| dc.description.abstract | Tissue regeneration has intrigued biologists since the eighteenth century. While
regeneration has been studied in many species, the cellular and molecular mechanisms
governing successful compensation for lost body parts are poorly defined.
This dissertation examines the cellular and molecular correlates of a form of
regeneration defined as morphallaxis. Morphallaxis does not involve cell proliferation,
but instead relies on the reorganization of existing tissues to recover body structure and
function. Morphallaxis is a mechanism used during segmental regeneration (i.e., head or
tail replacement) by the aquatic oligochaete, Lumbriculus variegatus. Here,
morphallaxis of the nervous system is documented during segmental regeneration of
Lumbriculus and during asexual reproduction. The morphallactic processes, which
underlie changes in the neural anatomy and physiology of these worms, are reminiscent
of mechanisms utilized by other neural plasticity events, including learning and memory.
Proteomic and biochemical studies focus on a molecular marker of neural morphallaxis.
The expression patterns of morphallaxis-associated-protein 66, MP66, are differentially
regulated during both regeneration and asexual reproduction. This expression patterncorrelates with time-points of major cellular changes associated with neural
morphallaxis. Thus, cellular and molecular events, demonstrated as part of neural
morphallaxis in Lumbriculus, are recruited in two life-history contexts. Chemical
disruption experiments, where either segmental regeneration or asexual fission are
blocked, reveal that morphallaxis can be mechanistically dissociated from regeneration
and reproduction. These results set a foundation for future investigations of specific
mechanisms that mediate this novel form of neural plasticity. | en |
