The formation of the dorsal-ventral (DV) axis is one of the most important events during the early development of bilaterian animals. It is widely accepted that a conserved molecular logic (BMP2/4 and Chordin) regulates tissue differentiation along the DV axis. Such DV patterning mechanism has been revealed in a wide range of bilaterian animals.

However, the DV patterning mechanism exhibits a considerable degree of variations in Spiralia, one of the three major clades of bilaterians. This unexpected diversity in the mechanism of a fundamental developmental event causes hot debates in the research field and is considered to be of great significance for understanding animal evolution.

A research team lead by Prof. Baozhong Liu of the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), has focused on the mechanisms underlying molluscan DV patterning.

Recently, the team revealed the roles of bmp2/4 and chordin in the DV patterning of the equal cleaving gastropod mollusk Lottia goshimai. The study was published in Molecular Biology and Evolution, which is the first report that the conserved DV patterning mechanism relying on BMP2/4-Chordin exists in Spiralia.

Based on thorough functional experiments, the study revealed that the conserved molecular logic BMP2/4-Chordin has been deeply integrated into the organizer function in spiralian development, which then mediates the DV patterning process.

Moreover, the study provides evidence that the DV patterning is likely connected to essential developmental events such as the blastoporal behavior and organization of the nervous system. These results provide insights into the unique developmental mode and the evolution of spiralians.

This work was supported by the National Key R&D Program of China, the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology (Qingdao), the China Agriculture Research System, the National Natural Science Foundation of China, the Youth Innovation Promotion Association CAS, etc.

Early expression patterns of bmp2/4 and gene knockdown phenotypes of L. goshimai with impaired DV patterning

Sujian Tan#, Pin Huan#, Baozhong Liu*. Molluscan dorsal-ventral patterning relying on BMP2/4 and Chordin provides insights into spiralian development and evolution. Molecular Biology and Evolution, 2021, DOI: 10.1093/molbev/msab322. https://academic.oup.com/mbe/advance-article-abstract/doi/10.1093/molbev/msab322/6424002

(Editor: ZHANG Yiyi)