Mechanisms for Coelom formation : Binary dicision of the lateral plate mesoderm

2003 Fiscal Year Final Research Report Summary

• Project/Area Number: 14570027
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: General anatomy (including Histology/Embryology)
• Research Institution: RIKEN (The Institute of Physical and Chemical Research)
• Principal Investigator: FUNAYAMA Noriko RIKEN (The Institute of Physical and Chemical Research), Group for Evolutionary Regeneration Biology, Researcher, 進化再生研究グループ, 研究員 (30276175)
• Project Period (FY): 2002 – 2003
• Keywords: Lateral plate mesoderm / Somatopleural mesoderm / Splanchnopleural mesoderm / Epithelialization / SHH / Chick embryo / Cyclopamin

Research Abstract

Most triploblastic animals including vertebrates have a coelomic cavity that separates the outer and inner components of the body. The coelom is lined by two different tissue components, somatopleure and splanchnopleure, which are derived from the lateral plate region. Thus, the coelom is constructed as a result of a binary decision during early specification of the lateral plate. In this report we studied the molecular mechanisms of this binary decision. We first demonstrate that the splitting of the lateral plate into the two cell sheets progresses in an anteroposterior order and this progression is not coordinated with that of the somitic segmentation. By a series of embryological manipulations we found that the ectoderm underneath the primitive lateral plate is also required for the Splanchnopleural mesoderm. From the barrier experiment, it was suggested that this inductive activity is depend on the secreting factor(s) from lateral plate endoderm. We also show that the inductive activity is mediated by SHH molecules that are localized in the lateral endoderm. Evolutionary aspects of the coelom formation are also considered.