Biology subjects

Dastgheyb, R.

Publications and source records attributed to Dastgheyb, R..

6 recordsLinked to original sources

bioRxiv2024

Altered development and network connectivity in a human neuronal model of 15q11.2 deletion-related neurodevelopmental disorders

The chromosome 15q11.2 locus is deleted in 1.5% of patients with genetic epilepsy and confers a risk for intellectual disability and schizophrenia. Individuals with this deletion demonstrate increased cortical thickness, decreased cortical surface area and white matter abnormalities. Human induced pluripotent stem cell (iPSC)-derived neural progenitor cells (NPC) from 15q11.2 deletion individuals exhibit early adhesion junction and migration abnormalities, but later neuronal development and function have not been fully assessed. Imaging studies indicating altered structure and network connectivity in the anterior brain regions and the cingulum suggest that in addition to alterations in progenitor dynamics, there may also be structural and functional changes within discrete networks of mature neurons. To explore this, we generated human forebrain cortical neurons from iPSCs derived from individuals with or without 15q11.2 deletion and used longitudinal imaging and multielectrode array analysis to evaluate neuronal development over time. 15q11.2 deleted neurons exhibited fewer connections and an increase in inhibitory neurons. Individual neurons had decreased neurite complexity and overall decreased neurite length. These structural changes were associated with a reduction in multiunit action potential generation, bursting and synchronization. The 15q11.2 deleted neurons also demonstrated specific functional deficits in glutamate and GABA mediated network activity and synchronization with a delay in the maturation of the inhibitory response to GABA. These data indicate that deletion of the 15q11.2 region is sufficient to impair the structural and functional maturation of cortical neuron networks which likely underlies the pathologic changes in humans with the 15q11.2 deletion.

neuroscience↗

bioRxiv2023

Phase-Amplitude Coupling Detection and Analysis of Human 2-Dimensional Neural Cultures in Multi-well Microelectrode Array in Vitro

Human induced pluripotent stem cell (hiPSC)- derived neurons offer the possibility of studying human-specific neuronal behaviors in physiologic and pathologic states in vitro. However, it is unclear whether these cultured neurons can achieve the fundamental network behaviors that are required to process information in the human brain. Investigating neuronal oscillations and their interactions, as occurs in cross-frequency coupling (CFC), is potentially a relevant approach. Microelectrode array culture plates provide a controlled framework to study populations of hiPSC-derived cortical neurons (hiPSC-CNs) and their electrical activity. Here, we examined whether networks of two-dimensional cultured hiPSC-CNs recapitulate the CFC that is present in networks in vivo. We analyzed the electrical activity recorded from hiPSC-CNs grown in culture with hiPSC-derived astrocytes. We employed the modulation index method for detecting phase-amplitude coupling (PAC) and used an offline spike sorting method to analyze the contribution of a single neurons spiking activities to network behavior. Our analysis demonstrates that the degree of PAC is specific to network structure and is modulated by external stimulation, such as bicuculine administration. Additionally, the shift in PAC is not driven by a single neurons properties but by network-level interactions. CFC analysis in the form of PAC explores communication and integration between groups of nearby neurons and dynamical changes across the entire network. In vitro, it has the potential to capture the effects of chemical agents and electrical or ultrasound stimulation on these interactions and may provide valuable information for the modulation of neural networks to treat nervous system disorders in vivo. SignificancePhase amplitude coupling (PAC) analysis demonstrates that the complex interactions that occur between neurons and network oscillations in the human brain, in vivo, are present in 2-dimensional human cultures. This coupling is implicated in normal cognitive function as well as disease states. Its presence in vitro suggests that PAC is a fundamental property of neural networks. These findings offer the possibility of a model to understand the mechanisms and of PAC more completely and ultimately allow us to understand how it can be modulated in vivo to treat neurologic disease.

neuroscience↗

bioRxiv2020

Connexin 43 hemichannels mediate spatial and temporal disease spread in ALS

Connexin 43 (Cx43) gap junctions and hemichannels mediate astrocyte intercellular communication in the central nervous system under normal conditions and may contribute to astrocyte-mediated neurotoxicity in amyotrophic lateral sclerosis (ALS). Here we show that astrocyte-specific knockout of Cx43 in a mouse model of ALS slows disease progression both spatially and temporally, provides motor neuron (MN) protection, and improves survival. In human ALS tissues and biofluids, we observe that higher levels of Cx43 correlate with accelerated disease progression. Using human iPSC-derived astrocytes (hiPSC-A) from both familial and sporadic ALS, we show that Cx43 is upregulated and that Cx43-hemichannels are enriched at the astrocyte membrane. We then demonstrate that the pharmacological blockade of Cx43-hemichannels in ALS astrocytes, during a specific temporal window, provides neuroprotection of hiPSC-MN and reduces ALS astrocyte-mediated neuronal hyperexcitability. Our data identify Cx43 hemichannels as novel conduits of astrocyte-mediated disease progression and a pharmacological target for disease-modifying ALS therapies.

neuroscience↗

bioRxiv2019

Loss of function variants in PCYT1A causing spondylometaphyseal dysplasia with cone/rod dystrophy have broad consequences on lipid metabolism, chondrocyte differentiation, and lipid droplet formation.

AbstractSpondylometaphyseal dysplasia with cone-rod dystrophy (SMD-CRD) is a rare autosomal recessive disorder of the skeleton and the retina caused by biallelic variants in PCYT1A, encoding the nuclear enzyme CTP:phosphocholine cytidylyltransferase (CCT), which catalyzes the rate-limiting step in phosphatidylcholine (PC) biosynthesis by the Kennedy pathway. As a first step in understanding the consequences of PCYT1A variants on SMD-CRD pathophysiology, we generated and characterized a series of cellular models for SMD-CRD, including CRISPR-edited PCYT1A-null HEK293 and ATDC5 cell lines. Immunoblot and PC synthesis assays of cultured skin fibroblasts from SMD-CRD patient cell lines revealed patient genotype-specific reductions in CCT steady state levels (10-75% of wild-type) and choline incorporation into PC (22-54% of wild-type). While PCYT1A-null HEK293 cells exhibited fewer and larger lipid droplets in response to oleate loading than their wild-type counterparts, SMD-CRD patient fibroblasts (p.Ser323Argfs*38 homozygotes) failed to show significant differences in lipid droplet numbers or sizes as compared to controls. Lipid droplet phenotypes in PCYT1A-null HEK293 cells were rescued by transfection with wild-type, p.Ala99Val, and p.Tyr240His human PCYT1A cDNAs. While both edited cellular models had normal morphology and proliferation rates compared to unedited controls, Pcyt1a-null ATDC5 cells demonstrated accelerated rates of chondrocyte differentiation as compared to their wild-type counterparts. Lipidomics revealed changes in 75-200 lipid levels in PCYT1A-null HEK293 and ATDC5 cells or in SMD-CRD patient fibroblasts as compared to wild-type controls. The specific lipids altered and extent of change varied by cell type. Importantly, both PCYT1A-null HEK293 cells and SMD-CRD patient fibroblast cell lines had decreased phosphatidylcholine:phosphatidylethanolamine (PC:PE) ratios and decreased levels of several lysophosphatidylcholine (LPC) species as compared to wild-type controls, suggesting compensatory PC production through increased LPC remodeling by LPCAT or decreased conversion of PC to LPC by phospholipase A2. Our results show that all tested PCYT1A alleles associated with SMD-CRD are hypomorphic and suggest involvement of PCYT1A in chondrocyte differentiation, PC:PE ratio maintenance and LPC metabolism, and lipid droplet formation. Author SummaryRare genetic disorders can reveal the function of genes on an organismal scale. When normal gene activity is lost, patients can experience a range of symptoms, often dependent on the residual activity of the encoded protein. Rare variants in the gene PCYT1A can cause multiple inherited disorders, including a disorder of the skeleton and the retina characterized by short stature, bone abnormalities, and blindness. PCYT1A is required for normal cellular function, particularly lipid metabolism, but the role of this gene in human disease is still poorly understood. To determine consequences of genetic variants in patients with this disorder, we made and studied a series of cellular models, including cells cultured from patients and CRISPR-edited cell lines lacking normal copies of PCYT1A. Here we show that patient variants lead to reduced PCYT1A expression and/or function and have adverse consequences on cell biology and lipid metabolism that are often cell-type specific. This work advances understanding of the role of lipid metabolism in skeletal and eye development.

genetics↗

bioRxiv2019

Monocarboxylate transporter 1 in Schwann cells is critical for maintenance of sensory nerve myelination during aging

Schwann cell (SC)-specific monocarboxylate transporter 1 (MCT1) knockout mice were generated by mating MCT1f/f mice with myelin protein zero (P0)-Cre mice. P0-Cre+/-, MCT1f/f mice have no detectable early developmental defects, but develop hypomyelination and reduced conduction velocity in sensory, but not motor, peripheral nerves during maturation and aging. Furthermore, enlarged node length and reduced mechanical sensitivity were evident in aged P0-Cre+/-, MCT1f/f mice. MCT1 deletion in SCs impairs both their glycolytic and mitochondrial functions, leading to altered lipid metabolism of triacylglycerides, diacylglycerides, and sphingomyelin, decreased expression of myelin-associated glycoprotein (MAG), and increased expression of c-Jun and p75-neurotrophin receptor, suggesting a regression of SCs to a less mature developmental state. Taken together, our results define the essential role of SC MCT1 in both SC metabolism and peripheral nerve maturation and aging.\n\nMain PointsO_LISC MCT1 deficiency causes hypomyelination of sensory, but not motor, axons during aging\nC_LIO_LIEnlarged node length of sensory axons is evident in mutant mouse with SC-specific MCT1 deletion\nC_LIO_LISelective ablation of MCT1 within SCs impairs glycolytic and mitochondrial functions\nC_LIO_LISC-specific MCT1 deficiency impairs proteins that regulate myelin and lipid metabolism in peripheral nerves\nC_LI

neuroscience↗

bioRxiv2019

Role of human induced pluripotent stem cell-derived spinal cord astrocytes in the functional maturation of motor neurons in a multielectrode array system

The ability to generate human induced pluripotent stem cell (hiPSC)-derived neural cells displaying region-specific phenotypes is of particular interest for modeling central nervous system (CNS) biology in vitro. We describe a unique method by which spinal cord hiPSC-derived astrocytes (hiPSC-A) are cultured with spinal cord hiPSC-derived motor neurons (hiPSC-MN) in a multielectrode array (MEA) system to record electrophysiological activity over time. We show that hiPSC-A enhance hiPSC-MN electrophysiological maturation in a time-dependent fashion. The sequence of plating, density, and age in which hiPSC-As are co-cultured with MN, but not their respective hiPSC line origin, are factors that influence neuronal electrophysiology. When compared to co-culture with mouse primary spinal cord astrocytes, we observe an earlier and more robust electrophysiological maturation in the fully human cultures, suggesting that the human origin is relevant to the recapitulation of astrocyte/motor neuron cross-talk. Finally, we test pharmacological compounds on our MEA platform and observe changes in electrophysiological activity which confirm hiPSC-MN maturation. These findings are supported by immunocytochemistry and real time PCR studies in parallel cultures demonstrating human astrocyte mediated changes in the structural maturation and protein expression profiles of the neurons. Interestingly, this relationship is reciprocal and co-culture with neurons influences astrocyte maturation as well. Taken together these data indicate that in a human in vitro spinal cord culture system, astrocytes alter hiPSC-MN maturation in a time-dependent and species specific manner and suggest a closer approximation of in vivo conditions.\n\nMain PointsO_LIWe developed a method for the co-culture of human iPSC-A/MN for multielectrode array recordings.\nC_LIO_LIThe morphological, molecular, pharmacological, and electrophysiological characterization of the co-cultures suggests bidirectional maturation.\nC_LI

neuroscience↗