Expression Of Syncytin In Denervated Gastrocnemius Of Mouse

Background and purpose:Motor neuron disease (MND) is a group of chronic progressive neurodegenerative diseases with unknown etiology, including amyotrophic lateral sclerosis (ALS), progressive spinal muscular atrophy, primary lateral sclerosis and progressive bulbar palsy. ALS is the most common MND. Family ALS accounts for approximately10%of all ALS cases and presents with autosomal dominant inheritance. The rest of ALS is sporadic ALS. Many factors might be involved in the pathogenesis of ALS, including peroxidation, the exitotoxicity of glutamate, mitochondrial dysfunction, protein misfolding, the disintegration of neurofilament, the axonal transport impairment, virus infections, poisoning, autoimmune mechanisms, and environmental factor. According to epidemiological studies, viral infection is one of the most important environmental predisposing factors.Clinical evidence shows that polio virus, enterovirus and retrovirus are related with the pathogenesis of ALS, but none specific pathogenic virus of ALS has been identified. Recent studies reported reverse transcriptase RNA expression in ALS patients as well as their first degree relatives. The activation of human endogenous retro viruses has been proposed in ALS.Oluwole et al detected the expression of HERV-W env gene (syncytin), which locates at chromosome7q21.2, in the affected muscles and unaffected muscles of MND patients as well as controls. The results showed that syncytin mRNA level is significantly higher in the affected muscles as compared to unaffected muscles and control muscles. To our knowledge, this is the first report regarding the aberrant transcription of syncytin in MND. However, the possible association and significance of this finding to MND need to be further studied.Wei Zhang et al detected the level of syncytin mRNA in gastrocnemius of mouse with sciatic never injury with real-time PCR. No significant differences of the mRNA level of syncytin were detected in the mouse with sciatic never injury as compared to controls. In order to eliminate the influences of operative trauma and acute inflammatory response following operation, the present study prolonged the experimental end point to14days after the operation. The level of syncytin mRNA was detected in the gastrocnemius of mouse14days after sciatic never injury and the association between syncytin expression and skeletal muscle denervation was explored.Materials and Methods:30Kunming mice were randomly divided into operation group, sham operation group and normal control. Ten mice each group.1. Measure the toes distance between both lower limbs prior to operation and on postoperative days1,5,9and13.2. Both sides of the gastrocnemius of the mice of operation group, the left side of the gastrocnemius of the mice of sham operation group and the normal group were collected on postoperative day14. Total RNA and total protein were extracted respectively.3. Detect the level of syncytin mRNA with real-time RT-PCR using the level of β-actin mRNA as internal reference.4. Detect the level of syncytin protein with western-blot and using the level of GAPDH as internal reference.5. Gastrocnemius was paraffin imbeded and sectioned, and the expression of syncytin in skeletal muscle was located by fluorescence immunohistochemistry.Results:1.There is no significant differences of the toe spacing preoperatively and on postoperative day1between the operation group and sham operation group. However, significant differences presented on postoperative days5,9and13between operation group and sham operation group.2. Compare to sham operation group and control groups, the mRNA level of syncytin elevated significantly in the denervated muscles of mice of the operation group on postoperative day14(all P<0.05).3. Compare to sham operation group and control groups, the protein level of syncytin elevated significantly in the denervated muscles of mice of the operation group on postoperative day14(all P<0.05).4. The fluorescence immunostaining of syncytin was distributed in the muscle membrane. Conclusions:With sciatic nerve transection, the mice presented with decreased motor function. Significant elevation of the level of syncytin mRNA and protein were detected in the denervated muscles of the mice suffered from sciatic nerve injury. The fluorescence immunostaining of syncytin was distributed in the muscle membrane. Our study suggests that the expression of membrane proteins of endogenous retroviruses—syncytin in the skeletal muscles may be affected by the muscular denervation resulted from sciatic nerve injury. These findings will probably add significance to further study of the pathophysiological roles of syncytin in motor nerve injury.