Bridging the translational gap: what can synaptopathies tell us about autism?

Multiple molecular pathways and cellular processes have been implicated in the neurobiology of autism and other neurodevelopmental conditions. There is a current focus on synaptic gene conditions, or synaptopathies, which refer to clinical conditions associated with rare genetic variants disrupting genes involved in synaptic biology. Synaptopathies are commonly associated with autism and developmental delay and may be associated with a range of other neuropsychiatric outcomes. Altered synaptic biology is suggested by both preclinical and clinical studies in autism based on evidence of differences in early brain structural development and altered glutamatergic and GABAergic neurotransmission potentially perturbing excitatory and inhibitory balance. This review focusses on the NRXN-NLGN-SHANK pathway, which is implicated in the synaptic assembly, trans-synaptic signalling, and synaptic functioning. We provide an overview of the insights from preclinical molecular studies of the pathway. Concentrating on NRXN1 deletion and SHANK3 mutations, we discuss emerging understanding of cellular processes and electrophysiology from induced pluripotent stem cells (iPSC) models derived from individuals with synaptopathies, neuroimaging and behavioural findings in animal models of Nrxn1 and Shank3 synaptic gene conditions, and key findings regarding autism features, brain and behavioural phenotypes from human clinical studies of synaptopathies. The identification of molecular-based biomarkers from preclinical models aims to advance the development of targeted therapeutic treatments. However, it remains challenging to translate preclinical animal models and iPSC studies to interpret human brain development and autism features. We discuss the existing challenges in preclinical and clinical synaptopathy research, and potential solutions to align methodologies across preclinical and clinical research. Bridging the translational gap between preclinical and clinical studies will be necessary to understand biological mechanisms, to identify targeted therapies, and ultimately to progress towards personalised approaches for complex neurodevelopmental conditions such as autism.

Further insight into the neurobehavioral pattern of children carrying the 2p16.3 heterozygous deletion involving NRXN1: Report of five new cases

Increasing evidence links heterozygosity for NRXN1 gene deletions to a clinically wide spectrum of neurodevelopmental, psychiatric, and neurological disorders. However, to date, the neurocognitive and social communication features of children carrying this genomic rearrangement have not been assessed in detail. The cognitive and behavioral profiles of five children carrying a heterozygous NRXN1 deletion were investigated through systematic assessment of the cognitive and developmental levels, adaptive profile and presence of behavioral symptoms and autistic features. Furthermore, four transmitting parents were assessed by means of cognitive, psychopathological and parental stress tests. A below-average cognitive level was documented in all children, and defective adaptive levels were observed in four of them. Three of the five children were diagnosed as having autism spectrum disorder in comorbidity with intellectual disability/global developmental delay, with a major impairment in social communication skills. The remaining two children presented with isolated intellectual disability and an unclassifiable neurodevelopmental disorder, respectively. This study provide data contributing to a more accurate characterization of the neurobehavioral phenotype of individuals carrying heterozygous NRXN1 deletions. This analysis indicates that these structural rearrangements are associated with a variable expression of neuropsychiatric symptoms, and cast some doubts about the incomplete penetrance of the disorder.