A cognitive fMRI study in non-manifesting LRRK2 and GBA carriers

Fiber-Specific White Matter Alterations in Parkinson's Disease Patients with GBA Gene Mutations

BACKGROUND

Patients with Parkinson's disease (PD) carrying GBA gene mutations (GBA-PD) have a more aggressive disease course than those with idiopathic PD (iPD).

OBJECTIVE

The objective of this study was to investigate fiber-specific white matter (WM) differences in nonmedicated patients with early-stage GBA-PD and iPD using fixel-based analysis, a novel technique to assess tract-specific WM microstructural and macrostructural features comprehensively.

METHODS

Fixel-based metrics, including microstructural fiber density (FD), macrostructural fiber-bundle cross section (FC), and a combination of FD and FC (FDC), were compared among 30 healthy control subjects, 16 patients with GBA-PD, and 35 patients with iPD. Associations between FDC and clinical evaluations were also explored using multiple linear regression analyses.

RESULTS

Patients with GBA-PD showed significantly lower FD in the fornix and superior longitudinal fasciculus than healthy control subjects, and lower FC in the corticospinal tract (CST) and lower FDC in the CST, middle cerebellar peduncle, and striatal-thalamo-cortical pathways than patients with iPD. Contrarily, patients with iPD showed significantly higher FC and FDC in the CST and striatal-thalamo-cortical pathways than healthy control subjects. In addition, lower FDC in patients with GBA-PD was associated with reduced glucocerebrosidase enzyme activity, lower cerebrospinal fluid total α-synuclein levels, lower Montreal Cognitive Assessment scores, lower striatal binding ratio, and higher Unified Parkinson's Disease Rating Scale Part III scores.

CONCLUSIONS

We report reduced fiber-specific WM density and bundle cross-sectional size in patients with GBA-PD, suggesting neurodegeneration linked to glucocerebrosidase deficiency, α-synuclein accumulation, and poorer cognition and motor functions. Conversely, patients with iPD showed increased fiber bundle size, likely because of WM reorganization. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Imaging Markers in Genetic Forms of Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by motor symptoms such as bradykinesia, rigidity, and resting tremor. While the majority of PD cases are sporadic, approximately 15-20% of cases have a genetic component. Advances in neuroimaging techniques have provided valuable insights into the pathophysiology of PD, including the different genetic forms of the disease. This literature review aims to summarize the current state of knowledge regarding neuroimaging findings in genetic PD, focusing on the most prevalent known genetic forms: mutations in the GBA1, LRRK2, and Parkin genes. In this review, we will highlight the contributions of various neuroimaging modalities, including positron emission tomography (PET), single-photon emission computed tomography (SPECT), and magnetic resonance imaging (MRI), in elucidating the underlying pathophysiological mechanisms and potentially identifying candidate biomarkers for genetic forms of PD.

Who is at Risk of Parkinson Disease? Refining the Preclinical Phase of GBA1 and LRRK2 Variant Carriers: a Clinical, Biochemical, and Imaging Approach

PURPOSE OF REVIEW

Genetic variants in GBA1 and LRRK2 genes are the commonest genetic risk factor for Parkinson disease (PD); however, the preclinical profile of GBA1 and LRRK2 variant carriers who will develop PD is unclear. This review aims to highlight the more sensitive markers that can stratify PD risk in non-manifesting GBA1 and LRRK2 variant carriers.

RECENT FINDINGS

Several case-control and a few longitudinal studies evaluated clinical, biochemical, and neuroimaging markers within cohorts of non-manifesting carriers of GBA1 and LRRK2 variants. Despite similar levels of penetrance of PD in GBA1 and LRRK2 variant carriers (10-30%), these individuals have distinct preclinical profiles. GBA1 variant carriers at higher risk of PD can present with prodromal symptoms suggestive of PD (hyposmia), display increased α-synuclein levels in peripheral blood mononuclear cells, and show dopamine transporter abnormalities. LRRK2 variant carriers at higher risk of PD might show subtle motor abnormalities, but no prodromal symptoms, higher exposure to some environmental factors (non-steroid anti-inflammatory drugs), and peripheral inflammatory profile. This information will help clinicians tailor appropriate screening tests and counseling and facilitate researchers in the development of predictive markers, disease-modifying treatments, and selection of healthy individuals who might benefit from preventive interventions.

The pathobiological basis of depression in Parkinson disease: challenges and outlooks

Depression, with an estimated prevalence of about 40% is a most common neuropsychiatric disorder in Parkinson disease (PD), with a negative impact on quality of life, cognitive impairment and functional disability, yet the underlying neurobiology is poorly understood. Depression in PD (DPD), one of its most common non-motor symptoms, can precede the onset of motor symptoms but can occur at any stage of the disease. Although its diagnosis is based on standard criteria, due to overlap with other symptoms related to PD or to side effects of treatment, depression is frequently underdiagnosed and undertreated. DPD has been related to a variety of pathogenic mechanisms associated with the underlying neurodegenerative process, in particular dysfunction of neurotransmitter systems (dopaminergic, serotonergic and noradrenergic), as well as to disturbances of cortico-limbic, striato-thalamic-prefrontal, mediotemporal-limbic networks, with disruption in the topological organization of functional mood-related, motor and other essential brain network connections due to alterations in the blood-oxygen-level-dependent (BOLD) fluctuations in multiple brain areas. Other hypothetic mechanisms involve neuroinflammation, neuroimmune dysregulation, stress hormones, neurotrophic, toxic or metabolic factors. The pathophysiology and pathogenesis of DPD are multifactorial and complex, and its interactions with genetic factors, age-related changes, cognitive disposition and other co-morbidities awaits further elucidation.

Possible association between the lrrk2 gene and anxiety behavior: a systematic literature review

Alterations to the LRRK2 gene have been associated with Parkinson's disease and alcohol consumption in animals and humans. Furthermore, these disorders are strongly related to anxiety disorders (ADs). Thus, we investigated how the LRRK2 gene might influence anxiety in humans and mice. We elaborated a systematic review based on the PRISMA Statement of studies that investigated levels of anxiety in animal or human models with alterations in the LRRK2 gene. The search was conducted in the PubMed, Scopus, and Web of Science databases, and in reference lists with descriptors related to ADs and the LRRK2. From the 62 articles assessed for eligibility, 16 were included: 11 conducted in humans and seven, in mice. Lrrk2 KO mice and the LRRK2 G2019S, LRRK2 R1441G, and LRRK2 R1441C variants were addressed. Five articles reported an increase in anxiety levels concerning the LRRK2 variants. Decreased anxiety levels were observed in two articles, one focusing on the LRRK2 G2019S and the other, on the Lrrk2 KO mice. Eight other articles reported no differences in anxiety levels in individuals with Lrrk2 alterations compared to their healthy controls. This study discusses a possible influence between the LRRK2 gene and anxiety, adding information to the existing knowledge respecting the influence of genetics on anxiety.

Cognitive deficits and altered cholinergic innervation in young adult male mice carrying a Parkinson's disease Lrrk2G2019S knockin mutation

Impaired executive function is a common and debilitating non-motor symptom of idiopathic and hereditary Parkinson's disease (PD), but there is little understanding of the underlying pathophysiological mechanisms and circuits. The G2019S mutation in the kinase domain of leucine-rich repeat kinase 2 (LRRK2) greatly increases risk for late-onset PD, and non-manifesting LRRK2^G2019S carriers can also exhibit early and significant cognitive impairment. Here, we subjected young adult male mice carrying a Lrrk2^G2019S knockin mutation to touchscreen-based operant tasks that measure attention, goal-directed learning and cognitive flexibility, all of which rely on frontal-striatal connectivity and are strongly modulated by cholinergic innervation. In a visuospatial attention task, mutant mice exhibited significantly more omissions and longer response latencies than controls that could not be attributed to deficits in motivation, visual sensory perception per se or locomotion, thereby suggesting impairments in divided attention and/or action-selection as well as generally slower information processing speed. Pretreating mice with the acetylcholinesterase inhibitor donepezil normalized both higher omission rates and longer response latencies in the mutants, but did not affect any performance metric in controls. Strikingly, cholinergic fiber density in cortical areas PL/IL and DMS (dorsomedial striatum) was significantly sparser in mutants than in controls, while further behavioral interrogation of the mutants revealed significant impairments in action-outcome associations but preserved cognitive flexibility. These data suggest that the Lrrk2^G2019S mutation negatively impacts cholinergic innervation anatomically and functionally by young adulthood, impairing corticostriatal network function in ways that may contribute to early PD-associated executive function deficits.

Neuroimaging in Glucocerebrosidase-Associated Parkinsonism: A Systematic Review

Background

Mutations in the GBA gene cause Gaucher's disease (GD) and constitute the most frequent genetic risk factor for idiopathic Parkinson's disease (iPD). Nonmanifesting carriers of GBA mutations/variants (GBA‐NMC) constitute a potential PD preclinical population, whereas PD patients carrying some GBA mutations/variants (GBA‐PD) have a higher risk of a more aggressive disease course. Different neuroimaging techniques are emerging as potential biomarkers in PD and have been used to study GBA‐associated parkinsonism.

Objective

The aim is to critically review studies applying neuroimaging to GBA‐associated parkinsonism.

Methods

Literature search was performed using PubMed and EMBASE databases (last search February 7, 2022). Studies reporting neuroimaging findings in GBA‐PD, GD with and without parkinsonism, and GBA‐NMC were included.

Results

Thirty‐five studies were included. In longitudinal studies, GBA‐PD patients show a more aggressive disease than iPD at both structural magnetic resonance imaging and 123‐fluoropropylcarbomethoxyiodophenylnortropane single‐photon emission computed tomography. Fluorodeoxyglucose‐positron emission tomography and brain perfusion studies reported a greater cortical involvement in GBA‐PD compared to iPD. Overall, contrasting evidence is available regarding GBA‐NMC for imaging and clinical findings, although subtle differences have been reported compared with healthy controls with no mutations.

Conclusions

Although results must be interpreted with caution due to limitations of the studies, in line with previous clinical observations, GBA‐PD showed a more aggressive disease progression in neuroimaging longitudinal studies compared to iPD. Cognitive impairment, a “clinical signature” of GBA‐PD, seems to find its neuroimaging correlate in the greater cortical burden displayed by these patients as compared to iPD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Aberrant dopamine transporter and functional connectivity patterns in LRRK2 and GBA mutation carriers

Non-manifesting carriers (NMCs) of Parkinson’s disease (PD)-related mutations such as LRRK2 and GBA are at an increased risk for developing PD. Dopamine transporter (DaT)-spectral positron emission computed tomography is widely used for capturing functional nigrostriatal dopaminergic activity. However, it does not reflect other ongoing neuronal processes; especially in the prodromal stages of the disease. Resting-state fMRI (rs-fMRI) has been proposed as a mode for assessing functional alterations associated with PD, but its relation to dopaminergic deficiency remains unclear. We aimed to study the association between presynaptic striatal dopamine uptake and functional connectivity (FC) patterns among healthy first-degree relatives of PD patients with mutations in LRRK2 and GBA genes. N = 85 healthy first-degree subjects were enrolled and genotyped. All participants underwent DaT and rs-fMRI scans, as well as a comprehensive clinical assessment battery. Between-group differences in FC within striatal regions were investigated and compared with striatal binding ratios (SBR). N = 26 GBA-NMCs, N = 25 LRRK2-NMCs, and N = 34 age-matched nonmanifesting noncarriers (NM-NCs) were included in each study group based on genetic status. While genetically-defined groups were similar across clinical measures, LRRK2-NMCs demonstrated lower SBR in the right putamen compared with NM-NCs, and higher right putamen FC compared to GBA-NMCs. In this group, higher striatal FC was associated with increased risk for PD. The observed differential SBR and FC patterns among LRRK2-NMCs and GBA-NMCs indicate that DaTscan and FC assessments might offer a more sensitive prediction of the risk for PD in the pre-clinical stages of the disease.

Cognitive Impairment in Genetic Parkinson's Disease

Cognitive impairment is common in idiopathic Parkinson's disease (PD). Knowledge of the contribution of genetics to cognition in PD is increasing in the last decades. Monogenic forms of genetic PD show distinct cognitive profiles and rate of cognitive decline progression. Cognitive impairment is higher in GBA- and SNCA-associated PD, lower in Parkin- and PINK1-PD, and possibly milder in LRRK2-PD. In this review, we summarize data regarding cognitive function on clinical studies, neuroimaging, and biological markers of cognitive decline in autosomal dominant PD linked to mutations in LRRK2 and SNCA, autosomal recessive PD linked to Parkin and PINK1, and also PD linked to GBA mutations.

Cognitive Functioning of Glucocerebrosidase (GBA) Non-manifesting Carriers

Mutations and variants in the glucocerebrosidase (GBA) gene are among the most common genetic risk factors for the development of Parkinson's disease (PD). Yet, penetrance is markedly reduced, and less is known about the burden of carrying a single mutation among those without diagnosed PD. Motor, cognitive, psychiatric, and olfactory functioning were assessed in 30 heterozygous GBA mutation carriers without PD (the majority of whom had mild GBA mutations) and 49 non-carriers without PD. Study focus was on domains affected in GBA mutation carriers with PD, as well as those previously shown to be abnormal in GBA mutation carriers without PD. GBA mutation carriers showed poorer performance on the Stroop interference measure of executive functioning when controlling for age. There were no group differences in verbal memory, Montreal Cognitive Assessment (MoCA), overall motor score, or presence of REM sleep behavior disorder or depression. Although total olfaction scores did not differ, GBA mutation carriers with hyposmia had lower global cognition scores than those without hyposmia. As anticipated by the low penetrance of GBA mutations, these findings suggest that pre-manifest non-motor or motor features of PD may not present in most GBA mutation carriers. However, there is support that there may be a subtle difference in executive functioning among some non-manifesting heterozygous GBA mutation carriers, and, combined with olfaction, this may warrant additional scrutiny as a potential biomarker for pre-manifest and pre-clinical GBA related PD.

Functional Connectivity Analysis in Heterozygous Glucocerebrosidase Mutation Carriers

BACKGROUND

There is evidence that alterations in functional connectivity (FC) of the striatocortical circuits may appear before the onset of clinical symptoms of Parkinson's disease (PD).

OBJECTIVE

The aim of this study was to investigate FC of the striatocortical circuitry in asymptomatic carriers of heterozygous glucocerebrosidase (GBA) mutations, which pose a significant risk for developing PD.

METHODS

Twenty-one parents of confirmed Gaucher disease patients who were carrying heterozygous GBA mutations and 18 healthy individuals matched for age and gender were included. GBA mutation analysis was performed in all participants. Clinical evaluation included neurological examination, Mini Mental State Examination, and UPDRS Part III. Structural and functional MRI data of 18 asymptomatic GBA mutation carriers (asGBAmc) and 17 healthy controls (HC) were available. FC was analyzed with seed-based approach.

RESULTS

Eleven asymptomatic mutation carriers had heterozygous p.L483P mutation, 6 subjects heterozygous p.N409S mutation and 1 subject heterozygous p.R392G mutation in GBA gene. Mini-Mental State Examination mean score was 28.77 (±1.16) and 29.64 (±0.70) in asGBAmc and HC groups, respectively (p = 0.012). Significant increased connectivityConclusion:Our results suggest that alterations in striatocortical FC can be detected in asymptomatic heterozygous GBA mutation carriers who are at risk of developing PD. These findings may provide insight into network changes during the asymptomatic phase of PD.

A novel CERNNE approach for predicting Parkinson's Disease-associated genes and brain regions based on multimodal imaging genetics data

The detection and pathogenic factors analysis of Parkinson's disease (PD) has a practical significance for its diagnosis and treatment. However, the traditional research paradigms are commonly based on single neural imaging data, which is easy to ignore the complementarity between multimodal imaging genetics data. The existing researches also pay little attention to the comprehensive framework of patient detection and pathogenic factors analysis for PD. Based on functional magnetic resonance imaging (fMRI) data and single nucleotide polymorphism (SNP) data, a novel brain disease multimodal data analysis model is proposed in this paper. Firstly, according to the complementarity between the two types of data, the classical correlation analysis method is used to construct the fusion feature of subjects. Secondly, based on the artificial neural network, the fusion feature analysis tool named clustering evolutionary random neural network ensemble (CERNNE) is designed. This method integrates multiple neural networks constructed randomly, and uses clustering evolution strategy to optimize the ensemble learner by adaptive selective integration, selecting the discriminative features for PD analysis and ensuring the generalization performance of the ensemble model. By combining with data fusion scheme, the CERNNE is applied to forming a multi-task analysis framework, recognizing PD patients and predicting PD-associated brain regions and genes. In the multimodal data experiment, the proposed framework shows better classification performance and pathogenic factors predicting ability, which provides a new perspective for the diagnosis of PD.

Clinical and dopamine transporter imaging characteristics of non-manifest LRRK2 and GBA mutation carriers in the Parkinson's Progression Markers Initiative (PPMI): a cross-sectional study

BACKGROUND

The Parkinson's Progression Markers Initiative (PPMI) is an ongoing observational, longitudinal cohort study of participants with Parkinson's disease, healthy controls, and carriers of the most common Parkinson's disease-related genetic mutations, which aims to define biomarkers of Parkinson's disease diagnosis and progression. All participants are assessed annually with a battery of motor and non-motor scales, 123-I Ioflupane dopamine transporter (DAT) imaging, and biological variables. We aimed to examine whether non-manifesting carriers of LRRK2 and GBA mutations have prodromal features of Parkinson's disease that correlate with reduced DAT binding.

METHODS

This cross-sectional analysis is based on assessments done at enrolment in the subset of non-manifesting carriers of LRRK2 and GBA mutations enrolled into the PPMI study from 33 participating sites worldwide. The primary objective was to examine baseline clinical and DAT imaging characteristics in non-manifesting carriers with GBA and LRRK2 mutations compared with healthy controls. DAT deficit was defined as less than 65% of putamen striatal binding ratio expected for the individual's age. We used t tests, χ² tests, and Fisher's exact tests to compare baseline demographics across groups. An inverse probability weighting method was applied to control for potential confounders such as age and sex. To account for multiple comparisons, we applied a family-wise error rate to each set of analyses. This study is registered with ClinicalTrials.gov, number NCT01141023.

FINDINGS

Between Jan 1, 2014, and Jan 1, 2019, the study enrolled 208 LRRK2 (93% G2019S) and 184 GBA (96% N370S) non-manifesting carriers. Both groups were similar with respect to mean age, and about 60% were female. Of the 286 (73%) non-manifesting carriers that had DAT imaging results, 18 (11%) LRRK2 and four (3%) GBA non-manifesting carriers had a DAT deficit. Compared with healthy controls, both LRRK2 and GBA non-manifesting carriers had significantly increased mean scores on the Movement Disorders Society Unified Parkinson's Disease Rating Scale (total score 4·6 [SD 4·4] healthy controls vs 8·4 [7·3] LRRK2 vs 9·5 [9·2] GBA, p<0·0001 for both comparisons) and the Scale for Outcomes for PD - autonomic function (5·8 [3·7] vs 8·1 [5·9] and 8·4 [6·0], p<0·0001 for both comparisons). There was no difference in daytime sleepiness, anxiety, depression, impulsive-compulsive disorders, blood pressure, urate, and rapid eye movement (REM) behaviour disorder scores. Hyposmia was significantly more common only in LRRK2 non-manifesting carriers (69 [36%] of 194 healthy controls vs 114 [55%] of 208 LRRK2 non-manifesting carriers; p=0·0003). Finally, GBA but not LRRK2 non-manifesting carriers showed increased DAT striatal binding ratios compared with healthy controls in the caudate (healthy controls 2·98 [SD 0·63] vs GBA 3·26 [0·63]; p<0·0001), putamen (2·15 [0·56] vs 2·48 [0·52]; p<0·0001), and striatum (2·56 [0·57] vs 2·87 [0·55]; p<0·0001).

INTERPRETATION

Our data show evidence of subtle motor and non-motor signs of Parkinson's disease in non-manifesting carriers compared with healthy controls that can precede DAT deficit. Longitudinal data will be essential to confirm these findings and define the trajectory and predictors for development of Parkinson's disease.

FUNDING

Michael J Fox Foundation for Parkinson's Research.

Parkinsonisms and Glucocerebrosidase Deficiency: A Comprehensive Review for Molecular and Cellular Mechanism of Glucocerebrosidase Deficiency

In the last years, lysosomal storage diseases appear as a bridge of knowledge between rare genetic inborn metabolic disorders and neurodegenerative diseases such as Parkinson’s disease (PD) or frontotemporal dementia. Epidemiological studies helped promote research in the field that continues to improve our understanding of the link between mutations in the glucocerebrosidase (GBA) gene and PD. We conducted a review of this link, highlighting the association in GBA mutation carriers and in Gaucher disease type 1 patients (GD type 1). A comprehensive review of the literature from January 2008 to December 2018 was undertaken. Relevance findings include: (1) There is a bidirectional interaction between GBA and α- synuclein in protein homeostasis regulatory pathways involving the clearance of aggregated proteins. (2) The link between GBA deficiency and PD appears not to be restricted to α–synuclein aggregates but also involves Parkin and PINK1 mutations. (3) Other factors help explain this association, including early and later endosomes and the lysosomal-associated membrane protein 2A (LAMP-2A) involved in the chaperone-mediated autophagy (CMA). (4) The best knowledge allows researchers to explore new therapeutic pathways alongside substrate reduction or enzyme replacement therapies.

Structural and Functional MRI in Familial Parkinson's Disease

Between 10 and 15% of Parkinson disease (PD) cases can be traced to a genetically identified causative mutation which currently number over 40. This enables the study of both "at risk" populations for future development of PD and a unique sub-group of genetically determined patient population. Structural and functional magnetic imaging has the potential of assisting diagnosis, early detection and disease progression as it is relatively cheap and easy to implement. However, the large variety of imaging options and different analytical approaches hamper the pursuit of a unified imaging biomarker. This chapter details the current imaging options and summarizes the findings among both genetically determined patients with PD and their non-manifesting first degree relatives, speculating on possible compensational mechanisms while mapping future directions in order to better utilize MRI in the research of genetic PD.

Cognition among individuals along a spectrum of increased risk for Parkinson's disease

INTRODUCTION

Several characteristics associated with increased risk for Parkinson's disease (PD) have been identified, including specific genotypes and various non-motor symptoms. Characterizing non-motor features, such as cognitive abilities, among individuals considered at-risk for PD is essential to improving prediction of future neurodegeneration.

METHODS

Participants belonging to the following cohorts of the Parkinson Progression Markers Initiative (PPMI) study were included: de novo PD with dopamine transporter binding deficit (n = 423), idiopathic REM sleep behavior disorder (RBD, n = 39), hyposmia (n = 26) and non-PD mutation carrier (NMC; Leucine-rich repeat kinase 2 (LRRK2) G2019S (n = 88) and glucocerebrosidase (GBA) gene (n = 38) mutations)). Inclusion criteria enriched the RBD and hyposmia cohorts, but not the NMC cohort, with individuals with dopamine transporter binding deficit. Baseline neuropsychological performance was compared, and analyses were adjusted for age, sex, education, and depression.

RESULTS

The RBD cohort performed significantly worse than the hyposmia and NMC cohorts on Symbol Digit Modality Test (mean (SD) 32.4 (9.16) vs. 41.8 (9.98), p = 0.002 and vs. 45.2 (10.9), p<0.001) and Judgment of Line Orientation (11.3 (2.36) vs.12.9 (1.87), p = 0.004 and vs. 12.9 (1.87), p<0.001). The RBD cohort also performed worse than the hyposmia cohort on the Montreal Cognitive Assessment (25.5 (4.13) vs. 27.3 (1.71), p = 0.02). Hyposmics did not differ from PD or NMC cohorts on any cognitive test score.

CONCLUSION

Among individuals across a spectrum of risk for PD, cognitive function is worse among those with the characteristic most strongly associated with future risk of PD or dementia with Lewy bodies, namely RBD.

Cognitive and motor functioning in elderly glucocerebrosidase mutation carriers

Mutations in the glucocerebrosidase (GBA) gene are a strong genetic risk factor for the development of Parkinson's disease and dementia with Lewy Bodies. However the penetrance of GBA mutations is low for these diseases in heterozygous carriers. The aim of this study was to examine the relationship between mutation status and cognitive and motor functioning in a sample of community-dwelling older adults. Using linear mixed effects models, we examined the effect of heterozygous mutation status on 736 community-dwelling older adults (≥70 years) without dementia or Parkinson's disease assessed over an average of 6 years, 28 of whom had a single GBA mutation (primarily N370S). Verbal memory was measured using the picture version of the Free and Cued Selective Reminding Test, and carriers showed significantly (p < 0.05) greater decline in verbal memory over time. There was no difference in motor function or any other cognitive domain. Taken together, these results suggest an effect, but an overall limited burden, of harboring a single GBA mutation in aging mutation carriers.