Hemispheric asymmetry and theory of mind: Is there an association?

Introduction. In autism and schizophrenia attenuated/atypical functional hemispheric asymmetry and theory of mind impairments have been reported, suggesting common underlying neuroscientific correlates. We here investigated whether impaired theory of mind performance is associated with attenuated/atypical hemispheric asymmetry. An association may explain the co-occurrence of both dysfunctions in psychiatric populations. Methods. Healthy participants (n 129) performed a left hemisphere (lateralised lexical decision task) and right hemisphere (lateralised face decision task) dominant task as well as a visual cartoon task to assess theory of mind performance. Results. Linear regression analyses revealed inconsistent associations between theory of mind performance and functional hemisphere asymmetry: enhanced theory of mind performance was only associated with (1) faster right hemisphere language processing, and (2) reduced right hemisphere dominance for face processing (men only). Conclusions. The majority of non-significant findings suggest that theory of mind and functional hemispheric asymmetry are unrelated. Instead of ''overinterpreting'' the two significant results, discrepancies in the previous literature relating to the problem of the theory of mind concept, the variety of tasks, and the lack of normative data are discussed. We also suggest how future studies could explore a possible link between hemispheric asymmetry and theory of mind.

Roles of mGluR5 in synaptic function and plasticity of the mouse thalamocortical pathway.

The group I metabotropic glutamate receptor 5 (mGluR5) has been implicated in the development of cortical sensory maps. However, its precise roles in the synaptic function and plasticity of thalamocortical (TC) connections remain unknown. Here we first show that in mGluR5 knockout (KO) mice bred onto a C57BL6 background cytoarchitectonic differentiation into barrels is missing, but the representations for large whiskers are identifiable as clusters of TC afferents. The altered dendritic morphology of cortical layer IV spiny stellate neurons in mGluR5 KO mice implicates a role for mGluR5 in the dendritic morphogenesis of excitatory neurons. Next, in vivo single-unit recordings of whisker-evoked activity in mGluR5 KO adults demonstrated a preserved topographical organization of the whisker representation, but a significantly diminished temporal discrimination of center to surround whiskers in the responses of individual neurons. To evaluate synaptic function at TC synapses in mGluR5 KO mice, whole-cell voltage-clamp recording was conducted in acute TC brain slices prepared from postnatal day 4-11 mice. At mGluR5 KO TC synapses, N-methyl-D-aspartate (NMDA) currents decayed faster and synaptic strength was more easily reduced, but more difficult to strengthen by Hebbian-type pairing protocols, despite a normal developmental increase in alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated currents and presynaptic function. We have therefore demonstrated that mGluR5 is required for synaptic function/plasticity at TC synapses as barrels are forming, and we propose that these functional alterations at the TC synapse are the basis of the abnormal anatomical and functional development of the somatosensory cortex in the mGluR5 KO mouse.

Functional assessment of chest wall integrity after methylmethacrylate reconstruction.

BACKGROUND: All patients with extensive resection of the anterolateral chest wall and the sternum followed by reconstruction with methylmethacrylate substitutes were assessed prospectively 6 months after the operation to delineate chest wall integrity with pulmonary function and cine-magnetic resonance imaging. METHODS: Twenty-six patients underwent chest wall reconstruction by use of methylmethacrylate between 1994 and 1998 due to primary tumors in 35%, metastases in 27%, T3 lung cancer in 19%, and debridement for radionecrosis and osteomyelitis in 19% of patients. Three to eight ribs were resected and additional sternum resection was performed in 39% of patients. RESULTS: There was no 30-day mortality. All patients were extubated after the operation without need for reintubation. Prosthesis dislocation occurred in 1 patient and infection in 2 patients during follow-up. Nineteen patients (73%) suffered no restrictions of daily activities. Clinical examination revealed normal shoulder girdle function in 77% of patients. There was no significant difference between preoperative and postoperative FEV1 (forced expiratory volume in 1 second) measurements in patients with lobectomy or wedge resections. Cinemagnetic resonance imaging revealed concordant chest wall movements during respiration in 92% of patients without paradoxical movements or implant dislocations being observed. CONCLUSIONS: Large defects of the anterolateral chest wall and sternum can be reconstructed efficiently with methylmethacrylate substitutes with minimal morbidity and excellent cosmetic and functional outcome.

Melan-A-specific cytotoxic T cells are associated with tumor regression and autoimmunity following treatment with anti-CTLA-4.

PURPOSE: Ipilimumab is a monoclonal antibody that blocks the immune-inhibitory interaction between CTL antigen 4 (CTLA-4) and its ligands on T cells. Clinical trials in cancer patients with ipilimumab have shown promising antitumor activity, particularly in patients with advanced melanoma. Often, tumor regressions in these patients are correlated with immune-related side effects such as dermatitis, enterocolitis, and hypophysitis. Although these reactions are believed to be immune-mediated, the antigenic targets for the cellular or humoral immune response are not known. EXPERIMENTAL DESIGN: We enrolled patients with advanced melanoma in a phase II study with ipilimumab. One of these patients experienced a complete remission of his tumor. The specificity and functional properties of CD8-positive T cells in his peripheral blood, in regressing tumor tissue, and at the site of an immune-mediated skin rash were investigated. RESULTS: Regressing tumor tissue was infiltrated with CD8-positive T cells, a high proportion of which were specific for Melan-A. The skin rash was similarly infiltrated with Melan-A-specific CD8-positive T cells, and a dramatic (>30-fold) increase in Melan-A-specific CD8-positive T cells was apparent in peripheral blood. These cells had an effector phenotype and lysed Melan-A-expressing tumor cells. CONCLUSIONS: Our results show that Melan-A may be a major target for both the autoimmune and antitumor reactions in patients treated with anti-CTLA-4, and describe for the first time the antigen specificity of CD8-positive T cells that mediate tumor rejection in a patient undergoing treatment with an anti-CTLA-4 antibody. These findings may allow a better integration of ipilimumab into other forms of immunotherapy.

Draft genome of the globally widespread and invasive Argentine ant (Linepithema humile).

Ants are some of the most abundant and familiar animals on Earth, and they play vital roles in most terrestrial ecosystems. Although all ants are eusocial, and display a variety of complex and fascinating behaviors, few genomic resources exist for them. Here, we report the draft genome sequence of a particularly widespread and well-studied species, the invasive Argentine ant (Linepithema humile), which was accomplished using a combination of 454 (Roche) and Illumina sequencing and community-based funding rather than federal grant support. Manual annotation of >1,000 genes from a variety of different gene families and functional classes reveals unique features of the Argentine ant's biology, as well as similarities to Apis mellifera and Nasonia vitripennis. Distinctive features of the Argentine ant genome include remarkable expansions of gustatory (116 genes) and odorant receptors (367 genes), an abundance of cytochrome P450 genes (>110), lineage-specific expansions of yellow/major royal jelly proteins and desaturases, and complete CpG DNA methylation and RNAi toolkits. The Argentine ant genome contains fewer immune genes than Drosophila and Tribolium, which may reflect the prominent role played by behavioral and chemical suppression of pathogens. Analysis of the ratio of observed to expected CpG nucleotides for genes in the reproductive development and apoptosis pathways suggests higher levels of methylation than in the genome overall. The resources provided by this genome sequence will offer an abundance of tools for researchers seeking to illuminate the fascinating biology of this emerging model organism.

Red cell distribution width does not predict stroke severity or functional outcome.

INTRODUCTION: Red cell distribution width was recently identified as a predictor of cardiovascular and all-cause mortality in patients with previous stroke. Red cell distribution width is also higher in patients with stroke compared with those without. However, there are no data on the association of red cell distribution width, assessed during the acute phase of ischemic stroke, with stroke severity and functional outcome. In the present study, we sought to investigate this relationship and ascertain the main determinants of red cell distribution width in this population. METHODS: We used data from the Acute Stroke Registry and Analysis of Lausanne for patients between January 2003 and December 2008. Red cell distribution width was generated at admission by the Sysmex XE-2100 automated cell counter from ethylene diamine tetraacetic acid blood samples stored at room temperature until measurement. An χ(2) -test was performed to compare frequencies of categorical variables between different red cell distribution width quartiles, and one-way analysis of variance for continuous variables. The effect of red cell distribution width on severity and functional outcome was investigated in univariate and multivariate robust regression analysis. Level of significance was set at 95%. RESULTS: There were 1504 patients (72±15·76 years, 43·9% females) included in the analysis. Red cell distribution width was significantly associated to NIHSS (β-value=0·24, P=0·01) and functional outcome (odds ratio=10·73 for poor outcome, P<0·001) at univariate analysis but not multivariate. Prehospital Rankin score (β=0·19, P<0·001), serum creatinine (β=0·008, P<0·001), hemoglobin (β=-0·009, P<0·001), mean platelet volume (β=0·09, P<0·05), age (β=0·02, P<0·001), low ejection fraction (β=0·66, P<0·001) and antihypertensive treatment (β=0·32, P<0·001) were independent determinants of red cell distribution width. CONCLUSIONS: Red cell distribution width, assessed during the early phase of acute ischemic stroke, does not predict severity or functional outcome.

Thyroid hormone enhances transected axonal regeneration and muscle reinnervation following rat sciatic nerve injury.

Improvement of nerve regeneration and functional recovery following nerve injury is a challenging problem in clinical research. We have already shown that following rat sciatic nerve transection, the local administration of triiodothyronine (T3) significantly increased the number and the myelination of regenerated axons. Functional recovery is a sum of the number of regenerated axons and reinnervation of denervated peripheral targets. In the present study, we investigated whether the increased number of regenerated axons by T3-treatment is linked to improved reinnervation of hind limb muscles. After transection of rat sciatic nerves, silicone or biodegradable nerve guides were implanted and filled with either T3 or phosphate buffer solution (PBS). Neuromuscular junctions (NMJs) were analyzed on gastrocnemius and plantar muscle sections stained with rhodamine alpha-bungarotoxin and neurofilament antibody. Four weeks after surgery, most end-plates (EPs) of operated limbs were still denervated and no effect of T3 on muscle reinnervation was detected at this stage of nerve repair. In contrast, after 14 weeks of nerve regeneration, T3 clearly enhanced the reinnervation of gastrocnemius and plantar EPs, demonstrated by significantly higher recovery of size and shape complexity of reinnervated EPs and also by increased acetylcholine receptor (AChRs) density on post synaptic membranes compared to PBS-treated EPs. The stimulating effect of T3 on EP reinnervation is confirmed by a higher index of compound muscle action potentials recorded in gastrocnemius muscles. In conclusion, our results provide for the first time strong evidence that T3 enhances the restoration of NMJ structure and improves synaptic transmission.

SNARE protein expression in synaptic terminals and astrocytes in the adult hippocampus: a comparative analysis.

Several evidences suggest that astrocytes release small transmitter molecules, peptides, and protein factors via regulated exocytosis, implying that they function as specialized neurosecretory cells. However, very little is known about the molecular and functional properties of regulated secretion in astrocytes in the adult brain. Establishing these properties is central to the understanding of the communication mode(s) of these cells and their role(s) in the control of synaptic functions and of cerebral blood flow. In this study, we have set-up a high-resolution confocal microscopy approach to distinguish protein expression in astrocytic structures and neighboring synaptic terminals in adult brain tissue. This approach was applied to investigate the expression pattern of core SNARE proteins for vesicle fusion in the dentate gyrus and CA1 regions of the mouse hippocampus. Our comparative analysis shows that astrocytes abundantly express, in their cell body and main processes, all three protein partners necessary to form an operational SNARE complex but not in the same isoforms expressed in neighbouring synaptic terminals. Thus, SNAP25 and VAMP2 are absent from astrocytic processes and typically concentrated in terminals, while SNAP23 and VAMP3 have the opposite expression pattern. Syntaxin 1 is present in both synaptic terminals and astrocytes. These data support the view that astrocytes in the adult hippocampus can communicate via regulated exocytosis and also indicates that astrocytic exocytosis may differ in its properties from action potential-dependent exocytosis at neuronal synapses, as it relies on a distinctive set of SNARE proteins.

BAFF is a survival and maturation factor for mouse B cells.

Human B cell-activating factor (BAFF) induces mouse surface IgM+ B cells of the immature type from bone marrow and of the immature types 1 and 2 from spleen, as well as of the mature type from spleen to increased longevity in tissue culture. BAFF does so polyclonally and without inducing proliferation in any of these B cell subpopulations. BAFF induces phenotypic and functional maturation of immature to mature B cells so that all immature cells loose C1qRp (AA4.1, 493) expression and type 1 immature cells up-regulate IgD, CD21 and CD23. Immature B cells of types 1 and 2, upon pre-incubation with BAFF, change their reactiveness to Ig-specific antibodies so that they no longer enter apoptosis but now proliferate. However, BAFF does not seem to overcome negative selection of developing immature B cells in vitro.

Birth and expression evolution of mammalian microRNA genes.

MicroRNAs (miRNAs) are major post-transcriptional regulators of gene expression, yet their origins and functional evolution in mammals remain little understood due to the lack of appropriate comparative data. Using RNA sequencing, we have generated extensive and comparable miRNA data for five organs in six species that represent all main mammalian lineages and birds (the evolutionary outgroup) with the aim to unravel the evolution of mammalian miRNAs. Our analyses reveal an overall expansion of miRNA repertoires in mammals, with threefold accelerated birth rates of miRNA families in placentals and marsupials, facilitated by the de novo emergence of miRNAs in host gene introns. Generally, our analyses suggest a high rate of miRNA family turnover in mammals with many newly emerged miRNA families being lost soon after their formation. Selectively preserved mammalian miRNA families gradually evolved higher expression levels, as well as altered mature sequences and target gene repertoires, and were apparently mainly recruited to exert regulatory functions in nervous tissues. However, miRNAs that originated on the X chromosome evolved high expression levels and potentially diverse functions during spermatogenesis, including meiosis, through selectively driven duplication-divergence processes. Overall, our study thus provides detailed insights into the birth and evolution of mammalian miRNA genes and the associated selective forces.

Construction and Quantitative Evaluation of a Dual Specific Promoter System for Monitoring the Expression Status of Stra8 and c-kit Genes.

Applications of genetic constructs with multiple promoters, which are fused with reporter genes and simultaneous monitoring of various events in cells, have gained special attention in recent years. Lentiviral vectors, with their distinctive characteristics, have been considered to monitor the developmental changes of cells in vitro. In this study, we constructed a novel lentiviral vector (FUM-M), containing two germ cell-specific promoters (Stra8 and c-kit), fused with ZsGreen and DsRed2 reporter genes, and evaluated its efficiency in different cells following treatments with retinoic acid and DMSO. Several cell lines (P19, GC-1 spg and HEK293T) were transduced with this vector, and functional capabilities of the promoters were verified by flow cytometry and quantitative RT-PCR. Our results indicate that FUM-M shows dynamic behavior in the presence and absence of extrinsic factors. A correlation was also observed between the function of promoters, present in the lentiviral construct and the endogenous level of the Stra8 and c-kit mRNAs in the cells. In conclusion, we recommend this strategy, which needs further optimization of the constructs, as a beneficial and practical way to screen chemical inducers involved in cellular differentiation toward germ-like cells.

NS2 Proteins of GB Virus B and Hepatitis C Virus Share Common Protease Activities and Membrane Topologies.

GB virus B (GBV-B), which is hepatotropic in experimentally infected small New World primates, is a member of the Hepacivirus genus but phylogenetically relatively distant from hepatitis C virus (HCV). To gain insights into the role and specificity of hepaciviral nonstructural protein 2 (NS2), which is required for HCV polyprotein processing and particle morphogenesis, we investigated whether NS2 structural and functional features are conserved between HCV and GBV-B. We found that GBV-B NS2, like HCV NS2, has cysteine protease activity responsible for cleavage at the NS2/NS3 junction, and we experimentally confirmed the location of this junction within the viral polyprotein. A model for GBV-B NS2 membrane topology was experimentally established by determining the membrane association properties of NS2 segments fused to green fluorescent protein (GFP) and their nuclear magnetic resonance structures using synthetic peptides as well as by applying an N-glycosylation scanning approach. Similar glycosylation studies confirmed the HCV NS2 organization. Together, our data show that despite limited amino acid sequence similarity, GBV-B and HCV NS2 proteins share a membrane topology with 3 N-terminal transmembrane segments, which is also predicted to apply to other recently discovered hepaciviruses. Based on these data and using trans-complementation systems, we found that intragenotypic hybrid NS2 proteins with heterologous N-terminal membrane segments were able to efficiently trans-complement an assembly-deficient HCV mutant with a point mutation in the NS2 C-terminal domain, while GBV-B/HCV or intergenotypic NS2 chimeras were not. These studies indicate that virus- and genotype-specific intramolecular interactions between N- and C-terminal domains of NS2 are critically involved in HCV morphogenesis. IMPORTANCE: Nonstructural protein 2 (NS2) of hepatitis C virus (HCV) is a multifunctional protein critically involved in polyprotein processing and virion morphogenesis. To gain insights into NS2 mechanisms of action, we investigated whether NS2 structural and functional features are conserved between HCV and GB virus B (GBV-B), a phylogenetically relatively distant primate hepacivirus. We showed that GBV-B NS2, like HCV NS2, carries cysteine protease activity. We experimentally established a model for GBV-B NS2 membrane topology and demonstrated that despite limited sequence similarity, GBV-B and HCV NS2 share an organization with three N-terminal transmembrane segments. We found that the role of HCV NS2 in particle assembly is genotype specific and relies on critical interactions between its N- and C-terminal domains. This first comparative analysis of NS2 proteins from two hepaciviruses and our structural predictions of NS2 from other newly identified mammal hepaciviruses highlight conserved key features of the hepaciviral life cycle.

Effects of antibacterial agents and drugs monitored by atomic force microscopy.

Originally invented for topographic imaging, atomic force microscopy (AFM) has evolved into a multifunctional biological toolkit, enabling to measure structural and functional details of cells and molecules. Its versatility and the large scope of information it can yield make it an invaluable tool in any biologically oriented laboratory, where researchers need to perform characterizations of living samples as well as single molecules in quasi-physiological conditions and with nanoscale resolution. In the last 20 years, AFM has revolutionized the characterization of microbial cells by allowing a better understanding of their cell wall and of the mechanism of action of drugs and by becoming itself a powerful diagnostic tool to study bacteria. Indeed, AFM is much more than a high-resolution microscopy technique. It can reconstruct force maps that can be used to explore the nanomechanical properties of microorganisms and probe at the same time the morphological and mechanical modifications induced by external stimuli. Furthermore it can be used to map chemical species or specific receptors with nanometric resolution directly on the membranes of living organisms. In summary, AFM offers new capabilities and a more in-depth insight in the structure and mechanics of biological specimens with an unrivaled spatial and force resolution. Its application to the study of bacteria is extremely significant since it has already delivered important information on the metabolism of these small microorganisms and, through new and exciting technical developments, will shed more light on the real-time interaction of antimicrobial agents and bacteria.

Surgery for Hirschsprung's disease: comparison between the Duhamel method and the transanal endorectal pull-through based on 59 patients and a review of the literature

Background:¦Hirschsprung's disease (HSCR) is a congenital malformation of the enteric nervous system due to the¦arrest of migration of neural crest cells to form the myenteric and submucosal plexuses. It leads to an anganglionic intestinal segment, which is permanently contracted causing intestinal obstruction. Its incidence is approximately 1/5000 birth, and males are more frequently affected with a male/female ratio of 4/1. The diagnosis is in most cases made within the first year of life. The rectal biopsy of the mucosa and sub-mucosa is the diagnostic gold standard.¦Purpose:¦The aim of this study was to compare two surgical approaches for HSCR, the Duhamel technique and the transanal endorectal pull-through (TEPT) in term of indications, duration of surgery, duration of hospital stay, postoperative treatment, complications, frequency of enterocolitis and functional outcomes.¦Methods:¦Fifty-nine patients were treated for HSCR by one of the two methods in our department of pediatric¦surgery between 1994 and 2010. These patients were separated into two groups (I: Duhamel, II: TEPT), which were compared on the basis of medical records. Statistics were made to compare the two groups (ANOVA test). The first group includes 43 patients and the second 16 patients. It is noteworthy that twenty-four patients (about 41% of all¦patients) were referred from abroad (Western Africa). Continence was evaluated with the Krickenbeck's score.¦Results:¦Statistically, this study showed that operation duration, hospital stay, postoperative fasting and duration of postoperative antibiotics were significantly shorter (p value < 0.05) in group II (TEPT). But age at operation and length of aganglionic segment showed no significant difference between the two groups. The continence follow-up showed generally good results (Krickenbeck's scores 1; 2.1; 3.1) in both groups with a slight tendency to constipation in group I and soiling in group II.¦Conclusion:¦We found two indications for the Duhamel method that are being referred from a country without¦careful postoperative surveillance and/or having a previous colostomy. Even if the Duhamel technique tends to be replaced by the TEPT, it remains the best operative approach for some selected patients. TEPT has also proved some advantages but must be followed carefully because, among other points, of the postoperative dilatations. Our postoperative standards, like digital rectal examination and anal dilatations seem to reduce the occurrence of complications like rectal spur and anal/anastomosis stenosis, respectively in the Duhamel method and the TEPT technique.

Molecular basis of interaction between Na,K-ATPase and FXYD proteins.

Résumé au large public Notre corps est constitué de différents types de cellules. La condition minimale ou primordiale pour la survie des cellules est d'avoir de l'énergie. Cette tâche est assumée en partie par une protéine qui se situe dans la membrane de chaque cellule. Nommé Na, K¬ATPase ou pompe à sodium, c'est une protéine pressente dans toutes les cellules chez les mammifères est composée de deux sous-unités, α et β. En transportant 3 ions de sodium hors de la cellule et 2 ions de potassium à l'intérieur de la cellule, elle transforme l'énergie chimique sous forme de l'ATP en énergie motrice, qui permet aux cellules par la suite d'échanger des matériaux entre l'espace intracellulaire et extracellulaire ainsi que d'ingérer des nutriments provenant de son environnement. Le manque de cette protéine chez la souris entraîne la mort de l'embryon. Des défauts fonctionnels de cette protéine sont responsables de plusieurs maladies humaines comme par exemple, un type de migraine. En dehors de sa fonction vitale, cette protéine est également engagée dans diverses activités physiologiques comme la contractilité musculaire, l'activité nerveuse et la régulation du volume sanguin. Vue l'importance de cette protéine, sa découverte par Jens C. Skou en 1957 a été honorée d'un Prix Noble de chimie quarante ans plus tard. Depuis lors, nous connaissons de mieux en mieux les mécanismes de fonctionnement de la Na, K-ATPase. Entre autre, sa régulation par une famille de protéines appelées protéines FXYD. Cette famille contient 7 membres (FXYD 1-7). L'un d'entre eux nommé FXYD 2 est lié à une maladie héréditaire connue sous le nom de hypomagnesemia. Nous disposons actuellement d'informations concernant les conséquences de la régulation par les protéines FXYD sur activité de la Na, K-ATPase, mais nous savons très peu sur le mode d'interaction entre les protéines FXYD et la Na, K-ATPase. Dans ce travail de thèse, nous avons réussi à localiser des zones d'interaction dans la sous- unité a de la Na, K-ATPase et dans FXYD 7. En même temps, nous avons déterminé un 3ème site de liaison spécifique au sodium de la Na, K-ATPase. Une partie de ce site se situe à l'intérieur d'un domaine protéique qui interagit avec les protéines FXYD. De plus, ce site a été démontré comme responsable d'un mécanisme de transport de la Na, K-ATPase caractérisé par un influx ionique. En conclusion, les résultats de ce travail de thèse fournissent de nouvelles preuves sur les régions d'interaction entre la Na, K-ATPase et les protéines FXYD. La détermination d'un 3ème site spécifique au sodium et sa relation avec un influx ionique offrent la possibilité 1) d'explorer les mécanismes avec lesquels les protéines FXYD régulent l'activité de la Na, ATPase et 2) de localiser un site à sodium qui est essentielle pour mieux comprendre l'organisation et le fonctionnement de la Na, K-ATPase. Résumé Les gradients de concentration de Na+ et de K+ à travers la membrane plasmatique des cellules animales sont cruciaux pour la survie et l'homéostasie de cellules. De plus, des fonctions cellulaires spécifiques telles que la reabsorption de Na dans le rein et le côlon, la contraction musculaire et l'excitabilité nerveuse dépendent de ces gradients. La Na, K¬ATPase ou pompe à sodium est une protéine membranaire ubiquitaire. Elle crée et maintient ces gradients en utilisant l'énergie obtenu par l'hydrolyse de l'adénosine triphosphate. L'unité fonctionnelle minimale de cette protéine se compose d'une sous-unité catalytique α et d'une sous-unité régulatrice β. Récemment, il a été montré que des membres de la famille FXYD, sont des régulateurs tissu-spécifiques de la Na, K-ATPase qui influencent ses propriétés de transport. Cependant, on connaît peu de chose au sujet de la nature moléculaire de l'interaction entre les protéines FXYD et la Na, K-ATPase. Dans cette étude, nous fournissons, pour la première fois, l'évidence directe que des résidus du domaine transmembranaire (TM) 9 de la sous-unité α de la Na, K-ATPase sont impliqués dans l'interaction fonctionnelle et structurale avec les protéines FXYD. De plus nous avons identifié des régions dans le domaine transmembranaire de FXYD 7 qui sont importantes pour l'association stable avec la Na, K-ATPase et une série de résidus responsables des régulations fonctionnelles. Nous avons aussi montré les contributions fonctionnelles du TM 9 de la Na, K-ATPase à la translocation de Na + en déterminant un 3ème site spécifique au Na+. Ce site se situe probablement dans un espace entre TM 9, TM 6 et TM 5 de la sous-unité α de la pompe à sodium. De plus, nous avons constaté que le 3ème site de Na + est fonctionnellement lié à un courant entrant de la pompe sensible à l'ouabaïne et activé par le pH acide. En conclusion, ce travail donne de nouvelles perspectives de l'interaction structurale et fonctionnelle entre les protéines FXYD et la Na, K-ATPase. En outre, les contributions fonctionnelles de TM 9 offrent de nouvelles possibilités pour explorer le mécanisme par lequel les protéines FXYD régulent les propriétés fonctionnelles de la Na, K-ATPase. La détermination du 3ème site au Na + fournit une compréhension avancée du site spécifique au Na + de la Na, K-ATPase et du mécanisme de transport de la Na, K-ATPase. Summary The Na+ and K+ gradients across the plasma membrane of animal cells are crucial for cell survival and homeostasis. Moreover, specific tissue functions such as Na+ reabsorption in kidney and colon, muscle contraction and nerve excitability depend on the maintenance of these gradients. Na, K-ATPase or sodium pump, an ubiquitous membrane protein, creates and maintains these gradients by using the energy from the hydrolysis of ATP. The minimal functional unit of this protein is composed of a catalytic α subunit and a regulatory β subunit. Recently, members of the FXYD family, have been reported to be tissue-specific regulators of Na, K-ATPase by influencing its transport properties. However, little is known about the molecular nature of the interaction between FXYD proteins and Na, K-ATPase. In this study, we provide, for the first time, direct evidence that residues from the transmembrane (TM) domain 9 of the α subunit of Na, K-ATPase are implicated in the functional and structural interaction with FXYD proteins. Moreover, we have identified regions in the TM domain of FXYD 7 important for the stable association with Na, K-ATPase and a stretch of residues responsible for the functional regulations. We have further revealed the functional contributions of TM 9 of the Na, K-ATPase α subunit to the Na+ translocation by determining a 3rd Na+-specific cation binding site. This site is likely in a space between TM 9, TM 6 and TM 5 of the a subunit of the sodium pump. Moreover, we have found that the 3rd Na+ binding site is functionally linked to an acidic pH- activated ouabain-sensitive inward pump current. In conclusion, this work gives new insights into the structural and functional interaction between FXYD proteins and Na, K-ATPase. Functional contributions of TM 9 offer new possibilities to explore the mechanism by which FXYD proteins regulate functional properties of Na, K-ATPase. The determination of the 3rd Na+ binding site provides an advanced understanding concerning the Na+ -specific binding site of Na, K-ATPase and the 3rd Na+ site related transport mechanism.