Gene mutation leading to autism found to overstimulate brain cells

Summary: A gene associated with autism overstimulates brain cells much more than neurons without the mutation.

Font: Rutgers University

Scientists seeking to understand the underlying brain mechanisms of autism spectrum disorder have discovered that a genetic mutation known to be associated with the disorder causes much greater overstimulation of brain cells than is seen in neural cells without the mutation.

The Rutgers-led study, which spanned seven years, employed some of the most advanced approaches available in the scientific toolbox, including growing human brain cells from stem cells and transplanting them into mouse brains.

The work illustrates the potential for a new approach to studying brain disorders, the scientists said.

Describing the study in the journal, Molecular Psychiatrythe researchers reported a mutation – R451C in the gene neurologin-3, It is known to cause autism in humans: it was found to cause an increased level of communication between a network of human brain cells transplanted into the brains of mice.

This overexcitation, quantified in experiments conducted by the scientists, manifests as a burst of electrical activity more than twice the level seen in brain cells without the mutation.

“We were surprised to find an improvement, not a deficit,” said Zhiping Pang, associate professor in the Department of Neuroscience and Cell Biology at the New Jersey Institute of Children’s Health at Rutgers Robert Wood Johnson Medical School and lead author of the study. to study.

“This gain of function in those specific cells, revealed by our study, causes an imbalance within the brain’s neural network, disrupting the normal flow of information.”

The mesh of interconnected cells that makes up the human brain contains specialized “excitatory” cells that stimulate electrical activity, balanced by “inhibitory” brain cells that reduce electrical pulses, Pang said. The scientists found that the large burst of electrical activity caused by the mutation threw the mice’s brains out of balance.

Autism spectrum disorder is a developmental disability caused by differences in the brain. About 1 in 44 children have been identified with the disorder, according to estimates from the Centers for Disease Control and Prevention.

Studies suggest that autism could result from interruptions in normal brain growth very early in development, according to the National Institute of Neurological Disorders and Stroke at the National Institutes of Health. These disruptions may be the result of mutations in genes that control brain development and regulate how brain cells communicate with each other, according to the NIH.

“Many of the underlying mechanisms in autism are unknown, making it difficult to develop effective therapies,” Pang said. “Using human neurons generated from human stem cells as a model system, we wanted to understand how and why a specific mutation causes autism in humans.”

The researchers used CRISPR technology to alter the genetic material of human stem cells to create a line of cells that contained the mutation they wanted to study, and then derived human neural cells that carried this mutation. CRISPR, an acronym for Clustered Regularly Interspaced Short Palindromic Repeats, is a unique gene editing technology.

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The work illustrates the potential for a new approach to studying brain disorders, the scientists said. The image is in the public domain.

In the study, the human neural cells that were generated, half with the mutation, half without it, were implanted into the brains of mice. From there, the researchers measured and compared the electrical activity of specific neurons using electrophysiology, a branch of physiology that studies the electrical properties of biological cells. Changes in voltage or electrical current can be quantified on a variety of scales, depending on the dimensions of the object of study.

“Our findings suggest that the NLGN3 R451C mutation dramatically affects excitatory synaptic transmission in human neurons, triggering changes in the general properties of the network that may be related to mental disorders,” Pang said. “We see this as very important information for the field.”

Pang said that he hopes that many of the techniques developed to perform this experiment will be used in future scientific research based on other brain disorders, such as schizophrenia.

“This study highlights the potential of using human neurons as a model system to study mental disorders and develop novel therapies,” he said.

Other Rutgers scientists involved in the study include Le Wang, a postdoctoral associate in Pang’s lab, and Vincent Mirabella, who is earning doctoral and medical degrees as part of the MD-PhD student at Robert Wood Johnson Medical School. ; Davide Comoletti, assistant professor, Matteo Bernabucci, postdoctoral fellow, Xiao Su, doctoral student, and Ishnoor Singh, graduate student, all from Rutgers Child Health Institute of New Jersey; Ronald Hart, professor, Peng Jiang and Kelvin Kwan, assistant professors, and Ranjie Xu and Azadeh Jadali, postdoctoral fellows, all from the Department of Cell Biology and Neuroscience, Rutgers School of Arts and Sciences.

Thomas C. Südhof, a 2013 Nobel laureate and professor in Stanford University’s Department of Molecular and Cellular Physiology, contributed to the study, as did scientists from Central South University in Changsha, China; SUNY Upstate Medical Center in Syracuse, NY; University of Massachusetts at Amherst, Mass.; Shaanxi Normal University in Shaanxi, China; and Victoria University in Wellington, New Zealand.

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About this research news on ASD and genetics

Author: Patti Zielinski
Font: Rutgers University
Contact: Patti Zielinski – Rutgers University
Image: The image is in the public domain.

original research: closed access.
“Analyses of the autism-associated neuroligin-3 R451C mutation in human neurons reveal a synaptic gain-of-function mechanism” by Zhiping Pang et al. Molecular Psychiatry


Summary

Analyzes of the autism-associated neuroligin-3 R451C mutation in human neurons reveal a synaptic gain-of-function mechanism

Mutations in many synaptic genes are associated with autism spectrum disorders (ASDs), suggesting that synaptic dysfunction is a key factor in the pathogenesis of ASDs. Among these mutations, the R451C substitution in the NLGN3 The gene encoding the neuroligin-3 postsynaptic adhesion molecule is noteworthy because it was the first specific ASD-related mutation.

In mice, the corresponding nlgn3 The R451C-knockin mutation recapitulates the social interaction deficits of patients with ASD and produces synaptic abnormalities, but the impact of the NLGN3 The R451C mutation has not been investigated in human neurons.

Here, we generate human knockin neurons with the NLGN3 R451C and NLGN3 null mutations. Surprisingly, the analyzes of NLGN3 R451C mutant neurons revealed that the R451C mutation decreased NLGN3 protein levels but improved the strength of excitatory synapses without affecting inhibitory synapses; Meanwhile NLGN3 The knockout neurons showed a reduction in excitatory synaptic forces.

Furthermore, overexpression of NLGN3 R451C recapitulated synaptic enhancement in human neurons. In particular, the increase in excitatory transmission was confirmed in vivo with human neurons transplanted into mouse forebrain.

Using single cell RNA-seq experiments with cocultured exciters and inhibitors NLGN3 R451C mutant neurons, we identified differentially expressed genes in relatively mature human neurons corresponding to synaptic gene expression networks. In addition, gene ontology and enrichment analyzes revealed convergent gene networks associated with ASDs and other mental disorders.

Our findings suggest that the NLGN3 The R451C mutation induces a gain-of-function enhancement in excitatory synaptic transmission that may contribute to the pathophysiology of ASD.

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