The Gecko Cd59 Is Implicated In Proximodistal Identity During The Tail Regeneration

Blastemal cells of amphibians limb obtain instructions to precisely re-create the missing structures after amputation by acquiring positional information regulated by cell surface molecule Prod1, an analogue of CD59. When the hand of an axolotl (or newt) is cut off then the hand regenerates beginning at the level of the carpals, but when the whole arm is cut off then a new arm regenerates beginning from the level of the humerus. The same is true at any intermediate level.Reptiles such as adult Gekko japonicus have the same ability to regenerate its tail after amputation precisely. A full length cDNA encoding gecko CD59 protein was isolated from a brain and spinal cord cDNA library . Gecko CD59 transcripts displayed a graded expression in an adult gecko spinal cord with the highest level in the anterior segment, while kept a stable expression along the normal tail. After tail amputation, CD59 transcripts in the spinal cord proximal to the injury sites increased markedly at 1 day, and decreased at 3 days until 1 week. The significant increase of CD59 mRNA was seen again at 2 weeks. In situ hybridization of blastemas demonstrated that strong positive signals were detectable at the end of original medulla spinalis, and mild staining in the blastemal cells at 1 week after amputation. While at 20 days, CD59 transcript was strongly detected along the boundary of amputation, and gradually decreased along the PD axis of the blastema. When treated with RA after amputation, CD59 transcript post amputation was found to be upregulated in the blastema. PD confrontation assays revealed that the proximal blastema engulfed the distal one after in vitro culture, and CD59 antibody was able to block this PD engulfment[6]. Our results suggested that gecko CD59 is implicated in proximodistal identity during the tail regeneration.