linked to phase-separation of vertebrate transcription factors

Although large exons cannot be readily recognized by the spliceosome, many are evolutionarily conserved and constitutively spliced for inclusion in the processed transcript. Furthermore, whether large exons may be enriched in a certain subset of proteins, or mediate specific functions, has remained unclear. Here, we identify a set of nearly 3,000 SRSF3-dependent large constitutive exons (S3-LCEs) in human and mouse cells. These exons are enriched for cytidine-rich sequence motifs, which bind and recruit the splicing factors hnRNP K and SRSF3. We find that hnRNP K suppresses S3-LCE splicing, an effect that is mitigated by SRSF3 to thus achieve constitutive splicing of S3-LCEs. S3-LCEs are enriched in genes for components of transcription machineries, including mediator and BAF complexes, and frequently contain intrinsically disordered regions (IDRs). In a subset of analyzed S3-LCE-containing transcription factors, SRSF3 depletion leads to deletion of the IDRs due to S3-LCE exon skipping, thereby disrupting phase-separated assemblies of these factors. Cytidine enrichment in large exons introduces proline/serine codon bias in intrinsically disordered regions and appears to have been evolutionarily acquired in vertebrates. We propose that layered splicing regulation by hnRNP K and SRSF3 ensures proper phase-separation of these S3-LCE-containing transcription factors in vertebrates.

Simultaneous assessment of coronary flow reserve and left ventricular function during vasodilator stress evaluated by 13N-ammonia hybrid PET/MRI

AIM

To explore changes in left ventricular (LV) function and the relationship of these changes with myocardial blood flow (MBF) evaluated by ¹³N-ammonia hybrid positron-emission tomography (PET)/magnetic resonance imaging (MRI) during vasodilator stress in patients with suspected coronary artery disease (CAD).

MATERIALS AND METHODS

Fifty-two consecutive patients with suspected CAD, who underwent ¹³N-ammonia PET/MRI, were enrolled. Vasodilator stress was induced by intravenous injection of adenosine. MBF and coronary flow reserve (CFR) were calculated from dynamic acquisition of ¹³N-ammonia PET. LV function was evaluated by MRI both at rest and during vasodilator stress. An abnormal perfusion on myocardial images was defined as a summed difference score of ≥4.

RESULTS

MRI showed that the LV end-diastolic volume, LV end-systolic volume, and LV ejection fraction (LVEF) remained unchanged during vasodilator stress in all patients (n=52) as well as in the patients with CFR of <2 (n=27), stress MBF of <1.3 ml/g/min (n=28), abnormal myocardial perfusion (n=30), and more than one diseased vessel (n=46). In only four patients, the LVEF measured by MRI decreased by >5% during vasodilator stress. In these four patients, CFR was lower (1.57 ± 0.12 versus 2.18 ± 0.86, p<0.01) and the number of diseased vessels was higher (2.75 ± 0.50 versus 1.48 ± 0.92, p<0.01) than in patients without post-stress LV dysfunction.

CONCLUSION

The LV volume and systolic function evaluated by cardiac MRI remained unchanged during vasodilator stress; however, LV dysfunction during vasodilator stress may occur in patients with severe CAD.

Gene Expression Profile at the Motor Endplate of the Neuromuscular Junction of Fast-Twitch Muscle

The neuromuscular junction (NMJ) is a prototypic chemical synapse between the spinal motor neuron and the motor endplate. Gene expression profiles of the motor endplate are not fully elucidated. Collagen Q (ColQ) is a collagenic tail subunit of asymmetric forms of acetylcholinesterase and is driven by two distinct promoters. pColQ1 is active throughout the slow-twitch muscle, whereas pColQ1a is active at the motor endplate of fast-twitch muscle. We made a transgenic mouse line that expresses nuclear localization signal (NLS)-attached Cre recombinase under the control of pColQ1a (pColQ1a-Cre mouse). RiboTag mouse expresses an HA-tagged ribosomal subunit, RPL22, in cells expressing Cre recombinase. We generated pColQ1a-Cre:RiboTag mouse, and confirmed that HA-tagged RPL22 was enriched at the NMJ of tibialis anterior (TA) muscle. Next, we confirmed that Chrne and Musk that are specifically expressed at the NMJ were indeed enriched in HA-immunoprecipitated (IP) RNA, whereas Sox10 and S100b, markers for Schwann cells, and Icam1, a marker for vascular endothelial cells, and Pax3, a marker for muscle satellite cells, were scarcely detected. Gene set enrichment analysis (GSEA) of RNA-seq data showed that “phosphatidylinositol signaling system” and “extracellular matrix receptor interaction” were enriched at the motor endplate. Subsequent analysis revealed that genes encoding diacylglycerol kinases, phosphatidylinositol kinases, phospholipases, integrins, and laminins were enriched at the motor endplate. We first characterized the gene expression profile under translation at the motor endplate of TA muscle using the RiboTag technique. We expect that our gene expression profiling will help elucidate molecular mechanisms of the development, maintenance, and pathology of the NMJ.

CTGF/CCN2 facilitates LRP4-mediated formation of the embryonic neuromuscular junction

At the neuromuscular junction (NMJ), lipoprotein-related receptor 4 (LRP4) mediates agrin-induced MuSK phosphorylation that leads to clustering of acetylcholine receptors (AChRs) in the postsynaptic region of the skeletal muscle. Additionally, the ectodomain of LRP4 is necessary for differentiation of the presynaptic nerve terminal. However, the molecules regulating LRP4 have not been fully elucidated yet. Here, we show that the CT domain of connective tissue growth factor (CTGF/CCN2) directly binds to the third beta-propeller domain of LRP4. CTGF/CCN2 enhances the binding of LRP4 to MuSK and facilitates the localization of LRP4 on the plasma membrane. CTGF/CCN2 enhances agrin-induced MuSK phosphorylation and AChR clustering in cultured myotubes. Ctgf-deficient mouse embryos (Ctgf^-/- ) have small AChR clusters and abnormal dispersion of synaptic vesicles along the motor axon. Ultrastructurally, the presynaptic nerve terminals have reduced numbers of active zones and mitochondria. Functionally, Ctgf^-/- embryos exhibit impaired NMJ signal transmission. These results indicate that CTGF/CCN2 interacts with LRP4 to facilitate clustering of AChRs at the motor endplate and the maturation of the nerve terminal.

tRIP-seq reveals repression of premature polyadenylation by co-transcriptional FUS-U1 snRNP assembly

RNA processing occurs co-transcriptionally through the dynamic recruitment of RNA processing factors to RNA polymerase II (RNAPII). However, transcriptome-wide identification of protein-RNA interactions specifically assembled on transcribing RNAPII is challenging. Here, we develop the targeted RNA immunoprecipitation sequencing (tRIP-seq) method that detects protein-RNA interaction sites in thousands of cells. The high sensitivity of tRIP-seq enables identification of protein-RNA interactions at functional subcellular levels. Application of tRIP-seq to the FUS-RNA complex in the RNAPII machinery reveals that FUS binds upstream of alternative polyadenylation (APA) sites of nascent RNA bound to RNAPII, which retards RNAPII and suppresses the recognition of the polyadenylation signal by CPSF. Further tRIP-seq analyses demonstrate that the repression of APA is achieved by a complex composed of FUS and U1 snRNP on RNAPII, but not by either one alone. Moreover, our analysis reveals that FUS mutations in familial amyotrophic lateral sclerosis (ALS) that impair the FUS-U1 snRNP interaction aberrantly activate the APA sites. tRIP-seq provides new insights into the regulatory mechanism of co-transcriptional RNA processing by RNA processing factors.

Ubiquitination of DNA Damage-Stalled RNAPII Promotes Transcription-Coupled Repair

Transcription-coupled nucleotide excision repair (TC-NER) is initiated by the stalling of elongating RNA polymerase II (RNAPIIo) at DNA lesions. The ubiquitination of RNAPIIo in response to DNA damage is an evolutionarily conserved event, but its function in mammals is unknown. Here, we identified a single DNA damage-induced ubiquitination site in RNAPII at RPB1-K1268, which regulates transcription recovery and DNA damage resistance. Mechanistically, RPB1-K1268 ubiquitination stimulates the association of the core-TFIIH complex with stalled RNAPIIo through a transfer mechanism that also involves UVSSA-K414 ubiquitination. We developed a strand-specific ChIP-seq method, which revealed RPB1-K1268 ubiquitination is important for repair and the resolution of transcriptional bottlenecks at DNA lesions. Finally, RPB1-K1268R knockin mice displayed a short life-span, premature aging, and neurodegeneration. Our results reveal RNAPII ubiquitination provides a two-tier protection mechanism by activating TC-NER and, in parallel, the processing of DNA damage-stalled RNAPIIo, which together prevent prolonged transcription arrest and protect against neurodegeneration.

Inhibition of cyclooxygenase-1 by nonsteroidal anti-inflammatory drugs demethylates MeR2 enhancer and promotes Mbnl1 transcription in myogenic cells

Muscleblind-like 1 (MBNL1) is a ubiquitously expressed RNA-binding protein, which is highly expressed in skeletal muscle. Abnormally expanded CUG-repeats in the DMPK gene cause myotonic dystrophy type 1 (DM1) by sequestration of MBNL1 to nuclear RNA foci and by upregulation of another RNA-binding protein, CUG-binding protein 1 (CUGBP1). We previously reported that a nonsteroidal anti-inflammatory drug (NSAID), phenylbutazone, upregulates MBNL1 expression in DM1 mouse model by demethylation of MeR2, an enhancer element in Mbnl1 intron 1. NSAIDs inhibit cyclooxygenase (COX), which is comprised of COX-1 and COX-2 isoforms. In this study, we screened 29 NSAIDs in C2C12 myoblasts, and found that 13 NSAIDs enhanced Mbnl1 expression, where COX-1-selective NSAIDs upregulated Mbnl1 more than COX-2-selective NSAIDs. Consistently, knockdown of COX-1, but not of COX-2, upregulated MBNL1 expression in C2C12 myoblasts and myotubes, as well as in myotubes differentiated from DM1 patient-derived induced pluripotent stem cells (iPSCs). Luciferase assay showed that COX-1-knockdown augmented the MeR2 enhancer activity. Furthermore, bisulfite sequencing analysis demonstrated that COX-1-knockdown suppressed methylation of MeR2. These results suggest that COX-1 inhibition upregulates Mbnl1 transcription through demethylation of the MeR2 enhancer. Taken together, our study provides new insights into the transcriptional regulation of Mbnl1 by the COX-1-mediated pathway.

Mianserin suppresses R-spondin 2-induced activation of Wnt/β-catenin signaling in chondrocytes and prevents cartilage degradation in a rat model of osteoarthritis

Aberrant activation of the Wnt/β-catenin signaling pathway promotes the progression of osteoarthritis (OA). We previously reported that R-spondin 2 (Rspo2), an activator of the Wnt/β-catenin signaling, facilitates differentiation of proliferating chondrocytes into hypertrophic chondrocytes by enhancing Wnt/β-catenin signaling in endochondral ossification. However, the role of Rspo2 in OA remains elusive. Here, we showed that the amounts of Rspo2 protein in synovial fluid were increased in OA patients. We searched for a preapproved drug that suppresses Rspo2-induced Wnt/β-catenin signaling in chondrogenic cells and reduces joint pathology in a rat model of OA. In Rspo2-treated ATDC5 cells, mianserin, a tetracyclic antidepressant, inhibited Wnt/β-catenin signaling, increased proteoglycan production, and upregulated chondrogenic marker genes. Mianserin suppressed Rspo2-induced accumulation of β-catenin and phosphorylation of Lrp6. We identified that mianserin blocked binding of Rspo2 to its receptor Lgr5. We also observed that intraarticular administration of mianserin suppressed β-catenin accumulation and prevented OA progression in a rat model of OA. We conclude that mianserin suppresses abnormally activated Wnt/β-catenin signaling in OA by inhibiting binding of Rspo2 to Lgr5.

Differential effects of spinal motor neuron-derived and skeletal muscle-derived Rspo2 on acetylcholine receptor clustering at the neuromuscular junction

We recently reported that R-spondin 2 (Rspo2), a secreted activator of Wnt/β-catenin signaling, promotes acetylcholine receptor (AChR) clustering and neuromuscular junction (NMJ) formation via its receptor, Lgr5. Rspo2 is expressed highly in spinal motor neurons (SMNs) and marginally in the skeletal muscle, but the origin of Rspo2 at the NMJ remains elusive. We rescued Rspo2-deficient (Rspo2-/-) mice by specifically expressing Rspo2 in the skeletal muscle and SMNs. SMN-specific Rspo2 mitigated or over-corrected abnormal features of the NMJs and AChR clusters observed in Rspo2-/- mice including (i) abnormal broadening of enlarged AChR clusters, (ii) three of six abnormal ultrastructural features, and (iii) abnormal expression of nine genes in SMNs and the diaphragm. In contrast, muscle-specific Rspo2 normalized all six abnormal ultrastructural features, but it had no effect on AChR clustering and NMJ formation at the light microscopy level or on abnormal gene expression in SMNs and the diaphragm. These results suggest that SMN-derived Rspo2 plays a major role in AChR clustering and NMJ formation in the postsynaptic region, and muscle-derived Rspo2 also plays a substantial role in juxtaposition of the active zones and synaptic folds.

[Tricuspid Valve Infective Endocarditis with Ventricular Septal Defect]

Right-sided infective endocarditis (IE) accounts for 3-14% of all cases of IE. Compared with leftsided IE, its antibiotic treatment is more effective. Therefore, the timing of its surgical treatment is still controversial. We report 2 cases of tricuspid valve IE and ventricular septal defect (VSD) associated with multiple lung abscesses and infarctions. After successful antibiotic treatment, they underwent vegetectomy, tricuspid valve plasty and VSD patch closure. Antibacterial treatment preceding surgical treatment is effective for tricuspid endocarditis complicated with multiple lung abscesses.

MYRF is associated with encephalopathy with reversible myelin vacuolization

OBJECTIVE

Reversible myelin vacuolization is associated with variable conditions including mild encephalitis/encephalopathy with a reversible splenial lesion (MERS), which is characterized by mildly impaired consciousness and transient splenial lesion. Familial and/or recurrent cases with a clinical diagnosis of MERS suggest the presence of genetic factors.

METHODS

We examined a family in which the proband presented with a history of recurrent encephalopathy with extensive but reversible cerebral myelin vacuolization and neurological symptoms similar to those of MERS spanning 3 generations. Whole-exome sequencing was performed in family members.

RESULTS

Eight rare nonsynonymous single-nucleotide variants shared by all patients were identified. By filtering genes expressed in the corpus callosum, we identified a heterozygous c.1208A>G predicting p.Gln403Arg in the highly conserved DNA-binding domain in the myelin regulatory factor (MYRF) gene. We subsequently screened the coding regions of MYRF by Sanger sequencing in our cohort comprised of 33 sporadic cases with MERS and 3 cases in another family with extensive myelin vacuolization, and identified the same heterozygous c.1208A>G in all affected members in the second family. Luciferase assay revealed that transcriptional activity of the N-terminal region of MYRF was significantly diminished by introducing the c.1208A>G variant.

INTERPRETATION

MYRF is a transcriptional regulator that is necessary for oligodendrocyte differentiation and myelin maintenance. Functional defects of MYRF are likely to be causally associated with encephalopathy with extensive myelin vacuolization. We propose the term "MYRF-related mild encephalopathy with reversible myelin vacuolization." Our findings provide a new perspective on the pathogenesis of myelin vacuolization. Ann Neurol 2018;83:98-106.

Lack of Fgf18 causes abnormal clustering of motor nerve terminals at the neuromuscular junction with reduced acetylcholine receptor clusters

FGF receptor 2 is involved in the formation of the neuromuscular junction (NMJ), but its in vivo ligand remains to be determined. Laser capture microdissection of the mouse spinal motor neurons (SMNs) revealed that Fgf18 mRNA is highly expressed in SMNs in adults. Expression of Fgf18 mRNA was the highest in the spinal cord at embryonic day (E) 15.5, which gradually decreased to postnatal day 7. FGF18 protein was localized at the NMJs of the tibialis anterior muscle at E18.5 and in adults. Fgf18−/− mice at E18.5 showed decreased expressions of the NMJ-specific Chrne and Colq genes in the diaphragm. In Fgf18−/− diaphragms, the synaptophysin-positive areas at the nerve terminals and the acetylcholine receptor (AChR)-positive areas at the motor endplates were both approximately one-third of those in wild-type embryos. Fgf18−/− diaphragms ultrastructurally showed abnormal aggregation of multiple nerve terminals making a gigantic presynapse with sparse synaptic vesicles, and simplified motor endplates. In Fgf18−/− diaphragms, miniature endplate potentials were low in amplitude with markedly reduced frequency. In C2C12 myotubes, FGF18 enhanced AChR clustering, which was blocked by inhibiting FGFRs or MEK1. We propose that FGF18 plays a pivotal role in AChR clustering and NMJ formation in mouse embryogenesis.

Competitive regulation of alternative splicing and alternative polyadenylation by hnRNP H and CstF64 determines acetylcholinesterase isoforms

Acetylcholinesterase (AChE), encoded by the ACHE gene, hydrolyzes the neurotransmitter acetylcholine to terminate synaptic transmission. Alternative splicing close to the 3΄ end generates three distinct isoforms of AChE_T, AChE_H and AChE_R. We found that hnRNP H binds to two specific G-runs in exon 5a of human ACHE and activates the distal alternative 3΄ splice site (ss) between exons 5a and 5b to generate AChE_T. Specific effect of hnRNP H was corroborated by siRNA-mediated knockdown and artificial tethering of hnRNP H. Furthermore, hnRNP H competes for binding of CstF64 to the overlapping binding sites in exon 5a, and suppresses the selection of a cryptic polyadenylation site (PAS), which additionally ensures transcription of the distal 3΄ ss required for the generation of AChE_T. Expression levels of hnRNP H were positively correlated with the proportions of the AChE_T isoform in three different cell lines. HnRNP H thus critically generates AChE_T by enhancing the distal 3΄ ss and by suppressing the cryptic PAS. Global analysis of CLIP-seq and RNA-seq also revealed that hnRNP H competitively regulates alternative 3΄ ss and alternative PAS in other genes. We propose that hnRNP H is an essential factor that competitively regulates alternative splicing and alternative polyadenylation.

Successful Treatment with 5-fluorouracil and Levofolinate Calcium in Advanced Gastric Cancer Patient with Disseminated Intravascular Coagulation

A 32-year-old woman was found to have a gastric adenocarcinoma with multiple bone metastases. Chemotherapy in the first, second and third-line was not effective. Blood examinations showed disseminated intravascular coagulation(DIC)at the end of the second-line chemotherapy. The fourth-line chemotherapy, infusional 5-fluorouracil and levofolinate calcium was performed. This resulted in a good response for DIC. This palliative therapy was effective and safety.

Fluoxetine ameliorates cartilage degradation in osteoarthritis by inhibiting Wnt/β-catenin signaling

Abnormal activation of the Wnt/β-catenin signaling is implicated in the osteoarthritis (OA) pathology. We searched for a pre-approved drug that suppresses abnormally activated Wnt/β-catenin signaling and has a potency to reduce joint pathology in OA. We introduced the TOPFlash reporter plasmid into HCS-2/8 human chondrosarcoma cells to estimate the Wnt/β-catenin activity in the presence of 10 μM each compound in a panel of pre-approved drugs. We found that fluoxetine, an antidepressant in the class of selective serotonin reuptake inhibitors (SSRI), down-regulated Wnt/β-catenin signaling in human chondrosarcoma cells. Fluoxetine inhibited both Wnt3A- and LiCl-induced loss of proteoglycans in chondrogenically differentiated ATDC5 cells. Fluoxetine increased expression of Sox9 (the chondrogenic master regulator), and decreased expressions of Axin2 (a marker for Wnt/β-catenin signaling) and Mmp13 (matrix metalloproteinase 13). Fluoxetine suppressed a LiCl-induced increase of total β-catenin and a LiCl-induced decrease of phosphorylated β-catenin in a dose-dependent manner. An in vitro protein-binding assay showed that fluoxetine enhanced binding of β-catenin with Axin1, which is a scaffold protein forming the degradation complex for β-catenin. Fluoxetine suppressed LiCl-induced β-catenin accumulation in human OA chondrocytes. Intraarticular injection of fluoxetine in a rat OA model ameliorated OA progression and suppressed β-catenin accumulation.

Six GU-rich (6GUR) FUS-binding motifs detected by normalization of CLIP-seq by Nascent-seq

FUS, an RNA-binding protein (RBP), is mutated or abnormally regulated in neurodegenerative disorders. FUS regulates various aspects of RNA metabolisms. FUS-binding sites are rich in GU contents and are highly degenerative. FUS-binding motifs of GGU, GGUG, GUGGU and CGCGC have been previously reported. These motifs, however, are applicable to a small fraction of FUS-binding sites. As CLIP-seq tags are enriched in genes that are highly expressed, we normalized CLIP-seq tags by Nascent-seq tags or RNA-seq tags of mouse N2a cells. Nascent-seq identifies nascent transcripts before being processed for splicing and polyadenylation. We extracted frequently observed 4-nt motifs from Nascent-seq-normalized CLIP regions, RNA-seq-normalized CLIP regions, and native CLIP regions. Specific GU-rich motifs were best detected in Nascent-seq-normalized CLIP regions. Analysis of structural motifs using Nascent-seq-normalized CLIP regions also predicted GU-rich sequence forming a stem structure. Sensitivity and specificity were calculated by examining whether the extracted motifs were present at the cross-linking-induced mutation sites (CIMS), where FUS was directly bound. We found that a combination of six motifs (UGUG, CUGG, UGGU, GCUG, GUGG, and UUGG), which were extracted from Nascent-seq-normalized CLIP-regions, had a better discriminative power than (i) motifs extracted from RNA-seq-normalized CLIP regions, (ii) motifs extracted from native CLIP regions, (iii) previously reported individual motifs, or (iv) 15 motifs in SpliceAid 2. Validation of the 6 GU-rich (6GU_R) motifs using CLIP-seq of the cerebrum and the whole brain showed that the 6GU_R motifs were specifically enriched in CIMS. The number of the 6GU_R motifs in an uninterrupted region was counted and multiplied by four to calculate the area, which was defined as the 6GU_R-Score. The 6GU_R-Score of 8 or more best discriminated CIMS from CIMS-flanking regions. We propose that the 6GU_R motifs predict FUS-binding sites more efficiently than previously reported individual motifs or 15 motifs in SpliceAid 2.

Splicing regulation and dysregulation of cholinergic genes expressed at the neuromuscular junction

We humans have evolved by acquiring diversity of alternative RNA metabolisms including alternative means of splicing and transcribing non-coding genes, and not by acquiring new coding genes. Tissue-specific and developmental stage-specific alternative RNA splicing is achieved by tightly regulated spatiotemporal regulation of expressions and activations of RNA-binding proteins that recognize their cognate splicing cis-elements on nascent RNA transcripts. Genes expressed at the neuromuscular junction are also alternatively spliced. In addition, germline mutations provoke aberrant splicing by compromising binding of RNA-binding proteins, and cause congenital myasthenic syndromes (CMS). We present physiological splicing mechanisms of genes for agrin (AGRN), acetylcholinesterase (ACHE), MuSK (MUSK), acetylcholine receptor (AChR) α1 subunit (CHRNA1), and collagen Q (COLQ) in human, and their aberration in diseases. Splicing isoforms of AChE_T , AChE_H , and AChE_R are generated by hnRNP H/F. Skipping of MUSK exon 10 makes a Wnt-insensitive MuSK isoform, which is unique to human. Skipping of exon 10 is achieved by coordinated binding of hnRNP C, YB-1, and hnRNP L to exon 10. Exon P3A of CHRNA1 is alternatively included to generate a non-functional AChR α1 subunit in human. Molecular dissection of splicing mutations in patients with CMS reveals that exon P3A is alternatively skipped by hnRNP H, polypyrimidine tract-binding protein 1, and hnRNP L. Similarly, analysis of an exonic mutation in COLQ exon 16 in a CMS patient discloses that constitutive splicing of exon 16 requires binding of serine arginine-rich splicing factor 1. Intronic and exonic splicing mutations in CMS enable us to dissect molecular mechanisms underlying alternative and constitutive splicing of genes expressed at the neuromuscular junction. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.

CHARACTERIZATION OF A THIN SILICON SENSOR FOR ACTIVE NEUTRON PERSONAL DOSEMETERS

A thin silicon sensor has been developed for active neutron personal dosemeters for use by aircrews and first responders. This thin silicon sensor is not affected by the funneling effect, which causes detection of cosmic protons and over-response to cosmic neutrons. There are several advantages to the thin silicon sensor: a decrease in sensitivity to gamma rays, an improvement of the energy detection limit for neutrons down to 0.8 MeV and an increase in the sensitivity to fast neutrons. Neutron response functions were experimentally obtained using 2.5 and 5 MeV monoenergy neutron beams and a (252)Cf neutron source. Simulation results using the Monte Carlo N-Particle transport code agree quite well with the experimental ones when an energy deposition region shaped like a circular truncated cone is used in place of a cylindrical region.

Molecular hydrogen suppresses activated Wnt/β-catenin signaling

Molecular hydrogen (H₂) is effective for many diseases. However, molecular bases of H₂ have not been fully elucidated. Cumulative evidence indicates that H₂ acts as a gaseous signal modulator. We found that H₂ suppresses activated Wnt/β-catenin signaling by promoting phosphorylation and degradation οf β-catenin. Either complete inhibition of GSK3 or mutations at CK1- and GSK3-phosphorylation sites of β-catenin abolished the suppressive effect of H₂. H₂ did not increase GSK3-mediated phosphorylation of glycogen synthase, indicating that H₂ has no direct effect on GSK3 itself. Knock-down of adenomatous polyposis coli (APC) or Axin1, which form the β-catenin degradation complex, minimized the suppressive effect of H₂ on β-catenin accumulation. Accordingly, the effect of H₂ requires CK1/GSK3-phosphorylation sites of β-catenin, as well as the β-catenin degradation complex comprised of CK1, GSK3, APC, and Axin1. We additionally found that H₂ reduces the activation of Wnt/β-catenin signaling in human osteoarthritis chondrocytes. Oral intake of H₂ water tended to ameliorate cartilage degradation in a surgery-induced rat osteoarthritis model through attenuating β-catenin accumulation. We first demonstrate that H₂ suppresses abnormally activated Wnt/β-catenin signaling, which accounts for the protective roles of H₂ in a fraction of diseases.

Global identification of hnRNP A1 binding sites for SSO-based splicing modulation

Background

Many pathogenic genetic variants have been shown to disrupt mRNA splicing. Besides splice mutations in the well-conserved splice sites, mutations in splicing regulatory elements (SREs) may deregulate splicing and cause disease. A promising therapeutic approach is to compensate for this deregulation by blocking other SREs with splice-switching oligonucleotides (SSOs). However, the location and sequence of most SREs are not well known.

Results

Here, we used individual-nucleotide resolution crosslinking immunoprecipitation (iCLIP) to establish an in vivo binding map for the key splicing regulatory factor hnRNP A1 and to generate an hnRNP A1 consensus binding motif. We find that hnRNP A1 binding in proximal introns may be important for repressing exons. We show that inclusion of the alternative cassette exon 3 in SKA2 can be significantly increased by SSO-based treatment which blocks an iCLIP-identified hnRNP A1 binding site immediately downstream of the 5’ splice site. Because pseudoexons are well suited as models for constitutive exons which have been inactivated by pathogenic mutations in SREs, we used a pseudoexon in MTRR as a model and showed that an iCLIP-identified hnRNP A1 binding site downstream of the 5′ splice site can be blocked by SSOs to activate the exon.

Conclusions

The hnRNP A1 binding map can be used to identify potential targets for SSO-based therapy. Moreover, together with the hnRNP A1 consensus binding motif, the binding map may be used to predict whether disease-associated mutations and SNPs affect hnRNP A1 binding and eventually mRNA splicing.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-016-0279-9) contains supplementary material, which is available to authorized users.

Phenylbutazone induces expression of MBNL1 and suppresses formation of MBNL1-CUG RNA foci in a mouse model of myotonic dystrophy

Myotonic dystrophy type 1 (DM1) is caused by abnormal expansion of CTG repeats in the 3′ untranslated region of the DMPK gene. Expanded CTG repeats are transcribed into RNA and make an aggregate with a splicing regulator, MBNL1, in the nucleus, which is called the nuclear foci. The nuclear foci sequestrates and downregulates availability of MBNL1. Symptomatic treatments are available for DM1, but no rational therapy is available. In this study, we found that a nonsteroidal anti-inflammatory drug (NSAID), phenylbutazone (PBZ), upregulated the expression of MBNL1 in C2C12 myoblasts as well as in the HSA^LR mouse model for DM1. In the DM1 mice model, PBZ ameliorated aberrant splicing of Clcn1, Nfix, and Rpn2. PBZ increased expression of skeletal muscle chloride channel, decreased abnormal central nuclei of muscle fibers, and improved wheel-running activity in HSA^LR mice. We found that the effect of PBZ was conferred by two distinct mechanisms. First, PBZ suppressed methylation of an enhancer region in Mbnl1 intron 1, and enhanced transcription of Mbnl1 mRNA. Second, PBZ attenuated binding of MBNL1 to abnormally expanded CUG repeats in cellulo and in vitro. Our studies suggest that PBZ is a potent therapeutic agent for DM1 that upregulates availability of MBNL1.

FUS-mediated regulation of alternative RNA processing in neurons: insights from global transcriptome analysis

Fused in sarcoma (FUS) is an RNA-binding protein that is causally associated with oncogenesis and neurodegeneration. Recently, the role of FUS in neurodegeneration has been extensively studied, because mutations in FUS are associated with amyotrophic lateral sclerosis (ALS), and the FUS protein has been identified as a major component of intracellular inclusions in neurodegenerative disorders including ALS and frontotemporal lobar degeneration. FUS is a key molecule in transcriptional regulation and RNA processing including processes such as pre-messenger RNA (mRNA) splicing and polyadenylation. Interaction of FUS with various components of the transcription machinery, spliceosome, and the 3'-end processing machinery has been identified. Furthermore, recent advances in high-throughput transcriptomic profiling approaches have enabled us to determine the mechanisms of FUS-dependent RNA processing networks at a cellular level. These analyses have revealed that depletion of FUS in neuronal cells affects alternative splicing and alternative polyadenylation of thousands of mRNAs. Gene ontology analysis has suggested that FUS-modulated genes are implicated in neuronal functions and development. CLIP-seq of FUS has shown that FUS is frequently clustered around these alternative sites of nascent RNA. ChIP-seq of RNA polymerase II (RNAP II) has demonstrated that an interaction between FUS and nascent RNA downregulates local transcriptional activity of RNAP II, which is critically involved in RNA processing. Both alternative splicing and alternative polyadenylation are fundamental processes by which cells expand their transcriptomic diversity, and are particularly essential in the nervous system. Dependence of transcriptomic diversity on FUS makes the nervous system vulnerable to neurodegeneration, when FUS is functionally compromised. WIREs RNA 2016, 7:330-340. doi: 10.1002/wrna.1338 For further resources related to this article, please visit the WIREs website.

Zonisamide Enhances Neurite Elongation of Primary Motor Neurons and Facilitates Peripheral Nerve Regeneration In Vitro and in a Mouse Model

No clinically applicable drug is currently available to enhance neurite elongation after nerve injury. To identify a clinically applicable drug, we screened pre-approved drugs for neurite elongation in the motor neuron-like NSC34 cells. We found that zonisamide, an anti-epileptic and anti-Parkinson’s disease drug, promoted neurite elongation in cultured primary motor neurons and NSC34 cells in a concentration-dependent manner. The neurite-scratch assay revealed that zonisamide enhanced neurite regeneration. Zonisamide was also protective against oxidative stress-induced cell death of primary motor neurons. Zonisamide induced mRNA expression of nerve growth factors (BDNF, NGF, and neurotrophin-4/5), and their receptors (tropomyosin receptor kinase A and B). In a mouse model of sciatic nerve autograft, intragastric administration of zonisamide for 1 week increased the size of axons distal to the transected site 3.9-fold. Zonisamide also improved the sciatic function index, a marker for motor function of hindlimbs after sciatic nerve autograft, from 6 weeks after surgery. At 8 weeks after surgery, zonisamide was protective against denervation-induced muscle degeneration in tibialis anterior, and increased gene expression of Chrne, Colq, and Rapsn, which are specifically expressed at the neuromuscular junction. We propose that zonisamide is a potential therapeutic agent for peripheral nerve injuries as well as for neuropathies due to other etiologies.

Arginine methylation of ubiquitin-associated protein 2-like is required for the accurate distribution of chromosomes

Proper bioriented attachment of microtubules and kinetochores is essential for the precise distribution of duplicated chromosomes to each daughter cell. An aberrant kinetochore-microtubule attachment results in chromosome instability, which leads to cellular transformation or apoptosis. In this article, we show that ubiquitin-associated protein 2-like (UBAP2L) is necessary for correct kinetochore-microtubule attachment. Depletion of UBAP2L inhibited chromosome alignment in metaphase and delayed progression to anaphase by activating spindle assembly checkpoint signaling. In addition, UBAP2L knockdown increased side-on attachment of kinetochores along the microtubules and suppressed stable kinetochore fiber formation. A proteomics analysis identified protein arginine methyltransferase (PRMT)1 as a direct interaction partner of UBAP2L. UBAP2L has an arginine- and glycine-rich motif called the RGG/RG or GAR motif in the N terminus. Biochemical analysis confirmed that arginine residues in the RGG/RG motif of UBAP2L were directly methylated by PRMT1. Finally, we demonstrated that the RGG/RG motif of UBAP2L is essential for the proper alignment of chromosomes in metaphase for the accurate distribution of chromosomes. Our results show a possible role for arginine methylation in UBAP2L for the progression of mitosis.

Position-specific binding of FUS to nascent RNA regulates mRNA length

More than half of all human genes produce prematurely terminated polyadenylated short mRNAs. Masuda et al. show that FUS is frequently clustered around an alternative polyadenylation (APA) site of nascent RNA, stalls RNAP II, and prematurely terminates transcription in neuronal cells. Position-specific regulation of mRNA lengths by FUS is operational in two-thirds of transcripts in neuronal cells, with enrichment in genes involved in synaptic activities.

More than half of all human genes produce prematurely terminated polyadenylated short mRNAs. However, the underlying mechanisms remain largely elusive. CLIP-seq (cross-linking immunoprecipitation [CLIP] combined with deep sequencing) of FUS (fused in sarcoma) in neuronal cells showed that FUS is frequently clustered around an alternative polyadenylation (APA) site of nascent RNA. ChIP-seq (chromatin immunoprecipitation [ChIP] combined with deep sequencing) of RNA polymerase II (RNAP II) demonstrated that FUS stalls RNAP II and prematurely terminates transcription. When an APA site is located upstream of an FUS cluster, FUS enhances polyadenylation by recruiting CPSF160 and up-regulates the alternative short transcript. In contrast, when an APA site is located downstream from an FUS cluster, polyadenylation is not activated, and the RNAP II-suppressing effect of FUS leads to down-regulation of the alternative short transcript. CAGE-seq (cap analysis of gene expression [CAGE] combined with deep sequencing) and PolyA-seq (a strand-specific and quantitative method for high-throughput sequencing of 3' ends of polyadenylated transcripts) revealed that position-specific regulation of mRNA lengths by FUS is operational in two-thirds of transcripts in neuronal cells, with enrichment in genes involved in synaptic activities.