Biology subjects

Peitz, M.

Publications and source records attributed to Peitz, M..

8 recordsLinked to original sources

bioRxiv2026

Glia-enriched human brain organoids for studying developmental alterations in leukodystrophies

Leukodystrophies (LKD) comprise mostly inherited white matter disorders whose developmental origins and underlying pathomechanisms remain poorly understood. Progress has been limited by restricted access to human primary tissue and by the inability of animal models to fully recapitulate human neurodevelopment. Human induced pluripotent stem cell-derived neural organoids provide an alternative approach, but most culture systems do not capture later, glia-rich developmental stages relevant to these diseases. Recent studies have shown that appropriate patterning cues and long in vitro differentiation can generate neuroglial spheroids comprising multiple neuronal and macroglial populations, including mature oligodendrocytes. Here, we adapt the human oligodendrocyte (hOLS) spheroid platform to establish 3D models of globoid cell leukodystrophy (GLD), 4H leukodystrophy (4H), and Canavan disease (CD). Here we adapt this organoid platform to establish 3D models of globoid cell leukodystrophy (GLD), 4H leukodystrophy (4H), and Canavan disease (CD). Across 150 days of differentiation, hOLS from different genetic backgrounds displayed largely comparable growth kinetics and developmental trajectories, comprising multiple neuroglial cell types with predominantly ventral forebrain and midbrain identities. Comparison of LKD and control hOLS revealed both shared and disease-specific alterations, with prominent transcriptional changes in lysosomal, metabolic, and stress-response pathways. Lineage-resolved pathway analysis further identified signatures across individual LKDs, including mitochondrial and translational stress in GLD glial lineages, disruption of RNA metabolic and cell-cycle pathways in 4H, and prominent astrocyte-centered metabolic dysregulation in CD. Our results establish hOLS as a human 3D in vitro platform for studying the impact of LKD-associated genetic variants on early neural development and for dissecting lineage-specific disease vulnerability.

neuroscience↗

bioRxiv2026

Presynaptic mechanism of epileptiform activities in forward-programmed human excitatory neuronal networks

Epilepsy is one of the most common neurological disorders, yet the mechanisms controlling seizure termination remain poorly understood. In particular, why rhythmic spike-wave discharges decelerate before stopping is unexplained. Here, using human iPSC-derived excitatory neurons differentiated via targeted forward-programming, we report a similar deceleration phenomenon in cultured neuronal networks. These networks exhibit glutamate-dependent, epileptiform 'super-bursts' with a slowing rhythm from ~4 Hz to ~2 Hz. Combining in silico simulations and in vitro experiments, we correlate this activity pattern with the hierarchical organization of presynaptic vesicle pools. Nested bursts link to the recycling pool (RP), and sub-bursts associate with the readily releasable pool (RRP). Decelerating RP-to-RRP vesicle translocation shortened the super-bursts, indicating that epileptiform dynamics depend heavily on this translocation process. These findings depict human neuronal networks derived from forward-programmed cells as a model for epileptology, revealing a presynaptic framework for rhythmic discharges in excitatory networks.

neuroscience↗

bioRxiv2025

Protracted fate acquisition and epigenetic de-aging during induced neural stem cell conversion of human blood cells

Transcription factor-based direct conversion of somatic cells represents an interesting avenue for generating induced neural stem cells (iNSCs) from peripheral blood without transit through a pluripotent stage. While this paradigm has been shown to be associated with epigenetic de-aging, the dynamics of this process have remained unclear. Here, we used overexpression of the two reprogramming factors SOX2 and cMYC to generate iNSC from erythroid progenitors of donors ranging from neonatal to 101 years of age. Using an epigenetic clock algorithm, we corroborated our previous finding that iNSCs generated from aged donors show pronounced epigenetic de-aging, preserving around 13 % and 5 % of the original donor age at low and high passages, respectively. Studying the dynamic of epigenetic de-aging during iNSC conversion across time, we found that this process is largely protracted, continuing for several weeks and even beyond forced neuronal differentiation of iNSCs. Transcriptomic differences between young and old donor-derived iNSCs dissipate with extended time in conversion, too. Concordant with this observation, established iNSC lines lack age-associated cellular hallmarks, similar to induced pluripotent stem cells and their derivatives. Interestingly, time course analysis of DNA methylation and RNA sequencing data revealed that acquisition of a bona fide NSC signature extends greatly beyond the time point when proliferative PAX6-positive iNSCs emerge. The unexpected slow dynamics of these processes makes iNSC conversion an attractive model for dissecting the mechanisms underlying somatic transdifferentiation and de-aging. Statement of Ethical ApprovalsThe collection of human somatic material (i.e., blood) from healthy donors for iPSC reprogramming and iNSC conversion was conducted in accordance with German law and approved by the Ethics Committee of the University of Bonn Medical Center (approval number: 275/08). All subjects gave written informed consent.

neuroscience↗

bioRxiv2025

Mapping human microglial morphological diversity via handcrafted and deep learning-derived image features

Microglia play critical roles in brain health and disease by adopting a spectrum of dynamic activation states. However, capturing this continuous heterogeneity in a scalable way remains a major challenge. To address this, we developed an imaging and data analysis framework to map the activation landscape of human iPSC-derived microglia (iMG) at single-cell resolution. We combined high-content imaging using two complementary strategies: a hypothesis-driven immunofluorescence (IF) panel targeting key activation markers (NF-{kappa}B, ASC, CD45) and a discovery-oriented, pan-morphological Cell Painting (CP) assay. Diverse phenotypes were captured through handcrafted and representation learning-based features. To classify cells, we applied Gaussian Mixture Models (GMMs) to image-derived features, enabling soft probabilistic assignments that capture transitional states between phenotypes. Compared to graph-based methods like the Leiden algorithm, GMMs provided comparable classification performance while offering a more nuanced and biologically interpretable view of microglial heterogeneity. We demonstrate that deep learning features from the targeted IF panel are most powerful, achieving high classification accuracy and strong correlation with biological states such as functional NLRP3 inflammasome activation. Our model system provides a robust and scalable platform for quantifying microglial heterogeneity, offering a new tool to identify novel disease-associated states and compounds that precisely modulate microglial phenotypes for therapeutic discovery.

neuroscience↗

bioRxiv2024

Protective variant in PLCgamma2 mitigates Alzheimer's disease associated pathology via enhancing beneficial microglia functions

BackgroundPLC{gamma}2-P522R (phospholipase C gamma 2, proline 522 to arginine) is a protective variant that reduces the risk for late onset Alzheimers disease. Recently, it was shown to decrease {beta}-amyloid pathology in 5XFAD mouse model of AD. In this study, our goal was to investigate the protective functions of PLC{gamma}2-P522R variant in a less aggressive mouse model of AD as well as to assess the underlying mechanisms at the molecular and cellular level using mouse and human microglia models. MethodsThe effects of the protective PLC{gamma}2-P522R variant on microglia activation, AD-related {beta}-amyloid and neuronal pathologies, as well as behavioral changes were investigated in PLC{gamma}2-P522R knock-in mice crossbred with APP/PS1 AD model mice. Transcriptomic, proteomic, and functional studies were carried out in cultured and acutely isolated adult PLC{gamma}2-P522R mouse microglia to study molecular mechanisms. Finally, microglia-like cell models generated from blood and skin biopsy samples of the PLC{gamma}2-P522R variant carriers were employed to translate the key findings to human cells. ResultsOur results demonstrate that the PLC{gamma}2-P522R variant reduced brain {beta}-amyloid plaque burden of APP/PS1 mice. Simultaneously, PLC{gamma}2-P522R variant increased non-proinflammatory microglia activation and microglia clustering around {beta}-amyloid plaques, leading to reduced {beta}-amyloid plaque-associated neuronal dystrophy. In cultured mouse primary microglia, PLC{gamma}2-P522R variant decreased accumulation of large lipid droplets, reduced cell stress, and increased acute response to strong inflammatory stimuli. Transcriptomic and proteomic analyses in acutely isolated adult mouse microglia as well as in human monocyte-derived microglial cells showed that PLC{gamma}2-P522R upregulates mitochondrial fatty acid oxidation and downregulates inflammatory/interferon signaling pathways. Accordingly, PLC{gamma}2-P522R increased mitochondrial respiration in iPSC-derived microglial cells. ConclusionsTogether, these findings suggest that PLC{gamma}2-P522R variant exerts protection against AD-associated {beta}-amyloid and neuronal pathologies via enhancing microglial barrier formation around {beta}-amyloid plaques and suppressing pro-inflammatory activation. Observed changes in fatty acid metabolism and mitochondrial flexibility as well as the downregulation of genes involved in inflammatory signaling pathways suggest that these protective effects of the PLC{gamma}2-P522R variant are mediated through an anti-ageing mechanism.

neuroscience↗

bioRxiv2022

Machine learning-aided multidimensional phenotyping of Parkinson's disease patient stem cell-derived midbrain dopaminergic neurons

Combining multiple Parkinsons disease (PD) relevant cellular phenotypes might increase the accuracy of midbrain dopaminergic (mDA) in vitro models. We differentiated patient-derived induced pluripotent stem cells (iPSCs) with a LRRK2 G2019S mutation, isogenic control and genetically unrelated iPSCs into mDA neurons. Using automated fluorescence microscopy in 384-well plate format, we identified elevated levels of -synuclein and Serine 129 phosphorylation (pS129), reduced dendritic complexity, and mitochondrial dysfunction. Next, we measured additional image-based phenotypes and used machine learning (ML) to accurately classify mDA neurons according to their genotype. Additionally, we show that chemical compound treatments, targeting LRRK2 kinase activity or -synuclein levels, are detectable when using ML classification based on multiple image-based phenotypes. We validated our approach using a second isogenic patient derived SNCA gene triplication mDA neuronal model. This phenotyping and classification strategy improves the exploitability of mDA neurons for disease modelling and the identification of novel PD drug targets.

neuroscience↗

bioRxiv2021

GDAP1 loss of function inhibits the mitochondrial pyruvate dehydrogenase complex by altering the actin cytoskeleton

Charcot-Marie-Tooth (CMT) disease 4A is an autosomal-recessive polyneuropathy caused by mutations of ganglioside-induced differentiation-associated protein 1 (GDAP1), a putative glutathione transferase, which affects mitochondrial shape and alters cellular Ca2+ homeostasis. Here, we identify the underlying mechanism. We found that patient-derived motoneurons and GDAP1 knockdown SH-SY5Y cells display two phenotypes: more tubular mitochondria and a metabolism characterized by glutamine dependence and fewer cytosolic lipid droplets. GDAP1 interacts with the actin-depolymerizing protein Cofilin-1 in a redoxdependent manner, suggesting a role for actin signaling. Consistently, GDAP1 loss causes less F-actin close to mitochondria, which restricts mitochondrial localization of the fission factor dynamin-related protein 1, instigating tubularity. Changes in the actin cytoskeleton also disrupt mitochondria-ER contact sites. This results in lower mitochondrial Ca2+ levels and inhibition of the pyruvate dehydrogenase complex, explaining the metabolic changes upon GDAP1 loss of function. Together, these findings reconcile GDAP1-associated phenotypes and implicate disrupted actin signaling in CMT4A pathophysiology.

neuroscience↗

bioRxiv2020

Comparative profiling of N-respirasomes predicts aberrant mitochondrial bioenergetics at single-cell resolution

AO_SCPLOWBSTRACTC_SCPLOWMitochondria sustain the energy demand of the cell. The composition and functional state of the mitochondrial oxidative phosphorylation system are informative indicators of organelle homeostasis and bioenergetic capacity. Here we describe a highly sensitive and reproducible method for single-cell visualization and quantification of mitochondrial respiratory supercomplexes as a novel means of measuring mitochondrial respiratory chain integrity. We apply a proximity ligation assay (PLA) and perform comparative studies of mitochondrial CI, CIII and CIV-containing supercomplexes (or N-respirasomes) in fixed human and mouse brain tissues, tumorigenic cells, iPSCs and iPSC-derived NPCs and neurons. Our optimized approach enables a quantitative in-situ assessment of even subtle mitochondrial lesions associated with aberrant respiration. By combining quantitative proteomics with single cell imaging analysis, we also report the mechanistic contribution of the MICOS complex subunit CHCHD3 in regulating N-respirasomes. Overall, our PLA-based profiling of N-respirasomes establishes a sensitive and complementary technique for detecting cell-type specific mitochondrial perturbations in fixed materials.

cell biology↗