Downregulation of Survivin contributes to cell-cycle arrest during postnatal cardiac development in a severe spinal muscular atrophy mouse model

Mitochondrial Dysfunction in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder caused by recessive mutations in the SMN1 gene, globally affecting ~8-14 newborns per 100,000. The severity of the disease depends on the residual levels of functional survival of motor neuron protein, SMN. SMN is a ubiquitously expressed RNA binding protein involved in a plethora of cellular processes. In this review, we discuss the effects of SMN loss on mitochondrial functions in the neuronal and muscular systems that are the most affected in patients with spinal muscular atrophy. Our aim is to highlight how mitochondrial defects may contribute to disease progression and how restoring mitochondrial functionality may be a promising approach to develop new therapies. We also collected from previous studies a list of transcripts encoding mitochondrial proteins affected in various SMA models. Moreover, we speculate that in adulthood, when motor neurons require only very low SMN levels, the natural deterioration of mitochondria associated with aging may be a crucial triggering factor for adult spinal muscular atrophy, and this requires particular attention for therapeutic strategies.

The Proteome Signatures of Fibroblasts from Patients with Severe, Intermediate and Mild Spinal Muscular Atrophy Show Limited Overlap

Most research to characterise the molecular consequences of spinal muscular atrophy (SMA) has focused on SMA I. Here, proteomic profiling of skin fibroblasts from severe (SMA I), intermediate (SMA II), and mild (SMA III) patients, alongside age-matched controls, was conducted using SWATH mass spectrometry analysis. Differentially expressed proteomic profiles showed limited overlap across each SMA type, and variability was greatest within SMA II fibroblasts, which was not explained by SMN2 copy number. Despite limited proteomic overlap, enriched canonical pathways common to two of three SMA severities with at least one differentially expressed protein from the third included mTOR signalling, regulation of eIF2 and eIF4 signalling, and protein ubiquitination. Network expression clustering analysis identified protein profiles that may discriminate or correlate with SMA severity. From these clusters, the differential expression of PYGB (SMA I), RAB3B (SMA II), and IMP1 and STAT1 (SMA III) was verified by Western blot. All SMA fibroblasts were transfected with an SMN-enhanced construct, but only RAB3B expression in SMA II fibroblasts demonstrated an SMN-dependent response. The diverse proteomic profiles and pathways identified here pave the way for studies to determine their utility as biomarkers for patient stratification or monitoring treatment efficacy and for the identification of severity-specific treatments.

The alteration of left ventricular strain in later-onset spinal muscular atrophy children

Background

Patients with spinal muscular atrophy (SMA) may suffer from multisystem injury, including an impaired cardiovascular system. However, M-mode echocardiography, the current dominant echocardiographic modality, is limited in the detection of myocardial injury. We considered the use of left ventricular strain imaging in detecting myocardial injury and explored the serum lipid profile related to cardiovascular disease in later-onset SMA children.

Methods

A case-control study involving 80 patients with later-onset SMA and 80 age-, gender-, and body surface area-matched control children was conducted in a single tertiary pediatric hospital in China. Data on the left ventricular strain measured using two-dimensional speckle tracking echocardiography, left ventricular function parameters assessed by M-mode echocardiography, and serum lipid profile of these two groups were retrospectively collected for differential analysis.

Results

The mean age of the 80 SMA patients were (6.87 ± 2.87) years, of which 46 were type 2 and 34 were type 3 patients. The global longitudinal strain (GLS) of the SMA group (−18.7 ± 2.9%, p < 0.001) was lower than that of the control group; the time to peak longitudinal strain (TTPLS) of the SMA group (22.9 ± 13.6 ms, p < 0.001) was higher than that of the control group, while left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS), measured by the Teichholz method of M-mode echocardiography, showed no significant differences between the two groups. In addition, independent indicators for cardiovascular risk, including total cholesterol (TC)/HDL, low-density lipoprotein (LDL)/HDL, and Apo B/Apo A1 levels, were higher in SMA children than in the control group.

Conclusion

Compared with healthy controls, later-onset SMA children presented with reduced GLS and prolonged TTPLS while the LVEF and LVFS values were within normal range. In particular, whether a reduced GLS or prolonged TTPLS in later-onset SMA compared to the control group can predict the risk of future cardiomyopathy remains to be investigated.

History of development of the life-saving drug “Nusinersen” in spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive disorder with an incidence of 1/6,000–1/10,000 and is the leading fatal disease among infants. Previously, there was no effective treatment for SMA. The first effective drug, nusinersen, was approved by the US FDA in December 2016, providing hope to SMA patients worldwide. The drug was introduced in the European Union in 2017 and China in 2019 and has so far saved the lives of several patients in most parts of the world. Nusinersen are fixed sequence antisense oligonucleotides with special chemical modifications. The development of nusinersen progressed through major scientific discoveries in medicine, genetics, biology, and other disciplines, wherein several scientists have made substantial contributions. In this article, we will briefly describe the pathogenesis and therapeutic strategies of SMA, summarize the timeline of important scientific findings during the development of nusinersen in a detailed, scientific, and objective manner, and finally discuss the implications of the development of nusinersen for SMA research.

Suppression of the necroptotic cell death pathways improves survival in Smn2B/− mice

Spinal muscular atrophy (SMA) is a monogenic neuromuscular disease caused by low levels of the Survival Motor Neuron (SMN) protein. Motor neuron degeneration is the central hallmark of the disease. However, the SMN protein is ubiquitously expressed and depletion of the protein in peripheral tissues results in intrinsic disease manifestations, including muscle defects, independent of neurodegeneration. The approved SMN-restoring therapies have led to remarkable clinical improvements in SMA patients. Yet, the presence of a significant number of non-responders stresses the need for complementary therapeutic strategies targeting processes which do not rely solely on restoring SMN. Dysregulated cell death pathways are candidates for SMN-independent pathomechanisms in SMA. Receptor-interacting protein kinase 1 (RIPK1) and RIPK3 have been widely recognized as critical therapeutic targets of necroptosis, an important form of programmed cell death. In addition, Caspase-1 plays a fundamental role in inflammation and cell death. In this study, we evaluate the role of necroptosis, particularly RIPK3 and Caspase-1, in the Smn^2B/− mouse model of SMA. We have generated a triple mutant (TKO), the Smn^2B/−; Ripk3^−/−; Casp1^−/− mouse. TKO mice displayed a robust increase in survival and improved motor function compared to Smn^2B/− mice. While there was no protection against motor neuron loss or neuromuscular junction pathology, larger muscle fibers were observed in TKO mice compared to Smn^2B/− mice. Our study shows that necroptosis modulates survival, motor behavior and muscle fiber size independent of SMN levels and independent of neurodegeneration. Thus, small-molecule inhibitors of necroptosis as a combinatorial approach together with SMN-restoring drugs could be a future strategy for the treatment of SMA.

Antisense Oligonucleotide Induction of the hnRNPA1b Isoform Affects Pre-mRNA Splicing of SMN2 in SMA Type I Fibroblasts

Spinal muscular atrophy (SMA) is a severe, debilitating neuromuscular condition characterised by loss of motor neurons and progressive muscle wasting. SMA is caused by a loss of expression of SMN1 that encodes the survival motor neuron (SMN) protein necessary for the survival of motor neurons. Restoration of SMN expression through increased inclusion of SMN2 exon 7 is known to ameliorate symptoms in SMA patients. As a consequence, regulation of pre-mRNA splicing of SMN2 could provide a potential molecular therapy for SMA. In this study, we explored if splice switching antisense oligonucleotides could redirect the splicing repressor hnRNPA1 to the hnRNPA1b isoform and restore SMN expression in fibroblasts from a type I SMA patient. Antisense oligonucleotides (AOs) were designed to promote exon 7b retention in the mature mRNA and induce the hnRNPA1b isoform. RT-PCR and western blot analysis were used to assess and monitor the efficiency of different AO combinations. A combination of AOs targeting multiple silencing motifs in hnRNPA1 pre-mRNA led to robust hnRNPA1b induction, which, in turn, significantly increased expression of full-length SMN (FL-SMN) protein. A combination of PMOs targeting the same motifs also strongly induced hnRNPA1b isoform, but surprisingly SMN2 exon 5 skipping was detected, and the PMO cocktail did not lead to a significant increase in expression of FL-SMN protein. We further performed RNA sequencing to assess the genome-wide effects of hnRNPA1b induction. Some 3244 genes were differentially expressed between the hnRNPA1b-induced and untreated SMA fibroblasts, which are functionally enriched in cell cycle and chromosome segregation processes. RT-PCR analysis demonstrated that expression of the master regulator of these enrichment pathways, MYBL2 and FOXM1B, were reduced in response to PMO treatment. These findings suggested that induction of hnRNPA1b can promote SMN protein expression, but not at sufficient levels to be clinically relevant.

Shikonin Inhibits Non-Small-Cell Lung Cancer H1299 Cell Growth through Survivin Signaling Pathway

Overexpressed survivin is associated with worse survival of several types of human tumors. In this study, the antitumor activity of shikonin in non-small-cell lung cancer (NSCLC) by regulating survivin pathway was investigated. Results showed that shikonin inhibited the NSCLC H1299 cell proliferation in a dose-dependent manner. Moreover, shikonin fits well with survivin by molecular docking. Shikonin also inhibited the mRNA expression and protein level of survivin in H1299 cells. Shikonin arrested H1299 cell cycle at the G0/G1 phase by regulating CDK/cyclin family members. In addition, shikonin regulated the expression of X-linked inhibitor of apoptosis- (XIAP-) mediated caspases 3 and 9, thus leading to the damage of mitochondrial membrane potential and induction of H1299 cell apoptosis. Overall, shikonin inhibited H1299 cell growth by inducing apoptosis and blocking the cell cycle. The underlying mechanism involves targeting survivin, which subsequently regulates the protein expression of XIAP/caspase 3/9, CDK2/4, and cyclin E/D1. Thus, shikonin, a survivin inhibitor, is a promising therapeutic strategy in NSCLC treatment.

Spinal Muscular Atrophy autophagy profile is tissue-dependent: differential regulation between muscle and motoneurons

Spinal muscular atrophy (SMA) is a neuromuscular genetic disease caused by reduced survival motor neuron (SMN) protein. SMN is ubiquitous and deficient levels cause spinal cord motoneurons (MNs) degeneration and muscle atrophy. Nevertheless, the mechanism by which SMN reduction in muscle contributes to SMA disease is not fully understood. Therefore, studies evaluating atrophy mechanisms in SMA muscles will contribute to strengthening current knowledge of the pathology. Here we propose to evaluate autophagy in SMA muscle, a pathway altered in myotube atrophy. We analized autophagy proteins and mTOR in muscle biopsies, fibroblasts, and lymphoblast cell lines from SMA patients and in gastrocnemius muscles from a severe SMA mouse model. Human MNs differentiated from SMA and unaffected control iPSCs were also included in the analysis of the autophagy. Muscle biopsies, fibroblasts, and lymphoblast cell lines from SMA patients showed reduction of the autophagy marker LC3-II. In SMA mouse gastrocnemius, we observed lower levels of LC3-II, Beclin 1, and p62/SQSTM1 proteins at pre-symptomatic stage. mTOR phosphorylation at Ser2448 was decreased in SMA muscle cells. However, in mouse and human cultured SMA MNs mTOR phosphorylation and LC3-II levels were increased. These results suggest a differential regulation in SMA of the autophagy process in muscle cells and MNs. Opposite changes in autophagy proteins and mTOR phosphorylation between muscle cells and neurons were observed. These differences may reflect a specific response to SMN reduction, which could imply diverse tissue-dependent reactions to therapies that should be taken into account when treating SMA patients.

Tart Cherry (Fruit of Prunus cerasus) Concentrated Powder (TCcp) Ameliorates Glucocorticoid-Induced Muscular Atrophy in Mice

Background and Objectives: The present study investigated the beneficial effects of tart cherry (fruit of Prunus cerasus) concentrated powder (TCcp) on glucocorticoid (GLU)-induced catabolic muscular atrophy in the skeletal muscle of mice. Furthermore, its potential mechanism was also studied. Materials and Methods: Changes in calf thickness, calf muscle weight, calf muscle strength, body weight, gastrocnemius muscle histology, immunohistochemistry, serum creatinine, creatine kinase, lactate dehydrogenase, and antioxidant defense systems were measured. Malondialdehyde, reactive oxygen species, glutathione content, catalase, and superoxide dismutase activities in the gastrocnemius muscle, and muscle-specific mRNA expressions were evaluated. Results: After 24 days, GLU control mice showed muscular atrophy at all criteria of indexes. The muscular atrophy symptoms were significantly inhibited by oral treatment with 250 mg/kg and 500 mg/kg of TCcp through antioxidative and anti-inflammatory modulated expression of genes involved in muscle protein degradation (myostatin, atrogin-1, SIRT1, and MuRF1) and synthesis (A1R, Akt1, TRPV4, and PI3K). Conclusions: This study shows that the TCcp (500 mg/kg and 250 mg/kg) could improve muscular atrophies caused by various etiologies.

Troponin T amino acid mutation (ΔK210) knock-in mice as a neonatal dilated cardiomyopathy model

BACKGROUND

Dilated cardiomyopathy (DCM) in children is often associated with poor morbidity and mortality and exhibits distinct pathological entities from those of adult DCM. Owing to the limited number of patients and the lack of a good animal model, the molecular mechanisms underlying pediatric DCM remain poorly understood. The purpose of this study is to establish an animal model of neonatal DCM and identify early progression factors.

METHODS

Cardiac phenotypes and comprehensive gene expression profiles in homozygous ΔK210 knock-in (TNNT2^{ΔK210/ΔK210}) mice were analyzed and compared to TNNT2^+/ΔK210 and wild-type mice at 0 days and 1 week of age.

RESULTS

Immediately after birth, the cardiac weight in TNNT2^{ΔK210/ΔK210} mice was already increased compared to that in TNNT2^+/ΔK210 and wild-type mice. Echocardiographic examination of 0-day-old and 1-week-old TNNT2^{ΔK210/ΔK210} mice revealed similar phenotypes of pediatric DCM. In addition, several genes were significantly upregulated in the ventricular tissues of TNNT2^{ΔK210/ΔK210} mice, and the KEGG PATHWAY analysis revealed several important pathways such as cancer and focal adhesion that might be associated with the pathogenesis and development of DCM.

CONCLUSIONS

TNNT2^{ΔK210/ΔK210} mice have already developed DCM at birth, indicating that they should be an excellent animal model to identify early progression factors of DCM.

IMPACT

TNNT2^{ΔK210/ΔK210} mice are excellent animal model for DCM. TNNT2^{ΔK210/ΔK210} mice are excellent animal model to identify early progression factors of DCM. KEGG PATHWAY analysis revealed that several important pathways such as cancer and focal adhesion might be associated with the pathogenesis and development of neonatal DCM.

In Search of a Cure: The Development of Therapeutics to Alter the Progression of Spinal Muscular Atrophy

Until the recent development of disease-modifying therapeutics, spinal muscular atrophy (SMA) was considered a devastating neuromuscular disease with a poor prognosis for most affected individuals. Symptoms generally present during early childhood and manifest as muscle weakness and progressive paralysis, severely compromising the affected individual’s quality of life, independence, and lifespan. SMA is most commonly caused by the inheritance of homozygously deleted SMN1 alleles with retention of one or more copies of a paralog gene, SMN2, which inversely correlates with disease severity. The recent advent and use of genetically targeted therapies have transformed SMA into a prototype for monogenic disease treatment in the era of genetic medicine. Many SMA-affected individuals receiving these therapies achieve traditionally unobtainable motor milestones and survival rates as medicines drastically alter the natural progression of this disease. This review discusses historical SMA progression and underlying disease mechanisms, highlights advances made in therapeutic research, clinical trials, and FDA-approved medicines, and discusses possible second-generation and complementary medicines as well as optimal temporal intervention windows in order to optimize motor function and improve quality of life for all SMA-affected individuals.

A novel indenone derivative selectively induces senescence in MDA-MB-231 (breast adenocarcinoma) cells

Triple-negative breast cancer is the most aggressive form of breast cancer with limited intervention options. Moreover, a number of belligerent therapeutic strategies adopted to treat such aggressive forms of cancer have demonstrated detrimental side effects. This necessitates exploration of targeted chemotherapeutics. We assessed the efficacy of a novel indenone derivative (nID) [(±)-N-(2-(-5-methoxy-1-oxo-3-(2-oxo-2-phenylethyl)-2,3-dihydro-1H-inden-2-yl)ethyl)-4-methylbenzenesulfonamide], synthesized by a novel internal nucleophile-assisted palladium-catalyzed hydration-olefin insertion cascade; against triple-negative breast cancer cells (MDA-MB-231). On 24 h treatment, the nID caused decline in the viability of MDA-MB-231 and MDA-MB-468 cells, but did not significantly (P < 0.05) affect WRL-68 (epithelial-like) cells. In fact, the nID demonstrated augmentation of p53 expression, and consequent p53-dependent senescence in both MDA-MB-231 and MDA-MB-468 cells, but not in WRL-68 cells. The breast cancer cells also exhibited reduced proliferation, downregulated p65/NF-κB and survivin, along with augmented p21Cip1/WAF1 expression, on treatment with the nID. This ensued cell cycle arrest at G1 stage, which might have driven the MDA-MB-231 cells to senescence. We observed a selectivity of the nID to target MDA-MB-231 cells, whereas WRL-68 cells did not show any considerable effect. The results underscored that the nID has potential to be developed into a cancer therapeutic.

Overturning the Paradigm of Spinal Muscular Atrophy as Just a Motor Neuron Disease

Spinal muscular atrophy is typically characterized as a motor neuron disease. Untreated patients with the most severe form, spinal muscular atrophy type 1, die early with infantile-onset progressive skeletal, bulbar, and respiratory muscle weakness. Such patients are now living longer due to new disease-modifying treatments such as gene replacement therapy (onasemnogene abeparvovec), recently approved by the US Food and Drug Administration, and nusinersen, a central nervous system-directed treatment which was approved by the US Food and Drug Administration three years ago. This has created an area of pressing clinical need: if spinal muscular atrophy is a multisystem disease, dysfunction of peripheral tissues and organs may become significant comorbidities as these patients survive into childhood and adulthood. In this review, we have compiled autopsy data, case reports, and cohort studies of peripheral tissue involvement in patients and animal models with spinal muscular atrophy. We have also evaluated preclinical studies addressing the question of whether peripheral expression of survival motor neuron is necessary and/or sufficient for motor neuron function and survival. Indeed, spinal muscular atrophy patient data suggest that spinal muscular atrophy is a multisystem disease with dysfunction in skeletal muscle, heart, kidney, liver, pancreas, spleen, bone, connective tissues, and immune systems. The peripheral requirement of SMN in each organ and how these contribute to motor neuron function and survival remains to be answered. A systemic (peripheral and central nervous system) approach to therapy during early development is most likely to effectively maximize positive clinical outcome.

Survival motor neuron protein protects H9c2 cardiomyocytes from hypoxia-induced cell injury by reducing apoptosis

BACKGROUND

Hypoxia induces cell injury in cardiomyocytes and leads to the development of cardiovascular diseases. The survival motor neuron protein (SMN) is a crucial ubiquitous protein whose functional deficiency causes motor neuron loss seen in spinal muscular atrophy. SMN has shown protective effects on the cardiovascular system and the aim of the present study was to investigate the cardioprotective effects of SMN on hypoxia-induced cell injury.

METHODS

Cobalt chloride (CoCl₂ ) was used to induce chemical hypoxia in H9c2 cardiomyocytes. Cell proliferation was determined by the MTT assay and the mRNA levels of SMN were evaluated by real-time polymerase chain reaction. The protein expression levels of SMN, hypoxia-inducible transcription factor 1α (HIF-1α), and apoptosis-related proteins, such as cytochrome c (Cyt c), B cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax), and cleaved caspase-3 were evaluated by western blot analysis. Cell apoptosis was analysed using annexin V/propidium iodide (PI) staining.

RESULTS

Treatment with CoCl₂ significantly reduced H9c2 cell viability; the level of HIF-1α, which is a hypoxia-related indicator increased whereas the expression of SMN protein decreased. Hypoxia also induced cardiomyocyte apoptosis, indicated by reduced Bcl-2 expression and elevated cleaved caspase-3, Bax, and cytochrome c levels. Interestingly, SMN, which is a neuron protection factor, ameliorated CoCl₂ -induced cell damage by reducing cardiomyocyte apoptosis through upregulation of Bcl-2 and inhibition of cytochrome c, cleaved caspase-3, and Bax expression.

CONCLUSION

Survival motor neuron prevents hypoxia-induced cell apoptosis through inhibition of the mitochondrial apoptotic pathway, and thereby exerts a protective effect on H9c2 cardiomyocytes.

Comparison of the efficacy of MOE and PMO modifications of systemic antisense oligonucleotides in a severe SMA mouse model

Spinal muscular atrophy (SMA) is a motor neuron disease. Nusinersen, a splice-switching antisense oligonucleotide (ASO), was the first approved drug to treat SMA. Based on prior preclinical studies, both 2′-O-methoxyethyl (MOE) with a phosphorothioate backbone and morpholino with a phosphorodiamidate backbone—with the same or extended target sequence as nusinersen—displayed efficient rescue of SMA mouse models. Here, we compared the therapeutic efficacy of these two modification chemistries in rescue of a severe mouse model using ASO10-29—a 2-nt longer version of nusinersen—via subcutaneous injection. Although both chemistries efficiently corrected SMN2 splicing in various tissues, restored motor function and improved the integrity of neuromuscular junctions, MOE-modified ASO10-29 (MOE10-29) was more efficacious than morpholino-modified ASO10-29 (PMO10-29) at the same molar dose, as seen by longer survival, greater body-weight gain and better preservation of motor neurons. Time-course analysis revealed that MOE10-29 had more persistent effects than PMO10-29. On the other hand, PMO10-29 appears to more readily cross an immature blood-brain barrier following systemic administration, showing more robust initial effects on SMN2 exon 7 inclusion, but less persistence in the central nervous system. We conclude that both modifications can be effective as splice-switching ASOs in the context of SMA and potentially other diseases, and discuss the advantages and disadvantages of each.

Integrative Cluster Analysis of Whole Hearts Reveals Proliferative Cardiomyocytes in Adult Mice

The recent development and broad application of sequencing techniques at the single-cell level is generating an unprecedented amount of data. The different techniques have their individual limits, but the datasets also offer unexpected possibilities when utilized collectively. Here, we applied snRNA-seq in whole adult murine hearts from an inbred (C57BL/6NRj) and an outbred (Fzt:DU) mouse strain to directly compare the data with the publicly available scRNA-seq data of the tabula muris project. Explicitly choosing a single-nucleus approach allowed us to pin down the typical heart tissue-specific technical bias, coming up with novel insights on the mammalian heart cell composition. For our integrated dataset, cardiomyocytes, fibroblasts, and endothelial cells constituted the three main cell populations accounting for about 75% of all cells. However, their numbers severely differed between the individual datasets, with cardiomyocyte proportions ranging from about 9% in the tabula muris data to around 23% for our BL6 data, representing the prime example for cell capture technique related bias when using a conventional single-cell approach for these large cells. Most strikingly in our comparison was the discovery of a minor population of cardiomyocytes characterized by proliferation markers that could not be identified by analyzing the datasets individually. It is now widely accepted that the heart has an, albeit very restricted, regenerative potential. However there is still an ongoing debate where new cardiomyocytes arise from. Our findings support the idea that the renewal of the cardiomyocyte pool is driven by cytokinesis of resident cardiomyocytes rather than differentiation of progenitor cells. We thus provide data that can contribute to an understanding of heart cell regeneration, which is a prerequisite for future applications to enhance the process of heart repair.

Rescue of spinal muscular atrophy mouse models with AAV9-Exon-specific U1 snRNA

Spinal Muscular Atrophy results from loss-of-function mutations in SMN1 but correcting aberrant splicing of SMN2 offers hope of a cure. However, current splice therapy requires repeated infusions and is expensive. We previously rescued SMA mice by promoting the inclusion of a defective exon in SMN2 with germline expression of Exon-Specific U1 snRNAs (ExspeU1). Here we tested viral delivery of SMN2 ExspeU1s encoded by adeno-associated virus AAV9. Strikingly the virus increased SMN2 exon 7 inclusion and SMN protein levels and rescued the phenotype of mild and severe SMA mice. In the severe mouse, the treatment improved the neuromuscular function and increased the life span from 10 to 219 days. ExspeU1 expression persisted for 1 month and was effective at around one five-hundredth of the concentration of the endogenous U1snRNA. RNA-seq analysis revealed our potential drug rescues aberrant SMA expression and splicing profiles, which are mostly related to DNA damage, cell-cycle control and acute phase response. Vastly overexpressing ExspeU1 more than 100-fold above the therapeutic level in human cells did not significantly alter global gene expression or splicing. These results indicate that AAV-mediated delivery of a modified U1snRNP particle may be a novel therapeutic option against SMA.

Lamin A/C dysregulation contributes to cardiac pathology in a mouse model of severe spinal muscular atrophy

Cardiac pathology is emerging as a prominent systemic feature of spinal muscular atrophy (SMA), but little is known about the underlying molecular pathways. Using quantitative proteomics analysis, we demonstrate widespread molecular defects in heart tissue from the Taiwanese mouse model of severe SMA. We identify increased levels of lamin A/C as a robust molecular phenotype in the heart of SMA mice and show that lamin A/C dysregulation is also apparent in SMA patient fibroblast cells and other tissues from SMA mice. Lamin A/C expression was regulated in vitro by knockdown of the E1 ubiquitination factor ubiquitin-like modifier activating enzyme 1, a key downstream mediator of SMN-dependent disease pathways, converging on β-catenin signaling. Increased levels of lamin A are known to increase the rigidity of nuclei, inevitably disrupting contractile activity in cardiomyocytes. The increased lamin A/C levels in the hearts of SMA mice therefore provide a likely mechanism explaining morphological and functional cardiac defects, leading to blood pooling. Therapeutic strategies directed at lamin A/C may therefore offer a new approach to target cardiac pathology in SMA.

A severe mouse model of spinal muscular atrophy develops early systemic inflammation

Spinal muscular atrophy (SMA) is a fatal genetic disease, mainly affecting children. A number of recent studies show, aside from lower motor neuron degeneration and atrophy of skeletal muscles, widespread defects present in the central nervous system (CNS) and peripheral non-neuronal cell types of SMA patients and mouse models, particularly of severe forms. However, molecular mechanisms underlying the multi-organ manifestations of SMA were hardly understood. Here, using histology, flow cytometry and gene expression analysis in both messenger RNA and protein levels in various tissues, we found that a severe SMA mouse model develops systemic inflammation in early symptomatic stages. SMA mice had an enhanced intestinal permeability, resulting in microbial invasion into the circulatory system. Expression of proinflammatory cytokines was increased in all tissues and the acute phase response in the liver was activated. Systemic inflammation further mobilized glucocorticoid signaling and in turn led to dysregulation of a large set of genes, including robust upregulation of FAM107A in the spinal cord, increased expression of which has been implicated in neurodegeneration. Moreover, we show that lipopolysaccharide challenge markedly suppressed survival of motor neuron 2 exon 7 splicing in all examined peripheral and CNS tissues, resulting in global survival of motor neuron level reduction. Therefore, we identified a novel pathological mechanism in a severe SMA mouse model, which affects phenotypic severity through multiple paths and should contribute to progression of broad neuronal and non-neuronal defects.

Survival Motor Neuron (SMN) Protein Insufficiency Exacerbates Renal Ischemia/Reperfusion Injury

The survival of motor neuron (SMN) protein is ubiquitously involved in spliceosome assembly and ribonucleoprotein biogenesis. SMN protein is expressed in kidney and can affect cell death processes. However, the role of SMN in acute kidney injury (AKI) is largely unknown. In the current study, we found that the expression of SMN in the kidney was significantly reduced in both clinical ischemic AKI and a mouse model of renal ischemia-reperfusion injury (IRI). We then used SMN heterozygous knockout (SMN+/-) mice and found that the declines in renal function, tubular injury, and tubular cell apoptosis after experimental IRI were significantly more severe in SMN+/- mice than those in their wild-type littermates. Concomitantly, the canonical transcription factor nuclear factor-κb (NFκb) signaling was enhanced in ischemic SMN+/- mice. In vitro, cobalt dichloride (CoCl₂) treatment reduced SMN expression in proximal tubular epithelial cells. In addition, CoCl₂-induced apoptosis and activation of NFκb signaling pathway were enhanced by transient transfection of a small-interfering RNA (siRNA) against SMN while attenuated by transient transfection of a full-length SMN plasmid. Taken together, this study for the first time supported the protective role of SMN in ischemic AKI.

Survivin is a prognostic indicator in glioblastoma and may be a target of microRNA-218

Accumulating evidence has revealed that survivin expression is associated with a malignant phenotype and poor prognosis in glioma. Survivin is also a potential target of microRNA (miRNA/miR)-218. The aim of the present study was to investigate the expression and function of survivin in glioblastoma, and to examine the association between survivin and miR-218. For that purpose, survivin mRNA levels were analyzed in 144 frozen samples of glioblastoma using whole-genome RNA sequencing. In vitro cell proliferation, migration, invasion and apoptosis assays were performed, and survivin expression was detected by western blotting. The results revealed that the mRNA expression levels of survivin were negatively and significantly associated with overall survival in glioblastoma. Further in vitro analyses suggested that miR-218 may inhibit the expression of survivin. Expression of miR-218 in the LN229 cell line was significantly lower than that in the immortalized human gliocyte HEB cell line. miR-218 markedly inhibited tumor cell proliferation, migration and invasion capacities, and decreased apoptosis. miR-218 also inhibited the expression of survivin. These results indicated that survivin may be a target of miR-218 and could serve as a predictive biomarker.

Adaptive EGF expression sensitizes pancreatic cancer cells to ionizing radiation through activation of the cyclin D1/P53/PARP pathway

It is well-known that the activation status of the P53, signal transducer and activator of transcription (Stat)3 and nuclear factor (NF)‑κB signaling pathways determines the radiosensitivity of cancer cells. However, the function of these pathways in radiosensitive vs radioresistant cancer cells remains elusive. The present study demonstrated that adaptive expression of epidermal growth factor (EGF) following exposure to ionizing radiation (IR) may induce radiosensitization of pancreatic cancer (PC) cells through induction of the cyclin D1/P53/poly(ADP‑ribose) polymerase pathway. By contrast, adaptively expressed interleukin (IL)‑6 and insulin‑like growth factor (IGF)‑1 may promote radioresistance of PC cells, likely through activation of the Stat3 and NF‑κB pathways. In addition, cyclin D1 and survivin, which are specifically expressed in the G1/S and G2/M phase of the cell cycle, respectively, are mutually exclusive in radiosensitive and radioresistant PC cells, while Bcl‑2 and Bcl‑xL expression does not differ between radiosensitive and radioresistant PC cells. Therefore, adaptively expressed EGF and IL‑6/IGF‑1 may alter these pathways to promote the radiosensitivity of PC cancers. The findings of the present study highlight potential makers for the evaluation of radiosensitivity and enable the development of effective regimens for cancer radiotherapy.

High expression of survivin independently correlates with tumor progression and mortality in patients with skull base chordomas

OBJECTIVE

The object of this study was to clarify the expression characteristics and prognostic value of survivin in skull base chordomas.

METHODS

In this retrospective study, the authors measured the expression of survivin at the mRNA level in 81 samples from 71 patients diagnosed with skull base chordomas at their hospital in the period from July 2005 to January 2015. Clinical data collection, follow-up, and survival analyses were performed, and correlations were analyzed.

RESULTS

Of the 71 patients, 50 had primary chordomas with a mean survivin expression level of 1.09; the other 21 patients had recurrent chordomas with a mean survivin expression level of 2.57, which was 2.36 times higher than the level in the primary chordoma patients (p < 0.001, Mann-Whitney U-test). In addition, an analysis of 18 paired samples derived from 9 patients showed that the expression level of survivin was 2.62 times higher in recurrent tumors than in primary tumors (p = 0.002, paired t-test). The Spearman rank correlation coefficient method showed that the expression level of survivin was positively correlated with the mean ratio of tumor signal intensity to the signal intensity of surrounding brainstem on T1-weighted sequences (RT1; rs = 0.274, p = 0.021) and was negatively correlated with the mean ratio of tumor signal intensity to the signal intensity of surrounding brainstem on T2-weighted sequences (RT2; rs = -0.389, p = 0.001). A multivariate Cox proportional-hazards model suggested that pathology (p = 0.041), survivin expression level (p = 0.018), preoperative Karnofsky Performance Status (KPS; p = 0.012), and treatment history (p = 0.009) were independent prognostic factors for tumor progression. Survivin expression level (p = 0.008), preoperative KPS (p = 0.019), tumor diameter (p = 0.027), and intraoperative blood loss (p = 0.015) were independent prognostic factors for death.

CONCLUSIONS

Survivin expression level and preoperative KPS were independent significant prognostic factors for tumor progression and death in skull base chordoma patients. Recurrent skull base chordomas and chordomas with high RT1 and low RT2 were likely to have high survivin expression. Other independent risk factors related to tumor progression included conventional pathology and treatment history, whereas additional mortality-related risk factors included larger tumor diameter and greater intraoperative blood loss.