The Src Homology and Collagen A (ShcA) adaptor protein is required for the spatial organization of the costamere/Z-disk network during heart development

ShcA (Src Homology and Collagen A) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca2+/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere

Early Stage Biomineralization in the Periostracum of the ‘Living Fossil’ Bivalve Neotrigonia

A detailed investigation of the shell formation of the palaeoheterodont ‘living fossil’ Neotrigonia concentrated on the timing and manufacture of the calcified ‘bosses’ which stud the outside of all trigonioid bivalves (extant and fossil) has been conducted. Electron microscopy and optical microscopy revealed that Neotrigonia spp. have a spiral-shaped periostracal groove. The periostracum itself is secreted by the basal cell, as a thin dark pellicle, becoming progressively transformed into a thin dark layer by additions of secretions from the internal outer mantle fold. Later, intense secretion of the internal surface of the outer mantle fold forms a translucent layer, which becomes transformed by tanning into a dark layer. The initiation of calcified bosses occurred at a very early stage of periostracum formation, deep within the periostracal groove immediately below the initialmost dark layer. At this stage, they consist of a series of polycyclically twinned crystals. The bosses grow as the periostracum traverse through the periostracal groove, in coordination with the thickening of the dark periostracal layer and until, upon reaching the mantle edge, they impinge upon each other and become transformed into large prisms separated by dark periostracal walls. In conclusion, the initial bosses and the external part of the prismatic layer are fully intraperiostracal. With later growth, the prisms transform into fibrous aggregates, although the details of the process are unknown. This reinforces the relationships with other groups that have the ability to form intraperiostracal calcifications, for example the unionoids with which the trigonioids form the clade Paleoheterodonta. The presence of similar structures in anomalodesmatans and other euheterodonts raises the question of whether this indicates a relationship or represents a convergence. The identification of very early calcification within an organic sheet has interesting implications for our understanding of how shells may have evolved.Coordinated Research Projects CGL2010-20748-C02-01 (AGC, EMH) and 02 (CS) (DGI, Spanish MICINN); the Research Group RNM363 (Consejería de Economía, Investigación, Ciencia y Empleo, Junta de Andalucía); and the FP7 COST Action TD0903 of the European Community

Le remplissage synrift au permien et au trias du bassin de Tahanaout (Haut Atlas de Marrakech, Maroc) géodynamique et organisation sédimentaire

The perno-triasic basin of Tahanaout reflects a tectono-sedimentary organization typical of synrift basins. The genetic modes of its replenishment, reviewed in light of the sedimentary heterogeneity and the position of the sediments reveal an evolution in 3 episodes: individualization, differentiation and homogenization. The tectonics expresses itself every time, by a reorganization of the deposit areas, a dissymmetry of the syntectonic gutters and structures in the tilled blocks, within a NS extensional regime (episode 1) and NW-SE even (episode 11 and 111). The intermediate sequences follow each other in sequences of deposit that reflect and evolve in fluvio-deltaic environments, since the cone toward the alluvial or deltaic plain according to a topographic gradient. The sedimentary model suggests the existance basins in vertical relays in severa1 lateral progradation phases interrupted by phases of silt-clay sedimentary aggradations. The generalized semi-arid climate and the closed country environment plays an important role in the configuration of this type of basins, whose borders are essentially clastics, of an extended alluvial plain.<br><br>Le bassin permo-triasique de Tahanaout refl&egrave;te une &eacute;volution typique des bassins synrifts. Les modalit&eacute;s g&eacute;n&eacute;tiques de son remplissage, r&eacute;v&egrave;lent une organisation en 3 &eacute;pisodes tectonos&eacute;dimentaires: l&rsquo;individualisation, la diff&eacute;renciation et l&rsquo;homog&eacute;n&eacute;isation du bassin. La tectonique s&rsquo;exprime par la cr&eacute;ation de goutti&egrave;res syntectoniques et de structures en blocs bascul&eacute;s et s&rsquo;inscrit dans un r&eacute;gime extensif N-S (&eacute;pisode I) puis NW-SE (&eacute;pisodes II et III). La s&eacute;dimentation continentale s&rsquo;organise en plusieurs cycles de progradation &ndash; r&eacute;trogradation; dans laquelle, les s&eacute;quences du milieu retracent toute la dynamique des environnements fluvio-delta&iuml;ques, depuis le cone vers la plaine alluviale ou delta&iuml;que selon un gradient topographique d&eacute;croissant. Le mod&egrave;le s&eacute;dimentaire propose un remplissage en plusieurs phases de progradation lat&eacute;rales interrompues par des phases d&rsquo;aggradations s&eacute;dimentaires silto-argileuses. Le climat semiaride g&eacute;n&eacute;ralis&eacute; joue un r&ocirc;le important dans la nature et l&rsquo;hydrodynamisme des apports ainsi que l&rsquo;&eacute;laboration des cycles s&eacute;dimentaires

The nuclear hormone receptor PPARγ counteracts vascular calcification by inhibiting Wnt5a signalling in vascular smooth muscle cells.

Vascular calcification is a hallmark of advanced atherosclerosis. Here we show that deletion of the nuclear receptor PPARγ in vascular smooth muscle cells of low density lipoprotein receptor (LDLr)-deficient mice fed an atherogenic diet high in cholesterol, accelerates vascular calcification with chondrogenic metaplasia within the lesions. Vascular calcification in the absence of PPARγ requires expression of the transmembrane receptor LDLr-related protein-1 in vascular smooth muscle cells. LDLr-related protein-1 promotes a previously unknown Wnt5a-dependent prochondrogenic pathway. We show that PPARγ protects against vascular calcification by inducing the expression of secreted frizzled-related protein-2, which functions as a Wnt5a antagonist. Targeting this signalling pathway may have clinical implications in the context of common complications of atherosclerosis, including coronary artery calcification and valvular sclerosis

ShcA promotes chondrocyte hypertrophic commitment and osteoarthritis in mice through RunX2 nuclear translocation and YAP1 inactivation

International audienceObjective: Chondrocyte hypertrophic differentiation, a key process in endochondral ossification, is also a feature of osteoarthritis leading to cartilage destruction. Here we investigated the role of the adaptor protein Src homology and Collagen A (ShcA) in chondrocyte differentiation and osteoarthritis.Methods: Mice ablated for ShcA in osteochondroprogenitor cells were generated by crossing mice carrying the Twist2-Cre transgene with ShcAflox/flox mice. Their phenotype (n = 5 to 14 mice per group) was characterized using histology, immuno-histology and western-blot. To identify the signaling mechanisms involved, in vitro experiments were conducted on wild type and ShcA deficient chondrocytes (isolated from n = 4 to 7 littermates) and the chondroprogenitor cell line ATDC5 (n = 4 independent experiments) using western-blot, cell fractionation and confocal microscopy.Results: Deletion of ShcA decreases the hypertrophic zone of the growth plate (median between group difference -11.37% [95% confidence interval -17.34 to -8.654]), alters the endochondral ossification process, and leads to dwarfism (3 months old male mice nose-to-anus length -1.48 cm [-1.860 to -1.190]). ShcA promotes ERK1/2 activation, nuclear translocation of RunX2, the master transcription factor for chondrocyte hypertrophy, while maintaining the Runx2 inhibitor, YAP1, in its cytosolic inactive form. This leads to hypertrophic commitment and expression of markers of hypertrophy, such as Collagen X. In addition, loss of ShcA protects from age-related osteoarthritis development in mice (2 years old mice OARSI score -6.67 [-14.25 to -4.000]).Conclusion: This study reveals ShcA as a new player in the control of chondrocyte hypertrophic differentiation and its deletion slows down osteoarthritis development

J Biol Chem

Src homology and collagen A (ShcA) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca(2+)/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere

Mutant APC reshapes Wnt signaling plasma membrane nanodomains by altering cholesterol levels via oncogenic β-catenin

Abstract Although the role of the Wnt pathway in colon carcinogenesis has been described previously, it has been recently demonstrated that Wnt signaling originates from highly dynamic nano-assemblies at the plasma membrane. However, little is known regarding the role of oncogenic APC in reshaping Wnt nanodomains. This is noteworthy, because oncogenic APC does not act autonomously and requires activation of Wnt effectors upstream of APC to drive aberrant Wnt signaling. Here, we demonstrate the role of oncogenic APC in increasing plasma membrane free cholesterol and rigidity, thereby modulating Wnt signaling hubs. This results in an overactivation of Wnt signaling in the colon. Finally, using the Drosophila sterol auxotroph model, we demonstrate the unique ability of exogenous free cholesterol to disrupt plasma membrane homeostasis and drive Wnt signaling in a wildtype APC background. Collectively, these findings provide a link between oncogenic APC, loss of plasma membrane homeostasis and CRC development

Na(+)/H (+) exchanger isoform 1 induced osteopontin expression in cardiomyocytes involves NFAT3/Gata4

Osteopontin (OPN), a multifunctional glycophosphoprotein, has been reported to contribute to the development and progression of cardiac remodeling and hypertrophy. Cardiac-specific OPN knockout mice were protected against hypertrophy and fibrosis mediated by Ang II. Recently, transgenic mice expressing the active form of the Na(+)/H(+) exchanger isoform 1 (NHE1) developed spontaneous hypertrophy in association with elevated levels of OPN. The mechanism by which active NHE1 induces OPN expression and contributes to the hypertrophic response remains unclear. To validate whether expression of the active form of NHE1 induces OPN, cardiomyocytes were stimulated with Ang II, a known inducer of both OPN and NHE1. Ang II induced hypertrophy and increased OPN protein expression (151.6 +/- 28.19 %, P \textless 0.01) and NHE1 activity in H9c2 cardiomyoblasts. Ang II-induced hypertrophy and OPN protein expression were regressed in the presence of an NHE1 inhibitor, EMD 87580, or a calcineurin inhibitor, FK506. In addition, our results indicated that activation of NHE1-induced NFAT3 translocation into the nucleus and a significant activation of the transcription factor Gata4 (NHE1: 149 +/- 28 % of control, P \textless 0.05). NHE1-induced activation of Gata4 was inhibited by FK506. In summary, our results suggest that activation of NHE1 induces hypertrophy through the activation of NFAT3/Gata4 and OPN expression