Regeneration: By Stefano Tiozzo, Ulrich Kuern and Michelle Roux
"There are colonies of pelagic tunicates which have taken shape like the finger of a glove. Each member of the colony is an individual animal, but the colony is another individual animal, not at all like the sum of its individuals... So a man of individualistic reason, if he must ask, 'Which is the animal, the colony or the individual?' must abandon his particular kind of reason and say, 'Why, it's two animals and they aren't alike in any more than the cells of my body are like me. I am much more than the sum of my cells, and, for all I know, they are much more than the division of me.'"
Steinbeck, The log from the Sea of Cortez
This is how John Steinbeck described colonies of ascidians such as Botryllus schlosseri, an enigmatic and bizarre member of the tunicates. Tunicates are sessile marine invertebrates that despite appearances, belongs to our own phylum: Chordata. Botryllus’ life cycle starts with a tadpole-like animal that possesses a rod of tissue called a notochord, the evolutionary precursor to the backbone. This tadpole swims in search of a suitable substrate (rock, seaweed, shell or the bottom of a boat in the marina) to settle and transform itself into a sessile polyp-like adult. The adult reproduces asexually by generating 1-3 genetically identical clones called buds. Once mature, the newly formed buds replace their parents: the old adults perish and shrink back to oblivion in an event called take over. This amazing regeneration happens weekly in a highly coordinate symphony of proliferation and death. Thus Botryllus uses two independent developmental pathways to create an identical adult body plan: one sexually, through fertilization and embryogenesis and the other via asexual budding.
We think that studying an organism that can rebuild its entire body on a weekly basis can not only help us to understand the molecular mechanics of tissue regeneration in chordates -and eventually in human- but will also provide insights into the evolution of development. Working with Dr. Tony De Tomaso we are identifying genes that are responsible for driving this unique regenerative plasticity. We are interested in how the same sets of genes are used in building/rebuilding identical structures using two very different means of development. Another exciting aspect of Botryllus research involves the search for primitive stem cells, which expand and differentiate throughout the life of a single colony. These stem cells contribute to both regeneration in the adult and the genetic make up of its offspring.
This is how John Steinbeck described colonies of ascidians such as Botryllus schlosseri, an enigmatic and bizarre member of the tunicates. Tunicates are sessile marine invertebrates that despite appearances, belongs to our own phylum: Chordata. Botryllus’ life cycle starts with a tadpole-like animal that possesses a rod of tissue called a notochord, the evolutionary precursor to the backbone. This tadpole swims in search of a suitable substrate (rock, seaweed, shell or the bottom of a boat in the marina) to settle and transform itself into a sessile polyp-like adult. The adult reproduces asexually by generating 1-3 genetically identical clones called buds. Once mature, the newly formed buds replace their parents: the old adults perish and shrink back to oblivion in an event called take over. This amazing regeneration happens weekly in a highly coordinate symphony of proliferation and death. Thus Botryllus uses two independent developmental pathways to create an identical adult body plan: one sexually, through fertilization and embryogenesis and the other via asexual budding.
We think that studying an organism that can rebuild its entire body on a weekly basis can not only help us to understand the molecular mechanics of tissue regeneration in chordates -and eventually in human- but will also provide insights into the evolution of development. Working with Dr. Tony De Tomaso we are identifying genes that are responsible for driving this unique regenerative plasticity. We are interested in how the same sets of genes are used in building/rebuilding identical structures using two very different means of development. Another exciting aspect of Botryllus research involves the search for primitive stem cells, which expand and differentiate throughout the life of a single colony. These stem cells contribute to both regeneration in the adult and the genetic make up of its offspring.