Expression of a novel somite-formation-related gene, AmphiSom, during amphioxus development.

A novel gene, AmphiSom, was identified in amphioxus Branchiostoma belcheri tsingtauense. Its sequence and developmental expression pattern were determined. AmphiSom transcripts were first detected in the presomitic mesoderm at the late gastrula stage and reached the highest level in the forming and nascent somites in neurulae. However, the expression of AmphiSom was rapidly down-regulated after somites were formed. It was maintained in the most anterior somite and most posterior somite at neurula stages. By 48 h, AmphiSom transcripts were detected only in the developing tail bud but were no longer detected in 72-h larva. Our data demonstrated that the AmphiSom gene is expressed during the development of somites in amphioxus and could play a role in somite formation.