Biology subjects

Ducotterd, F.

Publications and source records attributed to Ducotterd, F..

4 recordsLinked to original sources

bioRxiv2025

Generation of C9orf72 repeat knock-in iPSC lines for modelling ALS and FTD

Induced pluripotent stem cell (iPSC) models are powerful tools for neurodegenerative disease modelling, as they allow mechanistic studies in a human genetic environment and they can be differentiated into a range of neuronal and non-neuronal cells. However, these models come with inherent challenges due to line-to-line and clonal variability. To combat this issue, the iPSC Neurodegenerative Disease Initiative (iNDI) has generated an iPSC repository using a single clonal reference line, KOLF2.1J, into which disease-causing mutations and revertants are introduced via gene editing. Here we describe the generation and validation of lines carrying the most common causative mutation for amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), a repeat expansion in the C9orf72 gene, for the iNDI collection of neurodegenerative iPSC models. We demonstrate that these C9orf72 knock-in lines differentiate efficiently into neurons and display characteristic C9orf72-associated pathologies, including reduced C9orf72 levels and the presence of dipeptide repeat proteins (DPRs) and RNA foci, which increase in abundance over time in culture. These pathologies are not present in revertant cells lacking the repeat expansion. These repeat expansion and revertant cell lines are now available to academic and for-profit institutions through the JAX iPS cell repository and will help to facilitate and standardise iPSC-based ALS/FTD research.

neuroscience↗

bioRxiv2024

Mutations in PSEN1 predispose inflammation in an astrocyte model of familial Alzheimer's disease through disrupted regulated intramembrane proteolysis

Mutations in PSEN1 cause familial Alzheimers disease with almost complete penetrance. Age at onset is highly variable between different PSEN1 mutations and even within families with the same mutation. Current research into late onset Alzheimers disease implicates inflammation in both disease onset and progression. PSEN1 is the catalytic subunit of {gamma}-secretase, responsible for regulated intramembrane proteolysis of numerous substrates that include cytokine receptors. For this reason, we tested the hypothesis that mutations in PSEN1 impact inflammatory responses in astrocytes, thereby contributing to disease progression. Here, using iPSC-astrocytes, we show that PSEN1 is upregulated in response to inflammatory stimuli, and this upregulation is disrupted by pathological PSEN1 mutations. Using transcriptomic analyses, we demonstrate that PSEN1 mutant astrocytes have an augmented inflammatory profile in their basal state, concomitant with an upregulation of genes coding for regulated intramembrane proteolytic and robust activation of JAK-STAT signalling. Using JAK-STAT2 as an example signalling pathway, we show altered phosphorylation cascades in PSEN1 mutant astrocytes, reinforcing the notion of altered cytokine signalling cascades. Finally, we use small molecule modulators of {gamma}-secretase to confirm a role for PSEN1/{gamma}-secretase in regulating the astrocytic response to inflammatory stimuli. Together, these data suggest that mutations in PSEN1 enhance cytokine signalling via impaired regulated intramembrane proteolysis, thereby predisposing astrocytic inflammatory profiles. These findings support a two-hit contribution of PSEN1 mutations to fAD pathogenesis, not only impacting APP and A{beta} processing but also altering the cellular response to inflammation.

neuroscience↗

bioRxiv2024

Cortical layer-specific and cell type-specific dendritic expression of Arc (Arg 3.1) in an in vitro model of slow-wave sleep

An abundance of evidence shows sleep homeostatically regulates synaptic plasticity and memory consolidation but the underlying molecular regulators of this important function of sleep have been difficult to directly elucidate. Arc is an immediate early gene that has a fundamental role in several aspects of synaptic plasticity including regulation and maintenance. Using a physiological brain slice model of slow-wave sleep, here we show that Arc protein has a characteristic spatial and cell-type specific distribution during persistent sleep-related delta oscillations in neocortical slices, which may correlate with aspects of sleep-dependent regulation of synaptic plasticity in cortical regions. In delta oscillating slices, Arc is highly expressed in layer 2/3 dendrites of the primary and secondary association cortex and this dendritic localisation is specific to intrinsically bursting cells (IB) whose cell bodies are in layer 5. Moreover, Arc immunopositive dendrites are clustered together arranged in a quasi hexagonal arrangement with a spacing of [~] 50 {micro}m between clusters. The cytoarchitectural distribution of Arc across the association cortex has implications for the mechanisms of sleep and for the synaptic homeostasis hypothesis regarding the function of sleep.

neuroscience↗

bioRxiv2023

The hypermorphic PLCγ2 S707Y variant dysregulates microglial cell function: insight into PLCγ2 activation in brain health and disease, and opportunities for therapeutic modulation.

Phospholipase C-gamma 2 (PLC{gamma}2) is highly expressed in hematopoietic and immune cells, where it is a key signalling node enabling diverse cellular functions. Within the periphery, gain-of-function (GOF) PLC{gamma}2 variants, such as the strongly hypermorphic S707Y, cause severe immune dysregulation. The milder hypermorphic mutation PLC{gamma}2 P522R increases longevity and confers protection in central nervous system (CNS) neurodegenerative disorders, implicating PLC{gamma}2 as a novel therapeutic target for treating these CNS indications. Currently, nothing is known about what consequences strong PLC{gamma}2 GOF has on CNS functionality, and more precisely on the specific biological functions of microglia. Using the PLC{gamma}2 S707Y variant as a model of chronic activation we investigated the functional consequences of strong PLC{gamma}2 GOF on human microglia. PLC{gamma}2 S707Y expressing human inducible pluripotent stem cells (hiPSC)-derived microglia exhibited hypermorphic enzymatic activity under both basal and stimulated conditions, compared to PLC{gamma}2 wild type. Despite the increase in PLC{gamma}2 enzymatic activity, the PLC{gamma}2 S707Y hiPSC-derived microglia display diminished functionality for key microglial processes including phagocytosis and cytokine secretion upon inflammatory challenge. RNA sequencing revealed a downregulation of genes related to innate immunity and response, providing molecular support for the phenotype observed. Our data suggests that chronic activation of PLC{gamma}2 elicits a detrimental phenotype that is contributing to unfavourable CNS functions, and informs on the therapeutic window for targeting PLC{gamma}2 in the CNS. Drug candidates targeting PLC{gamma}2 will need to precisely mimic the effects of the PLC{gamma}2 P522R variant on microglial function, but not those of the PLC{gamma}2 S707Y variant. HighlightsO_LIThe impact of strongly hypermorphic variants of PLC{gamma}2 have not been studied in brain and yet PLC{gamma}2 is implicated in modifying risk of CNS disorders including Alzheimers disease C_LIO_LITo address this, we explored the role of the strongly hypermorphic PLC{gamma}2 S707Y variant in hiPSC-derived microglia C_LIO_LIS707Y increases PLC{gamma}2 enzymatic activity and intracellular calcium flux C_LIO_LIPhagocytosis and cytokine production are diminished in PLC{gamma}2 S707Y microglia C_LIO_LIPLC{gamma}2 S707Y downregulates expression of genes related to innate immunity and response C_LIO_LIModulation of PLC{gamma}2 for therapy must recapitulate the positive effects of moderate hypermorphic variants on microglial functions whilst avoiding detrimental effects of strongly hypermorphic variants like PLC{gamma}2 S707Y C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=188 SRC="FIGDIR/small/564579v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@9f0903org.highwire.dtl.DTLVardef@108d26forg.highwire.dtl.DTLVardef@2fb691org.highwire.dtl.DTLVardef@7af80c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗