mTOR-related synaptic pathology causes autism spectrum disorder-associated functional hyperconnectivity.

Postmortem studies have revealed increased density of excitatory synapses in the brains of individuals with autism spectrum disorder (ASD), with a putative link to aberrant mTOR-dependent synaptic pruning. ASD is also characterized by atypical macroscale functional connectivity as measured with resting-state fMRI (rsfMRI). These observations raise the question of whether excess of synapses causes aberrant functional connectivity in ASD. Using rsfMRI, electrophysiology and in silico modelling in Tsc2 haploinsufficient mice, we show that mTOR-dependent increased spine density is associated with ASD -like stereotypies and cortico-striatal hyperconnectivity. These deficits are completely rescued by pharmacological inhibition of mTOR. Notably, we further demonstrate that children with idiopathic ASD exhibit analogous cortical-striatal hyperconnectivity, and document that this connectivity fingerprint is enriched for ASD-dysregulated genes interacting with mTOR or Tsc2. Finally, we show that the identified transcriptomic signature is predominantly expressed in a subset of children with autism, thereby defining a segregable autism subtype. Our findings causally link mTOR-related synaptic pathology to large-scale network aberrations, revealing a unifying multi-scale framework that mechanistically reconciles developmental synaptopathy and functional hyperconnectivity in autism

Neuroimaging Evidence of Major Morpho-Anatomical and Functional Abnormalities in the BTBR T+TF/J Mouse Model of Autism

BTBR T+tf/J (BTBR) mice display prominent behavioural deficits analogous to the defining symptoms of autism, a feature that has prompted a widespread use of the model in preclinical autism research. Because neuro-behavioural traits are described with respect to reference populations, multiple investigators have examined and described the behaviour of BTBR mice against that exhibited by C57BL/6J (B6), a mouse line characterised by high sociability and low self-grooming. In an attempt to probe the translational relevance of this comparison for autism research, we used Magnetic Resonance Imaging (MRI) to map in both strain multiple morpho-anatomical and functional neuroimaging readouts that have been extensively used in patient populations. Diffusion tensor tractography confirmed previous reports of callosal agenesis and lack of hippocampal commissure in BTBR mice, and revealed a concomitant rostro-caudal reorganisation of major cortical white matter bundles. Intact inter-hemispheric tracts were found in the anterior commissure, ventro-medial thalamus, and in a strain-specific white matter formation located above the third ventricle. BTBR also exhibited decreased fronto-cortical, occipital and thalamic gray matter volume and widespread reductions in cortical thickness with respect to control B6 mice. Foci of increased gray matter volume and thickness were observed in the medial prefrontal and insular cortex. Mapping of resting-state brain activity using cerebral blood volume weighted fMRI revealed reduced cortico-thalamic function together with foci of increased activity in the hypothalamus and dorsal hippocampus of BTBR mice. Collectively, our results show pronounced functional and structural abnormalities in the brain of BTBR mice with respect to control B6 mice. The large and widespread white and gray matter abnormalities observed do not appear to be representative of the neuroanatomical alterations typically observed in autistic patients. The presence of reduced fronto-cortical metabolism is of potential translational relevance, as this feature recapitulates previously-reported clinical observations

Structural Analysis of Fagopyrin Extracts by HPLC-MS, NMR and CD

Fagopyrin is a phenantro-perylenequinone present in the flowers of Fagopyrum aesculentum (buckwheat), endowed with photodynamic activity and responsible of a certain number of photosensitizing syndromes in grazing animals (fagopyrism)1. This molecule was firstly extracted, more than 30 years ago, by Brockmann, who ascertained its chemical constitution.2 More accurate structural investigations, performed on the related compound hypericin, showed that a high degree of structural and conformational complexity might be present,3 as the aromatic system is involved in different equilibria of tautomerism, dissociation, torsional isomerism, and homoassociation. In the case of fagopyrin, the presence of two piperidine rings at positions 2 and 5 introduces two new stereogenic centres, in addition to the axial chirality of the aromatic system. Apart from the fundamental work of Brockmann, who did not establish the absolute configuration of the isolated fagopyrin, no other study has appeared, reporting a detailed analysis of the various stereogenic centres. Here, we wish to report our results regarding the stereochemistry of fagopyrin, as well as the composition of fagopyrin extracts; which actually proved to be complex mixtures of up to twenty molecules. Some of them are constituted by the same perylene-quinone, linked not only to piperidine, but also to pirrolidine moieties. This generates three different groups of closely related molecules (see Figure), depending on the nature of the linked heterocycles, with the generation of up to 8 stereoisomers within each family. The configuration of each stereocenter has been established by NMR and CD measurements, combined with ab-initio calculations (Gaussian03). Finally, the highly acidic hydroxyl groups allow the formation of zwitterionic species constituted by ion-pairs between the protonated amino groups and the negatively charged hypericinate ion. 1. Wender S. H., Gortner R. A., Inman O. L., J. Am. Chem. Soc., 1943, 65, 1733-1735. 2. Brockmann H., Lackner H., Tetrahedron Lett., 1979, 1575-1578. 3. Falk H., Angew. Chem. Int. Ed., 1999, 38, 3116-3136

Large-scale chromatin remodeling in germinal vesicle bovine oocytes: interplay with gap junction functionality and developmental competence

In mammals, oocyte acquires a series of competencies sequentially during folliculogenesis that play critical roles at fertilization and early stages of embryonic development. In mouse, chromatin in germinal vesicle (GV) undergoes dynamic changes during oocyte growth and its progressive condensation has been related to the achievement of developmental potential. Cumulus cells are essential for the acquisition of meiotic competence and play a role in chromatin remodeling during oocyte growth. This study is aimed to characterize the chromatin configuration of growing and fully grown bovine oocytes, the status of communications between oocyte and cumulus cells and oocyte developmental potential. Following nuclear staining, we identified four discrete stages of GV, characterized by an increase of chromatin condensation. GV0 stage represented 82% of growing oocytes and it was absent in fully grown oocytes. GV1, GV2, and GV3 represented, respectively, 24, 31, and 45% of fully grown oocytes. Our data indicated a moderate but significant increase in oocyte diameter between GV0 and GV3 stage. By dye coupling assay the 98% of GV0 oocytes showed fully open communications while the number of oocytes with functionally closed communications with cumulus cells was significantly higher in GV3 group than GV1 and GV2. However, GV0 oocytes were unable to progress through metaphase II while GV2 and GV3 showed the highest developmental capability. We conclude that in bovine, the progressive chromatin condensation is related to the sequential achievement of meiotic and embryonic developmental competencies during oocyte growth and differentiation. Moreover, gap-junction-mediated communications between oocyte and cumulus cells could be implicated in modulating the chromatin remodeling process

Biomechanical analysis of the muscular and ligament behavior of the knee joint through a subject-specific computational model

The interaction and load sharing between muscles, ligaments and articulating surfaces is crucial for the stability of the knee. The aim of the present work is to develop an effective multibody dynamics-based model that allows a quick subject-specific assessment of ligaments, muscular behavior and contact forces. This paper shows the results of ‘quasi-static’ simulations of a squat movement between 0° and 90° of flexion in gravitational force field. During this movement the lengths of anterior cruciate ligament (ACL) and lateral collateral ligament (LCL) decreased up to 21% and 10.5%, respectively, while the lengths of medial collateral ligament (MCL) and posterior cruciate ligament (PCL) increased. Quadriceps muscle force at equilibrium increased during flexion reaching a value of 3.88 body weight (BW) at 90° of flexion. Tibio-femoral contact forces changed non-linearly with joint angle and achieved a maximum value of 4.58 BW at 90° of flexion. Once completely developed this model could be used to investigate the effect of several key factors in the surgical planning that could affect the knee biomechanics and the results of the intervention