Among the major phytohormones, the cytokinin exhibits unique features for its ability to positively affect the developmental status of plastids. Even early on in its research, cytokinins were known to promote plastid differentiation and to reduce the loss of chlorophyll in detached leaves. Since the discovery of the components of cytokinin perception and primary signaling, the genes involved in photosynthesis and plastid differentiation have been identified as those directly targeted by type-B response regulators. Furthermore, cytokinins are known to modulate versatile cellular processes such as promoting the division and differentiation of cells and, in concert with auxin, initiating the de novo formation of shoot apical meristem (SAM) in tissue cultures. Yet how cytokinins precisely participate in such diverse cellular phenomena, and how the associated cellular processes are coordinated as a whole, remains unclear. A plausible presumption that would account for the coordinated gene expression is the tight and reciprocal communication between the nucleus and plastid. The fact that cytokinins affect plastid developmental status via gene expression in both the nucleus and plastid is interpreted here to suggest that cytokinin functions as an initiator of anterograde (nucleus-to-plastid) signaling. Based on this viewpoint, we first summarize the physiological relevance of cytokinins to the coordination of plastid differentiation with de novo shoot organogenesis in tissue culture systems. Next, the role of endogenous cytokinins in influencing plastid differentiation within the SAM of intact plants is discussed. Finally, a presumed plastid-derived signal in response to cytokinins for coupled nuclear gene expression is proposed.

No description available.

Introdução: A doença hepática gordurosa não alcoólica (DHGNA) é uma das formas mais comuns de doença hepática, que acomete cerca de 20% a 30% da população adulta, sendo encontrada mais frequentemente em indivíduos obesos (~90%). Dentre os principais fatores etiológicos estão: resistência à insulina, disfunção mitocondrial e estresse oxidativo. Até o presente momento não há tratamento farmacológico específico para a DHGNA, por isso modificações no estilo de vida como redução do peso corporal (PC), dieta e prática regular de exercício físico são eficazes no combate a DHGNA. Entretanto ainda não está elucidado quais os principais impactos do exercício físico na DHGNA. Objetivos: Com isso, propusemos um estudo experimental que avaliou o efeito do treinamento físico sobre metabolismo oxidativo, funcionalidade mitocondrial hepática e muscular (soléo) e lipogênese hepática em modelo de DHGNA em camundongos obesos (ob/ob). Métodos: Utilizou-se 14 (ob/ob) com déficit em leptina e forma divididos em dois grupos: Sedentário (SED)=7 e treinados (TF=7) de acordo com o equilíbrio na média do PC. Estes animais foram submetidos a um protocolo de 8 semanas de treinamento físico aeróbio (TFA) a 60% da velocidade máxima obtida no teste de corrida realizado no último dia da semana de adaptação ao TFA. Na quarta semana foi realizado o reajuste da intensidade apenas nos TF e o teste de capacidade de corrida foi aplicado na oitava semana em ambos os grupos para se avaliar o desempenho dos animais nas variáveis ligadas ao TFA. Avaliou-se durante todo o protocolo: peso corporal (PC) em média, percentual, evolução do PC e consumo de água e ração. Na expressão gênica intra-hepática e muscular foram analisados: PGC-1Alfa, CPT-1Alfa e PPAR-Alfa relacionados a funcionalidade mitocondrial, em adição analisou-se no fígado: SREBP1. No metabolismo oxidativo analisou-se: biomarcadores (MDA e carbonilas), atividade enzimática de SOD, CAT e GST, sistema antioxidante não enzimático: sulfidrilas, GSH e GSH/GSSG, enzimas metabólicas (Citrato sintase e Beta-HAD). Foi realizada análise histopatológica hepática por HE, além do peso absoluto e relativo dos tecidos hepático e adiposo branco retroperitoneal, periepididimal e inguinal. Resultados: Na análise intergrupo em relação ao PC, observou-se redução significativa no grupo TF, assim como nos consumos de água e ração que foram significativamente menores após 8 semanas: Na análise de expressão gênica hepática encontramos aumento de PGC-1Alfa (p=0,002) e menor de CPT-1Alfa p=0,03) no grupo LTF após 8 semanas de TFA. No músculo Soléo encontramos maior expressão dos genes: PGC-1Alfa (p=0,002) e CPT-1Alfa (p=0,01). Em relação a MDA e carbonilas não houve diferença intergrupo, assim como em SOD, CAT e GST. Entretanto, quando analisamos o sistema antioxidante não enzimático, encontramos que os TF obtiveram maior nível de: sulfídrilas (p=0,02), GSH (p=0,001) e GSH/GSSG (p=0,02), além maior ativação das enzimas metabólicas: citrato sintase (p=0,004) e Beta-HAD (p=0,01). No peso dos órgãos, o TF demonstrou menor peso absoluto e relativo hepático e retroperitoneal. Na análise histológica, não houve diferença significante. Conclusões: Nossos dados demonstram que TFA melhorou o controle do PC, hiperfagia e peso do fígado e retroperitoneal, funcionalidade mitocondrial e metabolismo oxidativo em (ob/ob) com DHGNA. Há necessidade uma intervenção a longo prazo com TFA, para que se posso visualizar possíveis melhorias histológicas / Non-alcoholic fatty liver disease (NAFLD) is one of the most common forms of liver disease, affecting about 20% to 30% of the adult population, being found more often in obese individuals (~ 90%). Among the main etiological factors are insulin resistance, mitochondrial dysfunction and oxidative stress. To date, no specific pharmacological treatment for NAFLD, so lifestyle modifications such as: reduction in BW, diet and regular practice of physical exercise are effective, however it is not yet elucidated what the main impacts of physical exercise on NAFLD. Therefore, we proposed an experimental study that evaluated the effect of physical training on oxidative metabolism, hepatic and muscular mitochondrial function (soles) and hepatic lipogenesis in an ob / ob model of NAFLD. We used 14 (ob / ob) with leptin deficiency and divided into two groups: Sedentary (SED) = 7 and Trained (TF = 7) according to the mean BW balance. These animals were submitted to an 8-week protocol of aerobic physical training (AET) at 60% of the maximum velocity obtained in the running test performed on the last day of the week of adaptation to AET. In the fourth week the intensity adjustment was only done in the TF and the running capacity test was amplified in the eighth week in both groups to evaluate the performance of the animals in the variables linked to the AET. It was evaluated throughout the protocol: body weight (BW) on average, percentage, BW evolution and water and feed consumption. In the intrahepatic and muscular gene expression were analyzed: PGC-1Alpha, CPT-1Alpha and PPAR-Alpha related to mitochondrial functionality, in addition liver was analyzed: SREBP1. In the oxidative metabolism, we analyzed: biomarkers (MDA and carbonyls), enzymatic activity of SOD, CAT and GST, non-enzymatic anti-oxidant system: sulfhydryl, GSH and GSH / GSSG, metabolic enzymes (Citrate synthase and Beta-HAD). Hepatic histopathological analysis was performed by HE, in addition to the absolute and relative weight of the hepatic and white retroperitoneal, periepididimal and inguinal adipose tissues. In the intergroup analysis in relation to BW, a significant reduction was observed in the TF group, as well as in the water and feed intakes that were significantly lower after 8 weeks: In the analysis of hepatic gene expression we found an increase of PGC-1Alpha (p = 0.002) and CPT-1 = 0.0Alpha 3) in the TF group after 8 weeks of AET. In the soleus we found higher expression of the genes: PGC-1Alpha (p= 0.002) and CPT-1Alpha (p = 0.01). In relation to MDA and carbonyls there was no intergroup difference, as in SOD, CAT and GST. When we analyzed the non-enzymatic anti-oxidant system, we found that the TF had a higher activity of: sulfhydryls (p = 0.02), GSH (p = 0.001) and GSH / GSSG (p = 0.02) metabolic enzymes: citrate synthase (p = 0.004) and Beta-HAD (p = 0.01). In the weight of the organs the TF showed lower absolute and relative hepatic and retroperitoneal weight. In the histological analysis, there was no significant difference. Our data demonstrate that AET improved BW control, hyperphagia and liver and retroperitoneal weight, mitochondrial functionality and oxidative metabolism in (ob / ob) with NAFLD. Long-term AET intervention is needed so that we can visualize possible histological improvements. We considered the effective AET to improve aspects related to NAFLD

Utilizing various systems such as cell-based assays but also multicellular organisms such as Drosophila melanogaster and C.elegans, for example, the endocytic system has been shown to consist of a network of biochemically and morphologically distinct organelles that carry out specialized tasks in the uptake, recycling and catabolism of growth factors and nutrients, serving a plethora of key biological functions (Mellman, 1996). Different classes of endosomes were found to exhibit a characteristic intracellular steady state distribution. This distribution pattern observed at steady state results from a dynamic interaction of endosomes with the actin and the microtubule cytoskeleton. It remains unclear, however, which microtubule-based motors besides Dynein control the intracellular distribution and motility of early endosomes and how their function is integrated with the sorting and transport of cargo. The first part of this thesis research outlines the search for such motor. I describe the identification of KIF16B which functions as a novel endocytic motor protein. This molecular motor, a kinesin-3, transports early endosomes to the plus end of microtubules, in a process regulated by the small GTPase Rab5 and its effector, the phosphatidylinositol-3-OH kinase hVPS34. In vivo, KIF16B overexpression relocated early endosomes to the cell periphery and inhibited transport to the degradative pathway. Conversely, expression of dominant-negative mutants or ablation of KIF16B by RNAi caused the clustering of early endosomes to the peri-nuclear region, delayed receptor recycling to the plasma membrane and accelerated degradation. These results suggest that KIF16B, by regulating the plus end motility of early endosomes, modulates the intracellular localization of early endosomes and the balance between receptor recycling and degradation. In displaying Rab5 and PI(3)P-containing cargo selectivity, a remarkable property of KIF16B is that it is subjected to the same regulatory principles governing the membrane tethering and fusion machinery (Zerial and McBride, 2001). Since KIF16B can modulate growth factor degradation, we propose that this motor could have also important implications for signaling. Importantly, KIF16B has provided novel insight into how intracellular localization of endosomes governs the transport activity of these organelles. The second part of this thesis describes the proof-of-principle of a genome-wide screening strategy aimed at gaining insights into the next level of understanding: How the spatial distribution of organelles is linked to their function in an experimental system which features cellular polarity, for example, a tissue or organ. The suitability of C. elegans as a model organism to identify genes functioning in endocytosis has been demonstrated by previous genetic screens (Grant and Hirsh 1999; Fares and Greenwald, 2001). Offering excellent morphological resolution and polarization, the nematode intestine represents a good system to study the apical sorting of a transmembrane marker. The steady state localization of such a marker is likely the result of a dynamic process that depends on biosynthetic trafficking to the apical surface, apical endocytosis and recycling occurring through apical recycling endosomes. Therefore, mis-sorting of this marker upon RNA-mediated interference will be indicative of a failure in one of the aforementioned processes. Furthermore, since it is still largely unclear why apical endosomes maintain their polarized localization, this screen will also monitor the morphology of this endocytic compartment using a second marker. Following image acquisition based on an automated confocal microscope, data can be analyzed using custom-built software allowing objective phenotypic analysis. The successful establishment of the proof-of-principle marks the current state-of-the-art of this large-scale screening project.

Mitochondria are essential eukaryotic organelles, acting as the sites for numerous crucial metabolic and signalling pathways. The biogenesis of mitochondria requires efficient targeting of several hundreds of proteins from the cytosol, to their varied functional locations within the organelle. The translocation of localized proteins across the inner membrane, and their subsequent folding is achieved by the ATP-dependent function of mitochondrial Hsp70 (mtHsp70). It is a bonafide member of the Hsp70 chaperone family, which are involved in a multitude of functions, together aimed at protein quality control and maintenance of cellular homeostasis. These varied functions of Hsp70 proteins require binding to exposed hydrophobic patches in substrate polypeptides thus preventing non-productive associations. The interaction with substrates occurs through the substrate-binding domain (SBD) and is regulated by the ATPase activity of the nucleotide-binding domain (NBD), through a series of conformational changes. Conversely, substrate binding to the SBD also stimulates ATP hydrolysis, and thereby the core activities of the two domains are regulated by mutual allosteric signalling. This mechanism of bidirectional inter-domain communication is indispensable for Hsp70 function, which is characterized by cycles of substrate binding and release, coupled to cycles of ATP binding and hydrolysis. The process of allosteric regulation in Hsp70 proteins has been comprehensively investigated, especially in the bacterial homolog, DnaK. However, the in vivo functional significance of inter-domain communication in the eukaryotic mtHsp70 system and the mechanism of its regulation remain unexplored. Furthermore, the complex physiological implications of impairment in allosteric communication and their correlation with diverse disease conditions, including Myelodysplastic syndrome (MDS), and Parkinson’s disease (PD), are yet to be elucidated. Based on this brief introduction, the primary research objectives set out in the present thesis were to: 1. uncover the regulation of ligand-modulated allosteric communication between the two domains of mtHsp70; and its in vivo significance in the context of protein import into the organelle. (Chapter 2) 2. understand the role of mtHsp70 in progression of Parkinson’s disease; and to study the modulation of α-synuclein toxicity by the protein quality control function of the mtHsp70 chaperone network. (Chapters 3 and 4) We have employed a battery of genetic and biochemical approaches to investigate the above questions using the Saccharomyces cerevisiae mtHsp70 protein, Ssc1; an essential protein that is involved in a plethora of critical functions in this eukaryotic model system. Objective 1: Structural studies, primarily in bacterial DnaK, have yielded mechanistic insights into its interactions with ligands and cochaperones, as well as conformational transitions in different ligand-bound states. In recent years, the availability of crystal structures of full-length DnaK and detailed information from NMR studies and single-molecule resolution spectroscopic analyses (both DnaK and eukaryotic Hsp70s), have significantly contributed to our understanding of the inter-domain interface, critical residues and contacts, and the energetics of the entire process of ligand-modulated conformational changes. Although eukaryotic mtHsp70s have a high degree of conservation with DnaK, they possess significant differences in their conformational and biochemical properties. They are essential for a vast repertoire of physiological functions, which are distinctly different from their bacterial counterpart. Using a combined in vivo and in vitro approach, we have uncovered specific structural elements within mtHsp70s, which are required for allosteric modulation of the chaperone cycle and maintenance of in vivo functions of the protein. Foremost, we demonstrate that a conserved SBD loop, L4,5 plays a critical role in inter-domain communication, and multiple mutations in this loop result in significant growth and protein translocation defects. The mutants are associated with a specific set of altered biochemical properties, which are indicative of impaired inter-domain communication. Using the loop L4,5 mutant, E467A as a template for genetic screening, we report a series of intragenic suppressor mutations, which are capable of correcting a distinct subset of the altered properties, and thereby leading to restoration of in vivo functions, including growth, preprotein import and mitochondria biogenesis. The suppressors modify the altered conformational landscape associated with E467A, and also provide us with information regarding unique aspects governing the regulation of allosteric communication, especially in physiological contexts. Strikingly, they reveal that restoration of communication in the NBD to SBD direction is sufficient for function, when the protein is primed in a high ATPase activity state. In this unique scenario, the requirement for ATPase stimulation upon substrate binding is rendered unnecessary, thereby making conformational changes in the SBD to NBD direction, dispensable for function. Further, we provide evidence to show that loop L4,5 functions synergistically with the linker region, working in tandem for organization of the inter-domain interface and propagation of communication. Together, our analyses provide the first insights into regulation of allosteric inter-domain communication in vivo and their implications in mitochondrial protein translocation and organelle biogenesis. Objective 2: Point mutations in the loop L4,5 have been associated with Myelodysplastic syndrome. Additionally, a mutation isolated in clinical cases of Parkinson’s disease was found to be impaired in allosteric communication. These observations further highlight the importance of efficient inter-domain communication in mtHsp70 in the complex physiological scenario of eukaryotic cells. Independent clinical screens of PD patients have revealed unique point mutations in the mtHsp70 and a strong association of the gene locus with the disease progression. This is also correlated with decreased mtHsp70 levels in affected neurons and the interactions of this protein with established PD-candidate proteins like α-synuclein and Dj-1. Further, mitochondrial dysfunction is a common phenomenon associated with neurodegenerative disorders. To understand the specific role of mtHsp70 in PD, we have developed a yeast model for studying the disease variants in isolation from other players of the multifactorial disease, and in complete absence of the wild type protein. We generated two analogous PD-mutations in Ssc1, R103W and P486S; which recapitulated the symptoms of mitochondrial dysfunction in affected neurons, including cell death, inner membrane depolarization, increased generation of ROS, and respiratory incompetence. At the molecular level, we observed an increased aggregation propensity of R103W, while P486S exhibited futile enhanced interaction with J-protein cochaperone partners thereby resulting in loss of chaperoning activity and impaired mitochondrial protein quality control. Remarkably, these altered biochemical properties mimicked similar defects in the human mtHsp70 variants, therefore, affirming the involvement of mtHsp70 in PD progression. To further investigate the relevance of impaired mitochondrial protein quality control in PD, we have explored whether mtHsp70 can act as a genetic modifier of α-synuclein toxicity. It is known that α-synuclein can act as an unfolded substrate for the Hsp70 chaperone system and also deposits as intracellular aggregates in PD-affected brains. Intriguingly, it is known to translocate into mitochondria under conditions of neuronal stress in spite of lacking a canonical mitochondrial signal sequence. Utilizing our yeast-PD model, we find that targeting of α-synuclein A30P disease variant into mitochondria leads to a severe mitochondrial dysfunction phenotype in the wild type Ssc1 background, but not the P486S mutant background. This results in multiple cellular manifestations, which are reversed upon overexpression of the Ssc1 chaperone. Significantly, increasing the J-protein cochaperone availability also leads to reversal of the mutant-associated defects. However, the simultaneous overexpression of both together does not additively improve the protective effects; highlighting the importance of the relative availability of chaperone and cochaperone proteins in preventing aggregation. Our analyses further reveal that while both the wild type and P486S Ssc1 proteins are equally capable of delaying aggregation of α-synuclein, only the wild-type chaperone is better able to prevent aggregation in the presence of its J-protein cochaperone, leading to accumulation of soluble oligomeric species. These observations raised the intriguing possibility, that the reduced chaperoning ability of the proline to serine PD-mutant is, in fact, a compensatory adaptation, favoring the aggregation of α-synuclein over its more toxic soluble oligomeric form. We verify this hypothesis with the aggregation kinetics of A30P α-synuclein, whose intrinsically lower aggregation tendency results in a pronounced delay in aggregation with the wild-type chaperone, thereby strongly favoring the toxic oligomeric species and correlating with the observed lethality in yeast cells. In conclusion, our study provides a model of α-synuclein aggregation-related toxicity and its modulation by the extent of protein quality control within the mitochondrial matrix, through the action of the mtHsp70 chaperone network.

Utilizing various systems such as cell-based assays but also multicellular organisms such as Drosophila melanogaster and C.elegans, for example, the endocytic system has been shown to consist of a network of biochemically and morphologically distinct organelles that carry out specialized tasks in the uptake, recycling and catabolism of growth factors and nutrients, serving a plethora of key biological functions (Mellman, 1996). Different classes of endosomes were found to exhibit a characteristic intracellular steady state distribution. This distribution pattern observed at steady state results from a dynamic interaction of endosomes with the actin and the microtubule cytoskeleton. It remains unclear, however, which microtubule-based motors besides Dynein control the intracellular distribution and motility of early endosomes and how their function is integrated with the sorting and transport of cargo. The first part of this thesis research outlines the search for such motor. I describe the identification of KIF16B which functions as a novel endocytic motor protein. This molecular motor, a kinesin-3, transports early endosomes to the plus end of microtubules, in a process regulated by the small GTPase Rab5 and its effector, the phosphatidylinositol-3-OH kinase hVPS34. In vivo, KIF16B overexpression relocated early endosomes to the cell periphery and inhibited transport to the degradative pathway. Conversely, expression of dominant-negative mutants or ablation of KIF16B by RNAi caused the clustering of early endosomes to the peri-nuclear region, delayed receptor recycling to the plasma membrane and accelerated degradation. These results suggest that KIF16B, by regulating the plus end motility of early endosomes, modulates the intracellular localization of early endosomes and the balance between receptor recycling and degradation. In displaying Rab5 and PI(3)P-containing cargo selectivity, a remarkable property of KIF16B is that it is subjected to the same regulatory principles governing the membrane tethering and fusion machinery (Zerial and McBride, 2001). Since KIF16B can modulate growth factor degradation, we propose that this motor could have also important implications for signaling. Importantly, KIF16B has provided novel insight into how intracellular localization of endosomes governs the transport activity of these organelles. The second part of this thesis describes the proof-of-principle of a genome-wide screening strategy aimed at gaining insights into the next level of understanding: How the spatial distribution of organelles is linked to their function in an experimental system which features cellular polarity, for example, a tissue or organ. The suitability of C. elegans as a model organism to identify genes functioning in endocytosis has been demonstrated by previous genetic screens (Grant and Hirsh 1999; Fares and Greenwald, 2001). Offering excellent morphological resolution and polarization, the nematode intestine represents a good system to study the apical sorting of a transmembrane marker. The steady state localization of such a marker is likely the result of a dynamic process that depends on biosynthetic trafficking to the apical surface, apical endocytosis and recycling occurring through apical recycling endosomes. Therefore, mis-sorting of this marker upon RNA-mediated interference will be indicative of a failure in one of the aforementioned processes. Furthermore, since it is still largely unclear why apical endosomes maintain their polarized localization, this screen will also monitor the morphology of this endocytic compartment using a second marker. Following image acquisition based on an automated confocal microscope, data can be analyzed using custom-built software allowing objective phenotypic analysis. The successful establishment of the proof-of-principle marks the current state-of-the-art of this large-scale screening project.

No description available.

博士(理学) / Doctor of Philosophy in Science / 同志社大学 / Doshisha University

No description available.

<p dir="ltr">Skeletal muscle accounts for 40% of total body weight and the homeostasis of muscle tissue is critical in maintaining proper body function. Skeletal muscle develops during the embryonic stages from the muscle progenitor cells derived from the dermomyotome structure. The myogenic progenitor cells contribute to the primary myogenesis by forming the primary myotubes which are the founding structures that the secondary myogenesis continues to build on. A portion of the myogenic progenitor cells makes up the adult muscle stem cells residing in homeostatic muscle tissue. The adult muscle stem cells contribute substantially for the adult muscle regeneration. Due to the significance of the muscle tissue and the importance of muscle stem cells, dysregulation of the muscle homeostasis or the muscle stem cell homeostasis will result in severe pathological conditions such as myopathy.</p><p dir="ltr">Mitochondria are cellular organelles that are responsible for generating energy needed for cellular processes, especially for muscle tissue where muscle contraction requires the presence of ATP. On the other hand, mitochondria also serve as signaling molecules and provide macromolecules for the biosynthesis. FAM210A (Family With Sequence Similarity 210 Member A) protein was shown to impact the lean mass of human subjects yet a detailed study on the effect of FAM210A in skeletal muscle was not performed, nor has the molecular mechanisms through which FAM210A function been elucidated. Therefore, I take on the task to unveil the function of FAM210A in muscle development, muscle homeostasis and muscle stem cell behavior by using a combination of mouse models with different myogenic promoters to target <i>Fam210a</i> at different developmental stages.</p><p dir="ltr">In the first part of the thesis, I investigated the role of FAM210A in post differentiation myofibers. Using the <i>Myl1</i>^<em>Cre</em> driven deletion of <i>Fam210a</i>, I found that <i>Fam210a</i>^<em>MKO</em> had normal development before 3 weeks of age, but the growth was stagnant from 4 weeks on, and the mice did not survive past 8 weeks of age. I found that the assembly of the ribosomes in the <i>Fam210a</i>^<em>MKO</em> was defective, leading to impaired translation which attenuated the muscle atrophy phenotype. I identified through proteomics that the mitochondrial autophagy and proteostatic control pathways were significantly induced yet mitochondrial organization and energetic proteins were downregulated. Metabolomics analysis showed that the signaling metabolite acetyl-CoA was increased in the <i>Fam210a</i>^<em>MKO</em> which led to increased protein acetylation, specifically, we showed that the ribosomal proteins were hyperacetylated, and that the acetylation increase was elicited by the <i>Fam210a</i>-null mitochondria.</p><p dir="ltr">In the second part of the thesis, I investigated the function of FAM210A in muscle progenitor cells. In the <i>FamMKO</i> mice, I found that deletion of <i>Fam210a</i> from embryonic myogenic progenitor cells led to developmental arrest and postnatal death at day 6. In the <i>FamPKO</i> mice, I found that <i>Fam210a</i> is needed for adult muscle stem cell to contribute to regeneration. Loss of <i>Fam210a</i> leads to the regenerative defects when the muscle was exposed to injury cues. We further showed that <i>Fam210a</i> deletion in muscle stem cells resulted in disruption of the proteostatic control over muscle stem cell activation, thereby forbidding the translational increase necessary to facilitate activation and proliferation. Furthermore, I showed that <i>Fam210a</i> deletion leads to excessive OPA1 cleavage, which contributes to the regenerative failure of muscle stem cells as fusion is required for the mitochondrial network remodeling during regeneration. Therefore, <i>Fam210a</i> safeguards the mitochondrial network and proteostasis during regeneration.</p><p dir="ltr">In summary, my studies characterized the functional contribution of FAM210A during embryonic muscle development, muscle mass maintenance and adult muscle stem cell homeostasis. The regulation of FAM210A in these three processes impinge on the translational regulation. My studies further demonstrated the importance of mitochondrial regulated protein translation in skeletal muscle and muscle stem cells.</p>