Posters

Introduction: In this work, we combine in-vivo ultra-high resolution 7T quantitative MRI (qMRI) metrics with molecular information from ex-vivo spatially resolved transcriptomics (SRT) data across cortical depths.

Methods: qMRI metrics were extracted from dorsolateral prefrontal cortical (DLPFC) layers in Parkinson’s disease (PD) and controls in-vivo. Glial cell-type counts, and myelin, iron, mineral, and lipid gene ontology (GO) pathway scores were quantified across DLPFC layers from post-mortem SRT data. Significant associations between qMRI and SRT values were examined. Leave-one-out cross validation (LOO-CV) was completed. qMRI metric differences between PD and controls were assessed. PD SRT score projections were generated. Gene set enrichment analysis was run on bulk RNAseq data. Glucosylceramide (GlcCer) was quantified.

Results: There were multiple significant associations between qMRI metrics and SRT-derived cell counts and GO pathways. LOO-CV was able to reliably predict SRT-derived scores from qMRI data. PD had lower MTsat and R1 versus controls in SpD1 of the DLPFC. PD-projected GO pathway scores were significantly lower for “regulation of oligodendrocyte differentiation”, and “glycolipid binding”. Bulk RNA-sequencing dataset showed oligodendrocyte maturation genes were significantly downregulated in PD versus controls. Lipidomic analysis revealed decreases in glycolipid precursor (GlcCer) concentration in PD superficial cortex.

Conclusions: We infer molecular features of neurodegenerative disease in-vivo using qMRI. In PD, we found decreases in myelin- and lipid-sensitive qMRI metrics, and a projected decrease in oligodendrocyte differentiation and glycolipid binding pathway scores, and found corresponding changes in independent post-mortem cohorts. This approach has potential to transform our understanding of neurodegenerative disease in living individuals.

Alzheimer's disease (AD) is a neurodegenerative condition distinguished by a deterioration in cognitive function and the loss of memory. The aggregation of amyloid-beta (Aβ) protein is a central pathological feature of this disease. Also, there is increasing recognition of the role of circadian disruptions in AD pathogenesis. The current knowledge about AD focuses on the independent impacts of circadian disturbances and Aβ pathology. However, the simultaneous effects of these elements have not been adequately investigated. Hence, this study examined the synergistic effects of specific Aβ isoforms (Aβ40, Aβ42, and Aβ42arc) and circadian disruption (cyc01 mutation) on Drosophila locomotor behaviour and lifespan. Locomotor activity in both female and male flies was evaluated using climbing assays at four key stages of their life cycle. The data were statistically analysed with repeated measures ANOVA in SPSS. Lifespan was monitored over time using Kaplan-Meier survival plots and log-rank tests in SPSS. Findings demonstrated exacerbated climbing deficits in Aβ-expressing flies with the cyc01 mutation compared to controls at later ages of life. The Aβ42 isoform significantly impaired locomotor function in both males and females. Survival assays showed the cyc01 mutation alone significantly shortened the lifespan, while the combined impacts with Aβ isoforms were varied. Especially, the Aβ42 isoform slightly mitigated the cyc01-induced lifespan reduction, unlike Aβ40 and Aβ42arc. These results indicate a complex relationship between Aβ and circadian disruption fromthe cyc01 mutation in modulating AD-related traits, highlighting the need for further research into mechanisms and potential therapies.

Background: The choroid plexus (CP) is involved in cerebrospinal fluid (CSF) production and forms part of the blood-CSF barrier, located in the ventricles of the brain. While CP enlargement is linked to aging, traumatic brain injury (TBI) and blast effects remains understudied in high-risk military cohorts. Given the sensitivity of tissue boundaries to blast exposure, we hypothesised that CP structure would particularly be vulnerable to these injuries.

Methods: We analysed a subset of 535 male UK servicemen from the ADVANCE Study (age M=39.7, SD=5.4). TBI exposure was classified using Mayo criteria (symptomatic (symTBI), mild (mTBI), and moderate-severe (msTBI)). CP volume, mean diffusivity (MD), and lateral ventricle (LV) volume were derived from MRI scans. We investigated associations between CP measures, LV volume, TBI, blast exposure, and age.

Results: Of the 380 participants reporting lifetime TBI (19.6% symTBI, 39.6% mTBI, 11.8% msTBI), 156 were blast-related. TBI exhibited associations with larger CP volume (p=0.028), increasing with injury severity (mTBI: p=0.042; msTBI: p=0.039), though findings did not survive correction. Blast exposure groups did not differ in CP structure. CP volume increased with age (pFDR<0.001), but TBI exposure did not moderate this relationship. CP volume increased with MD (pFDR<0.001) and LV volume (pFDR<0.001). Conclusion: TBI exposure showed nominal associations with CP enlargement, but not blast exposure in this cohort. This may require further stratification regarding the direction of blast or injury mechanism. Positive associations between CP volume and MD and LV volume suggests CP volume could potentially indicate broader changes in CSF-related structures.

Background: Quantitative Susceptibility Mapping (QSM) measures tissue magnetic susceptibility but cannot characterize sub-voxel distributions. Paramagnetic (iron) and diamagnetic (myelin) sources may coexist within voxels, with opposing contributions potentially masking pathological changes in Parkinson's disease (PD). DECOMPOSE-QSM addresses this by decomposing bulk susceptibility into Paramagnetic (PCS), Diamagnetic (DCS), and Composite (CompS) maps. We examined source-separated susceptibility in PD and controls, identifying regional differences and clinical associations.

Methods: 59 PD patients aged 50-80 (age=66.9±7.0, 20 female) within 10 years of diagnosis and 17 age-matched controls (age=67.7±6.0, 8 female) underwent 3T MRI with multi-echo gradient-echo acquisitions. DECOMPOSE-QSM generated PCS, DCS, and CompS maps. Cortical ROIs used the Schaefer atlas; subcortical ROIs used MRIcloud. ANOVAs assessed group differences and multiple linear regression examined associations with cognition (MoCA) and motor severity (UPDRS-III), controlling for age and sex with Fcorrection.

Results: Substantia nigra showed increased susceptibility in PD versus controls in paramagnetic and composite maps (PCS: p=0.0041; CompS: p=0.0023). Visual cortex demonstrated lower composite susceptibility in PD (pFDR=0.015). Higher MoCA scores correlated with increased composite (pFDR=0.022) and diamagnetic (pFDR=0.0098) susceptibility in temporal pole. Higher UPDRS-III scores correlated with increased composite susceptibility in visual cortex (pFDR=0.038).

Conclusions: Source-separated susceptibility mapping reveals cortical and subcortical differences between PD and controls. Increased substantia nigra composite and paramagnetic susceptibility replicated prior findings in a larger, more clinically diverse cohort. Reduced composite susceptibility was observed in visual cortex. Cortical susceptibility measures associated with cognition (MoCA) and motor severity (UPDRS-III), highlighting the clinical relevance of investigating paramagnetic and diamagnetic components separately.

Introduction: Axon outgrowth and regeneration are key determinants of sensory function and are frequently impaired in inherited neuropathies. However, many assays for iPSC-derived sensory neurons (iPSC-SNs) are inconsistent and inadequate. It is therefore essential to develop improved axon outgrowth and regeneration assays to study dysfunction in inherited neuropathies, including LOF mutations in NMNAT2 and LOF mutations in SETDB2 in a congenital insensitivity to pain (CIP) pedigree. Aim 1: Optimize microfluidic in-vitro neurite outgrowth and regeneration assays in human iPSC-SNs. Aim 2: Apply these assays to iPSC-SNs with loss of NMNAT2 or derived from SETDB2 LOF patients.

Methods: For assay assessment and optimization, human iPSCs and immortalized human DRG cells are differentiated into SNs, matured as radial aggregates or in microfluidic devices, and axotomized using vacuum or laser ablation. Optimized assays are then applied to NMNAT2 LOF and SETDB2 LOF iPSC-SNs. Results: Aim 1: Optimized assays include a microfluidic radial outgrowth and two-chamber vacuum ablation assay visualized with tdTomato AAV9 transfection. These methods facilitate time-lapse imaging, reduce debris, and limit samples required. Aim 2: NMNAT2 LOF SNs display significantly reduced baseline neurite outgrowth (p=0.015) and may exhibit reduced regeneration. SETDB2 LOF SNs display significantly reduced baseline neurite outgrowth (p=0.002) and regeneration (p<0.001) independent of initial outgrowth or cell survival.

Conclusion: This study has optimized neurite outgrowth and regeneration assays for iPSC-SNs and applied these assays to demonstrate impaired neurite outgrowth and regeneration in NMNAT2 LOF and SETDB2 LOF iPSC-SNs.