Biology subjects

Najdek, C.

Publications and source records attributed to Najdek, C..

3 recordsLinked to original sources

bioRxiv2026

The Alzheimer's disease-associated rs28834970 variant in PTK2B impairs electrical activity and regulates Tau phosphorylation and APP processing in human neuronal cultures

Background: Genome-wide association studies have identified the PTK2B gene, which encodes Proline-rich tyrosine kinase 2 (PYK2), as a genetic risk factor for Alzheimer's disease (AD). However, its role in AD aetiology remains to be understood, as a complex contribution to amyloid {beta} (A{beta}) toxicity, tauopathy and neuronal dysfunction is suggested by contradictory evidence. Determining how the causal variant among AD-associated PTK2B variants impairs PYK2 function to trigger AD hallmarks could bring clarification. Methods: We combined in silico prediction tools with luciferase reporter assays in neuroblastoma cells to prioritize potential AD-associated PTK2B functional variants. We generated isogenic KOLF2.1J induced pluripotent stem cells (iPSCs) carrying the most relevant functional variant using CRISPR-Cas9 and differentiated them into human neuronal cultures (hNCs). We assessed PYK2 expression via immunoblotting, performed transcriptomic profiling using RNA-sequencing, analyzed neuronal network activity via multielectrode array (MEA) recordings, quantified synaptic density through immunocytochemistry in microfluidic devices, and assessed Tau phosphorylation and amyloid-precursor protein (APP) metabolism. Results: The rs28834970 regulatory variant was identified as the most functionally relevant in our model, with the C risk allele promoting transcription factor C/EBP{beta} binding within a cis-regulatory element. In hNCs, the homozygous rs28834970 CC genotype reduced total PYK2 levels by more than 80%, while increasing the proportion of phosphorylated (activated) PYK2. Transcriptomic analysis revealed 724 downregulated and 113 upregulated gene sets, with altered expression of genes involved in extracellular matrix organization, cytoplasmic translation and neurotransmitter secretion. MEA recordings showed reduced network recruitment and altered burst organization. Immunocytochemistry in microfluidic devices consistently revealed that rs28834970 impacts dendritic development and postsynaptic maturation. The risk genotype significantly elevated Tau phosphorylation at pathological sites (Thr181, Thr217, Thr231, Ser202-Thr205, Ser396-Ser404), and enhanced APP processing, resulting in decreased levels of APP and CTF but increased levels of sAPP, sAPP{beta} and A{beta}. Conclusion: The rs28834970 C risk allele mechanistically links AD susceptibility to downregulation of PTK2B/PYK2 expression and to the increase in Tau pathology and A{beta} levels while compromising synaptic structure and function.

genetics↗

bioRxiv2025

BIN1 expression in the presynaptic compartment leads to isoform-specific synaptotoxicity

Alzheimers disease (AD) is characterized by a strong genetic predisposition and by an early loss of synaptic connectivity that strongly correlates with cognitive deficit. Some genetic determinants could contribute to synapse frailty toward AD pathology. However, the role of genetic determinants in AD pathogenesis remains poorly understood at the synaptic level. Here, we show that the expression of an isoform of the major AD susceptibility gene BIN1 in the presynaptic compartment results in synaptic loss. Using electrophysiology, we observed an early loss of synaptic transmission upon BIN1 isoform 1 (BIN1iso1) expression in Drosophila retinal photoreceptor neurons. This was not observed for the other human BIN1 isoforms tested, isoform 8 and isoform 9. Structural analysis of photoreceptor neuron synapses shows a strong accumulation of abnormally large vesicles in the presynaptic compartment, reminiscent of this same isoform-induced endosome defects in cell bodies. In addition, the expression of BIN1iso1 in motoneurons of the Drosophila neuromuscular junction alters the morphology of synaptic boutons, with a greater number and a smaller size of synaptic boutons, and the appearance of satellite boutons. As opposed to endosomal defects in cell body, modulating the Rab11 recycling endosome regulator did not prevent BIN1iso1 synaptotoxicity. To test if synaptic deficits are conserved in a mammalian model and to assert a presynaptic vs postsynaptic role for BIN1, we used rat primary neurons cultured in microfluidic devices that restrict gene expression modulation in particular neuron populations. We found a loss of synaptic connectivity only when expressing BIN1iso1 in the presynaptic compartment, which was confirmed by microelectrode array analysis. Together, our results suggest that BIN1 expression in the presynaptic terminal, but not the postsynaptic terminal leads to an isoform-specific, deleterious effect on synaptic integrity. BIN1 synaptotoxicity could contribute to the synapse loss observed early in AD. This supports the idea that genetic determinants could make synapses prone to failure in AD.

neuroscience↗

bioRxiv2024

Neuronal downregulation of PLCG2 impairs synaptic function and elicits Alzheimer disease hallmarks

We developed a high content screening to investigate how Alzheimer disease (AD) genetic risk factors may affect synaptic mechanisms in rat primary neuronal cultures. Out of the target genes identified, we found that Plcg2 downregulation in mouse dentate gyrus neurons consistently disrupted dendritic morphology and synaptic function. In human neuronal cultures (hNCs), PLCG2 downregulation also impaired synaptic function and increased A{beta} levels and Tau phosphorylation. Very rare PLCG2 loss-of-function (LoF) variants were associated with a 10-fold increased AD risk. PLCG2 LoF carriers exhibit low mRNA/protein PLCG2/PLC{gamma}2 levels and the R953* LoF mutation compromised synaptic function and increased AD hallmarks in hNCs. Single nuclei RNAseq analyses confirmed that the downregulation of PLCG2 impacted pathways related to synaptic and neuronal functions, potentially through neurexin in neurons. In conclusion, PLC{gamma}2 downregulation could increase AD risk by impairing synaptic functions and increasing the A{beta} levels and Tau phosphorylation in neurons.

neuroscience↗