Biology subjects

Cragg, S.

Publications and source records attributed to Cragg, S..

3 recordsLinked to original sources

bioRxiv2026

A human GBA-L444P transgene drives early and persistent dopamine neurotransmission deficits and alpha-synuclein pathology in a mouse model of early Parkinson's disease

BackgroundHeterozygous mutations in the GBA1 gene encoding the enzyme glucocerebrosidase (GCase) represent the most common genetic risk factor for developing Parkinsons disease (PD). The underlying mechanisms by which GBA1 mutations lead to PD through both loss- and gain-of-function effects remain unclear. There is a strong rationale for the generation and characterisation of a humanised GBA1 mouse model to allow the effect of GBA1 mutations on GCase function to be studied within the context of the human protein. MethodsWe have generated novel humanised mutant GBA-L444P and wild type GBA-WT mouse models using BAC recombineering and site-specific integration allowing the incorporation of the whole GBA1 locus as a transgene, including the endogenous promoter, all exons and introns, and flanking regions. Our experimental design crossed each GBA1 transgene onto a Gba+/- background and included Gba+/- littermate controls in our cohorts, allowing us to explore both the loss- and gain-of-function of GBA1 mutations. We have carried out "deep phenotyping" to characterise these mice by biochemical, stereological and behavioural testing, and assess dopamine release and content using fast-scan cyclic voltammetry and high performance liquid chromatography. ResultsThe GBA-L444P mice showed a significant reduction in GCase activity by 18 months of age and preferentially expressed a high molecular weight form of the GCase protein, likely due to retention in the ER and aberrant glycosylation. The GBA-L444P, but not Gba+/-, mice demonstrated an early and persistent reduction in dorsal striatal dopamine release in the absence of any dopaminergic cell loss or deficits in dopamine synthesis or reuptake, compared to human wild-type controls. GBA-L444P and Gba+/- mice developed an accumulation of oligomeric -synuclein pathology, but only GBA-L444P mice demonstrated subtle but significant changes in behaviour. ConclusionsThe novel humanised GBA-L444P mouse model described here helps to resolve gain- or loss-of-function effects of GBA1 mutations seen in Parkinsons as well as providing a novel set of models to investigate the human protein. Our work demonstrates that changes in dopamine release and behavioural deficits arise from a gain-of-function mechanism, whereas -synuclein pathology arises from GCase loss-of-function.

neuroscience↗

bioRxiv2026

An anatomical hotspot for striatal dopamine-acetylcholine interactions during reward and movement

Dopamine (DA) and acetylcholine (ACh) are key neuromodulators that regulate striatal circuits underlying movement and reinforcement learning. Evidence suggests that DA and ACh systems interact, but where and how interactions are expressed across striatal regions in behaviorally relevant release dynamics remains unknown. We applied micro-fiber arrays to simultaneously measure striatum-wide DA and ACh in behaving mice, revealing an anatomical organization in which DA-ACh anti-correlations were concentrated in a hotspot in the anterior dorsolateral striatum (aDLS). Anti-correlations resulted from temporally coincident pairs of spontaneous and event-locked transient peak and dip events occurring in a DA[->]ACh sequence. The aDLS localized hotspot was consistently expressed within distinct signals associated with unpredicted rewards, learned and extinguished Pavlovian cues, and locomotion initiation and invigoration phases, for which we revealed novel, opposing DA-ACh dynamics. Optogenetic activation of DA neurons selectively suppressed spontaneous ACh release within the aDLS hotspot, and ex vivo recordings revealed enhanced D2-mediated ACh inhibition in aDLS relative to ventral regions, suggesting a mechanistic basis for this spatial specificity. These findings demonstrate that DA-ACh interactions during behavior are spatially organized, rather than uniformly conserved, and shape behaviorally relevant dynamics to regulate region-specific functions in learning and movement control.

neuroscience↗

bioRxiv2024

An axonal brake on striatal dopamine output by cholinergic interneurons

Depolarisation of distal axons is necessary for neurons to translate somatic action potentials into neurotransmitter release. Studies have shown that striatal cholinergic interneurons (ChIs) can directly drive ectopic action potentials in dopamine (DA) axons and trigger DA release. However, here we show that this action occurs within a broader context of axonal signal integration whereby activation of ChIs and depolarisation of DA axons by nicotinic receptors (nAChRs) limits the subsequent depolarisation and release of DA in response to ensuing activity. We demonstrate that activation of ChIs and nAChRs in ex vivo mouse striatum, even when it does not trigger DA release that is detectable by fast-scan cyclic voltammetry, limits DA release for [~]100 ms by depressing subsequent axonal depolarisation and calcium summation. This axonal brake on DA release is stronger in dorsal than ventral striatum, and is unrelated to DA depletion. In vivo, antagonism of nAChRs in dorsal striatum elevated extracellular DA levels and promoted conditioned place-preference, underscoring its physiological relevance. Our findings reveal that under physiological conditions in vivo, ChIs acting via nAChRs dynamically attenuate DA output driven by DA neuron activity, leading to a predominantly inverse relationship between ACh and DA signalling that varies continuously with ChI activity.

neuroscience↗