Sensory processing in 16p11.2 deletion and 16p11.2 duplication

Tactile sensory processing deficits in genetic mouse models of autism spectrum disorder

Altered sensory processing is a common feature in autism spectrum disorder (ASD), as recognized in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Although altered responses to tactile stimuli are observed in over 60% of individuals with ASD, the neurobiological basis of this phenomenon is poorly understood. ASD has a strong genetic component and genetic mouse models can provide valuable insights into the mechanisms underlying tactile abnormalities in ASD. This review critically addresses recent findings regarding tactile processing deficits found in mouse models of ASD, with a focus on behavioral, anatomical, and functional alterations. Particular attention was given to cellular and circuit-level functional alterations, both in the peripheral and central nervous systems, with the objective of highlighting possible convergence mechanisms across models. By elucidating the impact of mutations in ASD candidate genes on somatosensory circuits and correlating them with behavioral phenotypes, this review significantly advances our understanding of tactile deficits in ASD. Such insights not only broaden our comprehension but also pave the way for future therapeutic interventions.

Association of behavioural and social-communicative profiles in children with 16p11.2 copy number variants: a multi-site study

BACKGROUND

Despite the established knowledge that recurrent copy number variants (CNVs) at the 16p11.2 locus BP4-BP5 confer risk for behavioural and language difficulties, limited research has been conducted on the association between behavioural and social-communicative profiles. The current study aims to further delineate the prevalence, nature and severity of, and the association between, behavioural and social-communicative features of school-aged children with 16p11.2 deletion syndrome (16p11.2DS) and 16p11.2 duplication (16p11.2Dup).

METHODS

A total of 68 individuals (n = 47 16p11.2DS and n = 21 16p11.2Dup) aged 6-17 years participated. Standardised intelligence tests were administered, and behavioural and social-communicative skills were assessed by standardised questionnaires. Scores of both groups were compared with population norms and across CNVs. The influence of confounding factors was investigated, and correlation analyses were performed.

RESULTS

Compared with the normative sample, children with 16p11.2DS showed high rates of social responsiveness (67%) and communicative problems (69%), while approximately half (52%) of the patients displayed behavioural problems. Children with 16p11.2Dup demonstrated even higher rates of social-communicative problems (80-90%) with statistically significantly more externalising and overall behavioural challenges (89%). In both CNV groups, there was a strong positive correlation between behavioural and social-communicative skills.

CONCLUSIONS

School-aged children with 16p11.2 CNVs show high rates of behavioural, social responsiveness and communicative problems compared with the normative sample. These findings point to the high prevalence of autistic traits and diagnoses in these CNV populations. Moreover, there is a high comorbidity between behavioural and social-communicative problems. Patients with difficulties in both domains are vulnerable and need closer clinical follow-up and care.

Circuit-level theories for sensory dysfunction in autism: convergence across mouse models

Individuals with autism spectrum disorder (ASD) exhibit a diverse range of behavioral features and genetic backgrounds, but whether different genetic forms of autism involve convergent pathophysiology of brain function is unknown. Here, we analyze evidence for convergent deficits in neural circuit function across multiple transgenic mouse models of ASD. We focus on sensory areas of neocortex, where circuit differences may underlie atypical sensory processing, a central feature of autism. Many distinct circuit-level theories for ASD have been proposed, including increased excitation-inhibition (E-I) ratio and hyperexcitability, hypofunction of parvalbumin (PV) interneuron circuits, impaired homeostatic plasticity, degraded sensory coding, and others. We review these theories and assess the degree of convergence across ASD mouse models for each. Behaviorally, our analysis reveals that innate sensory detection behavior is heightened and sensory discrimination behavior is impaired across many ASD models. Neurophysiologically, PV hypofunction and increased E-I ratio are prevalent but only rarely generate hyperexcitability and excess spiking. Instead, sensory tuning and other aspects of neural coding are commonly degraded and may explain impaired discrimination behavior. Two distinct phenotypic clusters with opposing neural circuit signatures are evident across mouse models. Such clustering could suggest physiological subtypes of autism, which may facilitate the development of tailored therapeutic approaches.

Rescue of neuropsychiatric phenotypes in a mouse model of 16p11.2 duplication syndrome by genetic correction of an epilepsy network hub

Neuropsychiatric disorders (NPDs) are frequently co-morbid with epilepsy, but the biological basis of shared risk remains poorly understood. The 16p11.2 duplication is a copy number variant that confers risk for diverse NPDs including autism spectrum disorder, schizophrenia, intellectual disability and epilepsy. We used a mouse model of the 16p11.2 duplication (16p11.2dup/+) to uncover molecular and circuit properties associated with this broad phenotypic spectrum, and examined genes within the locus capable of phenotype reversal. Quantitative proteomics revealed alterations to synaptic networks and products of NPD risk genes. We identified an epilepsy-associated subnetwork that was dysregulated in 16p11.2dup/+ mice and altered in brain tissue from individuals with NPDs. Cortical circuits from 16p11.2dup/+ mice exhibited hypersynchronous activity and enhanced network glutamate release, which increased susceptibility to seizures. Using gene co-expression and interactome analysis, we show that PRRT2 is a major hub in the epilepsy subnetwork. Remarkably, correcting Prrt2 copy number rescued aberrant circuit properties, seizure susceptibility and social deficits in 16p11.2dup/+ mice. We show that proteomics and network biology can identify important disease hubs in multigenic disorders, and reveal mechanisms relevant to the complex symptomatology of 16p11.2 duplication carriers.