Effects of bromo-cyclic GMP and bromo-cyclic AMP on embryonic developmentof Xenopus laevis

摘要

Low molecular signalling molecules such as cAMP and cGMP are expected to have important functions in early morphogenetic processes in animal development. We examined the effect of 8-bromocyclic GMP (Br-cGMP) on Xenopus embryogenesis, using 8-bromo-cyclic AMP (Br-cAMP) as a reference. When Xenopus gastrulae were cultured in the medium which contained these analogues, their development was affected in specific and dosage-dependent manners: While Br-cAMP induced anomaly only in head part (swelling of myelencephalon with enlarged ventricle), Br-cGMP induced shortening in body length often accompanied by bending of the cephalo-caudal axis. In embryos treated with Br-cGMP at a high dose, cellular movement was inhibited as revealed by SEM and this resulted in the formation of tadpoles with unclosed yolk plug. Br-cGMP at lower doses induced severe inhibition of the development of notochord and muscles. Since HPLC analyses revealed that both analogues were uptaken into embryonic cells, we assumed that the morphological effects observed were induced by the interference of the normal functioning of cGMP and cAMP, respectively, by Br-cGMP and Br-cAMP. Based on the results obtained, we assume that while cGMP is involved mainly in the differentiation of mesodermal structures, especially in formation of notochord and muscles, cAMP is involved mainly in the differentiation of neural structures.