Autism-associated variants of neuroligin 4X impair synaptogenic activity by various molecular mechanisms

Bridging Genetic Insights with Neuroimaging in Autism Spectrum Disorder-A Systematic Review

Autism Spectrum Disorder (ASD) is an early onset neurodevelopmental disorder characterized by impaired social interaction and communication, and repetitive patterns of behavior. Family studies show that ASD is highly heritable, and hundreds of genes have previously been implicated in the disorder; however, the etiology is still not fully clear. Brain imaging and electroencephalography (EEG) are key techniques that study alterations in brain structure and function. Combined with genetic analysis, these techniques have the potential to help in the clarification of the neurobiological mechanisms contributing to ASD and help in defining novel therapeutic targets. To further understand what is known today regarding the impact of genetic variants in the brain alterations observed in individuals with ASD, a systematic review was carried out using Pubmed and EBSCO databases and following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. This review shows that specific genetic variants and altered patterns of gene expression in individuals with ASD may have an effect on brain circuits associated with face processing and social cognition, and contribute to excitation-inhibition imbalances and to anomalies in brain volumes.

Cellular and molecular mechanisms underlying autism spectrum disorders and associated comorbidities: A pathophysiological review

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders that develop in early life due to interaction between several genetic and environmental factors and lead to alterations in brain function and structure. During the last decades, several mechanisms have been placed to explain the pathogenesis of autism. Unfortunately, these are reported in several studies and reviews which make it difficult to follow by the reader. In addition, some recent molecular mechanisms related to ASD have been unrevealed. This paper revises and highlights the major common molecular mechanisms responsible for the clinical symptoms seen in people with ASD, including the roles of common genetic factors and disorders, neuroinflammation, GABAergic signaling, and alterations in Ca⁺² signaling. Besides, it covers the major molecular mechanisms and signaling pathways involved in initiating the epileptic seizure, including the alterations in the GABAergic and glutamate signaling, vitamin and mineral deficiency, disorders of metabolism, and autoimmunity. Finally, this review also discusses sleep disorder patterns and the molecular mechanisms underlying them.

The role of NMDA receptor and neuroligin rare variants in synaptic dysfunction underlying neurodevelopmental disorders

Many genes encoding synaptic proteins are associated with neurodevelopmental disorders (NDDs) such as autism spectrum disorders (ASDs), intellectual disability (ID), and epilepsy. Here we review recent studies on the synaptic effects of disease-associated rare variants identified in two families of synaptic proteins: NMDA receptors (NMDARs) and the postsynaptic adhesion molecules neuroligins (NLGNs). Many NMDAR subunit genes (GRINs) are highly intolerant to variation, and both gain-of-function (GOF) and loss-of-function (LOF) variants are implicated in disease. NLGN genes are also associated with ASDs, and in some cases, contribute to the male bias identified in these patients. Understanding the molecular basis of synaptic dysfunction of rare variants in these genes will help the design of new therapeutic approaches.