51.5 Thursday, Jan. 5 A modern view of annelid “neoblasts”: live 4D imaging reveals widespread cell migration during annelid regeneration ZATTARA, E.E.*; BELY, A.E.; University of Maryland, College Park; University of Maryland, College Park firstname.lastname@example.org
The ability of some cell types to retain wide differentiation potential beyond embryogenesis is a crucial element of adult regenerative biology. One of the most well-known examples of totipotent adult stem cells are cells referred to as neoblasts, migratory cells with a large nucleus/cytoplasm ratios that have been described in both annelid and planarian regeneration. In annelids, neoblasts are thought to migrate along the ventral nerve cord to the wound site and proliferate to form a significant fraction of the regenerated tissues. This model has been widely accepted despite the fact that actual evidence for neoblast migration is only indirect, there has been an evident bias towards the study of large and histologically conspicuous cells, and there are no hard data on neoblast function or fate. While the neoblast model of regeneration has been well supported in planarians, the role of neoblasts in annelid regeneration is still unclear. We developed a novel 4D live imaging technique to obtain high-resolution time-lapse recordings of naidid annelids over many days, allowing us to capture the complete regeneration process. Using this technique, we have obtained the first direct evidence of cell migration towards wound sites, and characterized migration speeds, migration routes, and migrating cell types during regeneration. We find that the cell migration response to injury is much more widespread than what the current neoblast model suggests, involving diverse cell types and diverse migration routes. This study lays the groundwork for planned cell tracing and gene expression studies intended to test the role of neoblasts and other migratory cells in annelid regeneration.