PAX6 aniridia and interhemispheric brain anomalies.

PURPOSE: To report the clinical and genetic study of patients with autosomal dominant aniridia. METHODS: We studied ten patients with aniridia from three families of Egyptian origin. All patients underwent full ophthalmologic, general and neurological examination, and blood drawing. Cerebral magnetic resonance imaging was performed in the index case of each family. Genomic DNA was prepared from venous leukocytes, and direct sequencing of all the exons and intron-exon junctions of the Paired Box gene 6 (PAX6) was performed after PCR amplification. Phenotype description, including ophthalmic and cerebral anomalies, mutation detection in PAX6 and phenotype-genotype correlation was acquired. RESULTS: Common features observed in the three families included absence of iris tissue, corneal pannus with different degrees of severity, and foveal hypoplasia with severely reduced visual acuity. In Families 2 and 3, additional findings, such as lens dislocation, lens opacities or polar cataract, and glaucoma, were observed. We identified two novel (c.170-174delTGGGC [p.L57fs17] and c.475delC [p.R159fs47]) and one known (c.718C>T [p.R240X]) PAX6 mutations in the affected members of the three families. Systemic and neurological examination was normal in all ten affected patients. Cerebral magnetic resonance imaging showed absence of the pineal gland in all three index patients. Severe hypoplasia of the brain anterior commissure was associated with the p.L57fs17 mutation, absence of the posterior commissure with p.R159fs47, and optic chiasma atrophy and almost complete agenesis of the corpus callosum with p.R240X. CONCLUSIONS: We identified two novel PAX6 mutations in families with severe aniridia. In addition to common phenotype of aniridia and despite normal neurological examination, absence of the pineal gland and interhemispheric brain anomalies were observed in all three index patients. The heterogeneity of PAX6 mutations and brain anomalies are highlighted. This report emphasizes the association between aniridia and brain anomalies with or without functional impact, such as neurodevelopment delay or auditory dysfunction.

Automated quantitative histology reveals vascular morphodynamics during Arabidopsis hypocotyl secondary growth.

Among various advantages, their small size makes model organisms preferred subjects of investigation. Yet, even in model systems detailed analysis of numerous developmental processes at cellular level is severely hampered by their scale. For instance, secondary growth of Arabidopsis hypocotyls creates a radial pattern of highly specialized tissues that comprises several thousand cells starting from a few dozen. This dynamic process is difficult to follow because of its scale and because it can only be investigated invasively, precluding comprehensive understanding of the cell proliferation, differentiation, and patterning events involved. To overcome such limitation, we established an automated quantitative histology approach. We acquired hypocotyl cross-sections from tiled high-resolution images and extracted their information content using custom high-throughput image processing and segmentation. Coupled with automated cell type recognition through machine learning, we could establish a cellular resolution atlas that reveals vascular morphodynamics during secondary growth, for example equidistant phloem pole formation. DOI: http://dx.doi.org/10.7554/eLife.01567.001.

Paid employment and the changing system of gender relations: a cross-national comparison

Equality with men in the world of paid work has been a major feminist objective. Given that work in the `public' sphere has historically been shaped on the assumption that the `worker' will be male, then national employment systems which facilitate masculine employment patterns (i.e. full-time work and unbroken employment careers) might be expected to be more likely to generate gender equality. This paper compares women's employment in France (where `masculine' careers for women are common) and Britain (where part-time work and broken employment careers are more likely) at the macro, meso (occupational), and micro (individual) levels. The two occupations studied are finance and pharmacy. The evidence presented suggests that there are considerable similarities between women in the two countries at the occupational and individual level, despite national variations. In the light of this evidence, structural and individual explanations of women's employment behaviour are examined, and the continuing significance of structural constraint on the patterning of gender relations is emphasised.

Generation of cell polarity in plants links endocytosis, auxin distribution and cell fate decisions.

Dynamically polarized membrane proteins define different cell boundaries and have an important role in intercellular communication-a vital feature of multicellular development. Efflux carriers for the signalling molecule auxin from the PIN family are landmarks of cell polarity in plants and have a crucial involvement in auxin distribution-dependent development including embryo patterning, organogenesis and tropisms. Polar PIN localization determines the direction of intercellular auxin flow, yet the mechanisms generating PIN polarity remain unclear. Here we identify an endocytosis-dependent mechanism of PIN polarity generation and analyse its developmental implications. Real-time PIN tracking showed that after synthesis, PINs are initially delivered to the plasma membrane in a non-polar manner and their polarity is established by subsequent endocytic recycling. Interference with PIN endocytosis either by auxin or by manipulation of the Arabidopsis Rab5 GTPase pathway prevents PIN polarization. Failure of PIN polarization transiently alters asymmetric auxin distribution during embryogenesis and increases the local auxin response in apical embryo regions. This results in ectopic expression of auxin pathway-associated root-forming master regulators in embryonic leaves and promotes homeotic transformation of leaves to roots. Our results indicate a two-step mechanism for the generation of PIN polar localization and the essential role of endocytosis in this process. It also highlights the link between endocytosis-dependent polarity of individual cells and auxin distribution-dependent cell fate establishment for multicellular patterning.

Computer-assisted cup placement techniques in total hip arthroplasty improve accuracy of placement.

Malposition of the acetabular component during hip arthroplasty increases the occurrence of impingement, reduces range of motion, and increases the risk of dislocation and long-term wear. To prevent malpositioned hip implants, an increasing number of computer-assisted orthopaedic systems have been described, but their accuracy is not well established. The purpose of this study was to determine the reproducibility and accuracy of conventional versus computer-assisted techniques for positioning the acetabular component in total hip arthroplasty. Using a lateral approach, 150 cups were placed by 10 surgeons in 10 identical plastic pelvis models (freehand, with a mechanical guide, using computer assistance). Conditions for cup implantations were made to mimic the operating room situation. Preoperative planning was done from a computed tomography scan. The accuracy of cup abduction and anteversion was assessed with an electromagnetic system. Freehand placement revealed a mean accuracy of cup anteversion and abduction of 10 degrees and 3.5 degrees, respectively (maximum error, 35 degrees). With the cup positioner, these angles measured 8 degrees and 4 degrees (maximum error, 29.8 degrees), respectively, and using computer assistance, 1.5 degrees and 2.5 degrees degrees (maximum error, 8 degrees), respectively. Computer-assisted cup placement was an accurate and reproducible technique for total hip arthroplasty. It was more accurate than traditional methods of cup positioning.

Luxación cerrada de astrágalo: a propósito de un caso

Total and closed dislocation of the talus is a extremely rare injury characterized by a full disruption of the ankle, subtalar and talonavicular joints and it requires an emergency treatment consisting in early reduction of the dislocation. A young male patient a ected of a closed full dislocation of the talus after a tra c accident is presented. e bibliography of the condition is reviewed.

Retinoic acid signaling affects cortical synchrony during sleep.

Delta oscillations, characteristic of the electroencephalogram (EEG) of slow wave sleep, estimate sleep depth and need and are thought to be closely linked to the recovery function of sleep. The cellular mechanisms underlying the generation of delta waves at the cortical and thalamic levels are well documented, but the molecular regulatory mechanisms remain elusive. Here we demonstrate in the mouse that the gene encoding the retinoic acid receptor beta determines the contribution of delta oscillations to the sleep EEG. Thus, retinoic acid signaling, which is involved in the patterning of the brain and dopaminergic pathways, regulates cortical synchrony in the adult.

Contrapuntos de la invención

Un instrumento musical implica la presencia de un registro sonoro que afecta tanto a la organización de los sonidos, silencios y ruidos, como a la disposición corporal que con él se va forjando. Desde esta consideración, la organización de la música llevada a cabo con las tecnologías eléctricas y electrónicas supone una profunda modificación de ambos aspectos. La llegada de la electricidad implica una tripledislocación: respecto a la transmisión de lo sonoro, a su posibilidad de reproducción y a la escucha. Estas dislocaciones son puestas en relación con invenciones que, desde el órgano de Ctesibios hasta el clavecín ocular de Castel, nos dibujan un marco en el que música, técnica, sensibilidad y sistemaeconómico-social, tejen sus nexos. A lo largo de este recorrido se trazan lo que se ha denominado contrapuntos de la invención, que pueden tomar en las figuras de J.S. Bach y de J. Cage sus ejemplos más prominentes

Peritalar dislocations: a retrospective study of 18 cases.

The purpose of this study is to retrospectively evaluate 18 consecutive cases of peritalar dislocations referred to our department during a period of 25 years and to delineate the factors influencing long-term prognosis. There were 13 (73%) medial and 5 (27%) lateral dislocations. Six patients (33%) suffered an open injury, including 2 of 13 (15%) medial and 4 of 5 (80%) lateral dislocations. Associated fractures involving the hindfoot or forefoot were noted in 7 feet, including 3 of 5 lateral dislocation cases. Reduction was accomplished under general anesthesia; in no case was open reduction necessary. In 4 of 6 open injuries with associated fractures, temporary fixation with Kirschner wires was performed. Patients were immobilized in a plaster cast for 4 weeks, or for 6 weeks in the presence of fracture, followed by weightbearing as tolerated. At a mean follow-up of 10.2 years (range, 4 to 26 years), 10 patients (56%) showed excellent results; all had sustained a closed medial low-energy dislocation. There were 3 cases (17%) with fair results and 5 cases (28%) with poor results. Forty-five percent of patients showed a restriction of activity, a reduction of subtalar range of motion, and moderate or severe radiographic signs of hindfoot degenerative arthritis. There were no cases of talar avascular necrosis, and in no case was secondary surgery necessary. Lateral dislocation and open medial dislocations with concomitant fractures showed a greater potential for poor prognosis. The results were independent from period of cast immobilization, suggesting that 4 to 6 weeks of immobilization provides acceptable long-term results.

Linking temperature estimates and microstructures in deformed polymineralic mantle rocks

To constrain deformation temperatures of mantle shear zones, we studied a strike-slip shear zone (Hilti massif, Semail ophiolite, Oman) and focused on the interaction between microstructural mechanisms and chemical equilibration processes. Quantitative microfabric analysis on harzburgites with different deformation intensity (porphyroclastic tectonite, mylonite, and ultramylonite) was combined with orthopyroxene geothermometry. The average grain size of all phases decreases with decreasing shear zone thickness. Dynamic recrystallization of porphyroclasts in combination with dissolution-precipitation and nucleation result in small-sized, chemically equilibrated pyroxenes. The composition of orthopyroxene was used to calculate deformation temperatures. In the case of the porphyroclastic tectonites, the chemical composition of orthopyroxene has been reset by diffusion yielding temperature estimates of 880-900 degrees C. The mylonites were deformed by dislocation creep of olivine and show a broad range of calculated temperatures, which result from a combination of grain size reduction and inheritance of equilibrium compositions from earlier high-temperature events and diffusion. In mylonites, diffusion profiles combined with geothermometry and grain size analysis indicate a mylonitic deformation temperature of 800-900 degrees C possibly followed by diffusion. In ultramylonites, the smallest grains (<30 mu m) reveal equilibration at temperatures of similar to 700 degrees C during the last stages of ductile deformation, which was dominated by diffusion creep of olivine. Our results provide a crucial link between temperature and evolution of microstructures from dislocation creep to diffusion creep in mantle shear zones.

Functional implication of the vitamin A signaling pathway in the brain.

Vitamin A is necessary for normal embryonic development, but its role in the adult brain is poorly understood. Vitamin A derivatives, retinoids, are involved in a complex signaling pathway that regulates gene expression and, in the central nervous system, controls neuronal differentiation and neural tube patterning. Although a major functional implication of retinoic signaling has been repeatedly suggested in synaptic plasticity, learning and memory, sleep, schizophrenia, depression, Parkinson disease, and Alzheimer disease, the targets and the underlying mechanisms in the adult brain remain elusive.

Role of ATH5 in the specification of retinal ganglion cells and expression and cell compartmentalization of EFEMP1, a protein associated with Malattia Leventinese

ABSTRACT : The development of the retina is a very complex process, occurring through the progressive restriction of cell fates, from pluripotent cell populations to complex tissues and organs. In all vertebrate species analyzed so far, retinal differentiation starts with the generation of retinal ganglion cells (RGC)s. One of the documented key essential events in the specification of RGCs is the expression of ATHS, an atonal homolog encoding a bHLH transcription factor. Despite the putative role of master regulator of RGC differentiation, the mechanism of integrating its functions into a coherent program underlying the production of this subclass of retinal neurons has not yet been elucidated. By using chromatin immunoprecipitation combined with microarray (ChIP-on-chip) we have screened for ATH5 direct targets in the developing chick retina at two consecutive periods: E3.5 (stage HH22) and E6 (stage HH30), covering the stages of progenitor proliferation, neuroepithelium patterning, RGC specification, cell cycle exit and early neuronal differentiation. In parallel, complementary analysis with Affymetrix expression microarrays was conducted. We compared RGCs versus retina to see if the targets correspond to genes preferentially expressed in RGCs. We also precociously overexpressed ATH5 in the retina of individual embryo, and contralateral retina vas used as a control. Our integrated approach allowed us to establish a compendium of ATH5-targets and enabled us to position ATH5 in the transcription network underlying neurogenesis in the retina. Malattia Leventinese (ML) is an autosomal, dominant retinal dystrophy characterized by extracellular, amorphous deposits known as drusen, between the retinal pigment epithelium (RPE) and Bruch's membrane. On the genetic level, it has been associated with a single missense mutation (R345W) in a widely expressed gene with unknown function called EFEMP1. We determined expression patterns of the EFEMP1 gene in normal and ML human retinas. Our data shown that the upregulation of EFEMP1 is not specific to ML eye, except for the region of the ciliary body. We also analyzed the cell compartmentalization of different versions of the protein (both wild type and mutant). Our studies indicate that both abnormal expression of the EFEMP1 gene and mutation and accumulation of EFEMP 1 protein (inside or outside the cells) might contribute to the ML pathology. Résumé : 1er partie : L'ontogenèse de la rétine est un processus complexe au cours duquel des cellules progénitrices sont engagée, par vagues successives, dans des lignées où elles vont d'abord être déterminées puis vont se différencier pour finalement construire un tissu rétinien composé de cinq classes de neurones (les photorécepteurs, les cellules horizontales, bipolaires, amacrines et ganglionnaires) et d'une seule de cellules gliales (les cellules de Muller). Chez tous les vertébrés, la neurogenèse rétinienne est d'abord marquée par la production des cellules ganglionnaires (RGCs). La production de cette classe de neurone est liée à l'expression du gène ATH5 qui est un homologue du gène atonal chez la Drosophile et qui code pour un facteur de transcription de la famille des protéines basic Helix-Loop-Helix (bHLH). Malgré le rôle central que joue ATH5 dans la production des RGCs, le mécanisme qui intègre la fonction de cette protéine dans le programme de détermination neuronale et ceci en relation avec le développement de la rétine n'est pas encore élucidé. Grâce à une technologie qui permet de combiner la sélection de fragments de chromatine liant ATH5 et la recherche de séquences grâce à des puces d'ADN non-codants (ChIP-on-chip), nous avons recherché des cibles potentielles de la protéine ATH5 dans la rétine en développement. Nous avons conduit cette recherche à deux stades de développement de manière à englober la phase de prolifération cellulaire, la détermination des RGCs, la sortie du cycle cellulaire ainsi que les premières étapes de la différentiation de ces neurones. Des expériences complémentaires nous ont permis de définir les patrons d'expression des gènes sélectionnés ainsi que l'activité promotrice des éléments de régulation identifiés lors de notre criblage. Ces approches expérimentales diverses et complémentaires nous ont permis de répertorier des gènes cibles de la protéine ATH5 et d'établir ainsi des liens fonctionnels entre des voies métaboliques dont nous ne soupçonnions pas jusqu'alors qu'elles puissent être associées à la production d'une classe de neurones centraux. 2ème partie : Malattia Leventinese (ML) est une maladie génétique qui engendre une dystrophie de la rétine. Elle se caractérise par l'accumulation de dépôt amorphe entre l'épithélium pigmentaire et la membrane de Bruch et connu sous le nom de drusen. Cette maladie est liée à une simple mutation non-sens (R345W) dans un gène dénommé EFEMP1 qui est exprimé dans de nombreux tissus mais dont la fonction reste mal définie. Une étude détaillée de l'expression de ce gène dans des rétines humaines a révélé une expression à un niveau élevé du gène EFEMP1 dans divers tissus de l'oeil ML mais également dans des yeux contrôles. Alors que l'accumulation d'ARN messager EFEMP1 dans les cellules de l'épithélium pigmentaire n'est pas spécifique à ML, l'expression de ce gène dans le corps cilié n'a été observée que dans l'oeil ML. Nous avons également comparé la sécrétion de la protéine sauvage avec celle porteuse de la mutation. En résumé, notre étude révèle que le niveau élevé d'expression du gène EFEMP1 ainsi que l'accumulation de la protéine dans certains compartiments cellulaires pourraient contribuer au développement de pathologies rétiniennes liées à ML.

Bristle pattern formation in the thorax formation of Drosophila: a systems level approach

A fundamental question in developmental biology is how tissues are patterned to give rise to differentiated body structures with distinct morphologies. The Drosophila wing disc offers an accessible model to understand epithelial spatial patterning. It has been studied extensively using genetic and molecular approaches. Bristle patterns on the thorax, which arise from the medial part of the wing disc, are a classical model of pattern formation, dependent on a pre-pattern of trans-activators and –repressors. Despite of decades of molecular studies, we still only know a subset of the factors that determine the pre-pattern. We are applying a novel and interdisciplinary approach to predict regulatory interactions in this system. It is based on the description of expression patterns by simple logical relations (addition, subtraction, intersection and union) between simple shapes (graphical primitives). Similarities and relations between primitives have been shown to be predictive of regulatory relationships between the corresponding regulatory factors in other Systems, such as the Drosophila egg. Furthermore, they provide the basis for dynamical models of the bristle-patterning network, which enable us to make even more detailed predictions on gene regulation and expression dynamics. We have obtained a data-set of wing disc expression patterns which we are now processing to obtain average expression patterns for each gene. Through triangulation of the images we can transform the expression patterns into vectors which can easily be analysed by Standard clustering methods. These analyses will allow us to identify primitives and regulatory interactions. We expect to identify new regulatory interactions and to understand the basic Dynamics of the regulatory network responsible for thorax patterning. These results will provide us with a better understanding of the rules governing gene regulatory networks in general, and provide the basis for future studies of the evolution of the thorax-patterning network in particular.

Late migration of percutaneous bio-absorbable devices--a word of caution.

BACKGROUND: Closures of atrial septal defects or a patent foramen ovale (PFO) are increasingly performed percutaneously. The experience of late migration of a new bio-absorbable device is presented here, followed by conceptual discussion. METHODS: Six months post PFO closure with a BioSTAR® device a patient presented with chest pain. Echocardiography showed a hyperechogenic structure perforating the aortic wall. RESULTS: Surgical exploration showed a perforation of the ascending aorta by one metallic, non absorbable arm. This is the second case of late (>6 months) dislocation of the residual framework of the occluder. CONCLUSIONS: The overall incidence of perforation of cardiac structures due to secondary dislocation is low. However this complication exists and should kept in mind in symptomatic patients with new onset of chest pain, after percutaneous procedures. The concept of biodegradation, with residual, non absorbable metal braiding, should be reviewed, analyzing in particular long term results and incidence of secondary dislocation.

The Exotic Palaeo-Thethys Terrane in Central Iran: New geological data from Anarak, Jandaq and Posht-e-Badam areas

Résumé Le « terrane » d'Anarak-Jandak occupe une position géologique clé au nord-ouest du Microcontinent Centre-East Iranien (CE1M), connecté avec le Bloc du Grand Kavir et la ceinture métamorphique de Sanandaj-Sirjan. Nous discutons ici l'origine de ces différentes unités, reliées jusqu'à présent à des épisodes orogéniques d'âge Précambrien à Paléozoïque inférieur, pour conclure finalement de leur affinité paléotéthysienne. Leur histoire commence par un épisode de rifting d'âge Ordovicien supérieur-Dévonien inférieur, pour se terminer au Trias par la collision des blocs Cimmériens dérivé du Gondwana avec le Bloc du Turan d'affinité asiatique (événement Eocimmérien). La plus importante unité métamorphique affleurant au sud-ouest de la région de Jandak-Anarak-Kaboudan est une épaisse séquence silicoclastique à grains fins contenant des blocs ophiolitiques (marginal-sea-type), et des associations basalte-gabbro à signatures géochimiques de type supra-subduction. Dans la région de Nakhlak, nous avons daté ces gabbros par la méthode U-Pb à 387f0.11 Ma ; les roches métamorphiques pélitiques ont donné des âges de refroidissement Ar-Ar pour la muscovite de 320 à 333 Ma. Ce complexe d'accrétion "varisque" a été métamorphisé dans le faciès schiste vert-amphibolite au cours de l'accrétion de la ceinture granitique d'Airekan, d'âge Cambrien inférieur (549±15 Ma par la méthode U/Pb), qui affleure aujourd'hui à l'extrémité nord-ouest du terrane d'Anarak-Jandak . La subduction vers le nord de l'océan Paléotéthys depuis le Paléazoïque supérieur jusqu'au Trias, a permis l'accumulation de grandes quantités de matériel océanique dans la zone de subduction. Par exemple, une succession de guyots (Anarak, Kaboudan, et Meraji Seamounts) et de hauts sous-marins, entrés en collision oblique avec le prisme d'accrétion, est à l'origine d'un léger métamorphisme de type HP qui affecte ces séries {âges Ar-Ar de 280 à 230 Ma). De plus, le magmatisme bimodal de Chah Gorbeh est caractérisé d'une part par des roches de type trondjémite-gabbros (262 Ma), d'autre part par des laves en coussin de type basaltes alcalins-rhyolites; ces roches magmatiques ont recoupé l'ophiolite d'Anarak lors de la mise en place de cette dernière dans la fosse interne de subduction. Quant au prisme d'accrétion de Doshakh, d'âge essentiellement Permien supérieur, i1 a été accrété le long de la marge continentale et métamorphisé dans le faciès schiste vert. La fermeture de la Paléotéthys s'enregistre finalement par la sédimentation dans le bassin d'avant pays du flysch de Bayazeh, d'âge probable Triasique. Le matériel issu de l'arc magmatique de la Paléotéthys est très bien préservé dans les dépôts infra-arc Dévonien supérieur-Carbonifère de Godar-e-Siah, ainsi que dans la succession d'avant-arc de Nakhlak. Pendant l'intervalle Paléozoïque supérieur-Trias, la région de Jandak a été soumise à un régime extensif de type bassin d'arrière-arc, dont un témoin pourrait être la ceinture ophiolitique d'Arusan, elle-même comparable aux écailles ophiolitiques d'Aghdarband au nord-est de l'Iran. Cet ensemble métamorphique est recoupé par des granites d'arc à collisionnel datés à 215±15 Ma. Dans la région de Yazd, témoin de la marge passive Cimmérienne, la sédimentation syn-rift Silurienne à Dévonienne inférieure a été interrompue pendant l'intervalle Trias moyen-Trias supérieur; il en a été de même pour les dépôts de plate-forme Paléozoïque supérieur. L'érosion, qui dans ce dernier cas a atteint le Permien, pourrait être liée au bombement flexural de la marge passive. La collision finale n'a pas induit de déformations trop importantes, et se caractérise par la mise en place de nappes sur la marge passive. Cet événement est scellé par des dépôts molassique du Lias. D'un point de vue régional, la zone s'étendant actuellement de la Mer Noire au Pamir a été soumise à six épisodes d'extension-compression du Jurassique inférieur (début du l'ouverture en position arrière-arc de la Néotéthys) à l'Eocène moyen. Par exemple, le terrane d'AnarakJandak, probablement situé entre le Kopeh Dagh et la plate-forme nord Afghane, s'est complètement détaché de sa patrie d'origine au début du Crétacé supérieur. Des preuves de cet événement se retrouvent dans les séries de plate-forme de Khur (préservation de séries syn-rift puis de marge passive). Les ophiolites de Nain et de Sabzevar sont de plus interprétée comme un témoin de l'existence de ce bassin d'arrière-arc. Dans l'intervalle Eocène-Oligocène, l'indentation par la plaque indienne de l'Eurasie a été contemporaine de la rotation horaire de fragments de l'ancien microcontinent Iranien et de la formation du CEIM. Cette rotation est responsable du transport du terrane d'Anarak-Jandak vers sa position actuelle en Iran Central, et de la dislocation de Terranes de moindre importance, comme le bloc de Posht-e Badam. Depuis le Miocène supérieur, et à la suite de la collision entre l'Arabie et l'Iran, le ternane d'Anarak-Jandak a subi des déformations liées à l'activité d'une zone de cisaillement dextre parallèle à la suture du Zagros, à l'arrière de l'arc magmatique d'Uromieh-Dokhtar. Résumé large public Le Microcontinent Centre-Est Iranien occupe une position géologique clé au centre de l'Iran. Les différentes unités qui le composent, reliées jusqu'à présent à des épisodes orogéniques d'âge Précambrien à Paléozoïque inférieur, sont maintenant rajeunies et liés à la fermeture de l'océean Paléotéthys. Leur histoire commence par un épisode de rifting d'âge Ordovicien supérieur à Dévonien inférieur, pour se terminer au Trias par la collision des- blocs Cimmériens, dérivés du Gondwana, avec le Bloc du Turan d'affinité asiatique. Dans la marge active asiatique de la Paléotéthys, nous avons daté les restes d'un océan marginal à 387±0.11 Ma. Ce complexe d'accrétion a été métamorphisé au cours de la réaccrétion de la ceinture granitique d'Airekan, d'âge Cambrien inférieur (549±15 Ma), qui affleure aujourd'hui à l'extrémité nord-ouest du « terrane » d'Anarak-Jandak correspondant à la plus grande partie de la région étudiée. Le matériel issu de l'arc magmatique de la Paléotéthys est très bien préservé et daté du Dévonien supérieur-Carbonifère. Pendant l'intervalle Paléozoïque supérieur-Trias, la région a été soumise à un régime extensif de type bassin d'arrière-arc, dont un témoin pourrait être la ceinture ophiolitique d'Arusan, comparable aux écailles ophiolitiques d'Aghdarband au nord-est de l'Iran. Cet ensemble métamorphique est recoupé par des granites datés à 215±15 Ma. La subduction vers le nord de l'océan Paléotéthys depuis le Paléozoïque supérieur jusqu'au Trias, a permis l'accumulation de grandes quantités de matériel océanique dans la zone de subduction. Par exemple, une succession de volcans sous-marins, entrés en collision avec le prisme d'accrétion, est à l'origine d'un léger métamorphisme de type HP qui affecte ces séries (280 à 230 Ma). Quant au prisme d'accrétion de Doshakh, d'âge essentiellement Permien supérieur, il a été mis en place le long de la marge continentale et métamorphisé dans le faciès schiste vert. La fermeture de la Paléotéthys s'enregistre finalement par la sédimentation dans le bassin d'avant pays du flysch de Bayazeh, d'âge Triasique. Dans la région de Yazd, on trouve les témoins de la marge passive Cimmérienne, la sédimentation syn-rift Silurienne à Dévonienne inférieure a été interrompue pendant l'intervalle Trias moyen-Trias supérieur, marqué par la flexuration de la marge passive lorsqu'elle rentra en collision avec la marge active asiatique. Cet événement est scellé par des dépôts molassique à charbon du Lias. Le «terrane» d'Anarak-Jandak, probablement situé à l'origine entre le Kopeh Dagh et la plate-forme nord Afghane, s'est complètement détaché de cette région au début du Crétacé supérieur lors de l'ouverture d'un bassin d'arrière-arc, engendré, cette fois, par la subduction de l'océan Néotéthys situé au sud des blocs cimmériens. Des preuves de cet événement se retrouvent dans les séries syn-rift, puis de marge passive de Khour. Les ophiolites de Nain et de Sabzevar sont interprétées comme un témoin de l'existence de ce bassin d'arrière-arc. Dans l'intervalle Eocène-Oligocène, l'indentation de l'Eurasie par la plaque indienne a été contemporaine de la rotation horaire de fragments de l'ancien microcontinent centre-Iranien. Cette rotation de près de 90° est responsable du transport du « terrane » d'Anarak-Jandak vers sa position actuelle. Abstract The Anarak-Jandaq terrane occupies a strategic geological situation at the north-western part of the Central-East Iranian Microcontinent (CEIM) and in connection with the Great Kavir Block and Sanandaj-Sirjan metamorphic belt. Our recent findings redefine the origin of these mentioned areas so far attributed to the Precambrian-Early Palaeozoic orogenic episodes, to be now directly related to the tectonic evolution of the Palaeo-Tethys Ocean, commenced by Late Ordovician-Early Devonian rifting events and terminated in the Triassic by the Eocimmerian tectonic event due to the collision of the Cimmerian blocks with the Asiatic Turan block. The most distributed metamorphic unit that is exposed from the south-west of Jandaq to the Anarak and Kaboudan areas is a thick and fine grain siliciclastic sequence accompanied by marginal-sea-basin ophiolitic blocks including basalt-gabbro association with supra-subduction-geochemical signature. These gabbros in the Nakhlak area were dated by U/Pb method at 387.6 ± 0.11 Ma and the metamorphic pelitic rocks yielded a range of 320 to 333 Ma muscovite-cooling ages based on 40Ar/39 Ar method. This "Variscan" accretionary complex was metamorphosed in greenschist-amphibolite facies during accretion to the Lower Cambrian Airekan granitic belt (549 ± 15 Ma by U/Pb method) that crops out at the northwestern edge of the Anarak-Jandaq terrane. Continued northward subduction of the Palaeo-Tethys Ocean during the entire Late Palaeozoic-Middle Triassic brought huge amount of oceanic material to the subduction zone. One chain of Carboniferous-Triassic oceanic rises and seamounts (the Anarak, Kaboudan, and Meraji Seamounts) obliquely collided with the accretionary wedge and created a mild HP metamorphic event (280-230 Ma based on 40Ar/39Ar results). Bimodal magmatism of the Chah Gorbeh area is characterized by a 262 Ma trondjemite-gabbro as well as pillow alkalibasalts-rhyolites which intruded the Anarak ophiolite when it was being emplaced within the inner-wall trench. The mainly Late Permian-Triassic Doshakh wedge was accreted along the continent and metamorphosed under lower greenschist facies and the probable Triassic Bayazeh flysch filled the foreland basin during the final closure. The Palaeo-Tethys magmatic arc products have been well preserved in the Late Devonian-Carboniferous Godar-e-Siah intra-arc deposits and the Triassic Nakhlak fore-arc succession. During the Late Palaeozoic-Triassic times, the Jandaq area has been affected by back-arc extension and probably the Arusan ophiolitic belt is the remnant of this narrow basin comparable to the Aqdarband ophiolitic remnant in north-east Iran. This metamorphic belt was intruded by 215 ± 15 Ma arc to collisional granites. In the passive margin of the Cimmerian block, on the Yazd region, the Silurian-Early Devonian syn-rift succession as well as the nearly continuous Upper Palaeozoic platform-type deposition was interrupted during the Middle to Late Triassic time, local erosion down to Devonian levels may be related to flexural bulge erosion. The collision event was not so strong to generate intensive deformation but was accompanied by some nappe thrusting onto the passive margin. It is finally unconformably covered by Liassic continental molassic deposits. Related to the onset of Neo-Tethyan back-arc opening in Early Jurassic to Mid-Eocene times, six periods of extensional-compressional events have differently influenced an elongated area, extending from the West Black Sea to Pamir. The Anarak-Jandaq terrane which was situated somewhere in this affected area, probably between the Kopeh Dagh and North Afghan platform, was completely detached from its source at the beginning of the Late Cretaceous