The origin of bilateral animals has been debated for more than a hundred years. At the centre of this discussion has been the understanding of mechanisms that would lead the transition from radial to bilateral animals. 
At the core of most proposals there is a different inferred ancestral bilaterian, either a morphologically simple or a complex animal. During many years, the prevalent view has been that basal bilaterian groups didn’t exist and s complex organism was the better representation of the bilaterian ancestor. But in 1999 Ruiz-Trillo and collaborators suggested the possibility that an ancient group of bilaterians exists with us: the acoel flatworms. This position has been challenged recently by a phylogenomic stud¥ that suggests that acoels are, perhaps, a group of deuterostomes.
In order to understand both the phylogenetic position of these animals and the mechanisms that control their development (plus the relationship between genome structure and development) we have characterized the genes and genomes of two acoels, Symsagittifera roscoffensis and Isodiametra pulchra. From the control of their axis formation to the specification of the tissues, these problems have been dealt with using diverse techniques, from morphology to immunochemistry, molecular biology and genomics.
Staff
Dr. Pere Martínez
Dr. Jaume Baguñà
Dr. Pere Martínez
Postdocs
Johannes Achatz
PhD students
Alexander Alsén
Marta Chiodin
Elena Perea
Collaborators
Dr. Andreas Hejnol (SARS Center, Bergen, Noruega)
Dr. Albert Poustka (Max-Planck Institute of Molecular Genetics, Berlin, Alemanya)
Dr. Volker Hartenstein (Biology, UCLA, EUA)
Dr. Andreas Wanninger (Biology, University of Vienna)
2) Splox, a ParaHox gene involved in sea urchin gut regionalization
Over the last few years we have isolated and characterized a new homeobox gene from the sea urchin Srongylocentrotus purpuratus. This gene is an orthologue of the Xenopus XlHbox8 and mouse IPF-1 ParaHox genes. We have called it Splox. It is expressed during embryogenesis reaching its maximum level at 48 h (late gastrula). At the mesenchyme blastula stage, Splox is expressed in the vegetal plate. No message is detected in the skeletogenic mesenchyme. Later, during gastrulation, the transcript is preferentially localized in both ends of the archenteron (mainly around the blastopore and in the foregut region). The archenteron expression has clearly an oral bias. Knockout experiments have shown that in the absence of Splox, the foregut is not regionalized properly. The gene network involved in the specification of the different gut regions is under study.
Staff
Dr. Pere Martínez
Collaborator
Dr. Maria Ina Arnone (Stazione Zoologica, Nàpols, Itàlia)
3) Molecular basis of echinoderm arm, and CNS, regeneration
It has been shown in the few well-described cases of regeneration (some amphibians and flatworms) that those genes involved in the patterning of the major embryonic axes (mainly members of different classes of homeobox genes) are reused to pattern the regenerating structures.
In order to understand the role of homeobox-containing genes during regenerative processes in echinoderms we have isolated a complement of genes belonging to the Hox class that are expressed during this process in two major echinoderm groups: asteroids (Asterias rubens or Coscinasterias muricata) and ophiouroids (Amphiura filiformis), both well known for their extraordinary capacity for regeneration.
By exploiting the sequence conservation of the homeobox, putative orthologues of several Hox genes belonging to the anterior, medial and posterior groups have been isolated.
Recently in situ hybridization experiments have been started at KMF, Sweden.
A large collection of ESTs (approx. 500000 sequences from Coscinasterias muricata) have been sequenced and are currently being analyzed in detail, with the objective of characterizing the transcriptome in regenerative cells plus the identification of regulatory genes that will allow us to understand the mechanisms that control such an important biological process.
Staff
Dr. Pere Martínez
Collaborators
Prof. Michael Thorndyke (Kristineberg Marine Station, Royal Swedish Academy, Sweden)
Dr. Helen Nisson (Kristineberg Marine Station, Royal Swedish Academy, Sweden)
Dr. Josep Abril (Departament de Genètica, UB)
