Biology subjects

Zimmermann, A.-S.

Publications and source records attributed to Zimmermann, A.-S..

4 recordsLinked to original sources

bioRxiv2026

A primary human muscle cell-based assay for detecting myasthenia gravis autoantibody binding and assessing AChR cluster impairment

Myasthenia gravis (MG) is an autoimmune disease caused by pathogenic autoantibodies against proteins at the neuromuscular junction (NMJ). The diagnosis and clinical management of MG patients largely relies on the detection of antigen-specific autoantibodies targeting acetylcholine receptor (AChR) or muscle-specific kinase (MuSK). Yet a subset of patients remains seronegative for known MG autoantibodies, highlighting a critical need for alternative approaches to identify pathogenic NMJ antibodies. We established a new human in vitro model of the NMJ based on primary human muscle cells that recapitulates key features of the NMJ: differentiation to myotubes, expression of key NMJ proteins and formation of postsynaptic AChR clusters in response to agrin stimulation. The model allows new insights into myogenesis and genetic muscle diseases, and the new muscle cell-based assay (CBA) detected autoantibodies in sera from patients with AChR- and MuSK-positive MG with 96.43% sensitivity and 100% specificity, while healthy control sera showed no reactivity. Incubation with patient sera significantly reduced AChR clustering compared to controls, demonstrating functional pathogenic effects. Thus, we established a physiologically relevant human NMJ model that enables detection and functional characterization of neuromuscular autoantibodies. This novel approach addresses a key limitation of current antigen-specific diagnostics and provides a method for improved detection and characterization of MG antibodies, independent of antigen specificity. One Sentence SummaryWe established a postsynaptic human in vitro neuromuscular junction model to assess binding and pathogenicity of MG autoantibodies. Key messagesO_ST_ABSWhat is already known on this topic?C_ST_ABSCurrent diagnosis of myasthenia gravis (MG) relies largely on the detection of antigen-specific autoantibodies against AChR and MuSK, leaving a clinically relevant subset of patients seronegative. What are the new findings?We established a physiologically relevant human in vitro neuromuscular junction model based on primary human muscle cells and developed a novel muscle cell-based assay (CBA) for the detection of neuromuscular autoantibodies. How might this impact on clinical practice or future developments?The CBA detected autoantibodies in patients with AChR- or MuSK-positive MG with high sensitivity and specificity and demonstrated their functional pathogenic effects on AChR clustering. This antigen-independent approach may improve the detection and functional characterization of MG autoantibodies, particularly in patients who are seronegative in current diagnostic assays. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/743478v1_ufig1.gif" ALT="Figure 1000"> View larger version (38K): org.highwire.dtl.DTLVardef@c2e1fforg.highwire.dtl.DTLVardef@8336fforg.highwire.dtl.DTLVardef@8fa2b0org.highwire.dtl.DTLVardef@1d94e_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Examining Action Potential Waveform Diversity in Neuronal Populations of Midbrain Organoid Models

Over the last decade, pre-clinical research has witnessed the advancement of human induced pluripotent stem-cell derived 3D brain organoid models and their differentiation into specific brain regions. In the realm of Parkinsons disease research, development of midbrain-specific organoids has enabled studies of this neurodegenerative disorder in patient derived 3D organoid models that attempt to recapitulate the human brain complexity. Within this line of research, neural functionality of the organoid models is established through electrophysiology. As a novel methodological approach, this study aimed to establish whether clustering of electrophysiological activity originating from midbrain organoids would aid in identifying different types of action-potential waveforms exhibited by neurons within the organoid model. Long-term extracellular electrophysiological recordings were conducted by use of a multi-electrode array device. The local field potential signal was spike-sorted, and the extracted putative neuron units were clustered into groups of spike waveform profiles. After establishing this methodological analysis pipeline, the clusters of waveform types were further analyzed in terms of electrophysiology. Results revealed that the clustering approach was successful at identifying three types of spike waveforms categories. Furthermore, it was proposed that one spike waveform profile potentially originated from dopaminergic neurons, which were one on the neural cells populating the organoid models. Overall, this study has successfully established a new methodological clustering approach to analyze electrophysiological data recoded from 3D organoid models in the context of Parkinsons disease modelling and organoid model development research.

neuroscience↗

bioRxiv2025

Vascularized midbrain assembloids show neuroinflammation and dopaminergic neuron vulnerability in Parkinsons Disease

The use of micro-physiological systems has rapidly risen in the last years due to their translatability and complex cellular composition. Human midbrain-specific organoids contain neuroectoderm-derived cell types and are suitable for brain region-specific disease modeling. However, the lack of vasculature in these systems reduces oxygenation and nutrient supply. Furthermore, neurovascular interactions cannot be studied, and disease phenotypes affecting vascular and neurovascular structures cannot be assessed. To overcome these limitations, in this work, we successfully incorporated a vascular network into midbrain organoids by fusion with vascular organoids. Midbrain-vascular assembloids are enriched in vascular cells and microglia. We observed a decrease in hypoxia and cell death in these assembloids. Furthermore, microglia and endothelial cells increased their morphological complexity. Assembloids derived from a Parkinsons disease patient carrying a LRRK2-G2019S mutation displayed a pro-inflammatory phenotype and altered electrophysiological properties. Midbrain-vascular assembloids increase the midbrain model complexity and allow for neuroinflammation studies in Parkinsons disease.

neuroscience↗

bioRxiv2025

Parkinsons disease microglia induce endogenous alpha-Synuclein pathology in patient-specific midbrain organoids.

The accumulation of misfolded -synuclein and the loss of dopaminergic neurons are hallmarks of Parkinsons disease (PD), contributing to the development of synucleinopathies. Although considerable progress has been made in understanding -synucleins role in PD pathology, the precise mechanisms involved remain unclear. Human midbrain organoids (hMOs) have emerged as valuable models for studying PD, yet the lack of microglia limits the ability to investigate neuroimmune interactions. Recent studies show that integrating microglia into hMOs enhances neuronal maturation and functionality. Here, we generated a human midbrain assembloid model by incorporating iPSC-derived microglia into midbrain organoids from healthy control individuals and a PD patient carrying the SNCA triplication (3xSNCA) mutation. Our results show that 3xSNCA microglia alone are sufficient to induce early, endogenous formation of phosphorylated -synuclein (pS129) pathology in the absence of exogenous fibril seeding. This PD-pathology emerged as early as day 50 of culture and was not observed in models lacking microglia. These findings highlight a critical role for patient-derived microglia in driving - synuclein pathology and provide a physiologically relevant platform for studying early neuroimmune mechanisms in PD and testing potential therapeutic strategies.

neuroscience↗