ABSTRACT
The sea cucumber Holothuria glaberrima has the capacity to regenerate its internal organs, including the digestive tract with its enteric nervous systems (ENS). Tubulin, the main constituent of microtubules, has been used extensively as a marker to study regeneration in many organisms. We have identified a 2.1 kb -tubulin clone (Hgtub) from a regenerating intestine library of H. glaberrima. Northern blots of intestinal tissue done with a probe from the conserved coding region identified five bands, suggesting the presence of different -tubulin isoforms. Moreover, when an Hgtub 3UTR probe was used, a single band was obtained. This band up-regulates during late regenerative stages, concomitant with ENS regeneration. In fact, immunohistochemical studies using - and -tubulin antibodies and other ENS markers demonstrated: (1) an increase in nerve fiber density throughout the intestinal serosa and muscle layers as regeneration advances and (2) the existence of at least two populations of fibers, an extrinsic population that enters the regenerating intestine from the mesentery and that probably originates within the mesentery or body wall and an intrinsic population that appears to originate from neurons within the serosa that distributes homogeneously along the regenerating tissue. These results should provide a clear understanding on the regeneration of the digestive tract and in particular of its associated ENS. Funded by NSF/AGEP, NSF, MBRS, RCMI and the UPR.
