Kristineberg Marine Genomics

People involved:

Carl Dahlberg
Michael Thorndyke
Karen Wilson

Neuronal Regeneration

Amphiura (photo by Mattias Sköld)

Ciona intestinalis (courtesy of DOE Genome project)

Regenerating arm (Photo by Carl Dahlberg)

Ciona Ciliated Funnel (Confocal image Carl Dahlberg)

Many marine organisms have a remarkable ability to regenerate tissue even in their adult life phases. The echinoderms, of which the brittle star Amphiura filiformis is one of our model organisms, have the ability to regenerate full arms.

Our task is to investigate this phenomenon from the molecular side. We are looking at the different cells involved and analysing which of these give rise to the new tissue. What characteristics do these cells have? Are they pluripotent stem cells waiting to be activated or are they functional cells, which return to a more versatile state? We investigate growth factors regulating the outgrowth of the nerve. Are these factors that are important for other processes such as development, wound healing, nerve homeostasis or factors dedicated solely to this purpose?

The Animals

The brittle star Amphiura filiformis is a small, suspension feeding, reddish, creature with snakelike arms protruding from the central disc. They are spread out in the soft bottoms all over our oceans. If you go out to the Gullmar fjord and send down a probe to plug some mud you can get up to 1000 individuals/m2. This means that they are quite an important part of the biomass in our oceans and an important player in ecosystems.
The seasquirt (Ciona intestinalis) is a filter feeding chordate, which attaches to rock faces, ropes and other vertical objects in the water. It has a well developed pharynx, which filters large volumes of seawater. The urochordates of which Ciona is one are close relatives to the vertebrates. Ciona is quite similar to vertebrates during its early life stages, but when it settles the notochord and the neural tube regress and a simple neural complex 1x1 mm2 is formed. The fascinating thing is that the seasquirt can manage without this neural complex and even regenerates it if it is excised.

The Experiments

We isolate mRNA and do PCR with degenerate primers looking for genes important for neuronal development. In the case of Ciona, we utilise the recently sequenced genome to look for interesting genes with bioinformatics. Once we have our candidate genes we will look at expression patterns at different stages of regeneration.

Then we try to address what over expression of certain genes will do to the process and what inhibition of the same factors will cause. Techniques used will be transfection of regenerating tissue and RNAi (interference RNA).