A estimulação elétrica neuromuscular (EENM) é um importante recurso utilizado na medicina esportiva para acelerar processos de recuperação. O objetivo deste estudo foi analisar os efeitos da EENM durante a imobilização do músculo gastrocnêmio, em posições de alongamento (LP) e encurtamento (SP). Para tanto, 60 ratas fêmeas jovens WISTAR foram distribuídas em seis grupos e acompanhadas durante 7 dias: controle (C), eletroestimuladas (EE), imobilizadas em encurtamento (ISP), imobilizadas em alongamento (ILP), imobilizadas em encurtamento e eletroestimuladas (ISP+EE) e imobilizadas em alongamento e eletroestimuladas (ILP+EE). Para a imobilização, o membro posterior direito foi envolvido por uma malha tubular e ataduras de algodão juntamente à atadura gessada. A EENM foi utilizada com uma freqüência de 50 Hz, 10 minutos por dia, totalizando 20 contrações em cada sessão. Após 7 dias os animais foram submetidos à eutanásia e os músculos gastrocnêmios foram retirados para a realização do ensaio mecânico de tração em uma máquina universal de ensaios (EMIC®). A partir dos gráficos carga versus alongamento foram calculadas as seguintes propriedades mecânicas: alongamento no limite de proporcionalidade (ALP), carga no limite de proporcionalidade (CLP), alongamento no limite máximo (ALM), carga no limite máximo (CLM) e rigidez. As imobilizações SP e LP promoveram reduções significativas (p<0,05) nas propriedades de ALP, CLP, ALM e CLM sendo mais acentuada, principalmente, no grupo ISP. Quando utilizada a EENM, houve acréscimo significativo (p<0,05) destas propriedades somente no grupo ISP. Já, em relação à rigidez, foi observada redução significativa (p<0,05) somente do grupo C para o grupo ISP. Quando utilizada a EENM, a rigidez do grupo ILP+EE foi significativamente (p<0,05) maior e mais próxima do grupo C que a do grupo ISP+EE. Neste modelo experimental, a imobilização dos músculos em alongamento atrasou a queda das propriedades e a estimulação elétrica, contribuiu para a manutenção das propriedades mecânicas durante o período de imobilização, principalmente no grupo ILP+EE. / The neuromuscular electric stimulation (NMES) is an important tool used in sport medicine to accelerate the recovery process. The objective of this study was to analyze the effects of NMES during the immobilization of the gastrocnemius muscle, in lengthened (LP) and shortened positions (SP). Sixty young female rats WISTAR were distributed into six groups and followed for 7 days: control (C), electric stimulation (ES), immobilized in shortened (ISP), immobilized in lengthened (ILP), immobilized in shortened and electric stimulation (ISP+ES) and immobilized in lengthened and electric stimulation (ILP+ES). For the immobilization, the right hind limb was involved by a tubular mesh and cotton rolls and plaster. NMES was used in a frequency of 50 Hz, 10 minutes a day, totaling 20 contractions in each session. After 7 days the animals were killed and their gastrocnemius muscles of the right side were submitted to a mechanical test in traction in an universal test machine (EMIC®). From the curves load versus elongation the following mechanical properties were obtained: elongation in the yield limit (EPL), load in the yield limit (LPL), elongation in the ultimate load (EUL), ultimate load (UL) and stiffness. The immobilizations SP and LP promoted significant reductions (p<0,05) in the properties of EPL, LPL, EUL and UL being more accentuated mainly in group ISP. When used NMES, there was significant increment (p<0,05) of such properties only in group ISP. As for stiffness, significant reduction was observed (p<0,05) only of the group C for group ISP. When the NMES was used, the stiffness of group ILP+EE was significantly (p<0,05) higher and closer to group C than for group ISP+EE. We conclude that in this experimental model the immobilization of the muscles in the lengthened position delayed the reduction of the properties and the electric stimulation contributed to the maintenance of the mechanical properties during the immobilization period, mainly for group ILP+ES.

Spinal Muscular Atrophy (SMA) is a neurodegenerative, inherited disease caused by an insufficient amount of functional Survival of Motor Neurone protein (SMN), though the exact mechanism underlying this is not fully understood. The primary function of SMN is assembling a ring of Sm proteins around small nuclear RNA (snRNA) in an early, cytoplasmic stage of small nuclear ribonucleoprotein (snRNP) biogenesis, a process essential in eukaryotes. SMN, together with several mRNA binding proteins, has been linked to neural transport of mRNA towards areas of growth in Motor neurons for local translation of transcripts. Previous research in our group has found that this may involve Coatomer protein-containing vesicles transported by Dynein and requiring the Sm family protein, SmB, for maintenance. Little is known, however, about what other proteins are also present and required for correct transport and localisation of these vesicles. To further investigate this, we have produced plasmids expressing each Sm protein tagged to fluorescent proteins to help track their behaviour, in some cases for the first time, and developed a detergent-free fractionation protocol to enrich for SMN containing vesicles, providing tools that can be used to further probe behaviour and interactions in the future. Using these approaches, SmN, a neural specific Sm protein, was identified to also be present in SMN-containing vesicles similarly to SmB. Analysis of the interactomes of different Sm proteins identified a novel interactor of SMN, Neurochondrin (NCDN), that appears to be required for the correct localisation of SMN in neural cells. NCDN was found to not associate with snRNPs, indicating an snRNP-independent interaction with SMN. NCDN and SMN both independently associated and co-enriched with Rab5, indicating a potential endocytic and cell polarity role for the interaction. This interaction has the potential to be key in SMA pathology and may have therapeutic potential.

La myopathie centronucléaire autosomique dominante (MCN-AD) est une maladie congénitale rare liée à des mutations principalement retrouvées dans le gène dynamine-2. La majorité des patients atteints de MCN-AD présente une évolution lentement progressive, avec une perte de masse et de force musculaire. A ce jour, aucune thérapie n’est disponible pour la MCN-AD. Des interventions thérapeutiques visant à limiter la progression et la sévérité de l’atteinte musculaire ainsi qu’à améliorer la qualité de vie des patients, sont donc nécessaires. Nous faisons l’hypothèse qu’une hypertrophie induite par l’invalidation de la myostatine (mstn), régulateur négatif majeur de la masse musculaire, pourrait être bénéfique pour la souris modèle de cette pathologie (KI-Dnm2R465W/+), permettant notamment le maintien de la masse et de la force musculaire. Nous avons généré un modèle doublement muté résultant du croisement de souris KI-Dnm2R465W/+ myopathe avec des souris KO-mstn hypermusclées. Notre étude démontre que l'inactivation du gène mstn permet une amélioration de la masse et du volume musculaire, limite la perte de force et de motricité. Nos données suggèrent également que cette amélioration est majoritairement due à une diminution du niveau d’expression de certains acteurs impliqués dans le système catabolique ubiquitine-protéasome. De plus, nous montrons une accélèration de la diminution de la fréquence des anomalies histologiques caractéristiques de la myopathie chez les souris KI-Dnm2R465W/+. Nous proposons que ces anomalies pourraient être dues à une altération de la structure et/ou de la fonction mitochondriale. / Autosomal dominant centronuclear myopathy (AD-CNM) is a rare congenital muscle disease caused by mutations predominantly found in the dynamin 2 gene (DNM2). The clinical features generally reported are progressive muscle atrophy and weakness. To date, no treatment is available. The mouse model for AD-CNM harboring a mutation of the dynamin-2 gene (KI-Dnm2R465W/+) reproduces some of the human clinical features, notably muscle atrophy and weakness. Mstn, is a master negative regulator of skeletal muscle mass. We hypothesized that inactivation of mstn could limit muscle atrophy and weakness reported in the AD-CNM mouse model (KI-dnm2R465W/+). To test this hypothesis, we intercrossed KI-Dnm2R465W/+ mice with mice inactivated for mstn (KO-mstn) to generate a double mutated lineage (KIKO). The present study demonstrates that mstn gene inactivation allows for an improvement of muscle weight and volume, prevents muscle weakness and motor skill alterations. Our data also reveal that inactivation of mstn essentially downregulates some actors implicated in the catabolic ubiquitin-proteasome system. Furthermore, we show that inactivation of mstn decreases the frequency of of histological abnormalities characteristical in KI mice. We hypothesize that these abnormalities could be due to an alteration of mitochondrial function and network. The perspective to this work is to verify this hypothesis in the mouse model, which will contribute to a better understanding of the physiopathological mechanisms and can open new insight in the therapeutical approach to AD-CNM.

INTRODUÇÃO:A neuraminidase 1 (chamada a seguir por Neu1) regula o catabolismo de sialoglicoconjugados nos lisossomos. A deficiência congênita da Neu1 é a base da sialidose, doença neurossomática grave associada a deformidades osteoesqueléticas, hipotonia e fraqueza muscular. Camundongos com deficiência de Neu1 desenvolvem uma forma atípica de degeneração muscular caracterizada porproliferação anormal de fibroblastoslevando a invasão nas fibras musculares, expansão da matriz extracelular (MEC), fragmentação do citoplasma, formação vacuolar e atrofia muscular. A ocorrência de atrofia muscular indica que a deficiência da Neu1 podeestar relacionada com o controle da massa muscular, a qual é dependente do equilíbrio entre síntese e degradação proteica.Uma característica principalnaMacroautofagia (denominada a seguir por autofagia) é a principal via de degradação intracelular sendo expressamente essencial para a homeostase celular e remoção de materiais citoplasmáticos. Objetivos: Avaliarseos efeitos da deficiência da Neuraminidase 1 afetama indução de autofagia e a formação de autofagossomos e determinar os efeitos do bloqueio da função lisossomal sobre o fenótipo muscular na deficiência da Neuraminidase1.Metodologia:Camundongos Neu1+/-foram cruzados e os filhotes genotipados, onde camundongos Neu1-/-(nocaute) e Neu1+/+(normal),foram utilizados no estudon total=90, sendo 10 em padronizações, 20 para coleta de fibroblastos e 60 para procedimentos in vivo, os grupos experimentais foram divididos em privação alimentar por 2 dias que, por meio da inibição do mTOR, induz a autofagia;grupo detratamento com Colchicina por 4 dias onde irá impedir a junção autofagossomo/lisossomonão havendo a degradaçãolisossomaleadicionado nos dois últimos dias de privação alimentar e o grupo de tratamento comRapamicina por 7 dias, droga com função de inibir seletivamente o mTOR.Após os tratamentos, os animais foram eutanasiadospara coleta dos músculos gastrocnêmios e tibiais anterior. Os músculos foram analisados apósas coloraçõeshistológicas porHematoxilina & Eosina e Fosfatase Ácida; Imunofluorescência de LC3-I/II; Western Blottingdas proteínas LC3-I/II, Lamp-1 e p62/SQSTM e a análise Ultra-estrutural. Além disso, foi realizada cultura de fibroblastos, os quais foram submetidos à privação de nutrientes e ao tratamento com Rapamicina, seguidos dasmesmas metodologias de análise invivo. Resultados:As análises histológicas através de H&E e Fosfatase Ácida não revelaram alterações consistentes na musculatura esquelética de animais submetidos aos tratamentos, mostrando em animais com deficiência de Neu1 um aumento anormal do espaço endomisial, e aumento da atividade lisossomalintracitoplasmáticos. Na análise ultra-estruturalobservou-se em todos os grupos, a presença de diversas estruturas com aspecto autofágico, de diferentes tamanhos, formas e constituintes. Naanálise da expressão do LC3 através de Western Blottingmostrou importante ativação do LC3-II na privação alimentar (com e sem administração de Colchicina) tanto em animais controles quanto em animais com deficiência de Neu1 e uma importante ativação do LC3-I em Rapamicina em ambos os grupos mostrando assim que houve um aumento da via da autofagia através do bloqueio do mTOR. Já na análise de Imunofluorescência não foi possível observar diferença consistenteentre os grupos.A análise in vitrode Western Blottingmostrou que tal ativação foi similar entre fibroblastos Neu1+/+e Neu1-/-. Conclusão:Os experimentos relacionados com a ativação ou inibição da autofagia, não resultaram em diferenças consideráveis entre músculos normais e músculos com deficiência de Neu1. Desta forma, podemos concluir com estes experimentos que aparentemente a Neu1, apesar de ser uma importante enzima lisossomal, não interfere com o processo de autofagia / Introduction:Neuraminidase 1 (hereinafter Neu1) regulates the catabolism of sialoglycoconjugates in lysosomes. The congenital deficiency of Neu1 is the basis of sialidosis, a severe neurosomatic disease associated with osteo-skeletal deformities, hypotonia, and muscle weakness. Mice with Neu1deficient develop an atypical form of muscle degeneration characterized by abnormal fibroblast proliferation leading to muscle fiber invasion, extracellular matrix expansion (ECM), cytoplasm fragmentation, vacuolar formation, and muscle atrophy. The occurrence of muscle atrophy indicates that deficiencyofNeu1 may be related to the control of muscle mass, which is dependent on the balance between synthesis and protein degradation. A major feature in Macroautophagy (hereinafter referred to as autophagy) is the main pathway of intracellular degradation being expressly essential for cellular homeostasis and removal of cytoplasmic materials. Objectives:To evaluate whether the effects of neuraminidase 1 deficiency affect autophagy induction and autophagosome formation and to determine the effects of lysosomal function block on muscle phenotype in neuraminidase 1 deficiency. Methodos:Mice Neu1+/-were crossbred and the genotyped pups, where mice Neu1-/-(knockout) and Neu1+/+(normal), were used in the study ntotal = 90, 10 for standardization, 20 for fibroblast collection and 60 for in vivo procedures, experimental groups were divided into food deprivation for 2 days that, through mTOR inhibition, induces autophagy; Colchicine treatment group for 4 days whereit will prevent autophagosome/lysosome junction without lysosomal degradation and added in the last two days of food deprivation and Rapamycin treatment group for 7 days, drug with function to selectively inhibit mTOR. After the treatments, the animals were euthanized to collect the anterior gastrocnemius and tibial muscles. The muscles were analyzed after histological staining by Hematoxylin & Eosin and Acid Phosphatase; LC3-I/II immunofluorescence; Western Blottingof LC3-I/II, Lamp-1 and p62/SQSTM proteins and Ultra-structural analysis. In addition, fibroblasts were cultured and subjected to nutrient deprivation and Rapamycin treatment, followed by the same in vivo analysis methodologies. Results:Histological analyzes by H&E and Acid Phosphatase did notreveal consistent changes in skeletal muscle of animals submitted to treatments, showing in animals with Neu1 deficiency an abnormal increase in endomysial space and increased intracytoplasmic lysosomal activity.In ultrastructural analysis, it was observed in all groups, the presence of several structures with autophagic aspect, of different sizes, shapes and constituents. The analysis of LC3 expression by Western Blottingshowed important activation of LC3-II in food deprivation (with and without Colchicine administration) in both control and Neu1 deficient animals and an important activation of LC3-I in Rapamycininboth groups,thus showing an increase in the autophagy pathway through mTOR blockade. In the immunofluorescence analysis, it was not possible to observe consistent difference between the groups. In vitro Western Blottinganalysis showed that such activation was similar between Neu1+/+and Neu1-/-fibroblasts. Conclusion: Experiments related to activation or inhibition of autophagy did not result in considerable differencesbetween normal muscles and Neu1 deficient muscles. Thus, we can conclude from these experiments that apparently Neu1, despite being an important lysosomal enzyme, does not interfere with the autophagy process

Spinal muscular atrophy (SMA) is the leading genetic cause of death of young children. It is an autosomal recessive disease caused by the mutation and/or the deletion within the ubiquitously expressed survival motor neuron 1 (SMN1) gene. SMA pathology is characterized by spinal cord motor neuron degeneration, neuromuscular junction (NMJ) defects and muscular atrophy. Upon disease onset, SMA patients progressively become paralyzed and in the most severe cases, they die due to respiratory complications. Over the years, it has become clear that SMN is a multi-functional protein with important roles in small nuclear ribonucleoprotein (snRNP) assembly, RNA metabolism, axonal outgrowth and pathfinding, mRNA transport as well as in the functional development of NMJs, skeletal muscle and cardiac muscle. However, it remains unclear which of these functions, and the respective perturbed molecular pathways, dictate SMA pathogenesis. Here, we have established Smn-depleted PC12 cells and an intermediate SMA mouse model to characterize a role for Smn in the regulation of actin cytoskeleton dynamics. We find that Smn depletion results in the increased expression of profilin IIa and active RhoA (RhoA-GTP) as well as the decreased expression of plastin 3 and Cdc42. Importantly, the inhibition of rho-kinase (ROCK), a direct downstream regulator of RhoA, significantly increased the lifespan of SMA mice and shows beneficial potential as a therapeutic strategy for SMA. In an addition, we have uncovered a muscle- and motor neuron-independent role for SMN in the regulation of pancreatic development and glucose metabolism in SMA mice and type 1 SMA patients. This finding highlights the importance of combining a glucose tolerance assessment of SMA patients with their existing clinical care management. Thus, our work has uncovered two novel and equally important roles for the SMN protein, both of which contribute significantly to SMA pathogenesis.

Exquisite is defined as carefully selected or sought out. I believe myself to be a selected soul placed in a body of circumstance. My work is self-explorative and telling of those circumstances in hopes of evoking empathy. Our bodies function and exist on many different levels. What I understand as normal for most differs vastly from what is normal for me. I aim to offer my perspective on the world, establish understanding, and blur the lines of normalcy.

L’atròfia muscular espinal (AME) és una malaltia d’origen genètic que afecta, majoritàriament a la població infantil. La malaltia cursa amb una mort de les motoneurones  i atròfia muscular. El gen implicat és el survival motor neuron (SMN) que està delecionat en un 95% dels casos. El nostre estudi està dividit en dues parts: 1- l’aprofundiment de les alteracions musculars en dos models animals murins transgènics que pateixen les formes més greus d’AME (Tipus 1-2) i 2- estudi dels possibles efectes terapèutics del liti en un d’aquests models d’AME. S’ha trobat alteracions greus en les unions neuromusculars d’animals nounats i prenatals en marcadors relacionats amb l’ancoratge de les vesícules a la membrana presinàptica, organització dels canals de calci presinàptics i altres proteïnes presinàptiques, desorganització i apoptosi de les cèl•lules musculars, apoptosi massiva del timus i alteracions generalitzades en els òrgans limfoides. L’estudi ultraestructural del múscul ens indica que hi ha una mort, per apoptosi, de les cèl•lules satèl•lit, confirmat amb la tècnica de TUNEL. L’augment de les apoptosi, però no es reflexa en un increment, per altra banda esperat, de la densitat dels macròfags. El tractament amb concentracions terapèutiques del liti no millora l’evolució de la malaltia en els ratolins que manifesten l’AME, s’observa una acumulació progressiva dels nivells de liti, provocant toxicitat en l’animal. L’efecte del liti inhibint la GSK3 no es tradueix en el increment d’expressió de SMN, tal com s’ha deduït d’alguns experiments publicats. / La atrofia muscular espinal (AME) es una enfermedad de origen genético que afecta, mayoritariamente a la población infantil. La enfermedad cursa con muerte de las motoneuronas y atrofia muscular. El gen implicado es el “survival motor neuron” (SMN) que está delecionado en un 95% de los casos. Nuestro estudio está dividido en dos partes: 1 - la caracterización de las alteraciones musculares en dos modelos animales murinos transgénicos que sufren las formas más graves de AME (Tipo 1-2) y 2 - estudio de los posibles efectos terapéuticos del litio en uno de estos modelos. Se han encontrado alteraciones pre y postnatales graves en las sinapsis neuromusculares a nivel de marcadores relacionados con el anclaje de las vesículas en la membrana presináptica, en la organización de los canales de calcio presinápticos y en otras proteínas presinápticas, Asimismo se ha hallado desorganización y apoptosis de las células musculares, apoptosis masiva del timo y alteraciones generalizadas en los órganos linfoides. El estudio ultraestructural del músculo nos revela muerte, por apoptosis, de las células satélite, confirmado con la técnica de TUNEL. El aumento de las apoptosis muscular no conlleva un incremento, por otra parte esperado, de la densidad de los macrófagos. El tratamiento con litio no mejora la evolución de la enfermedad en los ratones con AME. Se observa un incremento progresivo de los niveles de litio, provocando toxicidad en el animal. Por otra parte, el efecto del litio inhibiendo la GSK3 no se traduce en un aumento de la expresión de SMN, tal como se ha deducido de algunos experimentos publicados. / The spinal muscular atrophy (SMA) is a pediatric genetic disease. The SMA is a motor neuron disease that affects the motor neurons causing its death and muscle atrophy. The gene involved is the survival motor neuron (SMN) that is mutated in the 95% of the cases. Our study is divided into two parts: 1 – studies of the neuromuscular junction in two transgenic SMA murine models that develop the most severe forms of SMA (type 1-2) and 2 - study of the possible therapeutic effects of lithium on one of these models of SMA. We found severe alterations in the neuromuscular junctions of newborn animals and also in prenatal markers related to the vesicle docking at the presynaptic membrane, lack of organization of presynaptic calcium channels and defects in the expression of other presynaptic proteins. We found also, disruption and apoptosis of muscular cells, massive apoptosis of the thymus and widespread alterations in lymphoid organs. The ultrastructural study of muscle identifies apoptotic satellite cells that was confirmed by the TUNEL technique. The increase in apoptosis is not followed by the expected increase, in the macrophage density. Treatment with therapeutic concentrations of lithium does not improve the course of the disease in SMA mice. There was a progressive accumulation of lithium, causing toxicity in the animal. The effect of lithium inhibiting GSK3 does not determine an increased expression of SMN, as could be deduced from some published experiments.

Spinal muscular atrophy (SMA) is the leading genetic cause of death of young children. It is an autosomal recessive disease caused by the mutation and/or the deletion within the ubiquitously expressed survival motor neuron 1 (SMN1) gene. SMA pathology is characterized by spinal cord motor neuron degeneration, neuromuscular junction (NMJ) defects and muscular atrophy. Upon disease onset, SMA patients progressively become paralyzed and in the most severe cases, they die due to respiratory complications. Over the years, it has become clear that SMN is a multi-functional protein with important roles in small nuclear ribonucleoprotein (snRNP) assembly, RNA metabolism, axonal outgrowth and pathfinding, mRNA transport as well as in the functional development of NMJs, skeletal muscle and cardiac muscle. However, it remains unclear which of these functions, and the respective perturbed molecular pathways, dictate SMA pathogenesis. Here, we have established Smn-depleted PC12 cells and an intermediate SMA mouse model to characterize a role for Smn in the regulation of actin cytoskeleton dynamics. We find that Smn depletion results in the increased expression of profilin IIa and active RhoA (RhoA-GTP) as well as the decreased expression of plastin 3 and Cdc42. Importantly, the inhibition of rho-kinase (ROCK), a direct downstream regulator of RhoA, significantly increased the lifespan of SMA mice and shows beneficial potential as a therapeutic strategy for SMA. In an addition, we have uncovered a muscle- and motor neuron-independent role for SMN in the regulation of pancreatic development and glucose metabolism in SMA mice and type 1 SMA patients. This finding highlights the importance of combining a glucose tolerance assessment of SMA patients with their existing clinical care management. Thus, our work has uncovered two novel and equally important roles for the SMN protein, both of which contribute significantly to SMA pathogenesis.

Spinal muscular atrophy (SMA) is a hereditary disease characterized by progressive loss of -motoneurons of the spinal front corners, the consequence of which atrofizaci of muscles occurs. As a result, children become disabled and infirm dependent on the help and care of others at an early age. This is a relatively rare disease, the prevalence is about 1: 6,000 children. Spinal muscular atrophy is divided into 4 types according to its severity and time of onset of symptoms. Despite significant longtime research, it has failed to find a drug that could cure this disease so far. To the present date, there are only methods that slow the progression. The survey also contained 4 research questions, namely: What are the principles of treating a child with spinal muscular atrophy ? What are the most common problems in the care of a child with spinal muscular atrophy ? Are parents adequately educated on the issue of child with spinal muscular atrophy ? What impact has the presence of a child with spinal muscular atrophy in his family? Qualitative research was used in the implementation of the empirical part . Two qualitative methods were used to collect the data, a semi-structured interview and a hidden observation of the participant . Interviews were conducted with 3 research files, with 11 general nurses from the České Budejovice Hospital and University Hospital Motol, 7 mothers of children with I and II. type SMA of a summer camp for children with SMA and with 5 personal assistants. This thesis should help nurses and the public to gain awareness of the disease of Spinal Muscular Atrophy. It refers to all aspects of care of such a sick child, with which their parents daily struggle. Caring for a child with SMA is very difficult for their caregivers and requires considerable restrictions for the whole family. Information observed during the research were presented at a seminar for nurses in the České Budejovice Hospital in January 2015.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by widespread loss of lower motor neurons from the spinal cord. Lower motor neuron degeneration leads to a progressive decline in motor development, manifesting as muscle atrophy and weakness. It is now well characterised that ubiquitin homeostasis is altered in SMA and that reduction of the ubiquitin-like modifier-activating enzyme 1 (UBA1) is central to this disruption. UBA1 is responsible for activating ubiquitin as the first step in the ubiquitin conjugation process, marking unwanted proteins for degradation by the proteasome. While it is known that therapies targeting UBA1 rescue neuromuscular phenotypes in SMA models, the mechanism by which UBA1 mediates neurodegeneration is unclear. In fact, very little is known about the function of UBA1 beyond its canonical role in the ubiquitin proteasome system. To better understand the role of UBA1 in motor neuron degeneration, a robust set of antibodies for both in vivo and in vitro work to study UBA1 have been identified. This enabled a novel characterisation of UBA1 distribution throughout disease progression in SMA spinal motor neurons to be performed, revealing that UBA1 reduction is an important pre-symptomatic molecular feature of SMA. To identify downstream targets of UBA1 critical for UBA1-mediated degeneration in SMA, label-free proteomics was performed on HEK293 cells after overexpression or knockdown of UBA1. The proteomics data was analysed across multiple platforms, including Biolayout, IPA and DAVID to identify UBA1-dependent pathways and demonstrated that modulation of UBA1 levels lead to disruption of key cellular pathways including translation elongation, nuclear transport, and tRNA synthetases. Validation of target proteins from these UBA1-dependent pathways identified that the tRNA synthetease GARS behaves in a UBA1-dependent manner across a range of model systems in vitro and in vivo. It was then identified that GARS expression is significantly dysregulated across a range of neuronal tissues in a mouse model of SMA. Interestingly, mutations in GARS cause Charcot-Marie-Tooth disease type 2D (CMT2D), an axonal neuropathy, in which a disruption to sensory neuron fate in dorsal root ganglia has recently been identified. In a mouse model of SMA we identified a phenotype consistent with that in the CMT2D mouse model and showed that disruption to sensory neuron fate is reversible and dependent on changes in UBA1 and GARS expression in SMA. In conclusion, modulation of UBA1 levels leads to disruption of key cellular pathways, with dysregulation of tRNA synthetases a prominent feature that is likely to play a role in the pathogenesis of SMA.