Biology subjects

Freude, K.

Publications and source records attributed to Freude, K..

4 recordsLinked to original sources

bioRxiv2026

Patient-Derived Air-Liquid Interface Forebrain Organoids Reveal Functional Synaptic Deficits in Schizophrenia

Schizophrenia (SCZ) is a severe and debilitating neurodevelopmental disorder with lifelong impact on everyday life. Disruptions in synapse functions play a key role in its complex and poorly understood etiological and pathological mechanisms. Here, we investigated both the molecular composition and the spontaneous and stimulated functional properties of synapses in neural organoids from SCZ individuals. Air-liquid interface forebrain organoids (ALI-FOs) were generated from induced pluripotent stem cells (iPSCs) derived from three individuals with SCZ and three healthy controls. At day 170 synaptosomes were enriched and analyzed by data-independent acquisition mass spectrometry to profile the proteome, alongside with TMT-labeled phosphoproteomics both before and after acute KCl-induced depolarization. In parallel, we characterized the PTMome of the surrounding cellular environment, comprising phosphorylation, peptides with free and reversibly modified cysteines, and sialylated N-linked glycopeptides. Functional glutamatergic and GABAergic activity was assessed using calcium imaging to capture spontaneous neuronal signaling. Both conditions exhibited mature synaptic structures, while growth cones were observed only in SCZ-derived ALI-FOs, indicative of ongoing or delayed synaptogenesis. Proteomic analysis of synaptosome preparations revealed 358 differentially regulated proteins between SCZ and controls and 125 phophoproteins with altered phosphorylation, which clustered into three major categories: (1) synaptogenesis and synapse signaling; (2) cytoskeleton and cell junctions; (3) growth cone dynamics and neurite outgrowth. Analysis of the PTMs in the surrounding cellular environment revealed regulation of key regulatory mechanisms in 526 proteins, supporting the synaptic alterations observed. Notably, components of the Wnt signaling pathway were consistently dysregulated across both the synaptosome preparation and the PTMome in SCZ-derived ALIFOs as compared to controls. Depolarization-induced phospho-signaling revealed SCZ-specific response enriched in synaptic vesicle trafficking pathways. Together, these findings provide new insights into early synaptic alterations in SCZ, highlighting changes not only in protein composition, but more in protein regulatory mechanisms underlying synaptic signaling.

neuroscience↗

bioRxiv2025

A multidisciplinary approach for the study of age-dependent expression patterns in porcine experimental wounds

Determining the age of wounds in both human and veterinary subjects is a critical aspect of forensic pathology. Gross and histopathological evaluations are used for age estimations, however, these evaluations are subjective as they rely on the opinion and experience of the examining pathologist. Therefore, the aim of the study was to create a multidisciplinary approach to discover accurate and objective indicators of wound age in veterinary forensic cases. In the present study we utilized a porcine experimental wound healing model. Granulation tissue from wounds at different ages (5, 10, 15, 20, 25, 30, and 35 days) (n=188) and control skin samples (n=47) from 47 experimental pigs were evaluated macroscopically, histologically, immunohistochemically, combined with digital pathology, and flow cytometry. Granulation tissue thickness peaked on day 10 post wounding. Full epithelialization was observed at the earliest on day 20 and the percentage of wound surface covered by epithelium increased with age. Leukocytes including hemosiderophages, neutrophils and accumulation of macrophages all displayed time-dependent infiltration into the wound bed. CD34 showed no time-dependent expression. CD105 expression peaked on day 15. CD45 showed a time-dependent expression pattern in the superficial part of the granulation tissue, with highest expression on day 5 and a decrease with increasing wound age. The findings of this multidisciplinary approach indicate the potential to achieve accurate and objective wound age estimations in veterinary and human forensic investigations.

cell biology↗

bioRxiv2025

Isolation and characterization of synaptic structures from human neural organoids

Human neural organoids (NOs) provide a powerful platform for investigating synaptic development and dysfunction during early neurodevelopment. However, methodologies for isolating functional synaptic structures from these models remain limited. Here, we present a differential centrifugation protocol enabling the enrichment of growth cone particles (GCPs) and immature synaptosomes from air-liquid interface cerebral organoids (ALI-COs) at distinct developmental stages (day 90 and 150). Notably, the method avoids density gradients, requires minimal starting material while maintaining reproducibility across human and murine tissues. Quantitative proteomic profiling revealed significant enrichment of growth cone markers (e.g. GAP43) and classical synaptosomal proteins (e.g. PCLO, BSN, SYN1). Transmission electron microscopy (TEM) confirmed the presence of membrane-enclosed GCPs with fibrous content and mitochondria in day 90 isolates, and immature synaptosomes containing synaptic vesicles on day 150. Functional viability of both types of synaptic structures was demonstrated through KCl-induced depolarization, which triggered phosphorylation changes in growth cone proteins (GAP43, MARCKS, MARCKSL1), cytoskeletal regulators (DCLK1, SHTN1, MARK4, MAP1B) and protein kinases (CAMK2G, PRKCE) in day 90 GCPs, as well as classical synaptic vesicle cycle proteins (SYN1, DNM1, RPH3A) at day 150. Overall, this study establishes a centrifugation-based protocol for isolating growth cones and immature synapses from human organoids, capturing key stages of synaptic development and enabling scalable, patient-compatible models to study synaptic function and dysfunction in neurodevelopmental and neurodegenerative disorders.

neuroscience↗

bioRxiv2022

Golgi Fragmentation - One of the Earliest Organelle Phenotypes in Alzheimer's Disease Neurons

Alzheimers disease (AD) is the most common cause of dementia, with no current cure. Consequently, alternative approaches focusing on early pathological events in specific neuronal populations, besides targeting the well-studied Amyloid beta (A{beta}) accumulations and Tau tangles, are needed. In this study, we have investigated disease phenotypes specific to glutamatergic forebrain neurons and mapped the timeline of their occurrence, by implementing familial and sporadic human induced pluripotent stem cell models as well as the 5xFAD mouse model. We recapitulated characteristic late AD disease phenotypes, such as increased A{beta} secretion and Tau hyperphosphorylation, as well as previously well documented mitochondrial and synaptic deficits. Intriguingly, we identified Golgi fragmentation as one of the earliest AD phenotypes, indicating potential impairments in protein processing and post-translational modifications. Computational analysis of RNA sequencing data revealed differentially expressed genes involved in glycosylation and glycan patterns, whilst total glycan profiling revealed minor glycosylation differences. This indicates general robustness of glycosylation besides the observed fragmented morphology. Importantly, we identified that genetic variants in Sortilin-related receptor 1 (SORL1) associated with AD could aggravate the Golgi fragmentation and subsequent glycosylation changes. In summary, we identified Golgi fragmentation as one of the earliest disease phenotypes in AD neurons in various in vivo and in vitro complementary disease models, which can be exacerbated via additional risk variants in SORL1. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/519571v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@98a8eeorg.highwire.dtl.DTLVardef@7aa7b7org.highwire.dtl.DTLVardef@991e33org.highwire.dtl.DTLVardef@8dabb4_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗