Myostatin-like proteins regulate synaptic function and neuronal morphology

A collection of split-Gal4 drivers targeting conserved signaling ligands in Drosophila

Communication between cells in metazoan organisms is mediated by a remarkably small number of highly conserved signaling pathways. Given this small number of signaling pathways, the existence of multiple related ligands for many of these pathways represents a key evolutionary innovation for encoding complexity into cell-cell signaling. Relatedly, crosstalk between pathways is another critical feature, which allows a modest number of pathways to ultimately generate an enormously diverse range of outcomes. It would thus be useful to have genetic tools to identify and manipulate not only those cells that express a given signaling ligand but also those cells that specifically coexpress pairs of signaling ligands. We present a collection of split-Gal4 knock-in lines targeting many of the ligands for highly conserved signaling pathways in Drosophila (Notch, Hedgehog, fibroblast growth factor (FGF), epidermal growth factor (EGF), transforming growth factor β (TGFβ), Janus kinase/signal transducer and activator of transcription (JAK/STAT), Jun kinase (JNK), and platelet-derived growth factor (PDGF)/vascular endothelial growth factor (VEGF)-related receptor (PVR). We demonstrate that these lines faithfully recapitulate the endogenous expression pattern of their targets and that they can be used to identify cells and tissues that coexpress pairs of ligands. As a proof of principle, we demonstrate that the 4th chromosome TGFβ ligands myoglianin and maverick are broadly coexpressed in muscles and other tissues of both larva and adults and that the JAK/STAT ligands upd2 and upd3 are partially coexpressed from cells of the midgut following gut damage. Together with our previously collection of split-Gal4 lines targeting the 7 Wnt ligands, this resource allows Drosophila researchers to identify and genetically manipulate cells that specifically express pairs of conserved ligands from nearly all the major intercellular signaling pathways.

A collection of split-Gal4 drivers targeting conserved signaling ligands in Drosophila

Communication between cells in metazoan organisms is mediated by a remarkably small number of highly conserved signaling pathways. Given the relatively small number of signaling pathways, the existence of multiple related ligands for many of these pathways is thought to represent a key evolutionary innovation for encoding complexity into cell-cell signaling. Relatedly, crosstalk and other interactions between pathways is another critical feature which allows a modest number pathways to ultimately generate an enormously diverse range of outcomes. It would thus be useful to have genetic tools to identify and manipulate not only those cells which express a given signaling ligand, but also those cells that specifically co-express pairs of signaling ligands. Here, we present a collection of split-Gal4 knock-in lines targeting many of the ligands for highly conserved signaling pathways in Drosophila (Notch, Hedgehog, FGF, EGF, TGFβ, JAK/STAT, JNK, and PVR). We demonstrate that these lines faithfully recapitulate the endogenous expression pattern of their targets, and that they can be used to specifically identify the cells and tissues that co-express pairs of signaling ligands. As a proof of principle, we demonstrate that the 4th chromosome TGFβ ligands myoglianin and maverick are broadly co-expressed in muscles and other tissues of both larva and adults, and that the JAK/STAT ligands upd2 and upd3 are partially co-expressed from cells of the midgut following gut damage. Together with our previously collection of split-Gal4 lines targeting the seven Wnt ligands, this resource allows Drosophila researchers to identify and genetically manipulate cells that specifically express pairs of conserved ligands from nearly all the major intercellular signaling pathways.

Neuron mapping in the Molly fish optic tectum: An emphasis on the adult neurogenesis process

Teleost fish exhibit the most pronounced and widespread adult neurogenesis. Recently, functional development and the fate of newborn neurons have been reported in the optic tectum (OT) of fish. To determine the role of neurogenesis in the OT, this study used histological, immunohistochemical, and electron microscopic investigations on 18 adult Molly fish specimens (Poecilia sphenops). The OT of the Molly fish was a bilateral lobed structure located in the dorsal part of the mesencephalon. It exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. The stratum opticum (SO) was supplied by optic nerve fibers, in which the neuropil was the main component. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). Furthermore, oligodendrocytes with their processes wrapped around the nerve fibers could be observed. The stratum album centrale (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. The neuronal cells of the SO and large tectal cells of the SAC expressed autophagy-related protein-5 (APG5). Interleukin-1β (IL-1β) was expressed in both neurons and glia cells of SGC. Additionally, inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventriculare (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. In all strata, S100 protein and Oligodendrocyte Lineage Transcription Factor 2 (Olig2) were expressed by microglia, oligodendrocytes, and astrocytes. In conclusion, it was possible to identify different varieties of neurons in the optic tectum, each with a distinct role. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT. RESEARCH HIGHLIGHTS: The OT of the Molly fish exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). The stratum album central (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. Inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventricular (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT.

Requirement of Myoglianin for metamorphosis in the beetle Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is a serious defoliating beetle attacking Solanaceae and Cucurbitaceae plants in many Asian countries. In the present paper, we identified a putative myoglianin (myo) gene. Hvmyo was actively transcribed throughout development, from embryo to adult. RNA interference (RNAi)-aided knockdown of Hvmyo delayed larval development by more than 2 days, reduced larval body size, inhibited the growth of antennae, wings and legs and disturbed gut purge. Knockdown of Hvmyo impaired the larval-pupal transition. All the Hvmyo RNAi larvae arrested at the larval stage or formed misshapen pupae or adults. The deformed pupae and adults were partially wrapped with exuviae, bearing separated wings. Moreover, the expression levels of five ecdysteroidogenesis genes (Hvspo, Hvphm, Hvdib, Hvsad and Hvshd), a prothocicotropic hormone (PTTH)/Torso pathway gene (Hvtorso), two 20E receptor genes (HvEcR and HvUSP), and two 20E signalling genes (HvE93 and HvFTZ-F1) were as a result of HvMyo RNAi significantly lowered. Conversely, the expression of a JH biosynthesis gene (Hvjhamt), a JH receptor gene HvMet and a JH signalling gene HvKr-h1 was greatly enhanced. Although ingestion of 20E and Hal rescued the 20E signal, it could not alleviate larval performance and defective phenotypes. Our results suggest that Myo exerts four distinctive roles in ecdysteroidogenesis, JH production, organ growth and larva-pupa-adult transformation in H. vigintioctopunctata.

Identification of the common neurobiological process disturbed in genetic and non-genetic models for autism spectrum disorders

Autism spectrum disorders (ASD) are neurodevelopmental disorders. Genetic factors, along with non-genetic triggers, have been shown to play a causative role. Despite the various causes, a triad of common symptoms defines individuals with ASD; pervasive social impairments, impaired social communication, and repeated sensory-motor behaviors. Therefore, it can be hypothesized that different genetic and environmental factors converge on a single hypothetical neurobiological process that determines these behaviors. However, the cellular and subcellular signature of this process is, so far, not well understood. Here, we performed a comparative study using "omics" approaches to identify altered proteins and, thereby, biological processes affected in ASD. In this study, we mined publicly available repositories for genetic mouse model data sets, identifying six that were suitable, and compared them with in-house derived proteomics data from prenatal zinc (Zn)-deficient mice, a non-genetic mouse model with ASD-like behavior. Findings derived from these comparisons were further validated using in vitro neuronal cell culture models for ASD. We could show that a protein network, centered on VAMP2, STX1A, RAB3A, CPLX2, and AKAP5, is a key convergence point mediating synaptic vesicle release and recycling, a process affected across all analyzed models. Moreover, we demonstrated that Zn availability has predictable functional effects on synaptic vesicle release in line with the alteration of proteins in this network. In addition, drugs that target kinases, reported to regulate key proteins in this network, similarly impacted the proteins' levels and distribution. We conclude that altered synaptic stability and plasticity through abnormal synaptic vesicle dynamics and function may be the common neurobiological denominator of the shared behavioral abnormalities in ASD and, therefore, a prime drug target for developing therapeutic strategies.

Ependymal and Neural Stem Cells of Adult Molly Fish (Poecilia sphenops, Valenciennes, 1846) Brain: Histomorphometry, Immunohistochemical, and Ultrastructural Studies

This study was conducted on 16 adult specimens of molly fish (Poecilia sphenops) to investigate ependymal cells (ECs) and their role in neurogenesis using ultrastructural examination and immunohistochemistry. The ECs lined the ventral and lateral surfaces of the optic ventricle and their processes extended through the tectal laminae and ended at the surface of the tectum as a subpial end-foot. Two cell types of ECs were identified: cuboidal non-ciliated (5.68 ± 0.84/100 μm2) and columnar ciliated (EC3.22 ± 0.71/100 μm2). Immunohistochemical analysis revealed two types of GFAP immunoreactive cells: ECs and astrocytes. The ECs showed the expression of IL-1β, APG5, and Nfr2. Moreover, ECs showed immunostaining for myostatin, S100, and SOX9 in their cytoplasmic processes. The proliferative activity of the neighboring stem cells was also distinct. The most interesting finding in this study was the glia-neuron interaction, where the processes of ECs met the progenitor neuronal cells in the ependymal area of the ventricular wall. These cells showed bundles of intermediate filaments in their processes and basal poles and were connected by desmosomes, followed by gap junctions. Many membrane-bounded vesicles could be demonstrated on the surface of the ciliated ECs that contained neurosecretion. The abluminal and lateral cell surfaces of ECs showed pinocytotic activities with many coated vesicles, while their apical cytoplasm contained centrioles. The occurrence of stem cells in close position to the ECs, and the presence of bundles of generating axons in direct contact with these stem cells indicate the role of ECs in neurogenesis. The TEM results revealed the presence of neural stem cells in a close position to the ECs, in addition to the presence of bundles of generating axons in direct contact with these stem cells. The present study indicates the role of ECs in neurogenesis.

The GDF11 Promotes Nerve Regeneration After Sciatic Nerve Injury in Adult Rats by Promoting Axon Growth and Inhibiting Neuronal Apoptosis

Introduction: Sciatic nerve injury is a common injury of the nervous system. Stem cell-based therapies, drug-based therapies and rehabilitation physiotherapy therapies are currently available, but their limited therapeutic efficacy limits their use. Here, we aimed to explore a novel lentiviral-based gene therapeutic strategy and to elaborate its mechanism.

Materials and Methods: Recombinant GDF11 protein was used for the in vitro treatment of dorsal root ganglion (DRG) cells. Lentivirus was used to construct a vector system for the in vivo expression of GDF11. The nerve conduction function was detected using action-evoked potentials at different time periods, and the regulatory effect of nerves on target organs was detected by weighing the gastrocnemius muscle. Immunofluorescence of NF200 and S100 was used to show the regeneration of the sciatic nerve, and myelin and Nissl staining were performed to observe the pathological features of the tissue. Western was used to validate signaling pathways. The expression of related genes was observed by qPCR and Western blotting, and cell apoptosis was detected by flow cytometry.

Result: GDF11 promotes the axonal growth of DRG cells and inhibits DGR cell apoptosis in vitro. GDF11 acts by activating the Smad pathway. GDF11 promotes the recovery of damaged sciatic nerve function in rats, the regeneration of damaged sciatic nerves in rats, and myelin regeneration of damaged sciatic nerves in rats. GDF11 also exerts a protective effect on neuronal cells in rats.

Conclusion: Based on the present study, we conclude that GDF11 promotes axonal growth and inhibits DRG cell apoptosis in vitro through the Smad pathway, and lentivirus-mediated GDF11 overexpression in vivo can promote the recovery of sciatic nerves after transection by promoting axonal growth and inhibiting neuronal apoptosis in the spinal cord.

An exon junction complex-independent function of Barentsz in neuromuscular synapse growth

The exon junction complex controls the translation, degradation, and localization of spliced mRNAs, and three of its core subunits also play a role in splicing. Here, we show that a fourth subunit, Barentsz, has distinct functions within and separate from the exon junction complex in Drosophila neuromuscular development. The distribution of mitochondria in larval muscles requires Barentsz as well as other exon junction complex subunits and is not rescued by a Barentsz transgene in which residues required for binding to the core subunit eIF4AIII are mutated. In contrast, interactions with the exon junction complex are not required for Barentsz to promote the growth of neuromuscular synapses. We find that the Activin ligand Dawdle shows reduced expression in barentsz mutants and acts downstream of Barentsz to control synapse growth. Both barentsz and dawdle are required in motor neurons, muscles, and glia for normal synapse growth, and exogenous Dawdle can rescue synapse growth in the absence of barentsz. These results identify a biological function for Barentsz that is independent of the exon junction complex.

ActRIIB:ALK4-Fc alleviates muscle dysfunction and comorbidities in murine models of neuromuscular disorders

Patients with neuromuscular disorders suffer from a lack of treatment options for skeletal muscle weakness and disease comorbidities. Here, we introduce as a potential therapeutic agent a heterodimeric ligand-trapping fusion protein, ActRIIB:ALK4-Fc, which comprises extracellular domains of activin-like kinase 4 (ALK4) and activin receptor type IIB (ActRIIB), a naturally occurring pair of type I and II receptors belonging to the TGF-β superfamily. By surface plasmon resonance (SPR), ActRIIB:ALK4-Fc exhibited a ligand binding profile distinctly different from that of its homodimeric variant ActRIIB-Fc, sequestering ActRIIB ligands known to inhibit muscle growth but not trapping the vascular regulatory ligand bone morphogenetic protein 9 (BMP9). ActRIIB:ALK4-Fc and ActRIIB-Fc administered to mice exerted differential effects - concordant with SPR results - on vessel outgrowth in a retinal explant assay. ActRIIB:ALK4-Fc induced a systemic increase in muscle mass and function in wild-type mice and in murine models of Duchenne muscular dystrophy (DMD), amyotrophic lateral sclerosis (ALS), and disuse atrophy. Importantly, ActRIIB:ALK4-Fc improved neuromuscular junction abnormalities in murine models of DMD and presymptomatic ALS and alleviated acute muscle fibrosis in a DMD model. Furthermore, in combination therapy ActRIIB:ALK4-Fc increased the efficacy of antisense oligonucleotide M12-PMO on dystrophin expression and skeletal muscle endurance in an aged DMD model. ActRIIB:ALK4-Fc shows promise as a therapeutic agent, alone or in combination with dystrophin rescue therapy, to alleviate muscle weakness and comorbidities of neuromuscular disorders.

GDF11 expressed in the adult brain negatively regulates hippocampal neurogenesis

Growth differentiation factor 11 (GDF11) is a transforming factor-β superfamily member that functions as a negative regulator of neurogenesis during embryonic development. However, when recombinant GDF11 (rGDF11) is administered systemically in aged mice, it promotes neurogenesis, the opposite of its role during development. The goal of the present study was to reconcile this apparent discrepancy by performing the first detailed investigation into the expression of endogenous GDF11 in the adult brain and its effects on neurogenesis. Using quantitative histological analysis, we observed that Gdf11 is most highly expressed in adult neurogenic niches and non-neurogenic regions within the hippocampus, choroid plexus, thalamus, habenula, and cerebellum. To investigate the role of endogenous GDF11 during adult hippocampal neurogenesis, we generated a tamoxifen inducible mouse that allowed us to reduce GDF11 levels. Depletion of Gdf11 during adulthood increased proliferation of neural progenitors and decreased the number of newborn neurons in the hippocampus, suggesting that endogenous GDF11 remains a negative regulator of hippocampal neurogenesis in adult mice. These findings further support the idea that circulating systemic GDF11 and endogenously expressed GDF11 in the adult brain have different target cells or mechanisms of action. Our data describe a role for GDF11-dependent signaling in adult neurogenesis that has implications for how GDF11 may be used to treat CNS disease.

Follistatin-induced muscle hypertrophy in aged mice improves neuromuscular junction innervation and function

Sarcopenia, or age-related loss of muscle mass and strength, is an important contributor to loss of physical function in older adults. The pathogenesis of sarcopenia is likely multifactorial, but recently the role of neurological degeneration, such as motor unit loss, has received increased attention. Here, we investigated the longitudinal effects of muscle hypertrophy (via overexpression of human follistatin, a myostatin antagonist) on neuromuscular integrity in C57BL/6J mice between the ages of 24 and 27 months. Following follistatin overexpression (delivered via self-complementary adeno-associated virus subtype 9 injection), muscle weight and torque production were significantly improved. Follistatin treatment resulted in improvements of neuromuscular junction innervation and transmission but had no impact on age-related losses of motor units. These studies demonstrate that follistatin overexpression-induced muscle hypertrophy not only increased muscle weight and torque production but also countered age-related degeneration at the neuromuscular junction in mice.

Ontogenetic and in silico models of spatial-packing in the hypermuscular mouse skull

Networks linking single genes to multiple phenotypic outcomes can be founded on local anatomical interactions as well as on systemic factors like biochemical products. Here we explore the effects of such interactions by investigating the competing spatial demands of brain and masticatory muscle growth within the hypermuscular myostatin-deficient mouse model and in computational simulations. Mice that lacked both copies of the myostatin gene (-/-) and display gross hypermuscularity, and control mice that had both copies of the myostatin gene (+/+) were sampled at 1, 7, 14 and 28 postnatal days. A total of 48 mice were imaged with standard as well as contrast-enhanced microCT. Size metrics and landmark configurations were collected from the image data and were analysed alongside in silico models of tissue expansion. Findings revealed that: masseter muscle volume was smaller in -/- mice at day 1 but became, and remained thereafter, larger by 7 days; -/- endocranial volumes begin and remained smaller; -/- enlargement of the masticatory muscles was associated with caudolateral displacement of the calvarium, lateral displacement of the zygomatic arches, and slight dorsal deflection of the face and basicranium. Simulations revealed basicranial retroflexion (flattening) and dorsal deflection of the face associated with muscle expansion and abrogative covariations of basicranial flexion and ventral facial deflection associated with endocranial expansion. Our findings support the spatial-packing theory and highlight the importance of understanding the harmony of competing spatial demands that can shape and maintain mammalian skull architecture during ontogeny.

Exercise associated with γ-oryzanol supplementation suppresses oxidative stress and prevents changes in locomotion in Drosophila melanogaster

Association to early mortality and sedentarism was already demonstrated in the literature; nevertheless, some possible biochemical mechanisms around physical inactivity still need answers. The use of an invertebrate model, such as Drosophila melanogaster, can reproduce reliable responses in inducing an exercise protocol with exogenous antioxidant supplementation. This study main evaluates the effect of exercise (EXE) associated with γ-oryzanol (ORY) supplementation to improve locomotor behavior, antioxidant defenses, and survival in Drosophila melanogaster. Two-day old flies were submitted to a protocol for seven days, divided into five groups: Control, Movement-Limited Flies (MLF), EXE, ORY [25 µM], and EXE + ORY [25 µM]. The survival rate was evaluated, followed by open field and negative geotaxis. Flies were euthanized and subjected to analysis for acetylcholinesterase (AChE) and antioxidant enzymes activity, glycidic and lipid parameters, body weight, reactive species (RS), and lipid peroxidation. EXE and EXE + ORY flies showed increased survival and locomotor activity, improved glycidic and lipid parameters, with a lower RS production, and increased antioxidant defenses compared to Control, and EXE + ORY when compared to the EXE group, obtained an increase in the ratio of protein levels/body weight, decreased ratio of triglyceride levels/body weight and decreased lipid peroxidation. However, MLF showed less survival and decreased locomotor activity, possibly due to increased AChE activity and reduced antioxidant defenses. The EXE and EXE + ORY demonstrate effective results in maintaining endogenous defenses, with increased locomotor activity, supporting evidence on EXE benefits, and supplementation with antioxidant compounds face of health paradigms.HighlightsNew protocol system of exercise on Drosophila melanogaster model.ORY demonstrates synergistic effect with EXE.Exercise with ORY supplementation increases locomotor behavior.Exercise with ORY supplementation decrease oxidative damages on flies.

Effects of Platelet-Rich Plasma on Cellular Populations of the Central Nervous System: The Influence of Donor Age

Platelet-rich plasma (PRP) is a biologic therapy that promotes healing responses across multiple medical fields, including the central nervous system (CNS). The efficacy of this therapy depends on several factors such as the donor's health status and age. This work aims to prove the effect of PRP on cellular models of the CNS, considering the differences between PRP from young and elderly donors. Two different PRP pools were prepared from donors 65‒85 and 20‒25 years old. The cellular and molecular composition of both PRPs were analyzed. Subsequently, the cellular response was evaluated in CNS in vitro models, studying proliferation, neurogenesis, synaptogenesis, and inflammation. While no differences in the cellular composition of PRPs were found, the molecular composition of the Young PRP showed lower levels of inflammatory molecules such as CCL-11, as well as the presence of other factors not found in Aged PRP (GDF-11). Although both PRPs had effects in terms of reducing neural progenitor cell apoptosis, stabilizing neuronal synapses, and decreasing inflammation in the microglia, the effect of the Young PRP was more pronounced. In conclusion, the molecular composition of the PRP, conditioned by the age of the donors, affects the magnitude of the biological response.

Similar sequences but dissimilar biological functions of GDF11 and myostatin

Growth differentiation factor 11 (GDF11) and myostatin (MSTN) are closely related TGFβ family members that are often believed to serve similar functions due to their high homology. However, genetic studies in animals provide clear evidence that they perform distinct roles. While the loss of Mstn leads to hypermuscularity, the deletion of Gdf11 results in abnormal skeletal patterning and organ development. The perinatal lethality of Gdf11-null mice, which contrasts with the long-term viability of Mstn-null mice, has led most research to focus on utilizing recombinant GDF11 proteins to investigate the postnatal functions of GDF11. However, the reported outcomes of the exogenous application of recombinant GDF11 proteins are controversial partly because of the different sources and qualities of recombinant GDF11 used and because recombinant GDF11 and MSTN proteins are nearly indistinguishable due to their similar structural and biochemical properties. Here, we analyze the similarities and differences between GDF11 and MSTN from an evolutionary point of view and summarize the current understanding of the biological processing, signaling, and physiological functions of GDF11 and MSTN. Finally, we discuss the potential use of recombinant GDF11 as a therapeutic option for a wide range of medical conditions and the possible adverse effects of GDF11 inhibition mediated by MSTN inhibitors.

Muscle-derived Myoglianin regulates Drosophila imaginal disc growth

Organ growth and size are finely tuned by intrinsic and extrinsic signaling molecules. In Drosophila, the BMP family member Dpp is produced in a limited set of imaginal disc cells and functions as a classic morphogen to regulate pattern and growth by diffusing throughout imaginal discs. However, the role of TGFβ/Activin-like ligands in disc growth control remains ill-defined. Here, we demonstrate that Myoglianin (Myo), an Activin family member, and a close homolog of mammalian Myostatin (Mstn), is a muscle-derived extrinsic factor that uses canonical dSmad2-mediated signaling to regulate wing size. We propose that Myo is a myokine that helps mediate an allometric relationship between muscles and their associated appendages.

Myostatin inhibition in combination with antisense oligonucleotide therapy improves outcomes in spinal muscular atrophy

BACKGROUND

Spinal muscular atrophy (SMA) is caused by genetic defects in the survival motor neuron 1 (SMN1) gene that lead to SMN deficiency. Different SMN-restoring therapies substantially prolong survival and function in transgenic mice of SMA. However, these therapies do not entirely prevent muscle atrophy and restore function completely. To further improve the outcome, we explored the potential of a combinatorial therapy by modulating SMN production and muscle-enhancing approach as a novel therapeutic strategy for SMA.

METHODS

The experiments were performed in a mouse model of severe SMA. A previously reported 25-mer morpholino antisense oligomer PMO25 was used to restore SMN expression. The adeno-associated virus-mediated expression of myostatin propeptide was used to block the myostatin pathway. Newborn SMA mice were treated with a single subcutaneous injection of 40 μg/g (therapeutic dose) or 10 μg/g (low-dose) PMO25 on its own or together with systemic delivery of a single dose of adeno-associated virus-mediated expression of myostatin propeptide. The multiple effects of myostatin inhibition on survival, skeletal muscle phenotype, motor function, neuromuscular junction maturation, and proprioceptive afferences were evaluated.

RESULTS

We show that myostatin inhibition acts synergistically with SMN-restoring antisense therapy in SMA mice treated with the higher therapeutic dose PMO25 (40 μg/g), by increasing not only body weight (21% increase in male mice at Day 40), muscle mass (38% increase), and fibre size (35% increase in tibialis anterior muscle in 3 month female SMA mice), but also motor function and physical performance as measured in hanging wire test (two-fold increase in time score) and treadmill exercise test (two-fold increase in running distance). In SMA mice treated with low-dose PMO25 (10 μg/g), the early application of myostatin inhibition prolongs survival (40% increase), improves neuromuscular junction maturation (50% increase) and innervation (30% increase), and increases both the size of sensory neurons in dorsal root ganglia (60% increase) and the preservation of proprioceptive synapses in the spinal cord (30% increase).

CONCLUSIONS

These data suggest that myostatin inhibition, in addition to the well-known effect on muscle mass, can also positively influence the sensory neural circuits that may enhance motor neurons function. While the availability of the antisense drug Spinraza for SMA and other SMN-enhancing therapies has provided unprecedented improvement in SMA patients, there are still unmet needs in these patients. Our study provides further rationale for considering myostatin inhibitors as a therapeutic intervention in SMA patients, in combination with SMN-restoring drugs.

Learning-induced mRNA alterations in olfactory bulb mitral cells in neonatal rats

In the olfactory bulb, a cAMP/PKA/CREB-dependent form of learning occurs in the first week of life that provides a unique mammalian model for defining the epigenetic role of this evolutionarily ancient plasticity cascade. Odor preference learning in the week-old rat pup is rapidly induced by a 10-min pairing of odor and stroking. Memory is demonstrable at 24 h, but not 48 h, posttraining. Using this paradigm, pups that showed peppermint preference 30 min posttraining were sacrificed 20 min later for laser microdissection of odor-encoding mitral cells. Controls were given odor only. Microarray analysis revealed that 13 nonprotein-coding mRNAs linked to mRNA translation and splicing and 11 protein-coding mRNAs linked to transcription differed with odor preference training. MicroRNA23b, a translation inhibitor of multiple plasticity-related mRNAs, was down-regulated. Protein-coding transcription was up-regulated for Sec23b, Clic2, Rpp14, Dcbld1, Magee2, Mstn, Fam229b, RGD1566265, and Mgst2. Gng12 and Srcg1 mRNAs were down-regulated. Increases in Sec23b, Clic2, and Dcbld1 proteins were confirmed in mitral cells in situ at the same time point following training. The protein-coding changes are consistent with extracellular matrix remodeling and ryanodine receptor involvement in odor preference learning. A role for CREB and AP1 as triggers of memory-related mRNA regulation is supported. The small number of gene changes identified in the mitral cell input/output link for 24 h memory will facilitate investigation of the nature, and reversibility, of changes supporting temporally restricted long-term memory.

A new protein curbs the hypertrophic effect of myostatin inhibition, adding remarkable endurance to motor performance in mice

Current efforts to improve muscle performance are focused on muscle trophism via inhibition of the myostatin pathway: however they have been unsuccessful in the clinic to date. In this study, a novel protein has been created by combining the soluble activin receptor, a strong myostatin inhibitor, to the C-terminal agrin nLG3 domain (ActR-Fc-nLG3) involved in the development and maintenance of neuromuscular junctions. Both domains are connected via the constant region of an Igg1 monoclonal antibody. Surprisingly, young male mice treated with ActR-Fc-nLG3 showed a remarkably increased endurance in the rotarod test, significantly longer than the single domain compounds ActR-Fc and Fc-nLG3 treated animals. This increase in endurance was accompanied by only a moderate increase in body weights and wet muscle weights of ActR-Fc-nLG3 treated animals and were lower than expected. The myostatin inhibitor ActR-Fc induced, as expected, a highly significant increase in body and muscle weights compared to control animals and ActR-Fc-nLG3 treated animals. Moreover, the prolonged endurance effect was not observed when ActR-Fc and Fc-nLG3 were dosed simultaneously as a mixture and the body and muscle weights of these animals were very similar to ActR-Fc treated animals, indicating that both domains need to be on one molecule. Muscle morphology induced by ActR-Fc-nLG3 did not appear to be changed however, close examination of the neuromuscular junction showed significantly increased acetylcholine receptor surface area for ActR-Fc-nLG3 treated animals compared to controls. This result is consistent with published observations that endurance training in rats increased acetylcholine receptor quantity at neuromuscular junctions and provide evidence that improving nerve-muscle interaction could be an important factor for sustaining long term muscle activity.

Follistatin expression in the central nervous system of the adult rat

Follistatin was initially cloned as a monomeric polypeptide that inhibits the release of follicle-stimulating hormone. Although follistatin also plays pivotal roles in skeletal muscle hypertrophy and immunoregulation in the epididymis, little information is available regarding follistatin function in the adult central nervous system (CNS). Hence, we investigated follistatin expression in the adult rat CNS using immunohistochemistry. Follistatin was intensely expressed in most neurons and their axons. Furthermore, oligodendrocytes, ependymal cells, and some astrocytes also expressed follistatin protein. These data indicate that follistatin is widely expressed throughout the adult CNS. The abundant expression of follistatin in the adult brain suggests that this protein plays important roles in the CNS.

Cataloguing and Selection of mRNAs Localized to Dendrites in Neurons and Regulated by RNA-Binding Proteins in RNA Granules

Spatiotemporal translational regulation plays a key role in determining cell fate and function. Specifically, in neurons, local translation in dendrites is essential for synaptic plasticity and long-term memory formation. To achieve local translation, RNA-binding proteins in RNA granules regulate target mRNA stability, localization, and translation. To date, mRNAs localized to dendrites have been identified by comprehensive analyses. In addition, mRNAs associated with and regulated by RNA-binding proteins have been identified using various methods in many studies. However, the results obtained from these numerous studies have not been compiled together. In this review, we have catalogued mRNAs that are localized to dendrites and are associated with and regulated by the RNA-binding proteins fragile X mental retardation protein (FMRP), RNA granule protein 105 (RNG105, also known as Caprin1), Ras-GAP SH3 domain binding protein (G3BP), cytoplasmic polyadenylation element binding protein 1 (CPEB1), and staufen double-stranded RNA binding proteins 1 and 2 (Stau1 and Stau2) in RNA granules. This review provides comprehensive information on dendritic mRNAs, the neuronal functions of mRNA-encoded proteins, the association of dendritic mRNAs with RNA-binding proteins in RNA granules, and the effects of RNA-binding proteins on mRNA regulation. These findings provide insights into the mechanistic basis of protein-synthesis-dependent synaptic plasticity and memory formation and contribute to future efforts to understand the physiological implications of local regulation of dendritic mRNAs in neurons.

Body Size and Tissue-Scaling Is Regulated by Motoneuron-Derived Activinß in Drosophila melanogaster

Correct scaling of body and organ size is crucial for proper development, and the survival of all organisms. Perturbations in circulating hormones, including insulins and steroids, are largely responsible for changing body size in response to both genetic and environmental factors. Such perturbations typically produce adults whose organs and appendages scale proportionately with final size. The identity of additional factors that might contribute to scaling of organs and appendages with body size is unknown. Here, we report that loss-of-function mutations in DrosophilaActivinβ (Actβ), a member of the TGF-β superfamily, lead to the production of small larvae/pupae and undersized rare adult escapers. Morphometric measurements of escaper adult appendage size (wings and legs), as well as heads, thoraxes, and abdomens, reveal a disproportional reduction in abdominal size compared to other tissues. Similar size measurements of selected Actβ mutant larval tissues demonstrate that somatic muscle size is disproportionately smaller when compared to the fat body, salivary glands, prothoracic glands, imaginal discs, and brain. We also show that Actβ control of body size is dependent on canonical signaling through the transcription-factor dSmad2 and that it modulates the growth rate, but not feeding behavior, during the third-instar period. Tissue- and cell-specific knockdown, and overexpression studies, reveal that motoneuron-derived Actβ is essential for regulating proper body size and tissue scaling. These studies suggest that, unlike in vertebrates, where Myostatin and certain other Activin-like factors act as systemic negative regulators of muscle mass, in Drosophila, Actβ is a positive regulator of muscle mass that is directly delivered to muscles by motoneurons. We discuss the importance of these findings in coordinating proportional scaling of insect muscle mass to appendage size.

A 5-gene prognostic nomogram predicting survival probability of glioblastoma patients

BACKGROUND

Glioblastoma (GBM) remains the most biologically aggressive subtype of gliomas with an average survival of 10 to 12 months. Considering that the overall survival (OS) of each GBM patient is a key factor in the treatment of individuals, it is meaningful to predict the survival probability for GBM patients newly diagnosed in clinical practice.

MATERIAL AND METHODS

Using the TCGA dataset and two independent GEO datasets, we identified genes that are associated with the OS and differentially expressed between GBM tissues and the adjacent normal tissues. A robust likelihood-based survival modeling approach was applied to select the best genes for modeling. After the prognostic nomogram was generated, an independent dataset on different platform was used to evaluate its effectiveness.

RESULTS

We identified 168 differentially expressed genes associated with the OS. Five of these genes were selected to generate a gene prognostic nomogram. The external validation demonstrated that 5-gene prognostic nomogram has the capability of predicting the OS of GBM patients.

CONCLUSION

We developed a novel and convenient prognostic tool based on five genes that exhibited clinical value in predicting the survival probability for newly diagnosed GBM patients, and all of these five genes could represent potential target genes for the treatment of GBM. The development of this model will provide a good reference for cancer researchers.

The influence of GDF11 on brain fate and function

Growth differentiation factor 11 (GDF11) is a transforming growth factor β (TGFβ) protein that regulates aspects of central nervous system (CNS) formation and health throughout the lifespan. During development, GDF11 influences CNS patterning and the genesis, differentiation, maturation, and activity of new cells, which may be primarily dependent on local production and action. In the aged brain, exogenous, peripherally delivered GDF11 may enhance neurogenesis and angiogenesis, as well as improve neuropathological outcomes. This is in contrast to a predominantly negative influence on neurogenesis in the developing CNS. Seemingly antithetical effects may correspond to the cell types and mechanisms activated by local versus circulating concentrations of GDF11. Yet undefined, distinct mechanisms of action in young and aged brains may also play a role, which could include differential receptor and binding partner interactions. Exogenously increasing circulating GDF11 concentrations may be a viable approach for improving deleterious aspects of brain aging and neuropathology. Caution is warranted, however, since GDF11 appears to negatively influence muscle health and body composition. Nevertheless, an expanding understanding of GDF11 biology suggests that it is an important regulator of CNS formation and fate, and its manipulation may improve aspects of brain health in older organisms.

Growth Differentiation Factor 11 treatment leads to neuronal and vascular improvements in the hippocampus of aged mice

Aging is the biggest risk factor for several neurodegenerative diseases. Parabiosis experiments have established that old mouse brains are improved by exposure to young mouse blood. Previously, our lab showed that delivery of Growth Differentiation Factor 11 (GDF11) to the bloodstream increases the number of neural stem cells and positively affects vasculature in the subventricular zone of old mice. Our new study demonstrates that GDF11 enhances hippocampal neurogenesis, improves vasculature and increases markers of neuronal activity and plasticity in the hippocampus and cortex of old mice. Our experiments also demonstrate that systemically delivered GDF11, rather than crossing the blood brain barrier, exerts at least some of its effects by acting on brain endothelial cells. Thus, by targeting the cerebral vasculature, GDF11 has a very different mechanism from that of previously studied circulating factors acting to improve central nervous system (CNS) function without entering the CNS.

Endocrine Regulation of Energy Balance by Drosophila TGF-β/Activins

The Transforming growth factor beta (TGF-β) family of secreted proteins regulates a variety of key events in normal development and physiology. In mammals, this family, represented by 33 ligands, including TGF-β, activins, nodal, bone morphogenetic proteins (BMPs), and growth and differentiation factors (GDFs), regulate biological processes as diverse as cell proliferation, differentiation, apoptosis, metabolism, homeostasis, immune response, wound repair, and endocrine functions. In Drosophila, only 7 members of this family are present, with 4 TGF-β/BMP and 3 TGF-β/activin ligands. Studies in the fly have illustrated the role of TGF-β/BMP ligands during embryogenesis and organ patterning, while the TGF-β/activin ligands have been implicated in the control of wing growth and neuronal functions. In this review, we focus on the emerging roles of Drosophila TGF-β/activins in inter-organ communication via long-distance regulation, especially in systemic lipid and carbohydrate homeostasis, and discuss findings relevant to metabolic diseases in humans.

The Drosophila TGF-beta/Activin-like ligands Dawdle and Myoglianin appear to modulate adult lifespan through regulation of 26S proteasome function in adult muscle

The Drosophila Activin signaling pathway employs at least three separate ligands – Activin-β (Actβ), Dawdle (Daw), and Myoglianin (Myo) – to regulate several general aspects of fruit fly larval development, including cell proliferation, neuronal remodeling, and metabolism. Here we provide experimental evidence indicating that both Daw and Myo are anti-ageing factors in adult fruit flies. Knockdown of Myo or Daw in adult fruit flies reduced mean lifespan, while overexpression of either ligand in adult muscle tissues but not in adipose tissues enhanced mean lifespan. An examination of ubiquitinated protein aggregates in adult muscles revealed a strong inverse correlation between Myo- or Daw-initiated Activin signaling and the amount of ubiquitinated protein aggregates. We show that this correlation has important functional implications by demonstrating that the lifespan extension effect caused by overexpression of wild-type Daw or Myo in adult muscle tissues can be completely abrogated by knockdown of a 26S proteasome regulatory subunit Rpn1 in adult fly muscle, and that the prolonged lifespan caused by overexpression of Daw or Myo in adult muscle could be due to enhanced protein levels of the key subunits of 26S proteasome. Overall, our data suggest that Activin signaling initiated by Myo and Daw in adult Drosophila muscles influences lifespan, in part, by modulation of protein homeostasis through either direct or indirect regulation of the 26S proteasome levels. Since Myo is closely related to the vertebrate muscle mass regulator Myostatin (GDF8) and the Myostatin paralog GDF11, our observations may offer a new experimental model for probing the roles of GDF11/8 in ageing regulation in vertebrates.

This article has an associated First Person interview with the first author of the paper.

Summary: This article has, for the first time, demonstrated that fruit fly TGF-beta, or Activin-type ligand Daw, or Myo-initiated Activin signaling in adult fruit fly muscle tissues works as an anti-ageing factor by regulating 26S proteasome activities in those tissues.

Complex roles of myoglianin in regulating adult performance and lifespan

Myoglianin, the Drosophila homolog of the secreted vertebrate proteins Myostatin and GDF-11, is an important regulator of neuronal modeling, and synapse function and morphology. While Myoglianin suppression during development elicits positive effects on the neuromuscular system, genetic manipulations of myoglianin expression levels have a varied effect on the outcome of performance tests in aging flies. Specifically, Myoglianin preserves jumping ability, has no effect on negative geotaxis, and negatively regulates flight performance in aging flies. In addition, Myoglianin exhibits a tissue-specific effect on longevity, with myoglianin upregulation in glial cells increasing the median lifespan. These findings indicate complex role for this TGF-β-like protein in governing neuromuscular signaling and consequent behavioral outputs and lifespan in adult flies.