Oculomotor Dysfunction in Idiopathic and LRRK2-Parkinson's Disease and At-Risk Individuals.

Background: Video-oculography constitutes a highly-sensitive method of characterizing ocular movements, which could detect subtle premotor changes and contribute to the early diagnosis of Parkinson's disease (PD). Objective: To investigate potential oculomotor differences between idiopathic PD (iPD) and PD associated with the G2019S variant of LRRK2 (L2PD), as well as to evaluate oculomotor function in asymptomatic carriers of the G2019S variant of LRRK2. Methods: The study enrolled 129 subjects: 30 PD (16 iPD, 14 L2PD), 23 asymptomatic carriers, 13 non-carrier relatives of L2PD patients, and 63 unrelated HCs. The video-oculographic evaluation included fixation, prosaccade, antisaccade, and memory saccade tests. Results: We did not find significant differences between iPD and L2PD. Compared to controls, PD patients displayed widespread oculomotor deficits including larger microsaccades, hypometric vertical prosaccades, increased latencies in all tests, and lower percentages of successful antisaccades and memory saccades. Non-carrier relatives showed oculomotor changes with parkinsonian features, such as fixation instability and hypometric vertical saccades. Asymptomatic carriers shared multiple similarities with PD, including signs of unstable fixation and hypometric vertical prosaccades; however, they were able to reach percentages of successful antisaccade and memory saccades similar to controls, although at the expense of longer latencies. Classification accuracy of significant oculomotor parameters to differentiate asymptomatic carriers from HCs ranged from 0.68 to 0.74, with BCEA, a marker of global fixation instability, being the parameter with the greatest classification accuracy. Conclusions: iPD and LRRK2-G2019S PD patients do not seem to display a differential oculomotor profile. Several oculomotor changes in asymptomatic carriers of LRRK2 mutations could be considered premotor biomarkers.

Differential serum microRNAs in premotor LRRK2 G2019S carriers from Parkinson's disease.

The LRRK2 G2019S pathogenic mutation causes LRRK2-associated Parkinson's disease (L2PD) with incomplete penetrance. LRRK2 non-manifesting carriers (L2NMC) are at PD high risk but predicting pheno-conversion is challenging given the lack of progression biomarkers. To investigate novel biomarkers for PD premotor stages, we performed a longitudinal microRNA (miRNA) assessment of serum samples from G2019S L2NMC followed-up over 8 years. Our cohort consisted of G2019S L2NMC stratified by dopamine transporter single-photon emission computed tomography (DaT-SPECT) into DaT-negative (n = 20) and DaT-positive L2NMC (n = 20), pheno-converted G2019S L2PD patients (n = 20), idiopathic PD (iPD) (n = 19), and controls (n = 40). We also screened a second cohort of L2PD patients (n = 19) and controls (n = 20) (Total n = 158). Compared to healthy controls, we identified eight deregulated miRNAs in DaT-negative L2NMC, six in DaT-positive L2NMC, and one in L2PD. Between groups, the highest miRNA differences, 24 candidate miRNAs, occurred between DaT-positive L2NMC and L2PD. Longitudinally, we found 11 common miRNAs with sustained variation in DaT-negative and DaT-positive L2NMCs compared to their baselines. Our study identifies novel miRNA alterations in premotor stages of PD co-occurring with progressive DaT-SPECT decline before motor manifestation, whose deregulation seems to attenuate after the diagnosis of L2PD. Moreover, we identified four miRNAs with relatively high discriminative ability (AUC = 0.82) between non-pheno-converted DaT-positive G2019S carriers and pheno-converted L2PD patients (miR-4505, miR-8069, miR-6125, and miR-451a), which hold potential as early progression biomarkers for PD.

Analysis of retinal nerve layers in idiopathic, LRRK2-associated Parkinson's disease and unaffected carriers of G2019S mutation.

INTRODUCTION: In both prodromal and early symptomatic stages of idiopathic PD (iPD) peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell layer (mGCL) thinning have been identified. Here we assessed whether these alterations can also be detected in symptomatic and presymptomatic stages of LRRK2-PD. METHODS: 218 eyes belonging to 20 iPD, 19 LRRK2-PD (L2PD), 24 LRRK2 non-manifesting carriers (L2NMC), and 46 controls (HCs). pRNFL, mGCL thickness (squares), and Bruch's membrane opening minimum rim width were evaluated by SD-OCT. In L2NMC, 123I-ioflupane SPECT (DaT-SPECT) with semi-quantitative analysis was carried out. RESULTS: Compared to HCs, iPD patients showed significant thinning of the temporal (BMO-MRW and pRNFL), superior-temporal (BMO-MRW), inferior-temporal (BMO-MRW), superior-nasal (BMO-MRW) and central sectors (BMO-MRW) (p < 0.05), as well as in five mGCL sectors (p < 0.05). No significant differences were found between the L2PD or L2NMC and HCs. BMO-MRW thickness in its temporal-superior, superior-nasal and middle sectors was influenced by disease duration (p < 0.05) and mGCL thickness in sectors TS1, TS2, TS3, NS1 and NS3 was influenced by UPDRSIII and age (p < 0.05). CONCLUSION: LRRK2-PD is distinguished from iPD by absent or less retinal nerve involvement, both in clinical and preclinical stages.

Sensor-based gait analysis in the premotor stage of LRRK2 G2019S-associated Parkinson's disease.

INTRODUCTION: There is a need for biomarkers to monitor the earliest phases of Parkinson's disease (PD), especially in premotor stages. Here, we studied whether there are early gait alterations in carriers of the G2019S mutation of LRRK2 that can be detected by means of an inertial sensor system. METHODS: Twenty-one idiopathic PD patients, 20 LRRK2-G2019S PD, 27 asymptomatic carriers of LRRK2-G2019S mutation (AsG2019S) and 36 controls walked equipped with 16 lightweight inertial sensors in three different experiments: i/normal gait, ii/fast gait and iii/dual-task gait. In the AsG2019S group, DaT-SPECT (123I-ioflupane) with semi-quantitative analysis was carried out. Motor and cognitive performance were evaluated using MDS-UPDRS-III and MoCA scales. We employed neural network techniques to classify individuals based on their walking patterns. RESULTS: PD patients and controls showed differences in speed, stride length and arm swing amplitude, variability and asymmetry in all three tasks (p < 0.01). In the AsG2019S group, the only differences were detected during fast walking, with greater step time on the non-dominant side (p < 0.05), lower step/stride time variability (p < 0.01) and lower step time asymmetry (p < 0.01). DaT uptake showed a significant correlation with step time during fast walking on the non-dominant side (r = -0.52; p < 0.01). The neural network was able to differentiate between AsG2019S and healthy controls with an accuracy rate of 82.5%. CONCLUSION: Our sensor-based analysis did not detect substantial and robust changes in the gait of LRRK2-G2019S asymptomatic mutation carriers. Nonetheless, step or stride time during fast walking, supported by the observed correlation with striatal DaT binding deserves consideration as a potential biomarker in future studies.

Serial DaT-SPECT imaging in asymptomatic carriers of LRRK2 G2019S mutation: 8 years' follow-up.

BACKGROUND: Carriers of the G2019S mutation of LRRK2 provide a great opportunity to investigate the premotor stages of Parkinson's disease (PD). We have studied by serial clinical and dopamine transporter single photon emission computed tomography (DaT-SPECT) evaluations a cohort of asymptomatic carriers of the LRRK2-G2019S mutation in order to evaluate the usefulness of these tools as biomarkers. Here we report the results of the extended follow-up of this cohort at 8 years. METHODS: Seventeen participants, of the 25 available from the 4-year evaluation, completed the 8-year assessment. UPDRS-III, UPSIT test and DaT-SPECT imaging (123 I-ioflupane) were performed. We used repeated-measures linear mixed effects models to examine the changes in DaT binding over time. RESULTS: Three carriers had converted to PD at 4 years. One additional carrier converted at 8 years. PD-converters had lower striatal DaT binding at baseline than non-converters. There was a significant decline of DaT binding over time, with a mean annual rate of 3.5%, with somewhat inter-individual and intra-individual variability and comparable between PD-converters and non-converters. No carrier with DAT binding ratio above an undefined threshold between 0.5 and 0.8 developed PD symptoms. The age-adjusted UPSIT score did not change significantly over time. CONCLUSIONS: The rate of conversion to PD at 8 years in this cohort aged ~58 years at baseline was 16%. The observed decline of DaT binding over time and its association with the phenotype render DaT-SPECT a potentially useful tool for monitoring the premotor stage of the disease, although at the individual level its ability to predict phenoconversion is limited.

Small-Molecule-Based Self-Assembled Ligands for G-Quadruplex DNA Surface Recognition.

Most drugs are small molecules because of their attractive pharmacokinetics, manageable development and manufacturing, and effective binding into the concave crevices of bio-macromolecules. Despite these features, they often fall short when it comes to effectively recognizing the surfaces of bio-macromolecules. One way to overcome the challenge of biomolecular surface recognition is to develop small molecules that become self-assembled ligands (SALs) prior to binding. Herein, we report SALs made from 8-aryl-2'-deoxyguanosine derivatives forming precise hydrophilic supramolecular G-quadruplexes (SGQs) with excellent size, shape, and charge complementarity to G-quadruplex DNA (QDNA). We show that only those compounds forming SGQs act as SALs, which in turn differentially stabilize QDNAs from selected oncogene promoters and the human telomeric regions. Fluorescence resonance energy-transfer melting assays are consistent with spectroscopic, calorimetric, and light scattering studies, showing the formation of a "sandwichlike" complex QDNA·SGQ·QDNA. These results open the door for the advent of SALs that recognize QDNAs and potentially the surfaces of other bio-macromolecules such as proteins.

Walking a supramolecular tightrope: a self-assembled dodecamer from an 8-aryl-2'-deoxyguanosine derivative.

Controlling the properties of self-assembled supramolecules via intrinsic parameters (i.e., structural information in the subunits) enables the reliable construction of assemblies of well-defined size and composition. Here we show that an optimum balance between repulsive (e.g., steric) and attractive (e.g., pi-pi, dipole-dipole) noncovalent interactions between subunits of a lipophilic 8-(3-pyridyl)-2'-deoxyguanosine derivative enables the high fidelity formation of a stable and discrete self-assembled dodecamer. In contrast, the isosteric 8-phenyl-2'-deoxyguanosine derivative assembles into an octamer because it cannot engage in additional dipole-dipole interactions. Adding dodecamers to a supramolecular construction toolbox, already containing octamers and hexadecamers made from other 8-aryl-2'-deoxyguanosine derivatives, should enable the preparation of a wide variety of self-assembled nanostructures where the size and the number of functional elements can be precisely fine-tuned for specific applications.

Synthesis of 8-Heteroaryl-2'-deoxyguanosine Derivatives.

We describe the synthesis of 8-heteroaromatic-2'-deoxyguanosine analogues using Suzuki-Miyaura or Stille conditions. Unprotected and protected 8-bromo-2'-deoxyguanosine was coupled with commercially available heteroarylboronic acids or the trialkyltin derivatives of 2-pyridylbromides either with or without microwave irradiation in good yields.

The impact of 8-aryl-and 8-heteroaryl-2'-deoxyguanosine derivatives on G-quadruplex formation.

Guanine and G-rich oligonucleotides are known to self-assemble in the presence of a variety of cations to form higher ordered structures known as Gquadruplexes. We have synthesized a library of 8-aryl/heteroaryl-2'-deoxyguanosine derivatives (8ArGs) that are also able to self-assemble into quadruplex structures. We demonstrate that the properties of such quadruplexes can be modulated by the nature of the groups attached to the guanine base. These supramolecules are potentially useful in the development of self-assembled nanodevices.