Impaired amino acid transport at the blood brain barrier is a cause of autism spectrum disorder

Autism spectrum disorders (ASD) are a group of genetic disorders often overlapping with other neurological conditions. We previously described abnormalities in the branched-chain amino acid (BCAA) catabolic pathway as a cause of ASD. Here, we show that the solute carrier transporter 7a5 (SLC7A5), a large neutral amino acid transporter localized at the blood brain barrier (BBB), has an essential role in maintaining normal levels of brain BCAAs. In mice, deletion of Slc7a5 from the endothelial cells of the BBB leads to atypical brain amino acid profile, abnormal mRNA translation, and severe neurological abnormalities. Furthermore, we identified several patients with autistic traits and motor delay carrying deleterious homozygous mutations in the SLC7A5 gene. Finally, we demonstrate that BCAA intracerebroventricular administration ameliorates abnormal behaviors in adult mutant mice. Our data elucidate a neurological syndrome defined by SLC7A5 mutations and support an essential role for the BCAA in human brain function

Characterization of Cellular Effects of Insulin in SW982 Fibroblast-like Synoviocytes

A Western diet is characterized by several components, but the main traits are a substantial consumption of red meats, refined carbohydrates and saturated fatty acids. Poor dietary choices and a low level of physical activity can quickly lead to lifestyle diseases like obesity and metabolic syndrome. It has previously been shown that the macronutrient composition of the diet affects the low-grade systemic inflammation in obese men. Both metabolic syndrome and obesity is linked to hyperinsulinemia and insulin resistance. Insulin signals through the insulin receptor (IR), which subsequently leads to many cellular responses including the activation of nuclear factor-κB (NF- κB) and induction of pro-inflammatory mediator production. Increasing body mass index has been linked to increasing disease activity scores (DAS28) for Rheumatoid Arthritis (RA) patients. RA is an autoimmune disease of the synovial membrane of joints, which becomes a hyperplastic, invasive tissue teeming with immunocompetent cells. This will eventually lead to excessive bone loss and chronic inflammation of the synovial membrane, a condition called synovitis. The effect of chronic elevated levels of insulin on disease activity of RA is not yet known. Here, we investigate the potential of insulin to activate cytosolic phospholipase A2α (cPLA2α), which has been shown to be a key regulator of inflammation in RA, in a cell model for synovitis (SW982). In this master s thesis we also investigate a potential role for insulin in regulating proliferation and gene expression in SW982. More specifically, the time-dependent regulation of the genes insulin receptor (IR), insulin-like growth factor 1 receptor (IGF1R), c-Myc, c-Fos and interleukin 6 (IL-6) was investigated. Detection of IR and IGF1R expression by real time quantitative polymerase chain reaction (RT-qPCR) in SW982 synoviocytes, validated for the first time that these cells express the respective receptors and that they are potentially susceptible to insulin signaling.The activity of cPLA2α in response to insulin was evaluated using a radioactive release assay in pre-labeled SW982 cells, which measures the activity of cPLA2α by measuring the amount of arachidonic acid (AA) released from the cells. These tests showed that insulin did not increase the release of AA. However, this test did reveal a trend of decreased release of oleic acid (OA) in response to insulin. These results suggest a PLA2 independent pathway for insulin signaling. Also, a pro-inflammatory role of insulin mediated through the hormone sensitive lipase (HSL) is speculated upon based on these results.MTT viability assay was used to evaluate the effect of insulin on the metabolic activity of cultured SW982s. We found that insulin increases the metabolic activity by ~50% in a time, confluency and dose dependent manner. However, these results were not validated as increased proliferation by flow cytometry. We speculate upon an activation of protein kinase B (PKB) by insulin, which signals increased survival of SW982 cells.By RT-qPCR we show that insulin downregulates IR expression, and a similar trend is observed for IGF1R. Insulin induced no change in c-Myc expression, and induced a downregulation of c-fos after 12 hours. Further, insulin induced a time-dependent trend of increase in IL-6 gene expression. Insulin also induced variation in the expression of the previously accepted reference gene 18S.More tests have to be conducted in order to validate/discard the hypotheses proposed in this study. Including the possible pro-inflammatory actions of insulin in synovial cells and other tissue, mediated through inhibition of HSL. The potential for insulin to induce hyper proliferation and increased survival of synovial cells through activation of PKB, and the potential for insulin to induce expression proliferative and inflammatory genes

Mutations in MBOAT7, Encoding Lysophosphatidylinositol Acyltransferase I, Lead to Intellectual Disability Accompanied by Epilepsy and Autistic Features

WOS: 000385333700011PubMed ID: 27616480The risk of epilepsy among individuals with intellectual disability (ID) is approximately ten times that of the general population. From a cohort of >5,000 families affected by neurodevelopmental disorders, we identified six consanguineous families harboring homozygous inactivating variants in MBOAT7, encoding lysophosphatidylinositol acyltransferase (LPIAT1). Subjects presented with ID frequently accompanied by epilepsy and autistic features. LPIAT1 is a membrane-bound phospholipid-remodeling enzyme that transfers arachidonic acid (AA) to lysophosphatidylinositol to produce AA-containing phosphatidylinositol. This study suggests a role for AA-containing phosphatidylinositols in the development of ID accompanied by epilepsy and autistic features.Howard Hughes Medical Institute; National Institute of Neurological Disorders and Stroke [R01NS098004, R01NS048453]; Eunice Kennedy Shriver National Institute of Child Health and Human Development [P01HD070494]; Qatar National Research Fund [NPRP6-1463]; Simons Foundation Autism Research Initiative [175303, 275275]; Deutsche Forschungsgemeinschaft (DFG) [AB393/2-2, AB393/4-1]; Canadian Institutes of Health Research [MOP-102758]; Pakistani Higher Education CommissionWe are grateful to the affected individuals and their families for their participation in the study. This study was supported by the Howard Hughes Medical Institute, National Institute of Neurological Disorders and Stroke (R01NS098004 and R01NS048453), Eunice Kennedy Shriver National Institute of Child Health and Human Development (P01HD070494), Qatar National Research Fund (NPRP6-1463), and Simons Foundation Autism Research Initiative (175303 and 275275). We thank the Broad Institute (U54HG003067 to E. Lander and HG00 8900 to D. MacArthur) and the Yale Center for Mendelian Disorders (U54HG006504 to R. Lifton, M. Gunel, M. Gerstein, and S. Mane) for sequencing support and analysis. This study was partially supported by grants from the Deutsche Forschungsgemeinschaft (DFG) to R.A.J. (AB393/2-2 and AB393/4-1), a grant from the Canadian Institutes of Health Research to J.B.V. (MOP-102758), and an award from the Pakistani Higher Education Commission to I.A

A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental disorder characterised by microcephaly epilepsy and autistic features

Background: Transport protein particle (TRAPP) is a multisubunit complex that regulates membrane trafficking through the Golgi apparatus. The clinical phenotype associated with mutations in various TRAPP subunits has allowed elucidation of their functions in specific tissues. The role of some subunits in human disease, however, has not been fully established, and their functions remain uncertain. Objective: We aimed to expand the range of neurodevelopmental disorders associated with mutations in TRAPP subunits by exome sequencing of consanguineous families. Methods: Linkage and homozygosity mapping and candidate gene analysis were used to identify homozygous mutations in families. Patient fibroblasts were used to study splicing defect and zebrafish to model the disease. Results: We identified six individuals from three unrelated families with a founder homozygous splice mutation in TRAPPC6B, encoding a core subunit of the complex TRAPP I. Patients manifested a neurodevelopmental disorder characterised by microcephaly, epilepsy and autistic features, and showed splicing defect. Zebrafish trappc6b morphants replicated the human phenotype, displaying decreased head size and neuronal hyperexcitability, leading to a lower seizure threshold. Conclusion: This study provides clinical and functional evidence of the role of TRAPPC6B in brain development and function

Mutations in LNPK, Encoding the Endoplasmic Reticulum Junction Stabilizer Lunapark, Cause a Recessive Neurodevelopmental Syndrome

The dynamic shape of the endoplasmic reticulum (ER) is a reflection of its wide variety of critical cell biological functions. Consequently, perturbation of ER-shaping proteins can cause a range of human phenotypes. Here, we describe three affected children (from two consanguineous families) who carry homozygous loss-of-function mutations in LNPK (previously known as KIAA1715); this gene encodes lunapark, which is proposed to serve as a curvature-stabilizing protein within tubular three-way junctions of the ER. All individuals presented with severe psychomotor delay, intellectual disability, hypotonia, epilepsy, and corpus callosum hypoplasia, and two of three showed mild cerebellar hypoplasia and atrophy. Consistent with a proposed role in neurodevelopmental disease, LNPK was expressed during brain development in humans and mice and was present in neurite-like processes in differentiating human neural progenitor cells. Affected cells showed the absence of full-length lunapark, aberrant ER structures, and increased luminal mass density. Together, our results implicate the ER junction stabilizer lunapark in establishing the corpus callosum

Mutations in MBOAT7, Encoding Lysophosphatidylinositol Acyltransferase I, Lead to Intellectual Disability Accompanied by Epilepsy and Autistic Features

The risk of epilepsy among individuals with intellectual disability (ID) is approximately ten times that of the general population. From a cohort of >5,000 families affected by neurodevelopmental disorders, we identified six consanguineous families harboring homozygous inactivating variants in MBOAT7, encoding lysophosphatidylinositol acyltransferase (LPIAT1). Subjects presented with ID frequently accompanied by epilepsy and autistic features. LPIAT1 is a membrane-bound phospholipid-remodeling enzyme that transfers arachidonic acid (AA) to lysophosphatidylinositol to produce AA-containing phosphatidylinositol. This study suggests a role for AA-containing phosphatidylinositols in the development of ID accompanied by epilepsy and autistic features

Zika Virus Protease Cleavage of Host Protein Septin-2 Mediates Mitotic Defects in Neural Progenitors

Zika virus (ZIKV) targets neural progenitor cells in the brain, attenuates cell proliferation, and leads to cell death. Here, we describe a role for the ZIKV protease NS2B-NS3 heterodimer in mediating neurotoxicity through cleavage of a host protein required for neurogenesis. Similar to ZIKV infection, NS2B-NS3 expression led to cytokinesis defects and cell death in a protease activity-dependent fashion. Among binding partners, NS2B-NS3 cleaved Septin-2, a cytoskeletal factor involved in cytokinesis. Cleavage of Septin-2 occurred at residue 306 and forced expression of a non-cleavable Septin-2 restored cytokinesis, suggesting a direct mechanism of ZIKV-induced neural toxicity. VIDEO ABSTRACT

Mutations in MBOAT7 , Encoding Lysophosphatidylinositol Acyltransferase I, Lead to Intellectual Disability Accompanied by Epilepsy and Autistic Features

The risk of epilepsy among individuals with intellectual disability (ID) is approximately ten times that of the general population. From a cohort of >5,000 families affected by neurodevelopmental disorders, we identified six consanguineous families harboring homozygous inactivating variants in MBOAT7, encoding lysophosphatidylinositol acyltransferase (LPIAT1). Subjects presented with ID frequently accompanied by epilepsy and autistic features. LPIAT1 is a membrane-bound phospholipid-remodeling enzyme that transfers arachidonic acid (AA) to lysophosphatidylinositol to produce AA-containing phosphatidylinositol. This study suggests a role for AA-containing phosphatidylinositols in the development of ID accompanied by epilepsy and autistic features

Exome sequencing links corticospinal motor neuron disease to common neurodegenerative disorders

Hereditary spastic paraplegias (HSPs) are neurodegenerative motor neuron diseases characterized by progressive age-dependent loss of corticospinal motor tract function. Although the genetic basis is partly understood, only a fraction of cases can receive a genetic diagnosis, and a global view of HSP is lacking. By using whole-exome sequencing in combination with network analysis, we identified 18 previously unknown putative HSP genes and validated nearly all of these genes functionally or genetically. The pathways highlighted by these mutations link HSP to cellular transport, nucleotide metabolism, and synapse and axon development. Network analysis revealed a host of further candidate genes, of which three were mutated in our cohort. Our analysis links HSP to other neurodegenerative disorders and can facilitate gene discovery and mechanistic understanding of disease

Impaired Amino Acid Transport At The Blood Brain Barrier Is A Cause Of Autism Spectrum Disorder

Autism spectrum disorders (ASD) are a group of genetic disorders often overlapping with other neurological conditions. We previously described abnormalities in the branched-chain amino acid (BCAA) catabolic pathway as a cause of ASD. Here, we show that the solute carrier transporter 7a5 (SLC7A5), a large neutral amino acid transporter localized at the bloodbrainbarrier (BBB), has an essential role in maintaining normal levels of brain BCAAs. In mice, deletion of Slc7a5 from the endothelial cells of theBBBleads to atypical brain amino acid profile, abnormal mRNA translation, and severe neurological abnormalities. Furthermore, we identified several patients with autistic traits and motor delay carrying deleterious homozygous mutations in the SLC7A5 gene. Finally, we demonstrate that BCAA intracerebroventricular administration ameliorates abnormal behaviors in adult mutant mice. Our data elucidate a neurological syndrome defined by SLC7A5 mutations and support an essential role for the BCAA in human brain function.WoSScopu