Back-to-back pathways

A Chinese research team has determined that a biochemical signaling pathway involving c-Jun N-terminal kinase (JNK) plays a significant role in establishing which side of the developing embryo will form the back.

After nearly 10 years of work on the JNK pathway, the team has found that when JNK is activated by the protein Axin, it can trigger a significant stage in embryological development known as dorsalization — part of the process of establishing the dorsal–ventral axis. This action is independent of the operation of the canonical Wnt signaling pathway where Axin inhibits the action of a key protein of dorsalization, β-catenin. These two opposing roles of Axin allow fine-tuning of dorsalization.

Axin acts as a platform or scaffold on which biochemical reactions take place, and in this way plays integral roles in initiating dorsalization. In a recent paper in Developmental Cell¹, the researchers detail how they also have discovered a gene product they named Aida which disrupts Axin activity by preventing Axin molecules from self-combining. Aida can thus act as a regulator by antagonizing Axin-JNK-mediated dorsalization. The next step says project-leader Sheng-Cai Lin of Xiamen University, is to find out what signals activate or inhibit Aida.