sirolimus and Autistic-Disorder

The mammalian target of rapamycin (mTOR) is a central regulator of a diverse array of cellular processes, including cell growth, proliferation, autophagy, translation, and actin polymerization. Components of the mTOR cascade are present at synapses and influence synaptic plasticity and spine morphogenesis. A prevailing view is that the study of mTOR and its role in autism spectrum disorders (ASDs) will elucidate the molecular mechanisms by which mTOR regulates neuronal function under physiological and pathological conditions. Although many ASDs arise as a result of mutations in genes with multiple molecular functions, they appear to converge on common biological pathways that give rise to autism-relevant behaviors. Dysregulation of mTOR signaling has been identified as a phenotypic feature common to fragile X syndrome, tuberous sclerosis complex 1 and 2, neurofibromatosis 1, phosphatase and tensin homolog, and potentially Rett syndrome. Below are a summary of topics covered in a symposium that presents dysregulation of mTOR as a unifying theme in a subset of ASDs.

Topics: Animals; Autistic Disorder; Disease Models, Animal; Humans; Models, Biological; Signal Transduction; Sirolimus

Tuberous sclerosis complex is an autosomal dominant disease, with variable expressivity and multisystemic involvement, which is characterised by the growth of benign tumours called hamartomas. The organs that are most commonly affected are the brain, skin, kidneys, eyes, heart and lungs. Of all the children with this disease, 85% present neurological manifestations that, due to their severity, are the main cause of morbidity and mortality. The most significant neurological manifestations are epilepsy, autism spectrum disorders and mental retardation. It has been shown that in tuberous sclerosis complex the genes TSC1 and TSC2 alter the mTOR enzyme cascade, which sets off inhibition of this pathway. The possibility of resorting to treatments applied at the origin, thus inhibiting this pathway, is currently being evaluated.

Topics: Anticonvulsants; Astrocytoma; Autistic Disorder; Brain Diseases; Brain Neoplasms; Drug Design; Epilepsy; Everolimus; Glioma, Subependymal; Hamartoma; Humans; Intellectual Disability; Learning Disabilities; Molecular Targeted Therapy; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tuberous Sclerosis; Tuberous Sclerosis Complex 1 Protein; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins

The mTOR signaling network functions as a pivotal regulatory cascade during the development of the cerebral cortex. Aberrant hyperactivation of mTOR as a consequence of loss-of-function gene mutations encoding mTOR inhibitor proteins such as TSC1, TSC2, PTEN and STRADα has been recently linked to developmental cortical malformations associated with epilepsy and neurobehavioral disabilities. Investigation of mTOR signaling in these disorders provides for the first time exciting future avenues for assessment of biomarkers, patient stratification and prognostic measures as well as the opportunity for targeted therapy to regulate mTOR activity across all age groups. As we learn more about mTOR and its activity in the developing brain, many challenges will arise that must be overcome before widespread clinical therapeutics can be implemented.

Topics: Adaptor Proteins, Vesicular Transport; Animals; Autistic Disorder; Biomarkers; Cerebral Cortex; Epilepsy; Humans; Malformations of Cortical Development; Mechanistic Target of Rapamycin Complex 1; Mice; Molecular Targeted Therapy; Multiprotein Complexes; Mutation; Protein Kinase Inhibitors; Proteins; PTEN Phosphohydrolase; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Tuberous Sclerosis Complex 1 Protein; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins

Autism is thought to be associated with both environmental and genetic factors. Phenanthrene (Phe) makes up a relatively high proportion of the low-ring polycyclic aromatic hydrocarbons. However, the association between exposure to Phe and Autism remain unclear. In this study, the effect and mechanisms of phenanthrene exposure on autistic behavior were investigated. Three-week-old male Kunming mice were exposed to doses of 5, 50, or 500 μg/kg/d Phe for 22 days. Exposure to phenanthrene induced a marked decrease in the activity of the mice in the central area in the open field test, and caused a significant decrease in communication with unfamiliar mice in the three-chambered social test. The hippocampus of the mice exposed to high concentrations of Phe showed pathological changes. Exposure to phenanthrene induced an increase in the levels of ROS and a decrease in levels of glutathione, and caused a significant decrease in the expression of Shank3 and Beclin1. This also led to an increase in the phosphorylation levels of Akt and mTOR. However, administering Rapamycin or vitamin E, inhibited the oxidative stress and activation of the mTOR pathway induced by Phe exposure, effectively alleviating the above-mentioned autistic-like anxious social behaviors. These results indicate that exposure to phenanthrene will lead to autism-like behavior. The underlying mechanism involves oxidative stress and the mTOR pathway.

Topics: Animals; Animals, Outbred Strains; Autistic Disorder; Behavior, Animal; Dose-Response Relationship, Drug; Glutathione; Hippocampus; Male; Mice; Oxidative Stress; Phenanthrenes; Sirolimus; TOR Serine-Threonine Kinases; Vitamin E

Despite a prevalence exceeding 1%, mechanisms underlying autism spectrum disorders (ASDs) are poorly understood, and targeted therapies and guiding parameters are urgently needed. We recently demonstrated that cerebellar dysfunction is sufficient to generate autistic-like behaviors in a mouse model of tuberous sclerosis complex (TSC). Here, using the mechanistic target of rapamycin (mTOR)-specific inhibitor rapamycin, we define distinct sensitive periods for treatment of autistic-like behaviors with sensitive periods extending into adulthood for social behaviors. We identify cellular and electrophysiological parameters that may contribute to behavioral rescue, with rescue of Purkinje cell survival and excitability corresponding to social behavioral rescue. In addition, using anatomic and diffusion-based MRI, we identify structural changes in cerebellar domains implicated in ASD that correlate with sensitive periods of specific autism-like behaviors. These findings thus not only define treatment parameters into adulthood, but also support a mechanistic basis for the targeted rescue of autism-related behaviors.

Topics: Animals; Autistic Disorder; Behavior, Animal; Cells, Cultured; Cerebellum; Immunosuppressive Agents; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Purkinje Cells; Sirolimus; TOR Serine-Threonine Kinases; Tuberous Sclerosis Complex 1 Protein

Phosphatase and tensin homolog (PTEN) is a major negative regulator of the Akt/mammalian target of rapamycin (MTOR) pathway. Mutations in PTEN have been found in a subset of individuals with autism and macrocephaly. Further, focal cortical dysplasia (FCD) has been observed in patients with PTEN mutations prompting us to examine the role of Pten in neuronal migration. The dentate gyrus of Pten(Flox/Flox) mice was injected with Cre- and non-Cre-expressing retroviral particles, which integrate into the dividing genome to birthdate cells. Control and Pten knockout (KO) cell position in the granule cell layer was quantified over time to reveal that Pten KO neurons exhibit an aberrant migratory phenotype beginning at 7.5days-post retroviral injection (DPI). We then assessed whether rapamycin, a mTor inhibitor, could prevent or reverse aberrant migration of granule cells. The preventative group received daily intraperitoneal (IP) injections of rapamycin from 3 to 14 DPI, before discrepancies in cell position have been established, while the reversal group received rapamycin afterward, from 14 to 24 DPI. We found that rapamycin prevented and reversed somal hypertrophy. However, rapamycin prevented, but did not reverse aberrant migration in Pten KO cells. We also find that altered migration occurs through mTorC1 and not mTorC2 activity. Together, these findings suggest a temporal window by which rapamycin can treat aberrant migration, and may have implications for the use of rapamycin to treat PTEN-mutation associated disorders.. Mutations in phosphatase and tensin homolog (PTEN) have been linked to a subset of individuals with autism and macrocephaly, as well as Cowden Syndrome and focal cortical dysplasia. Pten loss leads to neuronal hypertrophy, but the role of Pten in neuronal migration is unclear. Here we have shown that loss of Pten leads to aberrant migration, which can be prevented but not reversed by treatment with rapamycin, a mTor inhibitor. These results are important to consider as clinical trials are developed to examine rapamycin as a therapeutic for autism with PTEN mutations. Our findings show that some abnormalities cannot be reversed, and suggest the potential need for genetic screening and preventative treatment.

Topics: Animals; Autistic Disorder; Brain; Cell Movement; Disease Models, Animal; Mice, Knockout; Mutation; Neurons; Phenotype; PTEN Phosphohydrolase; Signal Transduction; Sirolimus

Epilepsy and autism spectrum disorder (ASD) are common comorbidities of one another. Despite the prevalent correlation between the two disorders, few studies have been able to elucidate a mechanistic link. We demonstrate that forebrain specific Tsc1 deletion in mice causes epilepsy and autism-like behaviors, concomitant with disruption of 5-HT neurotransmission. We find that epileptiform activity propagates to the raphe nuclei, resulting in seizure-dependent hyperactivation of mTOR in 5-HT neurons. To dissect whether mTOR hyperactivity in 5-HT neurons alone was sufficient to recapitulate an autism-like phenotype we utilized Tsc1flox/flox;Slc6a4-cre mice, in which mTOR is restrictively hyperactivated in 5-HT neurons. Tsc1flox/flox;Slc6a4-cre mice displayed alterations of the 5-HT system and autism-like behaviors, without causing epilepsy. Rapamycin treatment in these mice was sufficient to rescue the phenotype. We conclude that the spread of seizure activity to the brainstem is capable of promoting hyperactivation of mTOR in the raphe nuclei, which in turn promotes autism-like behaviors. Thus our study provides a novel mechanism describing how epilepsy can contribute to the development of autism-like behaviors, suggesting new therapeutic strategies for autism.

Topics: Animals; Autistic Disorder; Behavior, Animal; Disease Models, Animal; Epilepsy; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neurons; Protein Kinase Inhibitors; Raphe Nuclei; Serotonin; Sirolimus; TOR Serine-Threonine Kinases; Tuberous Sclerosis Complex 1 Protein; Tumor Suppressor Proteins

Developmental alterations of excitatory synapses are implicated in autism spectrum disorders (ASDs). Here, we report increased dendritic spine density with reduced developmental spine pruning in layer V pyramidal neurons in postmortem ASD temporal lobe. These spine deficits correlate with hyperactivated mTOR and impaired autophagy. In Tsc2 ± ASD mice where mTOR is constitutively overactive, we observed postnatal spine pruning defects, blockade of autophagy, and ASD-like social behaviors. The mTOR inhibitor rapamycin corrected ASD-like behaviors and spine pruning defects in Tsc2 ± mice, but not in Atg7(CKO) neuronal autophagy-deficient mice or Tsc2 ± :Atg7(CKO) double mutants. Neuronal autophagy furthermore enabled spine elimination with no effects on spine formation. Our findings suggest that mTOR-regulated autophagy is required for developmental spine pruning, and activation of neuronal autophagy corrects synaptic pathology and social behavior deficits in ASD models with hyperactivated mTOR.

Topics: Adolescent; Age Factors; Animals; Autistic Disorder; Autophagy; Child; Child, Preschool; Dendritic Spines; Disease Models, Animal; Exploratory Behavior; Female; Humans; Immunosuppressive Agents; Male; Mice; Mice, Transgenic; Neurons; Sirolimus; Synapses; Temporal Lobe; TOR Serine-Threonine Kinases; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins; Young Adult

Autism spectrum disorders (ASDs) are highly prevalent neurodevelopmental disorders, but the underlying pathogenesis remains poorly understood. Recent studies have implicated the cerebellum in these disorders, with post-mortem studies in ASD patients showing cerebellar Purkinje cell (PC) loss, and isolated cerebellar injury has been associated with a higher incidence of ASDs. However, the extent of cerebellar contribution to the pathogenesis of ASDs remains unclear. Tuberous sclerosis complex (TSC) is a genetic disorder with high rates of comorbid ASDs that result from mutation of either TSC1 or TSC2, whose protein products dimerize and negatively regulate mammalian target of rapamycin (mTOR) signalling. TSC is an intriguing model to investigate the cerebellar contribution to the underlying pathogenesis of ASDs, as recent studies in TSC patients demonstrate cerebellar pathology and correlate cerebellar pathology with increased ASD symptomatology. Functional imaging also shows that TSC patients with ASDs display hypermetabolism in deep cerebellar structures, compared to TSC patients without ASDs. However, the roles of Tsc1 and the sequelae of Tsc1 dysfunction in the cerebellum have not been investigated so far. Here we show that both heterozygous and homozygous loss of Tsc1 in mouse cerebellar PCs results in autistic-like behaviours, including abnormal social interaction, repetitive behaviour and vocalizations, in addition to decreased PC excitability. Treatment of mutant mice with the mTOR inhibitor, rapamycin, prevented the pathological and behavioural deficits. These findings demonstrate new roles for Tsc1 in PC function and define a molecular basis for a cerebellar contribution to cognitive disorders such as autism.

Topics: Animals; Autistic Disorder; Behavior, Animal; Cell Count; Cell Shape; Cerebellum; Grooming; Heterozygote; Maze Learning; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mutation; Purkinje Cells; Rotarod Performance Test; Sirolimus; Synapses; TOR Serine-Threonine Kinases; Tuberous Sclerosis; Tuberous Sclerosis Complex 1 Protein; Tumor Suppressor Proteins; Vocalization, Animal

PTEN (phosphatase and tensin homolog deleted on chromosome ten) is a lipid phosphatase that counteracts the function of phosphatidylinositol-3 kinase (PI3K). Loss of function of PTEN results in constitutive activation of AKT and downstream effectors and correlates with many human cancers, as well as various brain disorders, including macrocephaly, seizures, Lhermitte-Duclos disease, and autism. We previously generated a conditional Pten knock-out mouse line with Pten loss in limited postmitotic neurons in the cortex and hippocampus. Pten-null neurons developed neuronal hypertrophy and loss of neuronal polarity. The mutant mice exhibited macrocephaly and behavioral abnormalities reminiscent of certain features of human autism. Here, we report that rapamycin, a specific inhibitor of mammalian target of rapamycin complex 1 (mTORC1), can prevent and reverse neuronal hypertrophy, resulting in the amelioration of a subset of PTEN-associated abnormal behaviors, providing evidence that the mTORC1 pathway downstream of PTEN is critical for this complex phenotype.

Topics: Animals; Autistic Disorder; Female; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neurons; PTEN Phosphohydrolase; Sirolimus; Transcription Factors

Topics: Animals; Autistic Disorder; Drosophila; Fragile X Mental Retardation Protein; Fragile X Syndrome; Glutamic Acid; Humans; Immunosuppressive Agents; Methyl-CpG-Binding Protein 2; Mice; Protein Kinases; Rett Syndrome; Sirolimus; TOR Serine-Threonine Kinases; Tuberous Sclerosis; Tuberous Sclerosis Complex 1 Protein; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins