Characterization of Morphological and Cellular Events Underlying Oral Regeneration in the Sea Anemone, Nematostella vectensis

Abstract

Cnidarians, the extant sister group to bilateria, are well known for their impressive regenerative capacity. The sea anemone Nematostella vectensis is a well-established system for the study of development and evolution that is receiving increased attention for its regenerative capacity. Nematostella is able to regrow missing body parts within five to six days after its bisection, yet studies describing the morphological, cellular, and molecular events underlying this process are sparse and very heterogeneous in their experimental approaches. In this study, we lay down the basic framework to study oral regeneration in Nematostella vectensis. Using various imaging and staining techniques we characterize in detail the morphological, cellular, and global molecular events that define specific landmarks of this process. Furthermore, we describe in vivo assays to evaluate wound healing success and the initiation of pharynx reformation. Using our described landmarks for regeneration and in vivo assays, we analyze the effects of perturbing either transcription or cellular proliferation on the regenerative process. Interestingly, neither one of these experimental perturbations has major effects on wound closure, although they slightly delay or partially block it. We further show that while the inhibition of transcription blocks regeneration in a very early step, inhibiting cellular proliferation only affects later events such as pharynx reformation and tentacle elongation.

A transcriptional time-course analysis of oral vs. aboral whole-body regeneration in the Sea anemone Nematostella vectensis

“…It was also evident that the 24 and 72 h expression profiles are more similar to each other than they are to 8 h (Fig. 2b), which is in line with previous studies defining the first 6–8 h as a distinct wound-healing stage [53, 57]. The similarity in the overall expression patterns of the two regions of regeneration, at each individual time point, suggests that a large part of the regeneration response is of a general nature which may govern general wound healing and tissue growth at large, and that side-specific differential expression patterns may be more limited.…”

“…1b). At 24 h we observed that the mesenteries seemed to be attached to the center of the cut area in both the oral and aboral fragments as reported before for oral regeneration [53, 57]. At 72 h tentacle buds can begin to be detected in the regenerating oral side, and in the regenerating physa the mesenteries appeared disconnected from the previously wounded area and the physal end is more rounded and clear.…”

A bipolar role of the transcription factor ERG for cnidarian germ layer formation and apical domain patterning

“…However, the expression of the classical mesodermal marker brachyury [82] in the central ring, as well as the activation of a MEK/ERK/ERG pathway (required for mesoderm formation in bilaterians [83]) in the central domain, provide additional compelling evidence that both domains together form sub-regionalized territories of the cnidarian endomesoderm. Tissue tracking experiments using photo-convertible fluorescent proteins [84] are required to determine the fate of the central domain and ring. It might also be important to carry out a precise physiological analysis of the differentiated tissues that originated from the endomesodermal territory, to gain more insight in the evolutionary origin of mesoderm in bilaterians.…”

Trends in tissue repair and regeneration

“…The sea anemone Nematostella is emerging as a novel model of body regeneration (Amiel et al, 2015). Aldine Amiel (Röttinger laboratory, IRCAN, Nice, France) showed that tissue crosstalk between the mesenteries and the surrounding epithelia is required to induce a stem cell-based regenerative response, offering a new system to study cellular cooperation in tissue reprogramming.…”