Project description:Nemaline myopathy (NM) is a congenital myopathy that can result in lethal muscle dysfunction and is thought to be a disease of the sarcomere thin filament. Recently, several proteins of unknown function have been implicated in NM, and their role in the disease remains unresolved. Here, we demonstrate that loss of a muscle-specific protein, Klhl40, results in a nemaline-like myopathy in mice that closely phenocopies the muscle abnormalities observed KLHL40 deficient patients. We show that Klhl40 dynamically localizes to the sarcomere I-band and A-band and binds to Nebulin (Neb), a protein frequently implicated in NM, as well as a putative thin filament protein, Lmod3. Klhl40 belongs to the BTB-BACK-Kelch (BBK) family of proteins, some of which have been previously shown to promote degradation of their substrates. In contrast, we find that Klhl40 promotes stability of Neb and Lmod3 and blocks Lmod3 ubiquitination. Accordingly, loss of Klhl40 reduces Neb and Lmod3 protein in skeletal muscle of mice and KLHL40 deficient patients. Because loss of sarcomere thin filament proteins is a frequent cause of NM, our data establishes a possible molecular basis for NM in KLHL40 deficient patients by establishing a novel pro-stability function of Klhl40 for Neb and Lmod3.
Project description:Nemaline myopathy (NM) is a congenital myopathy that can result in lethal muscle dysfunction and is thought to be a disease of the sarcomere thin filament. Recently, several proteins of unknown function have been implicated in NM, and their role in the disease remains unresolved. Here, we demonstrate that loss of a muscle-specific protein, Klhl40, results in a nemaline-like myopathy in mice that closely phenocopies the muscle abnormalities observed KLHL40 deficient patients. We show that Klhl40 dynamically localizes to the sarcomere I-band and A-band and binds to Nebulin (Neb), a protein frequently implicated in NM, as well as a putative thin filament protein, Lmod3. Klhl40 belongs to the BTB-BACK-Kelch (BBK) family of proteins, some of which have been previously shown to promote degradation of their substrates. In contrast, we find that Klhl40 promotes stability of Neb and Lmod3 and blocks Lmod3 ubiquitination. Accordingly, loss of Klhl40 reduces Neb and Lmod3 protein in skeletal muscle of mice and KLHL40 deficient patients. Because loss of sarcomere thin filament proteins is a frequent cause of NM, our data establishes a possible molecular basis for NM in KLHL40 deficient patients by establishing a novel pro-stability function of Klhl40 for Neb and Lmod3. Total RNA was harvested from quadriceps muscle of three Klhl40 WT (control) and three Klhl40 KO mice. Each KO mouse was sacrificed with a corresponding WT littermate. Tissues were also taken at 0 days of age to minimize confounding gene changes occurring due to malnourishment as the phenotype worsens.
Project description:Nebulin is a giant filamentous protein that is coextensive with the actin filaments of the skeletal muscle sarcomere. Nebulin mutations are the main cause of nemaline myopathy (NEM), with typical NEM adult patients having low expression of nebulin, yet the roles of nebulin in adult muscle remain poorly understood. To establish nebulin’s functional roles in adult muscle we performed studies on a novel conditional nebulin KO (Neb cKO) mouse model in which nebulin deletion was driven by the muscle creatine kinase (MCK) promotor. Neb cKO mice are born with high nebulin levels in their skeletal muscle but within weeks after birth nebulin expression rapidly falls to barely detectable levels Surprisingly, a large fraction of the mice survives to adulthood with low nebulin levels (<5% of control), contain nemaline rods, and undergo fiber-type switching towards oxidative types. These microarrays investigate the changes in gene expression when nebulin is deficient.
Project description:Nebulin is a giant filamentous protein that is coextensive with the actin filaments of the skeletal muscle sarcomere. Nebulin mutations are the main cause of nemaline myopathy (NEM), with typical NEM adult patients having low expression of nebulin, yet the roles of nebulin in adult muscle remain poorly understood. To establish nebulin’s functional roles in adult muscle we performed studies on a novel conditional nebulin KO (Neb cKO) mouse model in which nebulin deletion was driven by the muscle creatine kinase (MCK) promotor. Neb cKO mice are born with high nebulin levels in their skeletal muscle but within weeks after birth nebulin expression rapidly falls to barely detectable levels Surprisingly, a large fraction of the mice survives to adulthood with low nebulin levels (<5% of control), contain nemaline rods, and undergo fiber-type switching towards oxidative types. These microarrays investigate the changes in gene expression when nebulin is deficient. Two skeletal muscle groups were studied: Quadriceps (which is markedly smaller in the Neb cKO mice relative to control) and Soleus (which is not significantly smaller in the Neb cKO relative to control). Six biological replicates for each muscle group were selected; all are age-matched males.
Project description:We present the application of large-scale multivariate mixed-model equations to the joint analysis of nine gene expression experiments in beef cattle muscle and fat tissues with a total of 147 hybridizations, and exploring 47 experimental conditions or treatments. Using a correlation-based method, we constructed a gene network for 822 genes. Modules of muscle structural proteins and enzymes, extracellular matrix, fat metabolism and protein synthesis were clearly evident. Detailed analysis of the network identified groupings of proteins on the basis of physical association. For example, expression of three components of the z-disk, MYOZ1, TCAP and PDLIM3, was significantly correlated. In contrast, expression of these z-disk proteins was not highly correlated with the expression of a cluster of thick (myosins) and thin (actin and tropomyosins) filament proteins, or titin, the third major filament system. However, expression of titin was itself not significantly correlated with the cluster of thick and thin filament proteins and enzymes. Correlation in expression of many fast twitch muscle structural proteins and enzymes was observed, but slow twitch specific proteins were not correlated with the fast twitch proteins or with each other. In addition, a number of significant associations between genes and transcription factors were also identified. Our results not only recapitulate the known biology of muscle, but have also started to reveal some of the underlying associations between and within the structural components of skeletal muscle. Analysis of nine gene expression experiments in beef cattle muscle and fat tissues with a total of 147 hybridizations, and exploring 47 experimental conditions or treatments.
Project description:We present the application of large-scale multivariate mixed-model equations to the joint analysis of nine gene expression experiments in beef cattle muscle and fat tissues with a total of 147 hybridizations, and exploring 47 experimental conditions or treatments. Using a correlation-based method, we constructed a gene network for 822 genes. Modules of muscle structural proteins and enzymes, extracellular matrix, fat metabolism and protein synthesis were clearly evident. Detailed analysis of the network identified groupings of proteins on the basis of physical association. For example, expression of three components of the z-disk, MYOZ1, TCAP and PDLIM3, was significantly correlated. In contrast, expression of these z-disk proteins was not highly correlated with the expression of a cluster of thick (myosins) and thin (actin and tropomyosins) filament proteins, or titin, the third major filament system. However, expression of titin was itself not significantly correlated with the cluster of thick and thin filament proteins and enzymes. Correlation in expression of many fast twitch muscle structural proteins and enzymes was observed, but slow twitch specific proteins were not correlated with the fast twitch proteins or with each other. In addition, a number of significant associations between genes and transcription factors were also identified. Our results not only recapitulate the known biology of muscle, but have also started to reveal some of the underlying associations between and within the structural components of skeletal muscle. Keywords: gene network
Project description:Morphological studies of skeletal muscle tissue have provided detailed insights into the architecture of muscle fibers, the surrounding cells, and the extracellular matrix. However, a spatial proteomics analysis of the skeletal muscle, including the muscle-tendon transition zone, is lacking. Here, we prepared thin cryotome muscle sections along the longitudinal axis of the mouse soleus muscle and measured each muscle slice using short LC-MS gradients. We generated more than 3000 high-resolution longitudinal protein profiles of central to distal skeletal muscle regions and created a molecular network of different skeletal muscle regions that reveals the complex architecture of the muscle-tendon transition zone. Among the proteins that show an increasing profile from muscle to tendon, we find proteins related to neuronal activity, fatty acid biosynthesis, and the renin-angiotensin system (RAS). Blocking the RAS in cultured mouse tenocytes using losartan reduces the synthesis of extracellular matrix proteins, including collagen and fibronectin. Overall, our analysis of thin cryotome sections provides a spatial proteome of skeletal muscle and reveals that the RAS acts as an additional regulator of the matrix within muscle-tendon junctions.