Neurological Proteins in Autism


Specific proteins

It must be remembered that some proteins have been taken from brain post mortem samples and which may be present for some other reason apart from the autism itself.

 

Proteins that are discussed in autism:

  • Neuropeptides e.g. VIP, neuropeptide Y, encephalins, secretin. Now, about 100 different peptides are known to be released by different populations of neurons in the mammalian brain. Metabolic or G-protein-coupled receptors expressed by selective populations of neurons. In essence they act as specific signals between one population of neurons and another.  Peptides have much more diverse effect than transmitters; amongst other things, they can affect gene expression. They are held in large dense-core vesicles, often found in all parts of a neuron, including the soma, dendrites, axonal swellings and nerve endings, whereas the small synaptic vesicles are mainly found in clusters at presynaptic locations.
  • Neurotrophins .  e.g. Brain-derived neurotrophic factor, neurotrophin-4, a family of proteins, which induce the survival of neurons.  They belong to a class of growth factors, secreted proteins, which are capable of signaling to particular cells to survive, differentiate, or grow…and they have involvement with immunity (see Vega).
  • Reelin.  This regulates telencephalitic and cerebellar lamination during mammalian development of rats.  It is present, however in all mammals and its action in them is not quite so clear.   The finding that in some cases in animal models the modification of the reelin gene will create brain activity changes. In humans they can show some genetic changes but in other cases it is a decrease in the expression of the gene, which itself may well be normal.
  • Phosphodiesterase 4.  The cyclic adenosine monophosphate-specific phosphodiesterase-4 (PDE4) gene family is the target of several potential therapeutic inhibitors and the PDE4B gene has been associated with schizophrenia and depression.
  • Aquaporin and Connexin 43.  These are peptides that are found to interact with neurones but are derived from glia. 
  • Glial fibrillary acid protein.  Glial fibrillary acidic protein (GFAP) is an intermediate filament protein expressed predominantly in astrocytes.
  • Glutamic acid decarboxylase.  Glutamic acid is a neurotransmitter that is present in the brain and, following its stimulation of a dendrite it is destroyed by the decarboxylase.  This report of a decrease in the enzyme suggests that there may be an increase in the glutamate, which may have effects on brain activity.
  • APO-E.  No association was found between the expression of Apolipoprotein E and autism, as opposed to several other brain conditions (CJD etc).
  • Secretin.   This is a hormone produced and used in the gut that is also found as a neuropeptide in the brain.
  • Serotonin transporter: see histopathology and serotonin

 

Others?

It is clear that there are many other genes and proteins that have not been investigated. See: Lam KS, Aman MG, Arnold LE. Neurochemical correlates of autistic disorder: a review of the literature. Res Dev Disabil. 2006 May-Jun;27(3):254-89. Epub 2005 Jul 5. a review. (Review of neurochemical investigations in autistic disorder revealed that a wide array of transmitter systems have been studied, including serotonin, dopamine, norepinephrine, acetylcholine, oxytocin, endogenous opioids, cortisol, glutamate, and gamma-aminobutyric acid (GABA).  Also it is clear that proteins in the brain of autistics are produced in vary different ratios compared with controls: see below. The worry is that many of the other findings are simply due to this factor makes some results difficult to interpret.

 

 

 

This shows how neurotrophins are released by dendrites and glia (like astrocytes) and are taken to the nucleus of the target neurone, which then makes the protein (small purple lines), which acts as a receptor for more of the neurotrophin

 

 

Neuropepetides and Neurotrophins in Autism

The complex nature of neuropeptides means that it is exceptionally difficult to be sure of their action in the normal brain.  They modify the reaction of neurones to classical transmitter compounds, which act to cause the electrical change in the cellular surface.  There are claims that some are produced as result of genetic changes.

 

Nelson KB, Grether JK, Croen LA, Dambrosia JM, Dickens BF, Jelliffe LL, Hansen RL, Phillips TM. Neuropeptides and neurotrophins in neonatal blood of children with autism or mental retardation. Ann Neurol. 2001 May;49(5):597-606. (Several neurotrophins –NTs- with potent immunomodulatory actions, including neuropeptide Y, substance P, calcitoningene-related peptide (CGRP), vasoactive intestinal peptide(VIP), BDNF, and NT-4/5, which have multiple affects on neurodevelopment and neuron maintenance, have been implicated in ASD. Analysis of neonatal blood spots by recyclingimmunoaffinity chromatography found that BDNF, VIP, CGRP,and NT-4/5 were elevated in ASD compared with typically developing control children but could not be distinguished from those with mental retardation).  Note that these may actually have something to do with the immune changes that are seen see: Vega JA, García-Suárez O, Hannestad J, Pérez-Pérez M, Germanà A. Neurotrophins and the immune system. J Anat. 2003 Jul;203(1):1-19.

 

Miyazaki K, Narita N, Sakuta R, Miyahara T, Naruse H, Okado N, Narita M. Serum neurotrophin concentrations in autism and mental retardation: a pilot study.  Brain Dev. 2004 Aug;26(5):292-5.  (serum levels of the brain-derived neurotrophic factor and neurotrophin-4 (NT-4) in the patients diagnosed with autism (n=18) and mental retardation (n=20), or healthy controls (n=16), using enzyme-linked immunosorbent assay. There tended to be a higher concentration of serum BDNF found in the autistic group ( P <0.05 by analysis of variance (ANOVA)) and the mental retardation group ( P <0.001 by ANOVA).

Autistic-like phenotypes in Cadps2-knockout mice and aberrant CADPS2 splicing in autistic patients.

Sadakata T, Washida M, Iwayama Y, Shoji S, Sato Y, Ohkura T, Katoh-Semba R, Nakajima M, Sekine Y, Tanaka M, Nakamura K, Iwata Y, Tsuchiya KJ, Mori N, Detera-Wadleigh SD, Ichikawa H, Itohara S, Yoshikawa T, Furuichi T.  J Clin Invest. 2007 Apr;117(4):931-43. Epub 2007 Mar 22.  This is an attempt in which a specific factor is removed from the genetics of mice that then decreases the release of neurotrophic factors from the developing mouse’s brain.  They then claim that the mice with this genetic modification have an series of autistic symdromes…but of course it is very difficult to demonstrate this.   This is agreed in the next article:

Alternative splicing variations in mouse CAPS2: differential expression and functional properties of splicing variants.

Sadakata T, Washida M, Furuichi T.  BMC Neurosci. 2007 Apr 12;8:25.  Ca2+-dependent activator protein 2 (CAPS2/CADPS2) is a secretory vesicle-associated protein involved in the release of neurotrophin. We recently reported that an aberrant, alternatively spliced CAPS2 mRNA that lacks exon 3 (CAPS2Deltaexon3) is detected in some patients with autism.  They then went on to produce specific variation splicings of the gene and look for its appearance in various parts of the brain.  They found that it was particularly found in the cerebellum, in the brain less, but not at all in the rest of the body.  It was very much associated with neurotrophic factor release in those sites. 

 

Young LJ, Pitkow LJ, Ferguson JN. Neuropeptides and social behaviour: animal models relevant to autism. Mol Psychiatry. 2002;7 Suppl 2:S38-9. (explains how the neuropeptide oxytocin results in voles’ receptor protein and this may explain some of the symptoms seen in autism)

 

Chen X, Liu H, Shim AH, Focia PJ, He X. Structural basis for synaptic adhesion mediated by neuroligin-neurexin interactions. Nat Struct Mol Biol. 2008 Jan;15(1):50-6. Epub 2007 Dec 16.

 

Vega JA, García-Suárez O, Hannestad J, Pérez-Pérez M, Germanà A. Neurotrophins and the immune system. J Anat. 2003 Jul;203(1):1-19. (this is a major review of the interaction between the peptides that are found in the brain to have interactive effects and the findings that they also interact with the immune system.  At this point there is almost certainly more information to be found but this is a useful reference article)

 

Meyer-Lindenberg A. Impact of prosocial neuropeptides on human brain function.  Prog Brain Res. 2008;170:463-70  (they are largely looking at oxytocin and vasopressin in the amygdala).

Bridging the synaptic gap: neuroligins and neurexin I in Apis mellifera.

Biswas S, Russell RJ, Jackson CJ, Vidovic M, Ganeshina O, Oakeshott JG, Claudianos C. PLoS One. 2008;3(10):e3542.  A lot of the data from this is to do with the genetics of these compounds and their association with ASD.  The idea being that the problem can always be in the receptor, the transmitter, and the creation enzymes for any or them. 

Impact of prosocial neuropeptides on human brain function.

Meyer-Lindenberg A. Prog Brain Res. 2008;170:463-70. Oxytocin and vasopressin are key effectors of social behaviour (Insel, T. R. and Fernald, R. D. (2004). Annu. Rev. Neurosci., 27: 697-722). Oxytocin effects in humans were recently demonstrated by a behavioural study showing selectively increased trust after hormone administration (Kosfeld, M., et al. (2005). Nature, 435: 673-676). Since this suggested involvement of the amygdala, which is linked to trust (Winston, J. S., et al. (2002). Nat. Neurosci., 5: 277-283) - presumably because of its role in danger monitoring - and highly expresses oxytocin receptors (Huber, D., et al. (2005). Science, 308: 245-248), we studied amygdala circuitry after double-blind crossover intranasal application of placebo or oxytocin (Kirsch, P., et al. (2005). J. Neurosci., 25: 11489-11493).  results indicate neural mechanisms for human social behaviour mediating genetic risk for autism through an impact on amygdala signalling.

 

Bartz JA, Hollander E.  Oxytocin and experimental therapeutics in autism spectrum disorders.  Prog Brain Res. 2008;170:451-62

 

Heinrichs M, Domes G. Neuropeptides and social behaviour: effects of oxytocin and vasopressin in humans. Prog Brain Res. 2008;170:337-50.

Receptor and behavioral pharmacology of WAY-267464, a non-peptide oxytocin receptor agonist.

Ring RH, Schechter LE, Leonard SK, Dwyer JM, Platt BJ, Graf R, Grauer S, Pulicicchio C, Resnick L, Rahman Z, Sukoff Rizzo SJ, Luo B, Beyer CE, Logue SF, Marquis KL, Hughes ZA, Rosenzweig-Lipson S.  Neuropharmacology. 2009 Jul 16.  Basically it seemed to work to get the receptor for oxytocin to stimulate  the nerve on which it sits.  It does not stop oxytocin from working itself.  WAY-267464 is a high-affinity, potent, and selective (vs. V1a, V2, V1b) agonist of the OTR. In assays measuring both behavioral (four-plate test, elevated zero maze) and autonomic (stress-induced hyperthermia) parameters of the anxiety response, WAY-267464 exhibits an anxiolytic-like profile similar to OT.

Arginine vasopressin and oxytocin modulate human social behavior.

Ebstein RP, Israel S, Lerer E, Uzefovsky F, Shalev I, Gritsenko I, Riebold M, Salomon S, Yirmiya N.  Ann N Y Acad Sci. 2009 Jun;1167:87-102.  two nonapeptides, arginine vasopressin and oxytocin, shape human social behavior in both nonclinical and clinical subjects. Evidence is discussed that in autism spectrum disorders genetic polymorphisms in the vasopressin-oxytocin pathway, notably the arginine vasopressin receptor 1a (AVPR1a), the oxytocin receptor (OXTR), neurophysin I and II, and CD38 (recently shown to be critical for social behavior by mediating oxytocin secretion) contribute to deficits in socialization skills in this group of patients. We also present first evidence that CD38 expression in lymphoblastoid cells derived from subjects diagnosed with autism is correlated with social skill phenotype inventoried by the Vineland Adaptive Behavioral Scales.  They also go into other factors such as genetics that may have involvement with these peptides. 

Consequences of early experiences and exposure to oxytocin and vasopressin are sexually dimorphic.

Carter CS, Boone EM, Pournajafi-Nazarloo H, Bales KL. Dev Neurosci. 2009;31(4):332-41.

Oxytocin, vasopressin, and human social behavior. 

Heinrichs M, von Dawans B, Domes G. Front Neuroendocrinol. 2009 Jun 6.  This tries going into the review of what is happening.

 

 

 


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Aquaporin and Connexin 43

 

Fatemi SH, Folsom TD, Reutiman TJ, Lee S. Expression of astrocytic markers aquaporin 4 and connexin 43 is altered in brains of subjects with autism. Synapse. 2008 Jul;62(7):501-7. (studies have provided evidence of neuroglial responses and neuroinflammation in autism. Postmortem brain tissues from Brodmann's Area 40 (BA40, parietal cortex), Brodmann's Area 9 (BA9, superior frontal cortex), and cerebella of subjects with autism and matched controls were subject to SDS-PAGE and western blotting. Connexin 43 expression was increased significantly in BA9. Aquaporin 4 expression was decreased significantly in cerebellum. These data suggest that changes are apparent in markers for abnormal glial-neuronal communication (connexin 43 and aquaporin 4) in brains of subjects with autism.


 

Phosphodiesterase 4

Braun NN, Reutiman TJ, Lee S, Folsom TD, Fatemi SH. Expression of phosphodiesterase 4 is altered in the brains of subjects with autism. Neuroreport. 2007 Nov 19;18(17):1841-4.  (they look for various phosphodiesterase forms exposed in areas of the brain of autistic children and compare them with controls.  The problem with this study is that they have looked for many different proteins and so they were very likely to find ones that were altered in autism)

Antipsychotic-like properties of phosphodiesterase 4 inhibitors: evaluation of 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (RO-20-1724) with auditory event-related potentials and prepulse inhibition of startle.

Halene TB, Siegel SJ.  J Pharmacol Exp Ther. 2008 Jul;326(1):230-9. Epub 2008 Apr 17.  This merely shows the effect of inhibitors on mice.  It was published in a journal concerning autism and discusses the possibility of either creating autistic mouse models or modifying them.  It does not claim great answers.

 


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Reelin

A protein of unknown value in humans that is found modified in some rats with a psychological modification.  Responsible for correct lamination of the brain during the embryonic period and cell signaling and synaptic plasticity in the adult life.

 

Fatemi SH, Snow AV, Stary JM, Araghi-Niknam M, Reutiman TJ, Lee S, Brooks AI, Pearce DA. Reelin signaling is impaired in autism. Biol Psychiatry. 2005 Apr 1;57(7):777-87.  (To further investigate these studies, brain levels of Reelin protein and mRNA and mRNAs for VLDLR, Dab-1, and GSK3 were investigated. METHODS: Postmortem superior frontal, parietal, and cerebellar cortices of age, gender, and postmortem interval-matched autistic and control subjects were subjected to SDS-PAGE and Western blotting of Reelin protein. Quantitative reverse transcriptase polymerase chain reaction analysis of Reelin, VLDL-R, Dab-1, and GSK3 mRNA species in superior frontal and cerebellar cortices of autistic and control subjects were also performed. RESULTS: Reelin 410, 330, and 180 kDa/beta-actin values were reduced significantly in frontal and cerebellar, and nonsignificantly in parietal, areas of autistic brains versus control subjects, respectively. The mRNAs for Reln and Dab-1 were reduced significantly whereas the mRNA for Reln receptor VLDLR was elevated significantly in superior frontal and cerebellar areas of autistic brains versus control brains, respectively. CONCLUSIONS: Reductions in Reelin protein and mRNA and Dab 1 mRNA and elevations in Reln receptor VLDLR mRNA demonstrate impairments in the Reelin signalling system in autism)

 

Bonora E, Beyer KS, Lamb JA, Parr JR, Klauck SM, Benner A, Paolucci M, Abbott A, Ragoussis I, Poustka A, Bailey AJ, Monaco AP; International Molecular Genetic Study of Autism (IMGSAC). Analysis of reelin as a candidate gene for autism. Mol Psychiatry. 2003 Oct;8(10):885-92.

 

Devlin B, Bennett P, Dawson G, Figlewicz DA, Grigorenko EL, McMahon W, Minshew N, Pauls D, Smith M, Spence MA, Rodier PM, Stodgell C, Schellenberg GD; CPEA Genetics Network. Alleles of a reelin CGG repeat do not convey liability to autism in a sample from the CPEA network. Am J Med Genet B Neuropsychiatr Genet. 2004 Apr 1;126(1):46-50.

 

Serajee FJ, Zhong H, Mahbubul Huq AH. Association of Reelin gene polymorphisms with autism. Genomics. 2006 Jan;87(1):75-83. Epub 2005 Nov 28.

 

Skaar DA, Shao Y, Haines JL, Stenger JE, Jaworski J, Martin ER, DeLong GR, Moore JH, McCauley JL, Sutcliffe JS, Ashley-Koch AE, Cuccaro ML, Folstein SE, Gilbert JR, Pericak-Vance MA. Analysis of the RELN gene as a genetic risk factor for autism. Mol Psychiatry. 2005 Jun;10(6):563-71.

 

Fatemi SH. Reelin glycoprotein in autism and schizophrenia. Int Rev Neurobiol. 2005;71:179-87. Review.

 

Fatemi SH. The role of Reelin in pathology of autism. Mol Psychiatry. 2002;7(9):919-20. Review.  (notably changes are seen in some cases genetically, and in some cases when investigated post mortem.  The article puts over the idea of Reelin as being a major genetic cause but this is not well demonstrated.  It is an editorial review of Zhang’s article below).

 

Zhang H, Liu X, Zhang C, Mundo E, Macciardi F, Grayson DR, Guidotti AR, Holden JJ. Reelin gene alleles and susceptibility to autism spectrum disorders. Mol Psychiatry. 2002;7(9):1012-7.

 

Dutta S, Guhathakurta S, Sinha S, Chatterjee A, Ahmed S, Ghosh S, Gangopadhyay PK, Singh M, Usha R. Reelin gene polymorphisms in the Indian population: a possible paternal 5'UTR-CGG-repeat-allele effect on autism. Am J Med Genet B Neuropsychiatr Genet. 2007 Jan 5;144(1):106-12

 

Ashley-Koch AE, Jaworski J, Ma de Q, Mei H, Ritchie MD, Skaar DA, Robert Delong G, Worley G, Abramson RK, Wright HH, Cuccaro ML, Gilbert JR, Martin ER, Pericak-Vance MA. Investigation of potential gene-gene interactions between APOE and RELN contributing to autism risk. Psychiatr Genet. 2007 Aug;17(4):221-6. (Thus, we conclude that there is no main effect of APOE in our autism data set, nor is there any evidence for a joint effect of APOE with RELN. RELN, however, remains a good candidate for autism susceptibility)

 

Fatemi SH, Stary JM, Egan EA. Reduced blood levels of reelin as a vulnerability factor in pathophysiology of autistic disorder. Cell Mol Neurobiol. 2002 Apr;22(2):139-52.

 

Fatemi SH. Reelin glycoprotein: structure, biology and roles in health and disease. Mol Psychiatry. 2005 Mar;10(3):251-7.

 

Dutta S, Sinha S, Ghosh S, Chatterjee A, Ahmed S, Usha R. Genetic analysis of reelin gene (RELN) SNPs: No association with autism spectrum disorder in the Indian population. Neurosci Lett. 2008 Aug 15;441(1):56-60. Epub 2008 Jun 13.  (Reelin gene (RELN) is located on chromosome 7q22; an important autism critical region identified through several genome-wide scans.  But, we failed to detect either preferential parental transmission of any alleles of the markers to affected offspring or any biased allelic or genotypic distribution between the cases and controls.)

Gene-environment interaction during early development in the heterozygous reeler mouse: clues for modelling of major neurobehavioral syndromes. Laviola G, Ognibene E, Romano E, Adriani W, Keller F. Neurosci Biobehav Rev. 2009 Apr;33(4):560-72.

 

Alleles of a reelin CGG repeat do not convey liability to autism in a sample from the CPEA network.

Devlin B, Bennett P, Dawson G, Figlewicz DA, Grigorenko EL, McMahon W, Minshew N, Pauls D, Smith M, Spence MA, Rodier PM, Stodgell C, Schellenberg GD; CPEA Genetics Network..  Am J Med Genet B Neuropsychiatr Genet. 2004 Apr 1;126B(1):46-50.  Clearly this is what they all really needed to know in a large study.  However the study is not adequately large to be certain that it is valid in all cases of autism.

 


 

Glial fibrillary acid protein

(NB see autoantibodies for GFAP and its presence in CSF)

 

Laurence JA, Fatemi SH. Glial fibrillary acidic protein is elevated in superior frontal, parietal and cerebellar cortices of autistic subjects. Cerebellum. 2005;4(3):206-10. (‘Immune system dysregulation has been hypothesized to be involved in this disorder. We quantified levels of glial fibrillary acidic protein (GFAP) and ss-actin in three areas of the brain, namely, area 9, area 40 and cerebellum, in age matched autistic and control postmortem specimen using SDS-PAGE and western blotting techniques. Significant elevations in levels of GFAP were observed in all three brain areas in autism. This report confirms a recent report showing microglial and astroglial activation in autism’)

Chronic psychotropic drug treatment causes differential expression of connexin 43 and GFAP in frontal cortex of rats.

Fatemi SH, Folsom TD, Reutiman TJ, Pandian T, Braun NN, Haug K.  Schizophr Res. 2008 Sep;104(1-3):127-134. Epub 2008 Jun 27.  They basically accepted the decrease in connexin and GFAP in the autistic children and looked to see if specific drugs made any difference to the proteins.  They found that some increased it (e.g. fluoxitine did) and some decreased it e.g. haloperidol.  The significance for treatment is not clear.

 

Fatemi SH, Araghi-Niknam M, Laurence JA, Stary JM, Sidwell RW, Lee S. Glial fibrillary acidic protein and glutamic acid decarboxylase 65 and 67 kDa proteins are increased in brains of neonatal BALB/c mice following viral infection in utero. Schizophr Res. 2004 Jul 1;69(1):121-3.

 

Antibodies against fetal brain in sera of mothers with autistic children.

Singer HS, Morris CM, Gause CD, Gillin PK, Crawford S, Zimmerman AW. J Neuroimmunol. 2008 Feb;194(1-2):165-72. Epub 2008 Feb 21.  They showed that the mothers had more and different bands of anti GFAP antibodies than the matched controls (without autistic children).  This seems a good paper but they admit that it was always difficult to carry out because the western blotting bands shown up were often more clear or greater in the mothers of the autistic children…but they could not say that this represented no more antibodies per se.

How relevant are GFAP autoantibodies in autism and Tourette Syndrome?

Kirkman NJ, Libbey JE, Sweeten TL, Coon HH, Miller JN, Stevenson EK, Lainhart JE, McMahon WM, Fujinami RS.

J Autism Dev Disord. 2008 Feb;38(2):333-41. Epub 2007 Jun 20.  They found a significant difference in autoantibody titers to GFAP, not accounted for by age, between the Tourette (significantly lower) and regressive autism groups. However, no differences were found between: classic/regressive; classic/controls; classic/Tourette; regressive/controls; or controls/Tourette. Autoantibody responses against GFAP are unlikely to play a pathogenic role in autism or Tourette Syndrome.  In the end they were rather disappointed with this one and decided that with the numbers that they were using they simply could not justify a statement that the autoantibodies were involved in the cause of the disease.

 

 


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Glutamic Acid Decarboxylase

 

Fatemi SH, Halt AR, Stary JM, Kanodia R, Schulz SC, Realmuto GR. Glutamic acid decarboxylase 65 and 67 kDa proteins are reduced in autistic parietal and cerebellar cortices. Biol Psychiatry. 2002 Oct 15;52(8):805-10. (‘We observed a lower expression of PDE4A5, PDE4B1, PDE4B3, PDE4B4, and PDE4B2 in the cerebella of subjects with autism when compared with matched controls. In BA9, we observed the opposite: a higher expression of PDE4AX, PDE4A1, and PDE4B2 in subjects with autism. No changes were observed in BA40. Our results demonstrate altered expressions of the PDE4A and PDE4B proteins’)

 

Fatemi SH. The hyperglutamatergic hypothesis of autism.  Prog Neuropsychopharmacol Biol Psychiatry. 2008 Apr 1;32(3):911, author reply 912-3. Epub 2007 Nov 13

Immune-glutamatergic dysfunction as a central mechanism of the autism spectrum disorders.  Blaylock RL, Strunecka A.  Curr Med Chem. 2009;16(2):157-70.  this is a review in which they try to fit everything together that might fit a genetic, toxic, anatomical etc format and they create an idea that it will involve the immune and glutamate pathways.

A pathogenetic model of autism involving Purkinje cell loss through anti-GAD antibodies. Rout UK, Dhossche DM. Med Hypotheses. 2008 Aug;71(2):218-21. They get to this one in that the lack of the gene for GAD seems to lead to the loss of Purkinje cells and that is associated with autism.  Therefore could it not be that the first thing that stops is the action of GAD?

 

A population-based association study of glutamate decarboxylase 1 as a candidate gene for autism. Buttenschøn HN, Lauritsen MB, El Daoud A, Hollegaard M, Jorgensen M, Tvedegaard K, Hougaard D, Børglum A, Thorsen P, Mors O. J Neural Transm. 2009 Mar;116(3):381-8.   The glutamate decarboxylase gene 1 (GAD1) located within chromosome 2q31 encodes the enzyme, GAD67, catalyzing the production of gamma-aminobutyric acid (GABA) from glutamate. Numerous independent findings have suggested the GABAergic system to be involved in autism. The present study investigates a Danish population-based, case-control sample of 444 subjects with childhood autism and 444 controls. Nine single nucleotide polymorphisms (SNPs) comprising the GAD1 gene and the microsatellite marker D2S2381 were examined for association with autism. We found no association between childhood autism and any single marker or 2-5 marker haplotypes. However, a rare nine-marker haplotype was associated with childhood autism. We cannot exclude neither GAD1 as a susceptibility gene nor the possibility of another susceptibility gene for autism to be located on chromosome 2q31.

 

Rabionet R, Jaworski JM, Ashley-Koch AE, Martin ER, Sutcliffe JS, Haines JL, Delong GR, Abramson RK, Wright HH, Cuccaro ML, Gilbert JR, Pericak-Vance MA. Analysis of the autism chromosome 2 linkage region: GAD1 and other candidate genes. Neurosci Lett. 2004 Dec 6;372(3):209-14. (they found no association)

Purkinje cell loss in autism may involve epigenetic changes in the gene encoding GAD.  Peedicayil J, Thangavelu P.  Med Hypotheses. 2008 Dec;71(6):978. Epub 2008 Sep 9.

 

 


 

ApoProtein-E (a protein found on the surface of cells)

 

Raiford KL, Shao Y, Allen IC, Martin ER, Menold MM, Wright HH, Abramson RK, Worley G, DeLong GR, Vance JM, Cuccaro ML, Gilbert JR, Pericak-Vance MA. No association between the APOE gene and autism. Am J Med Genet B Neuropsychiatr Genet. 2004 Feb 15;125(1):57-60


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Secretin  

This is generally thought of as a hormone but, like many other hormones it has a direct activity on neuronal tissue, and can commonly penetrate the blood brain barrier.  When secretin was inoculated into autistic children as a potential treatment it was considered that this was to do with gut modification that it would bring about.  However, the consideration that it may be acting directly on the brain came later. 

 

Ng SS, Yung WH, Chow BK. Secretin as a neuropeptide. Mol Neurobiol. 2002 Aug;26(1):97-107. (a review of the action of secretin neuropeptide: realising that there is a complex activity of secretin)

 

Banks WA, Goulet M, Rusche JR, Niehoff ML, Boismenu R. Differential transport of a secretin analog across the blood-brain and blood-cerebrospinal fluid barriers of the mouse. J Pharmacol Exp Ther. 2002 Sep;302(3):1062-9. (shows how the drug is passed across into the  brain from the blood system)

 

Toda Y, Mori K, Hashimoto T, Miyazaki M, Nozaki S, Watanabe Y, Kuroda Y, Kagami S. Administration of secretin for autism alters dopamine metabolism in the central nervous system. Brain Dev. 2006 Mar;28(2):99-103.  (a complex study in which they gave 12 autistic children some i.v. secretin and looked for improvements in biopterin, 5HIAA, and homovanillinic acid –taken as signs of irritation, serotonin turnover and dopamine turnover- these were found in 7 but all of those with raised biopterin results initially)

 

Welch MG, Keune JD, Welch-Horan TB, Anwar N, Anwar M, Ludwig RJ, Ruggiero DA. Secretin: hypothalamic distribution and hypothesized neuroregulatory role in autism. Cell Mol Neurobiol. 2004 Apr;24(2):219-41.

 

Nishijima I, Yamagata T, Spencer CM, Weeber EJ, Alekseyenko O, Sweatt JD, Momoi MY, Ito M, Armstrong DL, Nelson DL, Paylor R, Bradley A. Secretin receptor-deficient mice exhibit impaired synaptic plasticity and social behaviour. Hum Mol Genet. 2006 Nov 1;15(21):3241-50.  (this was an interesting finding in that it suggested that the social changes seen in brains that had no secretin receptor in the brain and hence put forward the idea that there was a genetic factor that may cause the autism.  Also it indicated that injected secretin would not be expected to work as a treatment unless it was the gene for secretin production that was affected).

 

Molloy CA, Manning-Courtney P, Swayne S, Bean J, Brown JM, Murray DS, Kinsman AM, Brasington M, Ulrich CD 2nd. Lack of benefit of intravenous synthetic human secretin in the treatment of autism. J Autism Dev Disord. 2002 Dec;32(6):545-51. (this is just one of the studies that found this.  Originally Horvath’s 3 cases to which he gave secretin have been interesting and certainly specific cases claim great improvements but the statistics will not stand up over larger studies)

 


 

Variation in the expression of proteins in the  brain

This is not surprising but and be shown clearly in brain samples.   Also see sections elsewhere, with the genetics etc. 

 

Garbett K, Ebert PJ, Mitchell A, Lintas C, Manzi B, Mirnics K, Persico AM. Immune transcriptome alterations in the temporal cortex of subjects with autism. Neurobiol Dis. 2008 Jun;30(3):303-11. Epub 2008 Mar 10.

Expression profiling of the superior temporal gyrus of six autistic subjects and matched controls revealed increased transcript levels of many immune system-related genes. We also noticed changes in transcripts related to cell communication, differentiation, cell cycle regulation and chaperone systems. Critical expression changes were confirmed by qPCR (BCL6, CHI3L1, CYR61, IFI16, IFITM3, MAP2K3, PTDSR, RFX4, SPP1, RELN, NOTCH2, RIT1, SFN, GADD45B, HSPA6, HSPB8 and SERPINH1).

 

Paşca SP, Dronca E, Nemeş B, Kaucsár T, Endreffy E, Iftene F, Benga I, Cornean R, Dronca M. Paraoxonase 1 activities and polymorphisms in autism spectrum disorders. J Cell Mol Med. 2008 Jun 28. [Epub ahead of print]

 

 


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