Change in the Gastro-Intestinal Tract by Overexpressed Activin Beta A.

Originally, activins were identified as stimulators of FSH release in reproduction. Other activities, including secondary axis formation in development, have since been revealed. Here, we investigated the influence of activin ßA on the body, including the gastro-intestinal (GI) tract. Initially, the activin ßA protein was detected in the serum proportional to the amount of pCMV-rAct plasmid injected. The induced level of activin ßA in muscle was higher in female than male mice. Subsequent results revealed that stomach and intestine were severely damaged in pCMV-rAct-injected mice. At the cellular level, loss of parietal cells was observed, resulting in increased pH within the stomach. This phenomenon was more severe in male than female mice. Consistent with damage of the stomach and intestine, activin ßA often led to necrosis in the tip of the tail or foot, and loss of body weight was observed in pCMV-rAct-injected male but not female mice. Finally, in pCMV-rAct-injected mice, circulating activin ßA led to death at supraphysiological doses, and this was dependent on the strain of mice used. Taken together, these results indicate that activin ßA has an important role outside of reproduction and development, specifically in digestion. These data also indicate that activin ßA must be controlled within a narrow range because of latent lethal activity. In addition, our approach can be used effectively for functional analysis of secreted proteins.

Changes in the reproductive function and developmental phenotypes in mice following intramuscular injection of an activin betaA-expressing plasmid.

BACKGROUND: The TGF-beta family protein activin has numerous reported activities with some uncertainty in the reproductive axis and development. The precise roles of activin in in vivo system were investigated using a transient gain of function model. METHODS: To this end, an expression plasmid, pCMV-rAct, with the activin betaA cDNA fused to the cytomegalovirus promoter, was introduced into muscle of the female adult mice by direct injection. RESULTS: Activin betaA mRNA was detected in the muscle by RT-PCR and subsequent Southern blot analysis. Activin betaA was also detected, and western blot analysis revealed a relatively high level of serum activin with correspondingly increased FSH. In the pCMV-rAct-injected female mice, estrus stage within the estrous cycle was extended. Moreover, increased numbers of corpora lutea and a thickened granulosa cell layer with a small antrum in tertiary follicles within the ovary were observed. When injected female mice were mated with males of proven fertility, a subset of embryos died in utero, and most of those that survived exhibited increased body weight. CONCLUSION: Taken together, our data reveal that activin betaA can directly influence the estrous cycle, an integral part of the reproduction in female mice and activin betaA can also influence the embryo development as an endocrine fashion.