Biology subjects

Nadif Kasri, N.

Publications and source records attributed to Nadif Kasri, N..

25 records · Page 2Linked to original sources

bioRxiv2020

Comparison of induced neurons reveals slower structural and functional maturation in humans than in apes

We generated induced excitatory sensory neurons (iNeurons, iNs) from chimpanzee, bonobo and human stem cells by expressing the transcription factor neurogenin-2 (NGN2). Single cell-RNA sequencing showed that genes involved in dendrite and synapse development are expressed earlier during iNs maturation in the chimpanzee than the human cells. In accordance, during the first two weeks of differentiation, chimpanzee and bonobo iNs showed repetitive action potentials and more spontaneous excitatory activity than human iNs, and extended neurites of higher total length. However, the axons of human iNs were slightly longer at 5 weeks of differentiation. The timing of the establishment of neuronal polarity did not differ between the species. Chimpanzee, bonobo and human neurites eventually reached the same level of structural complexity. Thus, human iNs develop slower than chimpanzee and bonobo iNs and this difference in timing likely depends on functions downstream of NGN2.

evolutionary biology↗

bioRxiv2020

Cadherin-13 is a critical regulator of GABAergic modulation in human stem cell derived neuronal networks

Activity in the healthy brain relies on concerted interplay of excitation (E) and inhibition (I) via balanced synaptic communication between glutamatergic and GABAergic neurons. A growing number of studies imply that disruption of this E/I balance is a commonality in many brain disorders, however, obtaining mechanistic insight into these disruptions, with translational value for the human patient, has typically been hampered by methodological limitations. Cadherin-13 (CDH13) has strongly been associated to attention-deficit/hyperactivity disorder and comorbid disorders such as autism and schizophrenia. CDH13 localises at inhibitory presynapses, specifically of parvalbumin (PV) and somatostatin (SST) expressing GABAergic neurons. However, the mechanism by which CDH13 regulates the function of inhibitory synapses in human neurons remains unknown. Starting from human induced pluripotent stem cells, we established a robust method to generate a homogenous population of SST and PV expressing GABAergic neurons (iGABA) in vitro, and co-cultured these with glutamatergic neurons at defined E/I ratios on micro-electrode arrays. We identified functional network parameters that are most reliably affected by GABAergic modulation as such, and through alterations of E/I balance by reduced expression of CDH13 in iGABAs. We found that CDH13-deficiency in iGABAs decreased E/I balance by means of increased inhibition. Moreover, CDH13 interacts with Integrin-{beta}1 and Integrin-{beta}3, which play opposite roles in the regulation of inhibitory synaptic strength via this interaction. Taken together, this model allows for standardized investigation of the E/I balance in a human neuronal background and can be deployed to dissect the cell-type specific contribution of disease genes to the E/I balance.

neuroscience↗

bioRxiv2019

The Object Space Task reveals a dissociation between semantic-like and episodic-like memory in a mouse model of Kleefstra Syndrome

Kleefstra syndrome is a disorder caused by a mutation in the EHMT1 gene characterized in humans by general developmental delay, mild to severe intellectual disability and autism. Here, we characterized semantic- and episodic-like memory in the Ehmt1+/- mouse model using the Object Space Task. We combined conventional behavioral analysis with automated analysis by deep-learning networks, a session-based computational learning model and a trial-based classifier. Ehmt1 +/- mice showed more anxiety-like features and generally explored objects less, but the difference decreased over time. Interestingly, when analyzing memory-specific exploration, Ehmt1 +/- show increased expression of semantic-like memory, but a deficit in episodic-like memory. A similar dissociation of semantic and episodic memory performance has been previously reported in humans with autism. Using our automatic classifier to differentiate between genotypes, we found that semantic-like memory features are better suited for classification than general exploration differences. Thus, detailed behavioral classification with the Object Space Task produced a more detailed behavioral phenotype of the Ehmt1 +/- mouse model.\n\nOne Sentence SummaryEhmt1 +/- mice show decreased exploration and episodic-like memory but increased semantic-like memory In the Object Space Task. (143 of 150)

neuroscience↗

bioRxiv2019

Brunner syndrome associated MAOA dysfunction in human iPSC derived dopaminergic neurons results in dysregulated NMDAR expression and increased network activity

Monoamine oxidase A (MAOA) is an enzyme that catalyzes the degradation of dopamine, noradrenaline, and serotonin. Regulation of monoamine neurotransmitter abundance through MAOA activity strongly affects motor control, emotion, and cognitive function. Mutations in MAOA cause Brunner Syndrome, which is characterized by impulsive aggressive behavior and mild intellectual disability (ID). The impaired MAOA activity in Brunner Syndrome patients results in bioamine aberration, but it is currently unknown how this affects neuronal function. MAOA is highly expressed in serotonergic and dopaminergic neurons, and dysfunction of both neurotransmission systems is associated with aggressive behavior in mice and humans. Research has so far mainly focused on the serotonergic system. Here, we generated human induced pluripotent stem cell-derived induced dopaminergic neurons (iDANs) from individuals with known MAOA mutations, to investigate MAOA-dependent effects on dopamine neuronal function in the context of Brunner Syndrome. We assessed iDAN lines from three patients and combined data from morphological analysis, gene expression, single-cell electrophysiology, and network analysis using micro-electrode arrays (MEAs). We observed mutation-dependent functional effects as well as overlapping changes in iDAN morphology. The most striking effect was a clear increase in N-methyl-D-aspartate (NMDA) receptor mRNA expression in all patient lines. A marked increase was also seen in coordinated network activity (network bursts) on the MEA in all patient lines, while single-cell intrinsic properties and spontaneous excitatory postsynaptic currents activity appeared normal. Together, our data indicate that dysfunction of MAOA leads to increased coordinated network activity in iDANs, possibly caused by increased synaptic NMDA receptor expression.

neuroscience↗

bioRxiv2019

Mitochondrial dysfunction impairs human neuronal development and reduces neuronal network activity and synchronicity

Epilepsy, intellectual and cortical sensory deficits and psychiatric manifestations are among the most frequent manifestations of mitochondrial diseases. Yet, how mitochondrial dysfunction affects neural structure and function remains largely elusive. This is mostly due to the lack of a proper in vitro translational neuronal model system(s) with impaired energy metabolism. Leveraging the induced pluripotent stem cell technology, from a cohort of patients with the common pathogenic m.3243A>G variant of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), we differentiated excitatory cortical neurons (iNeurons) with normal (low heteroplasmy) and impaired (high heteroplasmy) mitochondrial function on an isogenic nuclear DNA background. iNeurons with high levels of heteroplasmy exhibited mitochondrial dysfunction, delayed neural maturation, reduced dendritic complexity and fewer functional excitatory synapses. Micro-electrode array recordings of neuronal networks with high heteroplasmy displayed reduced network activity and decreased synchronous network bursting. The impaired neural energy metabolism of iNeurons compromising the structural and functional integrity of neurons and neural networks, could be the primary driver of increased susceptibility to neuropsychiatric manifestations of mitochondrial disease.

neuroscience↗

bioRxiv2019

Neuronal network dysfunction in a human model for Kleefstra syndrome mediated by enhanced NMDAR signaling

Epigenetic regulation of gene transcription plays a critical role in neural network development and in the etiology of Intellectual Disability (ID) and Autism Spectrum Disorder (ASD). However, little is known about the mechanisms by which epigenetic dysregulation leads to neural network defects. Kleefstra syndrome (KS), caused by mutation in the histone methyltransferase EHMT1, is a neurodevelopmental disorder with the clinical features of both ID and ASD. To study the impact of decreased EHMT1 function in human cells, we generated excitatory cortical neurons from induced pluripotent stem (iPS) cells derived from KS patients. In addition, we created an isogenic set by genetically editing healthy iPS cells. Characterization of the neurons at the single-cell and neuronal network level revealed consistent discriminative properties that distinguished EHMT1-mutant from wildtype neurons. Mutant neuronal networks exhibited network bursting with a reduced rate, longer duration, and increased temporal irregularity compared to control networks. We show that these changes were mediated by the upregulation of the NMDA receptor (NMDAR) subunit 1 and correlate with reduced deposition of the repressive H3K9me2 mark, the catalytic product of EHMT1, at the GRIN1 promoter. Furthermore, we show that EHMT1 deficiency in mice leads to similar neuronal network impairments and increased NMDAR function. Finally, we could rescue the KS patient-derived neuronal network phenotypes by pharmacological inhibition of NMDARs. Together, our results demonstrate a direct link between EHMT1 deficiency in human neurons and NMDAR hyperfunction, providing the basis for a more targeted therapeutic approach to treating KS.

neuroscience↗

bioRxiv2018

Distinct pathogenic genes causing intellectual disability and autism exhibit overlapping effects on neuronal network development

An intriguing question in medical biology is how mutations in functionally distinct genes can lead to similar clinical phenotypes. For example, patients with mutations in distinct epigenetic regulators EHMT1, MBD5, MLL3 or SMARCB1 share the core clinical features of intellectual disability (ID), autism spectrum disorder (ASD) and facial dysmorphisms. To elucidate how these phenotypic similarities are reflected by convergence at the molecular, cellular and neuronal network level, we directly compared the effects of their loss of function in neurons. Interestingly, knockdown of each gene resulted in hyperactive neuronal networks with altered patterns of synchronized activity. At the single-cell level, we found genotype-specific changes in intrinsic excitability and excitatory-inhibitory balance, but in all cases leading to increased excitability. Congruent with our physiological findings, we identified dysregulated genes that converge on biological and cellular pathways related to neuronal excitability and synaptic function, including genes previously implicated in ID/ASD. Yet, our data suggests that the common cellular phenotypes depend on the ensemble of dysregulated genes engaged in neuronal excitability rather than the direction of transcriptional changes of individual genes. The demonstration of increasing convergence from molecular pathways to neuronal networks may be a paradigm for other types of ID/ASD.

neuroscience↗