== Western blots showing expression of eEF1A2 and GAPDH (as a loading control) in muscle and brain tissue extracts from transgenic HSAEEF1A2 mice and nontransgenic mice

== Western blots showing expression of eEF1A2 and GAPDH (as a loading control) in muscle and brain tissue extracts from transgenic HSAEEF1A2 mice and nontransgenic mice. or time of death of wasted mice. Molecular markers of muscle mass atrophy such as Fbxo32 were dramatically upregulated at the RNA level in wasted mice, both in the presence and in the absence of musclespecific expression of eEF1A2, but the degree of upregulation at the protein level was significantly lower in those wasted mice without transgenederived expression of eEF1A2 in muscle mass. This provides the firstin vivoconfirmation that eEF1A2 plays an important role in translation. In spite of the inability of the nontransgenic wasted mice to upregulate key atrogenes at the protein level in response to denervation to the same degree as Enpep their transgenic counterparts, there were no measurable differences between transgenic and nontransgenic wasted mice in terms of excess weight loss, grip strength, or muscle mass pathology. This suggests that a compromised ability fully to execute the atrogene pathway in denervated muscle mass does not affect the process of muscle mass atrophy in the short term. Keywords:motor neuron degeneration, muscle Cynaropicrin mass atrophy, transgenic mice, translation elongation == Abbreviations == amyotrophic lateral sclerosis translation elongation factor 1A translation elongation factor 1A1 translation elongation factor 1A2 glyceraldehyde3phosphate dehydrogenase human skeletal actin motor neuron disease neuronspecific enolase spinal muscular atrophy survival motor Cynaropicrin neuron protein == Introduction == Motor neuron disease (MND) is the umbrella term for a group of neurodegenerative diseases primarily affecting the motor neurons of the spinal cord. The term covers both the earlyonset genetic disorder spinal muscular atrophy (SMA) and the adultonset forms of MND, both sporadic and genetic. The adult form is usually often referred to as amyotrophic lateral sclerosis (ALS). MND has a complex aetiology that has, until recently, often eluded characterization at a genetic level, with a few notable exceptions, many including defects in genes encoding molecules involved in RNA processing1, together with a recent discovery of a gene whose product is involved in protein degradation2. Severe muscle mass atrophy is seen in MND, and the mechanisms underlying this process have been analyzed in many animal and cellular models. A number of mouse models exist for both SMA and ALS forms of the disease. In some cases, these involve targeted mutations in genes that have previously been implicated in human forms of the disease, but there are also mouse mutants that model the neurodegenerative process without necessarily involving the same genetic basis. One such model is the wasted mouse, which arises from a spontaneous recessive mutation resulting in deletion of the promoter region and first noncoding exon of theEef1a2gene encoding translation elongation factor 1A2 (eEF1A2). This 15.8kb deletion completely abolishes eEF1A2 protein expression3. Mice homozygous for this deletion develop an earlyonset aggressive form of motor neuron degeneration, characterized by muscle mass atrophy, tremors and gait abnormalities soon after weaning. They then deteriorate rapidly and pass away, typically by 28 days4. The onset of this phenotype coincides with a developmental switch in eEF1A variants in muscle mass. You will find two independently encoded translation elongation factor 1A (eEF1A) isoforms in mammals, translation elongation factor 1A1 (eEF1A1) and eEF1A2. Whereas eEF1A1 is almost ubiquitously expressed, its expression in muscle mass starts at high levels at birth, but then declines to become almost undetectable by ~ 21 days. Meanwhile, eEF1A2 levels in muscle mass rise from very low levels at birth to high levels by 21 days after birth5. The loss of eEF1A1 in muscle mass thus corresponds precisely to the onset of the wasted phenotype. Within brain and spinal cord, there is exclusive expression of one or Cynaropicrin other eEF1A isoform, depending on cell type, with neurons expressing only eEF1A2 and glial cells expressing only eEF1A16. Wasted mice therefore have neither eEF1A1 nor eEF1A2 expression in muscle or motor neurons beyond 21 days of age. As eEF1A is essential forde novoprotein synthesis, it is assumed that both muscle cells and neurons will be severely affected by the mutation. Indeed, in addition to the loss of muscle bulk, motor neuron pathology is found in wasted mice3. From 17 days, nerves retract from motor endplates, and by 19 days reactive gliosis is seen in spinal cord sections. Neurofilament accumulation in the perikarya of motor neurons is then seen, and vacuolation and death of motor neurons is observable by 24 days. Previous transgenic Cynaropicrin studies in our laboratory have shown thatEef1a2is the only gene responsible for the wasted phenotype6. However, it has never been established whether the loss of muscle bulk, loss of muscle function and ultimate Cynaropicrin death of wasted mice results from the loss of eEF1A2 in muscle, or whether the muscle phenotype is caused by denervation atrophy resulting from loss of eEF1A2 in.