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Rhophilin 2 is a Rho GTPase binding protein initially isolated by differential screening of a chronically thyrotropin (TSH)-stimulated dog thyroid cDNA library. In thyroid cell culture, expression of rhophilin 2 mRNA and protein is enhanced following TSH stimulation of the cyclic AMP (cAMP) transduction cascade. Yeast two-hybrid screening and coimmunoprecipitation have revealed that the GTP-bound form of RhoB and components of the cytoskeleton are protein partners of rhophilin 2. These results led us to suggest that rhophilin 2 could play an important role downstream of RhoB in the control of endocytosis during the thyroid secretory process which follows stimulation of the TSH/cAMP pathway. To validate this hypothesis, we generated rhophilin 2-deficient mice and analyzed their thyroid structure and function. Mice lacking rhophilin 2 develop normally, have normal life spans, and are fertile. They have no visible goiter and no obvious clinical signs of hyper- or hypothyroidism. The morphology of thyroid cells and follicles in these mice were normal, as were the different biological tests performed to investigate thyroid function. Our results indicate that rhophilin 2 does not play an essential role in thyroid physiology., Journal Article, Research Support, Non-U.S. Gov't, info:eu-repo/semantics/published

info:eu-repo/semantics/published

Induction of cell proliferation by mitogen or growth factor stimulation leads to the specific induction or repression of a large number of genes. To identify genes differentially regulated by the cAMP-dependent transduction pathway, which is poorly characterized so far, we used the cDNA expression array technology. Hybridizations of Atlas human cDNA expression arrays with (32)P-labeled cDNA probes derived from control or thyrotropin (TSH)-stimulated dog thyrocytes in primary culture generated expression profiles of hundreds of genes simultaneously. Among the genes that displayed modified expression, we selected the transcription factor ID3, whose expression was increased by a cAMP-dependent stimulus. ID3 overexpression after TSH stimulation was first verified by Northern blotting analysis, and its mRNA regulation was then investigated in response to a variety of agents acting on thyrocyte proliferation and/or differentiation. We show that: (1) ID3 mRNA induction was stronger after stimulation of the cAMP cascade, but was not restricted to this signaling pathway, as phorbol myristate ester (TPA) and insulin also stimulated mRNA accumulation; (2) in contrast, powerful mitogens for thyroid cells, epidermal growth factor and hepatocyte growth factor, did not significantly modify ID3 mRNA levels; (3) ID3 protein levels closely parallelled mRNA levels, as revealed by immunofluorescence experiments showing a nuclear signal regulated by TSH; (4) in papillary thyroid carcinomas, ID3 mRNA was downregulated. Our results suggest that ID3 expression might be more related to the differentiating process induced by TSH than to the proliferative action of this hormone., Journal Article, Research Support, Non-U.S. Gov't, info:eu-repo/semantics/published

The aim of our work is to identify new genes and proteins involved in the control of the proliferation of thyroid cells as putative protooncogenes and antioncogenes. Several strategies are discussed. A first study has allowed to identify three new genes. Further search will use the differential display and gene arrays methodology. The role of the identified proteins coded by the genes is studied in vitro by the search of partner proteins by the double hybrid method and in vivo by mice gene knockout technology., Journal Article, Research Support, Non-U.S. Gov't, Review, info:eu-repo/semantics/published

SHIP2 is a new member of the inositol polyphosphate 5-phosphatase family showing homology to SHIP1. The structure of both enzymes is characterized by the presence of a 5' SH2 domain, a central catalytic domain, and a 3' proline-rich region. Recent results suggest that SHIP2 and SHIP1 act downstream of various receptors by removing a phosphate from the 5' position of the phosphatidylinositol 3'-kinase phosphatidylinositol 3,4, 5-triphosphate product and of inositol 1,3,4,5-tetrakisphosphate. Human SHIP2 is highly expressed in adult heart, skeletal muscle, and placenta, whereas SHIP1 expression is limited to the hematopoietic system. We report here the molecular analysis of the mouse SHIP2 cDNA and the corresponding protein, the structure of the gene, and the identification of its promoter. SHIP2 mRNA expression was analyzed in embryonic and adult mouse tissues by reverse transcription-polymerase chain reaction and in situ hybridization. In embryonic day 15.5 mice, SHIP2 was strongly expressed in the liver, specific regions of the central nervous system, the thymus, the lung, and the cartilage perichondrium. In adult mice, SHIP2 mRNA was markedly present in the brain and the thymus and at different stages of spermatozoa maturation in the seminiferous tubules. The subtle differences in the protein structure of SHIP2 and SHIP1 as well as their different patterns of expression are discussed., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published