[Molecular characterization of variable tandem repeat sequence determined during RAPD analysis among Posidonia oceanica insular and coastline populations]

The seagrass Posidonia oceanica plays a multifunctional role in the coastal area as an important and productive component of ecosystems in the Mediterranean Sea. We detected by RAPD analysis with two arbitrary primers genetic differences in P. oceanica collected from several sites in the Southern Mediterranean. By AMOVA analysis we observed a level of about 20% genetic difference among individuals within a population and 80% among populations. A common band of 200 bp was found in all the amplified samples. Cloning and sequencing analysis of this band revealed the presence of a simple tandem repeat sequence (minisatellite) that we called PoTR (Posidonia oceanica tandem repeat). Finally, the ability of PoTR to detect genetic variability in P. oceanica genome was demonstrated by the presence of amplification products of different lengths utilizing primers internal to this sequence.

Identification of an antigen related to the sea urchin RNA-binding protein LP54 in mammalian central nervous system

LP54 is an RNA-binding protein involved in localization of maternal messengers in sea urchin egg and embryos. Using a polyclonal antibody directed against Paracentrotus lividus LP54 we detected a 66-kDa cross-reacting antigen in undifferentiated and differentiated SH-SY5Y human neuroblastoma cells. After treatment of undifferentiated cells with detergent, the 66-kDa antigen was found to be enriched in the cytoskeletal fraction. By Western blot the expression of this antigen was also analyzed in regions of the CNS and in tissues of the adult rat and its exclusive presence in the hippocampus and thalamus was revealed. The immunoreactivity with P. lividus antibody against LP54 in hippocampal lysate was also confirmed throughout anti-LP54 immunoaffinity column and competition experiments. The results indicates that a related protein to the sea urchin LP54 is evolutionary conserved in mammalian CNS.

Bep4 Protein Is Involved in Patterning along the Animal–Vegetal Axis in the Paracentrotus lividus Embryo

In sea urchin embryos, the initial animal-vegetal (AV) axis is specified during oogenesis but the mechanism is largely unknown. By using chemical reagents such as lithium, it is possible to shift the principal embryonic territories toward a vegetal fate. We have investigated the possibility of obtaining the same morphological effect as with lithium by utilizing Fabs against the maternal Bep4 protein that is localized in the animal part of Paracentrotus lividus egg and embryos. Incubation of fertilized eggs with Fabs against Bep4 protein causes exogastrulation at 48 h of development of P. lividus embryos, similar to embryos treated with lithium. This vegetalizing effect was ascertained by utilizing territorial markers such as EctoV, EndoI, and Ig8. The effect of Fabs against Bep4 on gene expression was observed by monitoring spatial expression of the hatching enzyme gene. A decreased expression domain compared to its normal spatial distribution was detected and this effect was again comparable to those obtained with lithium treatment. Association of Bep4 with a cadherin was demonstrated by immunoprecipitation and immunostaining experiments, and an involvement in cell signaling is discussed. In addition, treatment of embryos with anti-Bep4 Fabs causes an enhancement in the level and an expansion in the pattern of nuclear beta-catenin. Moreover, this treatment also provokes a decrease of beta-catenin in adherens junctions. Together, these data indicate that anti-Bep4 Fabs provoke a shift of the animal-vegetal boundary toward the animal pole and suggest an active role of Bep4 protein in patterning along the AV axis.

Localization and association to cytoskeleton of COLL1alpha mRNA in Paracentrotus lividus egg requires cis- and trans-acting factors

COLL1alpha mRNA is asymmetrically distributed in the Paracentrotus lividus egg. Here we examine the involvement of the cytoskeleton in the localization process of collagen mRNA. The use of drugs such as colchicine and cytochalasin B reveals a perturbation of localization collagen mRNA. Moreover, the presence of specific cis-and trans-acting factors involved in cytoskeleton binding and the localization process was investigated. By Northwestern experiment we found that the 3'UTR of COLL1alpha mRNA is also able to bind two proteins of 54 and 40 kDa in a cellular fraction containing the cytoskeleton. Finally, we found that the protein of 54 kDa is LP54, a protein that binds the 3'UTRs of P. lividus maternal bep messengers and is necessary for their localization.