1) A proteomic and genomic study of the neoblasts, the totipotent planarian stem cells

The neoblasts are the only undifferentiated cell type and the only one with proliferative capacity present in the adult Platyhelminth. This cell behaviour is unique for the animal kingdom and is responsible for the high morphological plasticity in these organisms. The characterization of proteins and genes specific for the neoblasts will allow us to study molecules related to the maintenance of the undifferentiated stage, molecules related to the proliferation capacity and proteins responsible for the determination of the neoblasts into the different cell types present in the adult planarian. Earlier results on differential proteomics between organisms irradiated with X-rays and non-irradiated control organisms, together with other genomic results, have permitted us to detect the first differential gene products. We found for instance a protein with the PAZ-domain typical for the piwi genes responsible for the maintenance of the stem cells and a protein associated to the centromere like e.g. PUMA. We propose then to continue the characterization of new proteins by proteomic strategies together with genomic strategies, verifying their function by RNA interference or gain-of-function phenotypes.

Figure 1. Protein analysis in a bi-dimensional gel, SDS/PAGE.
The protein spots specific for the protein extraction
from non-irradiated planarians are marked in red.

Staff
Dr. Emili Saló


Postdocs
Dr. Pep Abril
Dr. Teresa Adell


Predocs
Mette Handberg-Thorsager
Kike Fernandez-Taboada


Technician
Dr. Roger Florensa


Collaborators
Prof. Juan-Carlos Izpisua-Belmonte & Dr. Ángel Raya (Salk Institute, California, USA;  Scientific director of “Instituto de Medicina Regenerativa”, Barcelona)




2) Functional characterization of genes responsible for the reconstitution of the pattern during the planarian regeneration

The great morphologic plasticity of the flatworms is accompanied by an infinite capacity to reconstitute the pattern from any small fragment of the organism. Previous studies made in our laboratory in the last 30 years, together with the recently obtained about apoptosis and the wnt signaling pathway, have been essential for the present knowledge about the cellular proliferation and migration behaviors. However, we still don't know some of the essential elements of these processes, as well as its regulation as a whole. In this objective, we propose the functional characterization of the wnt and BMP2-4 signaling pathways, from which some elements are already known in planarians, and also the characterization of new pathways, like the FGF or Insulin; we propose to study these processes from the point of view of the cellular competition.

Figure 2. Different stages of Schmidthea mediterranea head regeneration. The last one shows a complete regenerated head after two weeks at 17ºC

The approaching of this project requires the following steps:

 • Characterization of signaling pathways during pattern formation.

The great morphological plasticity of the Platyhelmintes permits them to regenerate the eyes in the short period of 5 days.  To the present time we have characterized the majority of genes of the eye network for the initial development of the eyes.  We do not know still some of the elements, as well as the interactions among all these genes.  Taking advantage of the accessibility of the complete genome of the species Schmidtea mediterranea, we propose to study the key genes of this process that have not yet been isolated.  At the same time, we will try to define the type of interactions that exist among these genes by means of the use of transgenesis, RNAi and microarrays.

Figure 3. Inhibition of eye regeneration by Gtsix-1 RNAi. Three weeks head regenerating planarians viewed dorsally. A) Bright field image shows the differentiated eyes in the regenerated head of a control organism. B) Bright field image shows the absence of eye differentiation in dsRNA Gtsix-1 injected at postblastema level after 3 weeks of regeneration. a, auricle; e, eye spot; pg, preiglobular unpigmented area. (bars, 0.4 mm)

The approach of this project requires the following steps:

 • Characterization of regulatory genes of the initial eye development in the species Schmidtea mediterranea.

 • Study of functions and interactions of these genes during the eye regeneration.