Novel treatments in autism spectrum disorders: from synaptic dysfunction to experimental therapeutics

Mechanistic perspective on the actions of vitamin a in autism spectrum disorder etiology

Vitamin A (VA) has many functions in the body, some of which are key for the development and functioning of the nervous system, while some others might indirectly influence neural function. Both hypovitaminosis and hypervitaminosis A can lead to clinical manifestations of concern for individuals and for general global health. Scientific evidence on the link between VA and autism spectrum disorder (ASD) is growing, with some clinical studies and accumulating results obtained from basic research using cellular and animal models. Remarkably, it has been shown that VA deficiency can exacerbate autistic symptomatology. In turn, VA supplementation has been shown to be able to improve autistic symptomatology in selected groups of individuals with ASD. However, it is important to recognize that ASD is a highly heterogeneous condition. Therefore, it is important to clarify how and when VA supplementation can be of benefit for affected individuals. Here we delve into the relationship between VA and ASD, discussing clinical observations and mechanistic insights obtained from research on selected autistic syndromes and laboratory models to advance in defining how the VA signaling pathway can be exploited for treatment of ASD.

Use of GFCF Diets in Children with ASD. An Investigation into Parents' Beliefs Using the Theory of Planned Behaviour

Gluten free/Casein free (GFCF) diets are one of the most common types of Complementary and Alternative Medicines (CAM) used in Autism Spectrum Disorders (ASD) despite little evidence to support positive effects. There has been no theory driven literature that has investigated parent’s reasons for their use. The Theory of Planned Behaviour (TPB) was used to examine parent’s intentions to use GFCF diets for their child with an ASD. Treatment and causal beliefs were also examined. Parents (n = 33, children aged 3–17 years) were influenced by anticipated regret, positive outcomes and attitude. Future interventions should provide information to parents and health professionals about the possible causes of ASD and therapy options which are in line with current recommendations.

A Child with Kabuki Syndrome and Autism Spectrum Disorder

Kabuki syndrome (KS) is characterized by skeletal abnormalities, short stature, characteristic facial features, postnatal growth delay, and mental retardation. There are only a few case reports that present the coexistence of KS with autism spectrum disorder (ASD) in the literature. Herein we present the case of a boy with KS and ASD and discuss the possible shared etiologies. A 4-year-old boy was brought by his parents with complaints of no speech, hyperactivity, enuresis complex, temper tantrum, self-injury, and harming people or objects. We determined the lack of speech and eye contact, stereotypical behavior, and impaired social interaction and diagnosed him with autism and severe mental retardation via a psychiatric assessment. He had been followed up by pediatricians until he was 2 years old. Pediatricians noted his long eyelids with eversion of the lateral third of the lower eyelid, depressed nasal tip, short stature, long palpebral fissures, brachydactyly, and fetal finger pads in their physical examination. The boy who has an operated ventral septal defect and seizures was diagnosed with KS when he was 5 years old. We recommended his parents to apply to a special education agency and kindergarten for him. Our case is a new example of the coexistence of KS and ASD in addition to the very few cases in the literature. Genetic analyses conducted in the existence of specific genetic syndromes, such as KS, may provide opportunities for understanding the genetic etiology of ASD and new scope in terms of novel treatment approaches.

Clustering autism: using neuroanatomical differences in 26 mouse models to gain insight into the heterogeneity

Autism is a heritable disorder, with over 250 associated genes identified to date, yet no single gene accounts for >1-2% of cases. The clinical presentation, behavioural symptoms, imaging and histopathology findings are strikingly heterogeneous. A more complete understanding of autism can be obtained by examining multiple genetic or behavioural mouse models of autism using magnetic resonance imaging (MRI)-based neuroanatomical phenotyping. Twenty-six different mouse models were examined and the consistently found abnormal brain regions across models were parieto-temporal lobe, cerebellar cortex, frontal lobe, hypothalamus and striatum. These models separated into three distinct clusters, two of which can be linked to the under and over-connectivity found in autism. These clusters also identified previously unknown connections between Nrxn1α, En2 and Fmr1; Nlgn3, BTBR and Slc6A4; and also between X monosomy and Mecp2. With no single treatment for autism found, clustering autism using neuroanatomy and identifying these strong connections may prove to be a crucial step in predicting treatment response.

Downregulation of GABAA receptor protein subunits α6, β2, δ, ε, γ2, θ, and ρ2 in superior frontal cortex of subjects with autism

We measured protein and mRNA levels for nine gamma-aminobutyric acid A (GABAA) receptor subunits in three brain regions (cerebellum, superior frontal cortex, and parietal cortex) in subjects with autism versus matched controls. We observed changes in mRNA for a number of GABAA and GABAB subunits and overall reduced protein expression for GABAA receptor alpha 6 (GABRα6), GABAA receptor beta 2 (GABRβ2), GABAA receptor delta (GABRδ), GABAA receptor epsilon (GABRε), GABAA receptor gamma 2 (GABRγ2), GABAA receptor theta (GABRθ), and GABAA receptor rho 2 (GABRρ2) in superior frontal cortex from subjects with autism. Our data demonstrate systematic changes in GABAA&B subunit expression in brains of subjects with autism, which may help explain the presence of cognitive abnormalities in subjects with autism.

Molecular handoffs in nitrergic neurotransmission

Postsynaptic density (PSD) proteins in excitatory synapses are relatively immobile components, while there is a structured organization of mobile scaffolding proteins lying beneath the PSDs. For example, shank proteins are located further away from the membrane in the cytosolic faces of the PSDs, facing the actin cytoskeleton. The rationale of this organization may be related to important roles of these proteins as “exchange hubs” for the signaling proteins for their migration from the subcortical cytosol to the membrane. Notably, PSD95 have also been demonstrated in prejunctional nerve terminals of nitrergic neuronal varicosities traversing the gastrointestinal smooth muscles. It has been recently reported that motor proteins like myosin Va play important role in transcytosis of nNOS. In this review, the hypothesis is forwarded that nNOS delivered to subcortical cytoskeleton requires interactions with scaffolding proteins prior to docking at the membrane. This may involve significant role of “shank,” named for SRC-homology (SH3) and multiple ankyrin repeat domains, in nitric oxide synthesis. Dynein light chain LC8–nNOS from acto-myosin Va is possibly exchanged with shank, which thereafter facilitates transposition of nNOS for binding with palmitoyl-PSD95 at the nerve terminal membrane. Shank knockout mice, which present with features of autism spectrum disorders, may help delineate the role of shank in enteric nitrergic neuromuscular transmission. Deletion of shank3 in humans is a monogenic cause of autism called Phelan–McDermid syndrome. One fourth of these patients present with cyclical vomiting, which may be explained by junctionopathy resulting from shank deficit in enteric nitrergic nerve terminals.

A blueprint for research on Shankopathies: a view from research on autism spectrum disorder

Autism spectrum disorders (ASD) are associated with mutations in a host of genes including a number that function in synaptic transmission. Phelan McDermid syndrome involves mutations in SHANK3 which encodes a protein that forms a scaffold for glutamate receptors at the synapse. SHANK3 is one of the genes that underpins the synaptic hypothesis for ASD. We discuss this hypothesis with a view to the broader context of ASD and with special emphasis on highly penetrant genetic disorders including Shankopathies. We propose a blueprint for near and longer-term goals for fundamental and translational research on Shankopathies.