Activating Transcription Factor 6 Promotes Neurorepair Of Adult Zebrafish After Spinal Cord Injury

Aims:To evaluate the effect and possible mechanism of activating transcription factor 6(ATF6)on spinal cord neuro-repair in spinal cord injury(SCI)zebrafish.Methods:Adult zebrafish(Danio rerio)SCI model were established on 4-6 months old zebrafish.Real-time quantitative PCR and in situ hybridization were used to detect the m RNA expression and location of ATF6 at 4 h,12 h,3 d and 7 d after SCI.Co-localization staining of ATF6 m RNA by ISH and motoneurons labeled with Islet-1 or radial glia cells labeled with GFAP by immunofluorescent staining was detected at 4 h,12 h,3 d and 7 d after SCI.Morpholino(MO)was used to knock down ATF6 expression in vivo after SCI to analysis the ability of locomotor recovery and axon regrowth in zebrafish.Further,real-time quantitative PCR was used to detect the m RNA expression of endoplasmic reticulum stress factor iconic immune heavy chain binding protein(binding immunoglobulin protein,BIP)BIP and C/EBP homologous protein(C/EBP homologus protein,CHOP)after SCI to explore the endoplasmic reticulum stress.Results:1.Compared with sham group(basal level),ATF6 m RNA level was increased at 12 h and 3 d and return to basal level at 7 d after SCI.2.ATF6 expression was increased significantly in the motoneurons surrounding the central canal at 12 h and 3 d after SCI when compared to the sham group.3.ATF6 expressed around the radial glia cells and there was no co-expression of ATF6 and astrocytes at the spinal cord in sham and SCI groups.4.The total swimming distance of zebrafish treated with ATF3 MO was reduced by52% at 2 W after SCI and 63% at 3 W after SCI,when compared to that of zebrafish treated with control MO respectively.5.Retrograde axon tracing showed that reduction of ATF6 protein expression impaired axon regrowth beyond the injury site at 6 w after SCI.6.The BIP m RNA expression was increased by two fold of sham group at 7 d after SCI.7.The CHOP m RNA expression was significantly increased by two fold of sham group at 4 h after SCI,and decreased by 38% of the control group at 7 d after SCI.Conclusion:ATF6 contributes to locomotor recovery and axon regrowth in zebrafish after SCI,possibly by activation of ATF6 promoting expression of survival molecule BIP and inhibiting the expression of CHOP to protect motor neurons homeostasis.