Decreased phenol sulfotransferase activities associated with hyperserotonemia in autism spectrum disorders.

Hyperserotonemia is the most replicated biochemical abnormality associated with autism spectrum disorders (ASD). However, previous studies of serotonin synthesis, catabolism, and transport have not elucidated the mechanisms underlying this hyperserotonemia. Here we investigated serotonin sulfation by phenol sulfotransferases (PST) in blood samples from 97 individuals with ASD and their first-degree relatives (138 parents and 56 siblings), compared with 106 controls. We report a deficient activity of both PST isoforms (M and P) in platelets from individuals with ASD (35% and 78% of patients, respectively), confirmed in autoptic tissues (9 pineal gland samples from individuals with ASD-an important source of serotonin). Platelet PST-M deficiency was strongly associated with hyperserotonemia in individuals with ASD. We then explore genetic or pharmacologic modulation of PST activities in mice: variations of PST activities were associated with marked variations of blood serotonin, demonstrating the influence of the sulfation pathway on serotonemia. We also conducted in 1645 individuals an extensive study of SULT1A genes, encoding PST and mapping at highly polymorphic 16p11.2 locus, which did not reveal an association between copy number or single nucleotide variations and PST activity, blood serotonin or the risk of ASD. In contrast, our broader assessment of sulfation metabolism in ASD showed impairments of other sulfation-related markers, including inorganic sulfate, heparan-sulfate, and heparin sulfate-sulfotransferase. Our study proposes for the first time a compelling mechanism for hyperserotonemia, in a context of global impairment of sulfation metabolism in ASD.

Mass-spectrometry analysis of the human pineal proteome during night and day and in autism.

The human pineal gland regulates day-night dynamics of multiple physiological processes, especially through the secretion of melatonin. Using mass-spectrometry-based proteomics and dedicated analysis tools, we identify proteins in the human pineal gland and analyze systematically their variation throughout the day and compare these changes in the pineal proteome between control specimens and donors diagnosed with autism. Results reveal diverse regulated clusters of proteins with, among others, catabolic carbohydrate process and cytoplasmic membrane-bounded vesicle-related proteins differing between day and night and/or control versus autism pineal glands. These data show novel and unexpected processes happening in the human pineal gland during the day/night rhythm as well as specific differences between autism donor pineal glands and those from controls.

Altered spinogenesis in iPSC-derived cortical neurons from patients with autism carrying de novo SHANK3 mutations.

The synaptic protein SHANK3 encodes a multidomain scaffold protein expressed at the postsynaptic density of neuronal excitatory synapses. We previously identified de novo SHANK3 mutations in patients with autism spectrum disorders (ASD) and showed that SHANK3 represents one of the major genes for ASD. Here, we analyzed the pyramidal cortical neurons derived from induced pluripotent stem cells from four patients with ASD carrying SHANK3 de novo truncating mutations. At 40-45 days after the differentiation of neural stem cells, dendritic spines from pyramidal neurons presented variable morphologies: filopodia, thin, stubby and muschroom, as measured in 3D using GFP labeling and immunofluorescence. As compared to three controls, we observed a significant decrease in SHANK3 mRNA levels (less than 50% of controls) in correlation with a significant reduction in dendritic spine densities and whole spine and spine head volumes. These results, obtained through the analysis of de novo SHANK3 mutations in the patients' genomic background, provide further support for the presence of synaptic abnormalities in a subset of patients with ASD.

Disruption of melatonin synthesis is associated with impaired 14-3-3 and miR-451 levels in patients with autism spectrum disorders.

Autism spectrum disorders (ASD) are characterized by a wide genetic and clinical heterogeneity. However, some biochemical impairments, including decreased melatonin (crucial for circadian regulation) and elevated platelet N-acetylserotonin (the precursor of melatonin) have been reported as very frequent features in individuals with ASD. To address the mechanisms of these dysfunctions, we investigated melatonin synthesis in post-mortem pineal glands - the main source of melatonin (9 patients and 22 controls) - and gut samples - the main source of serotonin (11 patients and 13 controls), and in blood platelets from 239 individuals with ASD, their first-degree relatives and 278 controls. Our results elucidate the enzymatic mechanism for melatonin deficit in ASD, involving a reduction of both enzyme activities contributing to melatonin synthesis (AANAT and ASMT), observed in the pineal gland as well as in gut and platelets of patients. Further investigations suggest new, post-translational (reduced levels of 14-3-3 proteins which regulate AANAT and ASMT activities) and post-transcriptional (increased levels of miR-451, targeting 14-3-3ζ) mechanisms to these impairments. This study thus gives insights into the pathophysiological pathways involved in ASD.

A de novo microdeletion of SEMA5A in a boy with autism spectrum disorder and intellectual disability.

Semaphorins are a large family of secreted and membrane-associated proteins necessary for wiring of the brain. Semaphorin 5A (SEMA5A) acts as a bifunctional guidance cue, exerting both attractive and inhibitory effects on developing axons. Previous studies have suggested that SEMA5A could be a susceptibility gene for autism spectrum disorders (ASDs). We first identified a de novo translocation t(5;22)(p15.3;q11.21) in a patient with ASD and intellectual disability (ID). At the translocation breakpoint on chromosome 5, we observed a 861-kb deletion encompassing the end of the SEMA5A gene. We delineated the breakpoint by NGS and observed that no gene was disrupted on chromosome 22. We then used Sanger sequencing to search for deleterious variants affecting SEMA5A in 142 patients with ASD. We also identified two independent heterozygous variants located in a conserved functional domain of the protein. Both variants were maternally inherited and predicted as deleterious. Our genetic screens identified the first case of a de novo SEMA5A microdeletion in a patient with ASD and ID. Although our study alone cannot formally associate SEMA5A with susceptibility to ASD, it provides additional evidence that Semaphorin dysfunction could lead to ASD and ID. Further studies on Semaphorins are warranted to better understand the role of this family of genes in susceptibility to neurodevelopmental disorders.

Three-dimensional Quantification of Dendritic Spines from Pyramidal Neurons Derived from Human Induced Pluripotent Stem Cells.

Dendritic spines are small protrusions that correspond to the post-synaptic compartments of excitatory synapses in the central nervous system. They are distributed along the dendrites. Their morphology is largely dependent on neuronal activity, and they are dynamic. Dendritic spines express glutamatergic receptors (AMPA and NMDA receptors) on their surface and at the levels of postsynaptic densities. Each spine allows the neuron to control its state and local activity independently. Spine morphologies have been extensively studied in glutamatergic pyramidal cells of the brain cortex, using both in vivo approaches and neuronal cultures obtained from rodent tissues. Neuropathological conditions can be associated to altered spine induction and maturation, as shown in rodent cultured neurons and one-dimensional quantitative analysis (1). The present study describes a protocol for the 3D quantitative analysis of spine morphologies using human cortical neurons derived from neural stem cells (late cortical progenitors). These cells were initially obtained from induced pluripotent stem cells. This protocol allows the analysis of spine morphologies at different culture periods, and with possible comparison between induced pluripotent stem cells obtained from control individuals with those obtained from patients with psychiatric diseases.

Genetic and functional abnormalities of the melatonin biosynthesis pathway in patients with bipolar disorder.

Patients affected by bipolar disorder (BD) frequently report abnormalities in sleep/wake cycles. In addition, they showed abnormal oscillating melatonin secretion, a key regulator of circadian rhythms and sleep patterns. The acetylserotonin O-methyltransferase (ASMT) is a key enzyme of the melatonin biosynthesis and has recently been associated with psychiatric disorders such as autism spectrum disorders and depression. In this paper, we analysed rare and common variants of ASMT in patients with BD and unaffected control subjects and performed functional analysis of these variants by assaying the ASMT activity in their B-lymphoblastoid cell lines. We sequenced the coding and the regulatory regions of the gene in a discovery sample of 345 patients with BD and 220 controls. We performed an association study on this discovery sample using common variants located in the promoter region and showed that rs4446909 was significantly associated with BD (P= 0.01) and associated with a lower mRNA level (P< 10(-4)) and a lower enzymatic activity (P< 0.05) of ASMT. A replication study and a meta-analysis using 480 independent patients with BD and 672 controls confirmed the significant association between rs4446909 and BD (P= 0.002). These results correlate with the general lower ASMT enzymatic activity observed in patients with BD (P= 0.001) compared with controls. Finally, several deleterious ASMT mutations identified in patients were associated with low ASMT activity (P= 0.01). In this study, we determined how rare and common variations in ASMT might play a role in BD vulnerability and suggest a general role of melatonin as susceptibility factor for BD.

Dynamics in enzymatic protein complexes offer a novel principle for the regulation of melatonin synthesis in the human pineal gland.

Time of day is communicated to the body through rhythmic cues, including pineal gland melatonin synthesis, which is restricted to nighttime. Whereas in most rodents transcriptional regulation of the arylalkylamine N-acetyltransferase (Aanat) gene is essential for rhythmic melatonin synthesis, investigations into nonrodent mammalian species have shown post-transcriptional regulation to be of central importance, with molecular mechanisms still elusive. Therefore, human pineal tissues, taken from routine autopsies were allocated to four time-of-death groups (night/dawn/day/dusk) and analyzed for daytime-dependent changes in phosphorylated AANAT (p31T-AANAT) and in acetyl-serotonin-methyltransferase (ASMT) expression and activity. Protein content, intracellular localization, and colocalization of p31T-AANAT and ASMT were assessed, using immunoblotting, immunofluorescence, and immunoprecipitation techniques. Fresh sheep pineal gland preparations were used for comparative purposes. The amount of p31T-AANAT and ASMT proteins as well as their intracellular localization showed no diurnal variation in autoptic human and fresh sheep pineal glands. Moreover, in human and sheep pineal extracts, AANAT could not be dephosphorylated, which was at variance to data derived from rat pineal extracts. P31T-AANAT and ASMT were often found to colocalize in cellular rod-like structures that were also partly immunoreactive for the pinealocyte process-specific marker S-antigen (arrestin) in both, human and sheep pinealocytes. Protein-protein interaction studies with p31T-AANAT, ASMT, and S-antigen demonstrated a direct association and formation of robust complexes, involving also 14-3-3. This work provides evidence for a regulation principle for AANAT activity in the human pineal gland, which may not be based on a p31T-AANAT phosphorylation/dephosphorylation switch, as described for other mammalian species.

Production of soluble, active acetyl serotonin methyl transferase in Leishmania tarentolae.

N-acetyl serotonin methyl transferase (ASMT) is the last enzyme in the melatonin synthesis pathway. Evidence linking autism-related disorders with disorders of melatonin metabolism, and, more specifically, with mutations of the gene encoding ASMT, prompted us to investigate the properties and localization of this enzyme. As a first step, we undertook to overproduce the protein in a recombinant host. Early attempts to produce ASMT in recombinant Escherichia coli yielded only insoluble and heavily degraded material. However, recombinant ASMT (rASMT) could be produced in soluble, active form and purified in milligram amounts when the gene was cloned and expressed in Leishmania tarentolae.

An investigation of ribosomal protein L10 gene in autism spectrum disorders.

BACKGROUND: Autism spectrum disorders (ASD) are severe neurodevelopmental disorders with the male:female ratio of 4:1, implying the contribution of X chromosome genetic factors to the susceptibility of ASD. The ribosomal protein L10 (RPL10) gene, located on chromosome Xq28, codes for a key protein in assembling large ribosomal subunit and protein synthesis. Two non-synonymous mutations of RPL10, L206M and H213Q, were identified in four boys with ASD. Moreover, functional studies of mutant RPL10 in yeast exhibited aberrant ribosomal profiles. These results provided a novel aspect of disease mechanisms for autism--aberrant processes of ribosome biosynthesis and translation. To confirm these initial findings, we re-sequenced RPL10 exons and quantified mRNA transcript level of RPL10 in our samples. METHODS: 141 individuals with ASD were recruited in this study. All RPL10 exons and flanking junctions were sequenced. Furthermore, mRNA transcript level of RPL10 was quantified in B lymphoblastoid cell lines (BLCL) of 48 patients and 27 controls using the method of SYBR Green quantitative PCR. Two sets of primer pairs were used to quantify the mRNA expression level of RPL10: RPL10-A and RPL10-B. RESULTS: No non-synonymous mutations were detected in our cohort. Male controls showed similar transcript level of RPL10 compared with female controls (RPL10-A, U = 81, P = 0.7; RPL10-B, U = 61.5, P = 0.2). We did not observe any significant difference in RPL10 transcript levels between cases and controls (RPL10-A, U = 531, P = 0.2; RPL10-B, U = 607.5, P = 0.7). CONCLUSION: Our results suggest that RPL10 has no major effect on the susceptibility to ASD.

Mutations in the gene encoding the synaptic scaffolding protein SHANK3 are associated with autism spectrum disorders.

SHANK3 (also known as ProSAP2) regulates the structural organization of dendritic spines and is a binding partner of neuroligins; genes encoding neuroligins are mutated in autism and Asperger syndrome. Here, we report that a mutation of a single copy of SHANK3 on chromosome 22q13 can result in language and/or social communication disorders. These mutations concern only a small number of individuals, but they shed light on one gene dosage-sensitive synaptic pathway that is involved in autism spectrum disorders.

Expression and genetic variability of PCDH11Y, a gene specific to Homo sapiens and candidate for susceptibility to psychiatric disorders.

Synaptogenesis, the formation of functional synapses, is a crucial step for the development of the central nervous system. Among the genes involved in this process are cell adhesion molecules, such as protocadherins and neuroligins, which are essential factors for the identification of the appropriate partner cell and the formation of synapses. In this work, we studied the expression and the genetic variability of two closely related members of the protocadherin family PCDH11X/Y, located on the X and the Y chromosome, respectively. PCDH11Y is one of the rare genes specific to the hominoid lineage, being absent in other primates. Expression analysis indicated that transcripts of the PCDH11X/Y genes are mainly detected in the cortex of the human brain. Mutation screening of 30 individuals with autism identified two PCDH11Y polymorphic amino acid changes, F885V and K980N. These variations are in complete association, appeared during human evolution approximately 40,000 years ago and represent informative polymorphisms to study Y chromosome variability in populations. We studied the frequency of these variants in males with autism spectrum disorders (n = 110), attention deficit hyperactivity disorder (ADHD; n = 61), bipolar disorder (n = 61), obsessive-compulsive disorder (n = 51), or schizophrenia (n = 61) and observed no significant differences when compared to ethnically-matched control populations. These findings do not support the role of PCDH11Y, or more generally of a frequent specific Y chromosome, in the susceptibility to these neuropsychiatric disorders.

Immunoregulatory properties of mast cell-derived exosomes.

Transmission of information from mast cells to neighboring or distant cells must be established continuously in order to ensure homeostasis or to initiate immune and inflammatory responses. Owing to their strategic location in peripheral tissues and their prompt response to various stimuli, mast cells can be considered as the cell prototype to fulfill such a sentinel function. There are several ways for mast cells to communicate with other cells including cell-cell interactions via membrane-associated receptors, cytokines and other soluble mediators, and a newly described messenger which consists of membrane vesicles called exosomes carrying a number of immunoregulatory molecules.