Biology subjects

Lieberam, I.

Publications and source records attributed to Lieberam, I..

4 recordsLinked to original sources

bioRxiv2025

Increased HCN1 activity in human excitatory neurons drives excessive network bursting in Dravet syndrome

Dravet syndrome (DS) is a severe childhood epilepsy caused by mutations of the sodium channel NaV1.1. These mutations are thought to compromise the ability of inhibitory interneurons to regulate network activity, leading to seizure events. However, standard treatments to restore inhibition have limited efficacy, suggesting the existence of additional pathological mechanisms. Here, we use hiPSC-derived neuronal networks containing both excitatory and inhibitory neurons to show that excessive bursting activity in DS cultures is driven by excitatory neurons. This rise in bursting frequency is caused by the increased expression of HCN1 "pacemaker" channels in excitatory neurons, and bursting activity can be normalised using a channel blocker. With this work, we propose a new pathophysiological mechanism in DS and identify HCN1 as a novel therapeutic target.

neuroscience↗

bioRxiv2025

ALS mutations do not alter perineuronal net formation in human stem cell-derived motor neurons

Perineuronal nets (PNNs) are extracellular matrix structures that stabilise synaptic inputs and regulate neuronal plasticity. Although PNN dysregulation is observed in several neurological disorders, their relevance to amyotrophic lateral sclerosis (ALS) remains unclear. In particular, the extent to which PNN alterations in ALS are motor neuron (MN)-intrinsic is unknown. We investigated whether human pluripotent stem cell-derived MNs form PNN-like structures in vitro, and whether ALS-associated mutations alter this process. We show that MNs generate PNN-like structures containing hyaluronan, tenascin-R, and aggrecan and that their formation and gene expression were not altered by ALS mutations. To explore whether PNN dysregulation reflects contributions from other cell types or selective MN vulnerability, we conducted meta-analyses of transcriptomic datasets from pluripotent stem cell-derived astrocytes carrying ALS-associated mutations, as well as datasets comparing MN populations with differential susceptibility to ALS. These analyses revealed no consistent differences in PNN-related gene expression in human stem cell-derived MN. In contrast, transcriptomic analyses of human post-mortem ALS tissues revealed significant dysregulation of PNN-related genes, including core PNN components and linker proteins. These findings suggest that PNN changes in ALS are not MN-intrinsic, but may result from interactions with other cell types in the central nervous system such as glia.

neuroscience↗

bioRxiv2022

Pathogenic TDP-43 Disrupts Axon Initial Segment Structure and Neuronal Excitability in a Human iPSC Model of ALS

Dysregulated neuronal excitability is a hallmark of amyotrophic lateral sclerosis (ALS). We sought to investigate how functional changes to the axon initial segment (AIS), the site of action potential generation, could impact neuronal excitability in a human iPSC model of ALS. We found that early (6-week) ALS-related TDP-43G298S motor neurons showed an increase in the length of the AIS, relative to CRISPR-corrected controls. This was linked to neuronal hyperexcitability and increased spontaneous contractions of hiPSC-myofibers in compartmentalised neuromuscular co-cultures. In contrast late (10-week) TDP-43G298S motor neurons showed reduced AIS length and hypoexcitability. At a molecular level aberrant expression of the AIS master scaffolding protein Ankyrin-G, and the AIS-specific voltage-gated ion channels SCN1A (Nav1.1) and SCN8A (Nav1.6) mirrored these dynamic changes in excitability. Finally, at all stages, TDP-43G298S motor neurons showed compromised activity-dependent plasticity of the AIS, further contributing to abnormal excitability. Our results point toward the AIS as an important subcellular target driving changes to neuronal excitability in ALS.

neuroscience↗

bioRxiv2021

Prospective isolation of mouse and human hematopoietic stem cells using Plexin domain containing 2

Numerous strategies exist to isolate hematopoietic stem cells (HSCs) using complex combinations of markers and flow cytometry. However, robust identification of HSCs using imaging techniques is substantially more challenging which has prompted the recent development of HSC reporter mice. To date, none of the molecules used in these reporters have been useful for human HSC identification. Here we report that PLXDC2 is a useful marker for both mouse and human HSCs. Using a green fluorescent protein (GFP) knock-in at the Plxdc2 locus in mice (hereafter denoted as Plxdc2-GFP), we showed that Plxdc2-GFP is highly expressed in HSCs with 1 in 2.8 Plxdc2-GFP+CD150+ cells giving long-term multi-lineage reconstitution in transplantation. Moreover, we developed a novel human PLXDC2 antibody and showed that human PLXDC2+ HSCs have stronger long-term multilineage reconstitution ability compared with PLXDC2- HSCs in a xenograft model. Thus, our study identifies PLXDC2 as a highly relevant molecule in HSC identification, potentially allowing greater purity and live in vivo tracking of these cells. SummaryTo date, few molecules are available for isolation of HSCs across species. The present study shows that PLXDC2 is a highly useful molecule for isolation of HSCs, which works across mouse and human.

cell biology↗