ROIG-LOPEZ, J.L.*; SANTIAGO, P.; NIEVES, L.; JIMENEZ, B.; GARCIA-ARRARAS, J.E.: Differential expression of actin isoforms during intestinal regeneration in the sea cucumber Holothuria glaberrima.

The regeneration capability of echinoderms is well known, however, few studies have focused on the cellular and molecular events underlying this phenomenon. We are using the sea cucumber Holothuria glaberrima as a model system to elucidate the molecular aspects of regeneration. Differential display analysis between normal and regenerated tissues produced a series of bands preferentially expressed in the regenerated tissue. These bands were used as probes to screen a regenerated tissue cDNA expression library, from which two actin cDNA clones, HgAct1 (2.0 Kb) and HgAct2 (2.2 Kb), were obtained. A possible third actin isoform HgAct3 (280 Bp) was cloned by PCR using rat actin primers. Two lines of evidence suggest that HgAct1 and HgAct2 are different isoforms: partial sequence analysis, including the 3′ UTR, show no significant similarities between them and northern blots with one probe show multiple bands with differential expression patterns at various regeneration stages. A prominent signal of approximately 2.5 Kb shows an up-regulation during early intestinal regeneration when compared to late regenerate and normal tissues. The expression of actin isoforms is known to be developmentally regulated during embryogenesis in vertebrate and invertebrate deuterostomes, but few studies have addressed their regulation during regeneration. The regulated expression of these actin isoforms can be associated with important events in the regeneration process, such as, cell differentiation and migration. Supported by: NSF-EPSCoR (OSR-9452893); NIH-MBRS (RR-8102-18); NIH-RCMI (RR03641-02); and the University of Puerto Rico.