Ziv Gan-Or

McGill University | McGill · Department of Neurology and Neurosurgery

Objective: The TMEM175/GAK/DGKQ locus is the 3rd strongest risk locus in genome-wide association studies (GWAS) of Parkinson disease (PD). We aimed to identify the specific disease-associated variants in this locus, and their potential implications. Methods: Full sequencing of TMEM175/GAK/DGKQ, followed by genotyping of specific associated varia...

Objective To study the role of GBA variants in the risk for isolated rapid-eye-movement (REM)-sleep behavior disorder (iRBD) and conversion to overt neurodegeneration. Methods A total of 4,147 individuals were included: 1,061 iRBD patients and 3,086 controls. GBA was fully sequenced using molecular inversion probes and Sanger sequencing. We analyz...

Genome-wide association studies (GWAS) have identified numerous loci associated with Parkinson's disease. The specific genes and variants that drive the associations within the vast majority of these loci are unknown. We aimed to perform a comprehensive analysis of selected genes to determine the potential role of rare and common genetic variants w...

Rapid-eye movement (REM) sleep behavior disorder (RBD), enactment of dreams during REM sleep, is an early clinical symptom of alpha-synucleinopathies and defines a more severe subtype. The genetic background of RBD and its underlying mechanisms are not well understood. Here, we perform a genome-wide association study of RBD, identifying five RBD ri...

The association between glucocerebrosidase (GCase), encoded by GBA, and Parkinson’s disease highlights the role of the lysosome in Parkinson’s disease pathogenesis. Genome-wide association studies (GWAS) in Parkinson’s disease have revealed multiple associated loci, including the GALC locus on chromosome 14. GALC encodes the lysosomal enzyme galact...

Background Several lysosomal genes are associated with Parkinson’s disease (PD), yet the association between PD and ARSA , which encodes for the enzyme arylsulfatase A, remains controversial. Objectives To evaluate the association between rare ARSA variants and PD. Methods To study possible association of rare variants (minor allele frequency<0.0...

MerTK is a receptor tyrosine kinase that mediates the immunologically silent phagocytic uptake of diverse types of cellular debris. Highly expressed on the surface of microglial cell, MerTK is of importance in brain development, homeostasis, plasticity, and disease. Yet, involvement of this receptor in the clearance of protein aggregates that accum...

Isolated rapid eye movement sleep behaviour disorder (iRBD) is a sleep disorder characterized by the loss of rapid eye movement sleep muscle atonia and the appearance of abnormal movements and vocalizations during rapid eye movement sleep. It is a strong marker of incipient synucleinopathy such as dementia with Lewy bodies and Parkinson’s disease....

Isolated/idiopathic REM sleep behavior disorder (iRBD) and Lewy body dementia (LBD) are synucleinopathies that have partial genetic overlap with Parkinson’s disease (PD). In this study, we examined if the human leukocyte antigen ( HLA ) locus plays a similar role in iRBD, LBD and PD. The DQA1*01:02∼DQB1*06:02∼DRB1*15:01 haplotype is associated with...

Background: GBA1 variants are among the most common genetic risk factors for Parkinson's disease (PD). GBA1 variants can be classified into three categories based on their role in Gaucher's disease (GD) or PD: severe, mild, and risk variant (for PD). Objective: This review aims to generate and share a comprehensive database for GBA1 variants rep...

Obesity has a strong genetic component, with up to 20% of variance in body mass index (BMI) being accounted for by common polygenic variation. Most genetic polymorphisms associated with BMI are related to genes expressed in the central nervous system. At the same time, higher BMI is associated with neurocognitive changes. However, the direct link b...

Genetic variants in GBA, encoding the lysosomal enzyme glucocerebrosidase (GCase), are common risk factors for Parkinson's disease (PD). Genotype-phenotype studies have demonstrated that different types of GBA variants have differential effects on the phenotype. Variants could be classified as mild or severe depending on the type of Gaucher disease...

Rapid-eye movement (REM) sleep behavior disorder (RBD), enactment of dreams during REM sleep, is an early clinical symptom of alpha-synucleinopathies and defines a more severe subtype. The genetic background of RBD and its underlying mechanisms are not well understood. Here, we perform a genome-wide association study of RBD, identifying five RBD ri...

Background Parkinson’s disease (PD) is genetically associated with the H1 haplotype of the MAPT 17q.21.31 locus, although the causal gene and variants underlying this association have not been identified. Methods To better understand the genetic contribution of this region to PD and to identify novel mechanisms conferring risk for the disease, we...

Parkinson’s disease is a complex neurodegenerative disorder with a strong genetic component, for which most known disease-associated variants are single nucleotide polymorphisms (SNPs) and small insertions and deletions (indels). DNA repetitive elements account for >50% of the human genome; however, little is known of their contribution to Parkinso...

NPC1 encodes a lysosomal protein involved in cholesterol transport. Biallelic mutations in this gene may lead to Niemann-Pick disease type C, a lysosomal storage disorder. The role of NPC1 in alpha synucleinopathies is still unclear, as different genetic, clinical, and pathological studies have reported contradictory results. This study aimed to ev...

An Xq22.2 region upstream of PLP1 has been proposed to underly a neurological disease trait when deleted in 46,XX females. Deletion mapping revealed that heterozygous deletions encompassing the smallest region of overlap (SRO) spanning six Xq22.2 genes (BEX3, RAB40A, TCEAL4, TCEAL3, TCEAL1, and MORF4L2) associate with an early-onset neurological di...

Background Epidemiological studies suggested an association between Parkinson’s disease (PD) and type 2 diabetes, but less is known about type 1 diabetes (T1D) and PD. Objectives To explore the association between T1D and PD. Methods We used Mendelian randomization, linkage disequilibrium score regression and transcriptome wide association analys...

Background: Neurodegeneration with brain iron accumulation (NBIA) represents a group of neurodegenerative disorders characterized by abnormal iron accumulation and the presence of axonal spheroids in the brain. In Parkinson's Disease (PD), iron accumulation is a cardinal feature of degenerating regions in the brain and seems to be a key player in m...

Background: GBA1 variants are among the most common genetic risk factors for Parkinson Disease (PD). GBA1 variants can be classified into three categories based on their role in Gaucher Disease (GD) or PD: severe, mild, and risk variant (for PD). Objectives: This paper aims to generate and share a comprehensive database for GBA1 variants reported i...

Isolated rapid eye movement sleep behavior disorder (iRBD) is a prodromal synucleinopathy characterized by several changes including brain atrophy. The mechanisms underlying atrophy in iRBD are poorly understood. Here, we performed imaging transcriptomics and comprehensive spatial mapping in a multicentric cohort of 171 polysomnography-confirmed iR...

Purpose The chaperone protein BiP is the master regulator of the unfolded protein response in the endoplasmic reticulum. BiP chaperone activity is regulated by the post-translational modification AMPylation, exclusively provided by FICD. We investigated whether FICD variants identified in patients with motor neuron disease could interfere with BiP...

Objectives Multiple risk loci for late-onset Alzheimer’s disease (LOAD) have been identified. Type 2 diabetes (T2D) is a risk factor for cognitive decline, dementia and Alzheimer’s disease (AD). We investigated the association of polygenic risk score (PRS) for LOAD with overall cognitive functioning and longitudinal decline, among older adults with...

It is clear that the immune system and inflammation have a role in Parkinson’s disease (PD), including sporadic PD and some genetic forms such as LRRK2-associated PD. One of the most important genes associated with PD is GBA1, as mutations in this gene are found in 5–20% of PD patients in different populations worldwide. Biallelic mutations in GBA1...

Epileptic encephalopathies comprise a clinically and genetically heterogenous group of disorders characterized by global developmental delay and ongoing seizure activity. It is generally considered that seizure activity is the primary pathology and leads to altered cognitive function. However, epileptic encephalopathy can also result from primary d...

Parkinson's disease (PD) is a complex neurodegenerative condition in which genetic and environmental factors interact to contribute to its etiology. Remarkable progress has been made in deciphering disease etiology through genetic approaches, but there is limited data about how environmental and genetic factors interact to modify penetrance, risk a...

Recessive mutations in PRKN, PARK7 and PINK1 are established causes of early-onset Parkinson's disease (EOPD). Previous studies have interrogated the role of heterozygous variants in these genes but mainly focused on rare (minor allele frequency [MAF] <1%) damaging variants or established mutations. Here, we assessed heterozygous private PRKN, PARK...

Obesity has a strong genetic component, with up to 20% of variance in body mass index (BMI) being accounted for by common polygenic variation. Most genetic polymorphisms associated with BMI are related to genes expressed in the central nervous system. At the same time, higher BMI is associated with neurocognitive changes. However, the direct link b...

Rabenosyn (RBSN) is a conserved endosomal protein necessary for regulating internalized cargo. Here, we present clinical, genetic, cellular and biochemical evidence that two distinct RBSN missense variants are responsible for a novel Mendelian disorder consisting of progressive muscle weakness, facial dysmorphisms, ophthalmoplegia and intellectual...

The association between glucocerebrosidase (GCase), encoded by GBA , and Parkinson’s disease highlights the role of the lysosome in Parkinson’s disease pathogenesis. Genome-wide association studies (GWAS) in Parkinson’s disease have revealed multiple associated loci, including the GALC locus on chromosome 14. GALC encodes the lysosomal enzyme galac...

The APOE locus is strongly associated with risk for developing Alzheimer's disease and dementia with Lewy bodies. In particular, the role of the APOE ϵ4 allele as a putative driver of α-synuclein pathology is a topic of intense debate. Here, we performed a comprehensive evaluation in 2466 dementia with Lewy bodies cases versus 2928 neurologically h...

Introduction: Spastic paraplegia type 4 (SPG4), resulting from heterozygous mutations in the SPAST gene, is the most common form among the heterogeneous group of hereditary spastic paraplegias (HSPs). We aimed to study genetic and clinical characteristics of SPG4 across Canada. Methods: The SPAST gene was analyzed in a total of 696 HSP patients fro...

This manuscript presents an overview of REM sleep behaviour disorder (RBD) with a special focus on European contributions. After an introduction examining the history of the disorder, we address the pathophysiological and clinical aspects, as well as the diagnostic issues. Further, implications of RBD diagnosis and biomarkers are discussed. Contrib...

Non-motor Parkinson's Disease is a burgeoning area of the movement disorders field, as patients increasingly live longer and encounter more late-stage symptoms. The spectrum of non-motor manifestations spans much of the body, with non-motor features occurring in all stages of the disease. Identification of symptoms is key for preserving quality of...

Recessive mutations in PRKN, PARK7 and PINK1 are established causes of early-onset Parkinson's disease (EOPD). Previous studies have interrogated the role of heterozygous variants in these genes but mainly focused on rare (minor allele frequency [MAF] <1%) damaging variants or established mutations. Here, we assessed heterozygous private PRKN, PARK...

Using genome-wide association data, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s (PD) or Alzheimer’s (AD) disease versus controls across ancestry groups. A shared genetic association was observed across diseases at rs601945 (PD: odds ratio (OR)=0.84; 95% confidence interval, [0.80; 0.88]; p=2.2...

Parkinson’s Disease (PD) is a progressive neurodegenerative disorder with a long prodromal course. Most cases are sporadic but a polygenic risk score (PRS) recently constructed from genome-wide association studies (GWAS) has identified 90 variants that contribute to disease vulnerability. While some of the genes identified affect known disease path...

Using genome-wide association data, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson's (PD) or Alzheimer's (AD) disease versus controls across ancestry groups. A shared genetic association was observed across diseases at rs601945 (PD: odds ratio (OR)=0.84; 95% confidence interval, [0.80; 0.88]; p=2.2...

Parkinson’s disease is a neurodegenerative movement disorder that currently has no disease-modifying treatment, partly owing to inefficiencies in drug target identification and validation. We use Mendelian randomization to investigate over 3,000 genes that encode druggable proteins and predict their efficacy as drug targets for Parkinson’s disease....

Background Parkinson’s disease (PD) is a neurodegenerative movement disorder affecting 1–5% of the general population for which neither effective cure nor early diagnostic tools are available that could tackle the pathology in the early phase. Here we report a multi-stage procedure to identify candidate genes likely involved in the etiopathogenesis...

Background: Alzheimer's disease (AD) and Parkinson's disease (PD) are the two most common neurodegenerative disorders. Dementia with Lewy bodies (DLB) has common clinical and pathological features with both AD and PD. Additionally, some genes were discovered as top hits in genome-wide association studies (GWASs) for multiple traits (i.e. MAPT, SNC...

SARM1, a protein with critical NADase activity, is a central executioner in a conserved programme of axon degeneration. We report seven rare missense or in-frame microdeletion human SARM1 variant alleles in patients with amyotrophic lateral sclerosis (ALS) or other motor nerve disorders that alter the SARM1 auto-inhibitory ARM domain and constituti...

Brain atrophy has been reported in the early stages of Parkinson’s Disease, but there have been few longitudinal studies. How intrinsic properties of the brain, such as anatomical connectivity, local cell type distribution and gene expression combine to determine the pattern of disease progression also remains unknown. One hypothesis proposes that...

Introduction: Spastic diplegia presenting in infancy is common to both cerebral palsy (CP) and hereditary spastic paraplegia (HSP). We report the clinical and genetic features of a cohort of Alberta patients with a diagnosis of HSP, who were initially diagnosed with CP. Methods: Fourteen patients with an initial diagnosis of CP were identified fr...

Background: Biallelic mutations in the GBA1 gene encoding glucocerebrosidase cause Gaucher's disease, whereas heterozygous carriers are at risk for Parkinson's disease (PD). Glucosylsphingosine is a clinically meaningful biomarker of Gaucher's disease but could not be assayed previously in heterozygous GBA1 carriers. Objective: The aim of this stu...

Background: PSAP encodes saposin C, the co-activator of glucocerebrosidase, encoded by GBA. GBA mutations are associated with idiopathic/isolated REM sleep behavior disorder (iRBD), a prodromal stage of synucleinopathy. Objective: To examine the role of PSAP mutations in iRBD. Methods: We fully sequenced PSAP and performed Optimized Sequence K...

Background: Parkinson's disease (PD) is a highly age-related disorder, where common genetic risk variants affect both disease risk and age at onset. A statistical approach that integrates these effects across all common variants may be clinically useful for individual risk stratification. A polygenic hazard score methodology, leveraging a time-to-e...

Rabenosyn (RBSN) is a conserved endosomal protein necessary for regulating internalized cargo. Here, we present genetic, cellular and biochemical evidence that two distinct RBSN missense variants are responsible for a novel Mendelian disorder consisting of progressive muscle weakness, facial dysmorphisms, ophthalmoplegia and intellectual disability...

Parkinson's disease (PD) is defined as a complex disorder with multifactorial pathogenesis, yet a more accurate definition could be that PD is not a single entity, but rather a mixture of different diseases with similar phenotypes. Attempts to classify subtypes of PD have been made based on clinical phenotypes or biomarkers. However, the most pract...

Introduction There have been no specific guidelines regarding which genes should be tested in the clinical setting for PD or parkinsonism. We evaluated the types of clinical genetic testing offered for Parkinson’s disease (PD) as the first step of our gene curation. Methods The National Institutes of Health (NIH) Genetic Testing Registry (GTR) was...

Background: Postoperative outcome following deep brain stimulation (DBS) of the subthalamic nucleus is variable, particularly with respect to axial motor improvement. We hypothesized a genetic underpinning to the response to surgical intervention, termed "surgicogenomics". Objective: We aimed to identify genetic variants associated with clinical...

We fine mapped the leukocyte antigen (HLA) region in 13,770 Parkinson's disease (PD) patients, 20,214 proxy-cases, and 490,861 controls of European origin. Four HLA types were associated with PD after correction for multiple comparisons, HLA-DQA1*03:01, HLA-DQB1*03:02, HLA-DRB1*04:01, and HLA-DRB1*04:04. Haplotype analyses followed by amino acid an...

Background: The leucine-rich repeat kinase 2 (LRRK2) gene harbors both rare highly damaging missense variants (eg, p.G2019S) and common noncoding variants (eg, rs76904798) with lower effect sizes that are associated with Parkinson's disease (PD) risk. Objectives: This study aimed to investigate in a large meta-analysis whether the LRRK2 Genome-Wid...

Mutations in the α-synuclein gene (SNCA) are well-established as a rare cause of inherited Parkinson’s disease (PD). A53T, A30P, E46K, G51D, and A53E are reported to cause an autosomal dominant form of PD. Recently, Liu et al pinpointed a novel SNCA mutation A30G (Chr4:90756730,c.89C>G) in five cases manifesting PD. The authors proposed A30G to pro...

MAPT encodes the microtubule-associated protein tau, which is the main component of neurofibrillary tangles (NFTs) and found in other protein aggregates. These aggregates are among the pathological hallmarks of primary tauopathies such as frontotemporal dementia (FTD). Abnormal tau can also be observed in secondary tauopathies such as Alzheimer’s d...

REM sleep behavior disorder (RBD) represents both an early marker and key symptom of synucleinopathies, mainly Parkinson disease (PD) and Lewy body dementia (LBD), and a strong opportunity for early clinical intervention for these conditions. Yet, the genetics of RBD are currently not well characterized. In this study, we perform the first genome-w...

Whole exome sequencing and linkage analysis were performed in a three gener-ational pedigree of Greek origin with a broad phenotypic spectrum spanning from Parkinson's disease and Parkinson's disease dementia to dementia of mixed type (Alzheimer disease and vascular dementia). We identified a novel heterozygous c.G1135T (p.G379W) variant in SORL1 w...

Parkinson's disease (PD) is a complex neurodegenerative disorder in which both rare and common genetic variants contribute to disease risk. Multiple genes have been reported to be linked to monogenic PD but these only explain a fraction of the observed familial aggregation. Rare variants in RIC3 have been suggested to be associated with PD in the I...

Subcellular membrane systems are highly enriched in dolichol, whose role in organelle homeostasis and endosomal-lysosomal pathway remains largely unclear besides being involved in protein glycosylation. DHDDS encodes for the catalytic subunit (DHDDS) of the enzyme cis-prenyltransferase (cis-PTase), involved in dolichol biosynthesis and dolichol-dep...

Subcellular membrane systems are highly enriched in dolichol, whose role in organelle homeostasis and endosomal-lysosomal pathway remains largely unclear besides being involved in protein glycosylation. DHDDS encodes for the catalytic subunit (DHDDS) of the enzyme cis-prenyltransferase (cis-PTase), involved in dolichol biosynthesis and dolichol-dep...

Objective To report the association between type 1 Gaucher disease (GD1) and amyotrophic lateral sclerosis (ALS) in 3 unrelated families and to explore whether GBA variants influence the risk of ALS. Methods We conducted retrospective chart reviews of patients with GD1 or their family members diagnosed with ALS. To further investigate whether ther...

Patients with isolated rapid-eye-movement sleep behaviour disorder (RBD) are commonly regarded as being in the early stages of a progressive neurodegenerative disease involving α-synuclein pathology, such as Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy. Abnormal α-synuclein deposition occurs early in the neurodegenerat...

Background: Most research in genomics of Parkinson's disease (PD) has been done in subjects of European ancestry, leading to sampling bias and leaving Latin American populations underrepresented. We sought to clinically characterize PD patients of Costa Rican origin and to sequence familial PD and atypical parkinsonism-associated genes in cases and...

Background: Spastic paraplegia type 4 (SPG4), resulting from heterozygous mutations in the SPAST gene, is the most common form among the heterogeneous group of hereditary spastic paraplegias (HSPs). Objective: To study genetic and clinical characteristics of SPG4 across Canada. Methods: The SPAST gene was analyzed in a total of 696 HSP patients fr...

PSAP encodes saposin C, the co-activator of glucocerebrosidase, encoded by GBA. Since GBA mutations are associated with idiopathic/isolated REM sleep behavior disorder (iRBD), a prodromal stage of synucleinopathy, we examined the role of PSAP mutations in iRBD. We fully sequenced PSAP and performed Optimized Sequence Kernel Association Test in 1,11...

Parkinson′s disease (PD) is a complex neurodegenerative disorder with a strong genetic component, where most known disease-associated variants are single nucleotide polymorphisms (SNPs) and small insertions and deletions (Indels). DNA repetitive elements account for >50% of the human genome, however little is known of their contribution to PD etiol...

A correction to this paper has been published: https://doi.org/10.1007/s00401-021-02309-z

Parkinson's disease (PD) is a complex neurodegenerative disorder in which both rare and common genetic variants contribute to disease risk. Multiple genes have been reported to be linked to monogenic PD, but these only explain a fraction of the observed familial aggregation. Rare variants in RIC3 have been suggested to be associated with PD in the...