Publications

Reticulomyxa filosa is a freshwater protist possessing fine granular, branching and anastomosing pseudopodia and therefore traditionally placed in the class Granuloreticulosea, order Athalamida, as a sister group to the order Foraminiferida. Recent studies have revealed remarkable similarities in pseudopodial motility and ultrastructure between R. filosa and foraminifera (e.g. Allogromia laticollaris), prompting us to conduct a molecular phylogenetic analysis of these seemingly disparate organisms. We sequenced the complete small-subunit of the ribosomal DNA of the cultured strain of R. filosa and compared it to the corresponding sequences of other protists including 12 species of foraminifera. We also sequenced and analyzed the actin coding genes from R. filosa and two species of foraminifera, Allogromia sp. and Ammonia sp. The analysis of both data sets clearly shows that R. filosa branches within the clade of foraminifera, suggesting that R. filosa is in fact a freshwater naked foraminiferan.

Lusitanichthys africanus n. sp. from Daoura, an Upper Cenomanian locality situated about 100 km south of Erfoud (southeastern Morocco), is described. L. africanus is very similar to L. characiformis. Lusitanichthys shows modifications of the first vertebral elements indicating the presence of a primitive Weberian apparatus. Clupavus maroccanus and Lusitanichthys belong to the clupavids. Anatomical characters of L. africanus from the Weberian apparatus and the caudal skeleton allow us to include it in Otophysi without sure indications of ordinal affinities.

Lethal hepatitis can be induced by an agonistic anti-Fas Ab in normal mice or by TNF in mice sensitized to d -(+)-galactosamine or actinomycin D. In all three models, we found that apoptosis of hepatocytes is an early and necessary step to cause lethality. In the three models, we observed activation of the major executioner caspases-3 and -7. Two acute-phase proteins, alpha1-acid glycoprotein and alpha1-antitrypsin, differentially prevent lethality: alpha1-acid glycoprotein protects in both TNF models and not in the anti-Fas model, while alpha1-antitrypsin confers protection in the TNF/d -(+)-galactosamine model only. The protection is inversely correlated with activation of caspase-3 and caspase-7. The data suggest that activation of caspase-3 and -7 is essential in the in vivo induction of apoptosis leading to lethal hepatitis and that acute phase proteins are powerful inhibitors of apoptosis and caspase activation. Furthermore, Bcl-2 transgenic mice, expressing Bcl-2 specifically in hepatocytes, are protected against a lethal challenge with anti-Fas or with TNF/d -(+)-galactosamine, but not against TNF/actinomycin D. The acute-phase proteins might constitute an inducible anti-apoptotic protective system, which in pathology or disturbed homeostasis prevents excessive apoptosis.

A new ichthyofauna from southeastern Morocco, comprising five forms, is briefly discussed. The faunal composition differs from the Early Cenomanian Kem Kem and Early Turonian Goulmima assemblages, but is close to that from Jebel Tselfat. We propose a Late Cenomanian age for the new fauna and that from Jebel Tselfat. The evolution of these fish assemblages shows the Moroccan fish faunas to have been related to those from South America until at least the Early Turonian. Central Tethyan influence on faunas seems to have been restricted to a short period of time during the beginning of the Late Cenomanian transgressive phase.

Cloning allows the asexual reproduction of selected individuals such that the offspring have an essentially identical nuclear genome. Cloning by nuclear transfer thus far has been reported only with freshly isolated cells and cells from primary cultures. We previously reported a method of cloning mice from adult somatic cells after nuclear transfer by microinjection. Here, we apply this method to clone mice from widely available, established embryonic stem (ES) cell lines at late passage. With the ES cell line R1, 29% of reconstructed oocytes developed in vitro to the morula/blastocyst stage, and 8% of these embryos developed to live-born pups when transferred to surrogate mothers. We thus cloned 26 mice from R1 cells. Nuclei from the ES cell line E14 also were shown to direct development to term. We present evidence that the nuclei of ES cells at G(1)- or G(2)/M-phases are efficiently able to support full development. Our findings demonstrate that late-passage ES cells can be used to produce viable cloned mice and provide a link between the technologies of ES cells and animal cloning. It thus may be possible to clone from a single cell a large number of individuals over an extended period.

A new Late Maastrichtian locality from the Petites-Pyrénées has yielded an important vertebrate fauna. It includes Chondrichthyes (undetermined neoselachian), Osteichthyes (Lepisosteidae, Phyllodontinae, Sparidae?), Chelonia (Pleurodira), Crocodylia, and Dinosauria (Theropoda, Hadrosauridae, Nodosauridae). It is the first mention of a Cretaceous phyllodontine and the first mention of an ankylosaur in the French Late Maastrichtian. Lestaillats is the richest Late Maastrichtian locality in southern France because of the occurrence of both a microfauna and macrovertebrates. It offers new perspectives for the knowledge of the diversity and the evolution of the European vertebrate assemblages in the Latest Cretaceous.

The vomeronasal system mediates pheromonal effects in mammals. We have employed gene targeting technology to introduce mutations in a putative pheromone receptor gene, VR2, in the germline of mice. By generating alleles differentially tagged with the histological markers taulacZ and tauGFP, we show that VR2 is monoallelically expressed in a given neuron. Axons of VR2-expressing neurons converge onto numerous glomeruli in the accessory olfactory bulb. The pattern of axonal projections is complex and variable. This wiring diagram is substantially different from that of the main olfactory system. The projection pattern is disrupted by deleting the coding region of VR2, but an unrelated seven-transmembrane protein, the odorant receptor M71, can partially substitute for VR2.

Homeobox genes located in the 5' part of the HoxA and HoxD complexes are required for proliferation of skeletal progenitor cells of the vertebrate limb. Specific combinations of gene products determine the length of the upper arm (genes belonging to groups 9 and 10), the lower arm (groups 10, 11 and 12) and the digits (groups 11, 12 and 13). In these different domains, individual gene products quantitatively contribute to an overall protein dose, with predominant roles for groups 11 and 13. Quantitative reduction in the gene dose in each set results in truncations of the corresponding anatomical regions. The physical order of the genes in the HoxA and HoxD complexes, as well as a unidirectional sequence in gene activation, allow for completion of the process in a precise order, which in turn makes possible the sequential outgrowth of the respective primordia. While the skeletal patterns of upper and lower limb are relatively stable throughout the tetrapods, more variation is seen in the digits. Molecular analysis of the underlying regulatory processes promises further exciting insights into the genetic control of development, pathology and the course of evolution.