Cloning, Identification And Characterization of Two MyD88s during Anterior Regeneration in Aeolosoma viride

Abstract

A 2 mm long freshwater annelid, belonging to Aeolosomatidae, with an exceptional regenerative ability, called Aeolosoma viride, serves as an excellent model for regenerative research. Additional reasons are its small size and semi‐transparent color, which allow manageable culture and experimentation. A. viride can regenerate its amputated head with a functional brain within 5 days. The regeneration process includes several steps, starting with wound repair followed by blastema formation and tissue remodeling. In addition, the immune system and inflammatory responses associated with injury to prevent deadly infections have been implicated as critical modulators during wound healing and regeneration. The aim of our study is to unravel the involvement of immune responses in A. viride regeneration. The Toll‐like receptor (TLR) signaling pathway is one of many pathogen recognition mechanisms, which initiates by ligand binding to the receptors and then recruits myeloid differentiation factor 88 (MyD88) to serve as an adaptor molecule to activate the transcription factor NF‐κB. Two MyD88 sequences have been cloned from A. viride. Based on blasting results, one of the sequences has two regular functional domains of MyD88, namely Toll/IL‐1R (TIR) domain and death domain. However, the other one lacks the TIR domain, responsible for TLR binding. Furthermore, we identified and analyzed their gene expressions during the regenerative process. Real‐time PCR results of blastemal tissue showed different expression patterns of these two genes. One is down‐regulated during blastema formation, while the other is up‐regulated during wound healing. Therefore, we propose the two MyD88s may play different roles during regeneration in A. viride. Avi‐MyD88a and Avi‐MyD88i may activate or inactive the TLR pathway.