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International audience; abstract simple

International audience

International audience; abstract simple

International audience; abstract simple

International audience

International audience

14th Annual V M Goldschmidt Conference, Univ Copenhagen, Copenhagen, DENMARK, JUN 05-11, 2004

Ciliopathies are a group of diseases that affect kidney and retina among other organs. Here, we identify a missense mutation in PIK3R4 (phosphoinositide 3-kinase regulatory subunit 4, named VPS15) in a family with a ciliopathy phenotype. Besides being required for trafficking and autophagy, we show that VPS15 regulates primary cilium length in human fibroblasts, as well as ciliary processes in zebrafish. Furthermore, we demonstrate its interaction with the golgin GM130 and its localization to the Golgi. The VPS15-R998Q patient mutation impairs Golgi trafficking functions in humanized yeast cells. Moreover, in VPS15-R998Q patient fibroblasts, the intraflagellar transport protein IFT20 is not localized to vesicles trafficking to the cilium but is restricted to the Golgi. Our findings suggest that at the Golgi, VPS15 and GM130 form a protein complex devoid of VPS34 to ensure the IFT20-dependent sorting and transport of membrane proteins from the cis-Golgi to the primary cilium.

International audience

Cleidocranial dysplasia (CCD) is an autosomal dominant disorder characterized by hypoplastic or absent clavicles, large fontanelles, dental anomalies and delayed skeletal development. The phenotype is suggestive of a generalized defect in ossification and is one of the most common skeletal dysplasias not associated with disproportionate stature. To date, no genetic determinants of ossification have been identified. CCD has been mapped to chromosome 6p21, where CBFA1, a gene encoding OSF2/CBFA1, a transcriptional activator of osteoblast differentiation, has been localized. Here, we describe two de novo missense mutations, Met175Arg and Ser191Asn, in the OSF2/CBFA1 gene in two patients with CCD. These two mutations result in substitution of highly conserved amino acids in the DNA-binding domain. DNA-binding studies with the mutant polypeptides show that these amino acid substitutions abolish the DNA-binding ability of OSF2/CBFA1 to its known target sequence. Concurrent studies show that heterozygous nonsense mutations in OSF2/CBFA1 also result in CCD, while mice homozygous for the osf2/cbfa1 mull allele exhibit a more severe lethal phenotype. Thus, these results together suggest that CCD is produced by haploinsufficiency of OSF2/CBFA1 and provide direct genetic evidence that the phenotype is secondary to an alteration of osteoblast differentiation.

Contaminated soils such as former mine sites are unsuitable for the food production. Metals and metalloids concentration are usually very high. The main aim of this thesis was the evaluation of the adaptation capacity of a bioenergetic plant, Miscanthus x giganteus, on soils developed from mining wastes contaminated in arsenic (10% in mass concentration) and lead (5%, mass concentration). Despite the contamination, results show that: (i) Miscanthus is able to adapt without any physiological stress, (ii) biomass yield is reduced, (iii) soil to plant transfer of As and Pb is low owing to a specific mineralogy limiting the elements solubilization, (iv) microorganisms involved in nitrate formation are present and (v) M. x giganteus is an excellent plant to phytostabilise the site. Frühere Bergbaustandorte weisen oft belastete Böden auf und sind für die Landwirtschaft nicht nutzbar, da sie eine hohe Konzentration vom Metallen und Halbmetallen (beispielsweise Arsen und Blei) haben. Das Hauptziel dieser Doktorarbeit bestand darin, die Anpassungsfähigkeit der Energiepflanze Miscanthus x giganteus abzuschätzen. Die Ergebnisse der Arbeit zeigen (i) Miscanthus besitzt eine hohe Anpassungsfähigkeit, (ii) Die Biomasse der Pflanze ist auf belasteten Böden reduziert (iii) der Transfer von Arsen und Blei vom Boden in die Pflanze war gering (iv) Mikroorganismen zur Nitrifizierung waren im Boden aktiv und (v) Miscanthus ist eine geeignete Pflanze zur Phytostabilisierung von Böden.

Diastrophic dysplasia (DTD) is a chondrodysplasia caused by mutations in the SLC26A2 gene, leading to reduced intracellular sulfate pool in chondrocytes, osteoblasts and fibroblasts. Hence, proteoglycans are undersulfated in the cartilage and bone of DTD patients. To characterize the bone phenotype of this skeletal dysplasia we used the Slc26a2 knock-in mouse (dtd mouse), that was previously validated as an animal model of DTD in humans. X-rays, bone densitometry, static and dynamic histomorphometry, and in vitro studies revealed a primary bone defect in the dtd mouse model. We showed in vivo that this primary bone defect in dtd mice is due to decreased bone accrual associated with a decreased trabecular and periosteal appositional rate at the cell level in one month-old mice. Although the osteoclast number evaluated by histomorphometry was not different in dtd compared to wild-type mice, urine analysis of deoxypyridinoline cross-links and serum levels of type I collagen C-terminal telopeptides showed a higher resorption rate in dtd mice compared to wild-type littermates. Electron microscopy studies showed that collagen fibrils in bone were thinner and less organized in dtd compared to wild-type mice. These data suggest that the low bone mass observed in mutant mice could possibly be linked to the different bone matrix compositions/organizations in dtd mice triggering changes in osteoblast and osteoclast activities. Overall, these results suggest that proteoglycan undersulfation not only affects the properties of hyaline cartilage, but can also lead to unbalanced bone modeling and remodeling activities, demonstrating the importance of proteoglycan sulfation in bone homeostasis., Highlights ► The osteopenic phenotype in a mouse model of proteoglycan undersulfation has been characterized. ► In vivo and in vitro studies revealed a primary bone defect in the dtd mouse model. ► Low bone mass in mutant mice is linked to bone matrix alterations triggering changes in osteoblast and osteoclast activities. ► Electron microscopy showed that collagen fibrils were thinner and less organized in mutant compared to wild-type mice. ► Results demonstrate that the SLC26A2 gene not only affects chondrogenesis, but also leads to unbalanced bone modeling and remodeling activities.