LRP10 genetic variants in familial Parkinson's disease and dementia with Lewy bodies: a genome-wide linkage and sequencing study

Advances in gene therapy approaches targeting neuro-inflammation in neurodegenerative diseases

Over the last three decades, neurodegenerative diseases (NDs) have increased in frequency. About 15% of the world's population suffers from NDs in some capacity, which causes cognitive and physical impairment. Neurodegenerative diseases, including Amyotrophic Lateral Sclerosis, Parkinson's disease, Alzheimer's disease, and others represent a significant and growing global health challenge. Neuroinflammation is recognized to be related to all NDs, even though NDs are caused by a complex mix of genetic, environmental, and lifestyle factors. Numerous genes and pathways such as NFκB, p38 MAPK, Akt/mTOR, caspase, nitric oxide, and COX are involved in triggering brain immune cells like astrocytes and microglia to secrete inflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, and IL-6. In AD, the binding of Aβ with CD36, TLR4, and TLR6 receptors results in activation of microglia which start to produce proinflammatory cytokines and chemokines. Consequently, the pro-inflammatory cytokines worsen and spread neuroinflammation, causing the deterioration of healthy neurons and the impairment of brain functions. Gene therapy has emerged as a promising therapeutic approach to modulate the inflammatory response in NDs, offering potential neuroprotective effects and disease-modifying benefits. This review article focuses on recent advances in gene therapy strategies targeting neuroinflammation pathways in NDs. We discussed the molecular pathways involved in neuroinflammation, highlighted key genes and proteins implicated in these processes, and reviewed the latest preclinical and clinical studies utilizing gene therapy to modulate neuroinflammatory responses. Additionally, this review addressed the prospects and challenges in translating gene therapy approaches into effective treatments for NDs.

Identification of gene biomarkers for brain diseases via multi-network topological semantics extraction and graph convolutional network

BACKGROUND

Brain diseases pose a significant threat to human health, and various network-based methods have been proposed for identifying gene biomarkers associated with these diseases. However, the brain is a complex system, and extracting topological semantics from different brain networks is necessary yet challenging to identify pathogenic genes for brain diseases.

RESULTS

In this study, we present a multi-network representation learning framework called M-GBBD for the identification of gene biomarker in brain diseases. Specifically, we collected multi-omics data to construct eleven networks from different perspectives. M-GBBD extracts the spatial distributions of features from these networks and iteratively optimizes them using Kullback-Leibler divergence to fuse the networks into a common semantic space that represents the gene network for the brain. Subsequently, a graph consisting of both gene and large-scale disease proximity networks learns representations through graph convolution techniques and predicts whether a gene is associated which brain diseases while providing associated scores. Experimental results demonstrate that M-GBBD outperforms several baseline methods. Furthermore, our analysis supported by bioinformatics revealed CAMP as a significantly associated gene with Alzheimer's disease identified by M-GBBD.

CONCLUSION

Collectively, M-GBBD provides valuable insights into identifying gene biomarkers for brain diseases and serves as a promising framework for brain networks representation learning.

LRP10 and α-synuclein transmission in Lewy body diseases

Autosomal dominant variants in LRP10 have been identified in patients with Lewy body diseases (LBDs), including Parkinson's disease (PD), Parkinson's disease-dementia (PDD), and dementia with Lewy bodies (DLB). Nevertheless, there is little mechanistic insight into the role of LRP10 in disease pathogenesis. In the brains of control individuals, LRP10 is typically expressed in non-neuronal cells like astrocytes and neurovasculature, but in idiopathic and genetic cases of PD, PDD, and DLB, it is also present in α-synuclein-positive neuronal Lewy bodies. These observations raise the questions of what leads to the accumulation of LRP10 in Lewy bodies and whether a possible interaction between LRP10 and α-synuclein plays a role in disease pathogenesis. Here, we demonstrate that wild-type LRP10 is secreted via extracellular vesicles (EVs) and can be internalised via clathrin-dependent endocytosis. Additionally, we show that LRP10 secretion is highly sensitive to autophagy inhibition, which induces the formation of atypical LRP10 vesicular structures in neurons in human-induced pluripotent stem cells (iPSC)-derived brain organoids. Furthermore, we show that LRP10 overexpression leads to a strong induction of monomeric α-synuclein secretion, together with time-dependent, stress-sensitive changes in intracellular α-synuclein levels. Interestingly, patient-derived astrocytes carrying the c.1424 + 5G > A LRP10 variant secrete aberrant high-molecular-weight species of LRP10 in EV-free media fractions. Finally, we show that this truncated patient-derived LRP10 protein species (LRP10splice) binds to wild-type LRP10, reduces LRP10 wild-type levels, and antagonises the effect of LRP10 on α-synuclein levels and distribution. Together, this work provides initial evidence for a possible functional role of LRP10 in LBDs by modulating intra- and extracellular α-synuclein levels, and pathogenic mechanisms linked to the disease-associated c.1424 + 5G > A LRP10 variant, pointing towards potentially important disease mechanisms in LBDs.

A primate nigrostriatal atlas of neuronal vulnerability and resilience in a model of Parkinson's disease

The degenerative process in Parkinson's disease (PD) causes a progressive loss of dopaminergic neurons (DaNs) in the nigrostriatal system. Resolving the differences in neuronal susceptibility warrants an amenable PD model that, in comparison to post-mortem human specimens, controls for environmental and genetic differences in PD pathogenesis. Here we generated high-quality profiles for 250,173 cells from the substantia nigra (SN) and putamen (PT) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonian macaques and matched controls. Our primate model of parkinsonism recapitulates important pathologic features in nature PD and provides an unbiased view of the axis of neuronal vulnerability and resistance. We identified seven molecularly defined subtypes of nigral DaNs which manifested a gradient of vulnerability and were confirmed by fluorescence-activated nuclei sorting. Neuronal resilience was associated with a FOXP2-centered regulatory pathway shared between PD-resistant DaNs and glutamatergic excitatory neurons, as well as between humans and nonhuman primates. We also discovered activation of immune response common to glial cells of SN and PT, indicating concurrently activated pathways in the nigrostriatal system. Our study provides a unique resource to understand the mechanistic connections between neuronal susceptibility and PD pathophysiology, and to facilitate future biomarker discovery and targeted cell therapy.

Naphthoquinones as a Promising Class of Compounds for Facing the Challenge of Parkinson's Disease

Parkinson's disease (PD) is a degenerative disease that affects approximately 6.1 million people and is primarily caused by the loss of dopaminergic neurons. Naphthoquinones have several biological activities explored in the literature, including neuroprotective effects. Therefore, this review shows an overview of naphthoquinones with neuroprotective effects, such as shikonin, plumbagin and vitamin K, that prevented oxidative stress, in addition to multiple mechanisms. Synthetic naphthoquinones with inhibitory activity on the P2X7 receptor were also found, leading to a neuroprotective effect on Neuro-2a cells. It was found that naphthazarin can act as inhibitors of the MAO-B enzyme. Vitamin K and synthetic naphthoquinones hybrids with tryptophan or dopamine showed inhibition of the aggregation of α-synuclein. Synthetic derivatives of juglone and naphthazarin were able to protect Neuro-2a cells against neurodegenerative effects of neurotoxins. In addition, routes for producing synthetic derivatives were also discussed. With the data presented, 1,4-naphthoquinones can be considered as a promising class in the treatment of PD and this review aims to assist the scientific community in the application of these compounds. The derivatives presented can also support further research that explores their structures as synthetic platforms, in addition to helping to understand the interaction of naphthoquinones with biological targets related to PD.

Synucleinopathies: Intrinsic and Extrinsic Factors

α-Synucleinopathies are a group of neurodegenerative disorders characterized by alterations in α-synuclein (α-syn), a protein associated with membrane phospholipids, whose precise function in normal cells is still unknown. These kinds of diseases are caused by multiple factors, but the regulation of the α-syn gene is believed to play a central role in the pathology of these disorders; therefore, the α-syn gene is one of the most studied genes. α-Synucleinopathies are complex disorders that derive from the interaction between genetic and environmental factors. Here, we offer an update on the landscape of the epigenetic regulation of α-syn gene expression that has been linked with α-synucleinopathies. We also delve into the reciprocal influence between epigenetic modifications and other factors related to these disorders, such as posttranslational modifications, microbiota participation, interactions with lipids, neuroinflammation and oxidative stress, to promote α-syn aggregation by acting on the transcription and/or translation of the α-syn gene.

Reprogramming iPSCs to study age-related diseases: Models, therapeutics, and clinical trials

The unprecedented rise in life expectancy observed in the last decades is leading to a global increase in the ageing population, and age-associated diseases became an increasing societal, economic, and medical burden. This has boosted major efforts in the scientific and medical research communities to develop and improve therapies to delay ageing and age-associated functional decline and diseases, and to expand health span. The establishment of induced pluripotent stem cells (iPSCs) by reprogramming human somatic cells has revolutionised the modelling and understanding of human diseases. iPSCs have a major advantage relative to other human pluripotent stem cells as their obtention does not require the destruction of embryos like embryonic stem cells do, and do not have a limited proliferation or differentiation potential as adult stem cells. Besides, iPSCs can be generated from somatic cells from healthy individuals or patients, which makes iPSC technology a promising approach to model and decipher the mechanisms underlying the ageing process and age-associated diseases, study drug effects, and develop new therapeutic approaches. This review discusses the advances made in the last decade using iPSC technology to study the most common age-associated diseases, including age-related macular degeneration (AMD), neurodegenerative and cardiovascular diseases, brain stroke, cancer, diabetes, and osteoarthritis.

Sex specific molecular networks and key drivers of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a progressive and age-associated neurodegenerative disorder that affects women disproportionally. However, the underlying mechanisms are poorly characterized. Moreover, while the interplay between sex and ApoE genotype in AD has been investigated, multi-omics studies to understand this interaction are limited. Therefore, we applied systems biology approaches to investigate sex-specific molecular networks of AD.

METHODS

We integrated large-scale human postmortem brain transcriptomic data of AD from two cohorts (MSBB and ROSMAP) via multiscale network analysis and identified key drivers with sexually dimorphic expression patterns and/or different responses to APOE genotypes between sexes. The expression patterns and functional relevance of the top sex-specific network driver of AD were further investigated using postmortem human brain samples and gene perturbation experiments in AD mouse models.

RESULTS

Gene expression changes in AD versus control were identified for each sex. Gene co-expression networks were constructed for each sex to identify AD-associated co-expressed gene modules shared by males and females or specific to each sex. Key network regulators were further identified as potential drivers of sex differences in AD development. LRP10 was identified as a top driver of the sex differences in AD pathogenesis and manifestation. Changes of LRP10 expression at the mRNA and protein levels were further validated in human AD brain samples. Gene perturbation experiments in EFAD mouse models demonstrated that LRP10 differentially affected cognitive function and AD pathology in sex- and APOE genotype-specific manners. A comprehensive mapping of brain cells in LRP10 over-expressed (OE) female E4FAD mice suggested neurons and microglia as the most affected cell populations. The female-specific targets of LRP10 identified from the single cell RNA-sequencing (scRNA-seq) data of the LRP10 OE E4FAD mouse brains were significantly enriched in the LRP10-centered subnetworks in female AD subjects, validating LRP10 as a key network regulator of AD in females. Eight LRP10 binding partners were identified by the yeast two-hybrid system screening, and LRP10 over-expression reduced the association of LRP10 with one binding partner CD34.

CONCLUSIONS

These findings provide insights into key mechanisms mediating sex differences in AD pathogenesis and will facilitate the development of sex- and APOE genotype-specific therapies for AD.

deCLUTTER2+ - a pipeline to analyze calcium traces in a stem cell model for ventral midbrain patterned astrocytes

Astrocytes are the most populous cell type of the human central nervous system and are essential for physiological brain function. Increasing evidence suggests multiple roles for astrocytes in Parkinson's disease, nudging a shift in the research focus, which historically pivoted around ventral midbrain dopaminergic neurons (vmDANs). Studying human astrocytes and other cell types in vivo remains challenging. However, in vitro-reprogrammed human stem cell-based models provide a promising alternative. Here, we describe a novel protocol for astrocyte differentiation from human stem cell-derived vmDAN-generating progenitors. This protocol simulates the regionalization, gliogenic switch, radial migration and final differentiation that occur in the developing human brain. We characterized the morphological, molecular and functional features of these ventral midbrain patterned astrocytes with a broad palette of techniques and identified novel candidate midbrain-astrocyte specific markers. In addition, we developed a new pipeline for calcium imaging data analysis called deCLUTTER2+ (deconvolution of Ca2+ fluorescent patterns) that can be used to discover spontaneous or cue-dependent patterns of Ca2+ transients. Altogether, our protocol enables the characterization of the functional properties of human ventral midbrain patterned astrocytes under physiological conditions and in disease.

Parkinson's disease - genetic cause

PURPOSE OF REVIEW

Our knowledge of the genetic architecture underlying Parkinson's disease has vastly improved in the past quarter century. About 5-10% of all patients suffer from a monogenic form of Parkinson's disease.

RECENT FINDINGS

Mutations in autosomal dominant genes (e.g. SNCA, LRRK2, VPS35) or autosomal recessive genes (e.g. PRKN, PINK1, DJ-1) can cause genetic Parkinson's disease. Recessive DNAJC6 mutations can present predominantly as atypical parkinsonism, but also rarely as typical Parkinson's disease. Majority of Parkinson's disease is genetically complex. Mutation in RIC3, a chaperone of neuronal nicotinic acetylcholine receptor subunit α-7 (CHRNA7), provides strong evidence for the role of cholinergic pathway, for the first time, in cause of Parkinson's disease. X-linked parkinsonism manifests at a young age accompanied by many (atypical) features such as intellectual disability, spasticity, seizures, myoclonus, dystonia, and have poor response to levodopa.

SUMMARY

This review article aims to provide a comprehensive overview on Parkinson's disease genetics. MAPT, which encodes the microtubule associated protein tau, TMEM230, LRP10, NUS1 and ARSA are the five new putative disease-causing genes in Parkinson's disease. The validation of novel genes and its association with Parkinson's disease remains extremely challenging, as genetically affected families are sparse and globally widespread. In the near future, genetic discoveries in Parkinson's disease will influence our ability to predict and prognosticate the disease, help in defining etiological subtypes that are critical in implementation of precision medicine.

Proton pump inhibitor use and the risk for Parkinson's disease: A nationwide population-based study in Taiwan

Previous studies have shown that proton pump inhibitors (PPIs) are associated with an increased risk of dementia. However, little is known about the relationship between PPIs use and Parkinson's disease (PD). This study aimed to examine whether PPI use was associated with an increased risk of developing clinically verified PD. This used data from the Taiwan National Health Insurance Research Database for the period between 1999 and 2011, and patients with PPI use were compared with 1 to 1 propensity score-matched controls by age, sex, cohort entry year, and comorbidity. A multivariate analysis was performed using Cox proportional hazards models to estimate the association between PPI use and PD risk. Subgroup analyses according to sex, age, and comorbidities were also conducted. In total, 56,785 PPI users and 56,785 matched controls were enrolled in this study. In the PPI cohort, 366 patients developed PD during a median follow-up of 5.0 years. The incidence rate of PD was 1.48-fold higher in PPI users than in non-PPI users (90.0 vs 133.2 per 100,000 person-years), with an adjusted hazard ratio of 1.76 (95% confidence interval, 1.48-2.08). In the subgroup analysis, the adjusted risk of PD in the PPI and non-PPI cohorts increased in the subgroups regardless of age, sex, and comorbidities. The results of this retrospective, nationwide, population-based cohort study in Taiwan indicate that PPI use is associated with the risk of PD development. Further mechanistic studies on the effect of PPI on PD are needed.

Genetic analysis of the LRP10 gene in Chinese patients with Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder characterized by resting tremor, bradykinesia, muscle rigidity, and abnormal gait. The low-density lipoprotein receptor-related protein 10 (LRP10) was recently shown to be a causal gene for PD, and different ethnic cohorts have distinct frequencies and spectrum of LRP10 variants.

METHODS

We sequenced the full coding regions and exon-intron boundaries of LRP10 in 129 patients with sporadic Chinese PD to further investigate the connection of LRP10 with PD in a sample of Chinese patients.

RESULTS

In this study, we identified four potentially pathogenic mutations, including one novel mutation of p.Gly328Asp and three known mutations of p.Cys165Tyr, p.Arg230Trp, and p.Arg661His in four of the 129 Chinese patients with PD.

CONCLUSION

According to our study, the LRP10 gene may attribute to PD pathogenesis.

Pathogenic Aspects and Therapeutic Avenues of Autophagy in Parkinson's Disease

The progressive aging of the population and the fact that Parkinson's disease currently does not have any curative treatment turn out to be essential issues in the following years, where research has to play a critical role in developing therapy. Understanding this neurodegenerative disorder keeps advancing, proving the discovery of new pathogenesis-related genes through genome-wide association analysis. Furthermore, the understanding of its close link with the disruption of autophagy mechanisms in the last few years permits the elaboration of new animal models mimicking, through multiple pathways, different aspects of autophagic dysregulation, with the presence of pathological hallmarks, in brain regions affected by Parkinson's disease. The synergic advances in these fields permit the elaboration of multiple therapeutic strategies for restoring autophagy activity. This review discusses the features of Parkinson's disease, the autophagy mechanisms and their involvement in pathogenesis, and the current methods to correct this cellular pathway, from the development of animal models to the potentially curative treatments in the preclinical and clinical phase studies, which are the hope for patients who do not currently have any curative treatment.

Genetic and clinical analysis of TP73 gene in amyotrophic lateral sclerosis patients from Chinese mainland

Introduction

TP73 was recently identified as a novel causative gene for amyotrophic lateral sclerosis (ALS). We aimed to determine the contribution of variations in TP73 in the Chinese ALS population and to further explore the genotype-phenotype correlations.

Methods

We screened rare, putative pathogenic TP73 mutations in a large Chinese ALS cohort and performed association analysis of both rare and common TP73 variations between cases and controls.

Results

Of the 985 ALS patients studied, six rare, heterozygous putative pathogenic variants in TP73 were identified among six unrelated sALS patients. Exon 14 of TP73 might be a mutant hotspot in our cohort. Patients with ALS with only rare, putative pathogenic TP73 mutations exhibited a characteristic clinical profile. Patients harboring multiple mutations in TP73 and other ALS-related genes displayed a significantly earlier onset of ALS. Association analysis revealed that rare TP73 variants in the untranslated regions (UTRs) were enriched among ALS patients; meanwhile, two common variants in the exon-intron boundary were discovered to be associated with ALS.

Discussion

We demonstrate that TP73 variations also have contributed to ALS in the Asian population and broaden the genotypic and phenotypic spectrum of TP73 variants in the ALS-frontotemporal dementia (FTD) spectrum. Furthermore, our findings first suggest that TP73 is not only a causative gene, but also exerts a disease-modifying effect. These results may contribute to a better understanding of the molecular mechanism of ALS.

Biomimetically Engineered Amyloid-Shelled Gold Nanocomplexes for Discovering α-Synuclein Oligomer-Degrading Drugs

The assembly of α-synuclein (αS) oligomers is recognized as the main pathological driver of synucleinopathies. While the elimination of toxic αS oligomers shows promise for the treatment of Parkinson's disease (PD), the discovery of αS oligomer degradation drugs has been hindered by the lack of proper drug screening tools. Here, we report a drug screening platform for monitoring the efficacy of αS-oligomer-degrading drugs using amyloid-shelled gold nanocomplexes (ASGNs). We fabricate ASGNs in the presence of dopamine, mimicking the in vivo generation process of pathological αS oligomers. To test our platform, the first of its kind for PD drugs, we use αS-degrading proteases and various small molecular substances that have shown efficacy in PD treatment. We demonstrate that the ASGN-based in vitro platform has strong potential to discover effective αS-oligomer-targeting drugs, and thus it may reduce the attrition problem in drug discovery for PD treatment.

Advancing the Genetics of Lewy Body Disorders with Disease-Modifying Treatments in Mind

In this article, a caveat for advancing the genetics of Lewy body disorders is raised, given the nosological controversy about whether to consider dementia with Lewy bodies (DLB) and Parkinson's disease (PD) as one entity or two separate entities. Using the framework of the sufficient and component causes model of causation, as further developed into an evolution-based model of causation, it is proposed that a disease of complex etiology is defined as having a relatively high degree of sharing of the component causes (a genetic or environmental factor), that is, a low degree of heterogeneity of the sufficient causes. Based on this definition, only if the sharing of component causes within each of two diseases is similar to their combined sharing can lumping be warranted. However, it is not known whether the separate and combined sharing are similar before conducting the etiologic studies. This means that lumping DLB and PD can be counterproductive as it can decrease the ability to detect component causes despite the potential benefit of conducting studies with larger sample sizes. In turn, this is relevant to the development of disease-modifying treatments, because non-overlapping causal genetic factors may result in distinct pathogenetic pathways providing promising targets for interventions.

Brain sex-dependent alterations after prolonged high fat diet exposure in mice

We examined effects of exposing female and male mice for 33 weeks to 45% or 60% high fat diet (HFD). Males fed with either diet were more vulnerable than females, displaying higher and faster increase in body weight and more elevated cholesterol and liver enzymes levels. Higher glucose metabolism was revealed by PET in the olfactory bulbs of both sexes. However, males also displayed altered anterior cortex and cerebellum metabolism, accompanied by a more prominent brain inflammation relative to females. Although both sexes displayed reduced transcripts of neuronal and synaptic genes in anterior cortex, only males had decreased protein levels of AMPA and NMDA receptors. Oppositely, to anterior cortex, cerebellum of HFD-exposed mice displayed hypometabolism and transcriptional up-regulation of neuronal and synaptic genes. These results indicate that male brain is more susceptible to metabolic changes induced by HFD and that the anterior cortex versus cerebellum display inverse susceptibility to HFD.

Association between the LRP1B and APOE loci in the development of Parkinson's disease dementia

Parkinson's disease is one of the most common age-related neurodegenerative disorders. Although predominantly a motor disorder, cognitive impairment and dementia are important features of Parkinson's disease, particularly in the later stages of the disease. However, the rate of cognitive decline varies among Parkinson's disease patients, and the genetic basis for this heterogeneity is incompletely understood. To explore the genetic factors associated with rate of progression to Parkinson's disease dementia, we performed a genome-wide survival meta-analysis of 3,923 clinically diagnosed Parkinson's disease cases of European ancestry from four longitudinal cohorts. In total, 6.7% of individuals with Parkinson's disease developed dementia during study follow-up, on average 4.4 ± 2.4 years from disease diagnosis. We have identified the APOE ε4 allele as a major risk factor for the conversion to Parkinson's disease dementia [hazards ratio = 2.41 (1.94-3.00), P = 2.32 × 10-15], as well as a new locus within the ApoE and APP receptor LRP1B gene [hazards ratio = 3.23 (2.17-4.81), P = 7.07 × 10-09]. In a candidate gene analysis, GBA variants were also identified to be associated with higher risk of progression to dementia [hazards ratio = 2.02 (1.21-3.32), P = 0.007]. CSF biomarker analysis also implicated the amyloid pathway in Parkinson's disease dementia, with significantly reduced levels of amyloid β42 (P = 0.0012) in Parkinson's disease dementia compared to Parkinson's disease without dementia. These results identify a new candidate gene associated with faster conversion to dementia in Parkinson's disease and suggest that amyloid-targeting therapy may have a role in preventing Parkinson's disease dementia.

Calabria as a Genetic Isolate: A Model for the Study of Neurodegenerative Diseases

Although originally multi-ethnic in its structure, nowadays the Calabria region of southern Italy represents an area with low genetic heterogeneity and a high level of consanguinity that allows rare mutations to be maintained due to the founder effect. A complex research methodology—ranging from clinical activity to the genealogical reconstruction of families/populations across the centuries, the creation of databases, and molecular/genetic research—was modelled on the characteristics of the Calabrian population for more than three decades. This methodology allowed the identification of several novel genetic mutations or variants associated with neurodegenerative diseases. In addition, a higher prevalence of several hereditary neurodegenerative diseases has been reported in this population, such as Alzheimer’s disease, frontotemporal dementia, Parkinson’s disease, Niemann–Pick type C disease, spinocerebellar ataxia, Creutzfeldt–Jakob disease, and Gerstmann–Straussler–Scheinker disease. Here, we summarize and discuss the results of research data supporting the view that Calabria could be considered as a genetic isolate and could represent a model, a sort of outdoor laboratory—similar to very few places in the world—useful for the advancement of knowledge on neurodegenerative diseases.

A multiplex pedigree with pathologically confirmed multiple system atrophy and Parkinson's disease with dementia

Multiple system atrophy is considered a sporadic disease, but neuropathologically confirmed cases with a family history of parkinsonism have been occasionally described. Here we report a North-Bavarian (colloquially, Lion’s tail region) six-generation pedigree, including neuropathologically confirmed multiple system atrophy and Parkinson’s disease with dementia.

Between 2012 and 2020, we examined all living and consenting family members of age and calculated the risk of prodromal Parkinson’s disease in those without overt parkinsonism. The index case and one paternal cousin with Parkinson’s disease with dementia died at follow-up and underwent neuropathological examination. Genetic analysis was performed in both and another family member with Parkinson’s disease. The index case was a female patient with cerebellar variant multiple system atrophy and a positive maternal and paternal family history for Parkinson’s disease and dementia in multiple generations. The families of the index case and her spouse were genealogically related, and one of the spouse's siblings met the criteria for possible prodromal Parkinson’s disease. Neuropathological examination confirmed multiple system atrophy in the index case and advanced Lewy body disease, as well as tau pathology in her cousin. A comprehensive analysis of genes known to cause hereditary forms of parkinsonism or multiple system atrophy lookalikes was unremarkable in the index case and the other two affected family members. Here, we report an extensive European pedigree with multiple system atrophy and Parkinson`s disease suggesting a complex underlying α-synucleinopathy as confirmed on neuropathological examination. The exclusion of known genetic causes of parkinsonism or multiple system atrophy lookalikes suggests that variants in additional, still unknown genes, linked to α-synucleinopathy lesions underlie such neurodegenerative clustering.

Modelling the Human Blood-Brain Barrier in Huntington Disease

While blood–brain barrier (BBB) dysfunction has been described in neurological disorders, including Huntington’s disease (HD), it is not known if endothelial cells themselves are functionally compromised when promoting BBB dysfunction. Furthermore, the underlying mechanisms of BBB dysfunction remain elusive given the limitations with mouse models and post mortem tissue to identify primary deficits. We established models of BBB and undertook a transcriptome and functional analysis of human induced pluripotent stem cell (iPSC)-derived brain-like microvascular endothelial cells (iBMEC) from HD patients or unaffected controls. We demonstrated that HD-iBMECs have abnormalities in barrier properties, as well as in specific BBB functions such as receptor-mediated transcytosis.

Psychosis in Parkinson's Disease: A Lesson from Genetics

Psychosis in Parkinson's disease (PDP) represents a common and debilitating condition that complicates Parkinson's disease (PD), mainly in the later stages. The spectrum of psychotic symptoms are heterogeneous, ranging from minor phenomena of mild illusions, passage hallucinations and sense of presence to severe psychosis consisting of visual hallucinations (and rarely, auditory and tactile or gustatory) and paranoid delusions. PDP is associated with increased caregiver stress, poorer quality of life for patients and carers, reduced survival and risk of institutionalization with a significant burden on the healthcare system. Although several risk factors for PDP development have been identified, such as aging, sleep disturbances, long history of PD, cognitive impairment, depression and visual disorders, the pathophysiology of psychosis in PD is complex and still insufficiently clarified. Additionally, several drugs used to treat PD can aggravate or even precipitate PDP. Herein, we reviewed and critically analyzed recent studies exploring the genetic architecture of psychosis in PD in order to further understand the pathophysiology of PDP, the risk factors as well as the most suitable therapeutic strategies.

Monogenic Parkinson’s Disease: Genotype, Phenotype, Pathophysiology, and Genetic Testing

Parkinson’s disease may be caused by a single pathogenic variant (monogenic) in 5–10% of cases, but investigation of these disorders provides valuable pathophysiological insights. In this review, we discuss each genetic form with a focus on genotype, phenotype, pathophysiology, and the geographic and ethnic distribution. Well-established Parkinson’s disease genes include autosomal dominant forms (SNCA, LRRK2, and VPS35) and autosomal recessive forms (PRKN, PINK1 and DJ1). Furthermore, mutations in the GBA gene are a key risk factor for Parkinson’s disease, and there have been major developments for X-linked dystonia parkinsonism. Moreover, atypical or complex parkinsonism may be due to mutations in genes such as ATP13A2, DCTN1, DNAJC6, FBXO7, PLA2G6, and SYNJ1. Furthermore, numerous genes have recently been implicated in Parkinson’s disease, such as CHCHD2, LRP10, TMEM230, UQCRC1, and VPS13C. Additionally, we discuss the role of heterozygous mutations in autosomal recessive genes, the effect of having mutations in two Parkinson’s disease genes, the outcome of deep brain stimulation, and the role of genetic testing. We highlight that monogenic Parkinson’s disease is influenced by ethnicity and geographical differences, reinforcing the need for global efforts to pool large numbers of patients and identify novel candidate genes.

Current Status of Next-Generation Sequencing Approaches for Candidate Gene Discovery in Familial Parkinson´s Disease

Parkinson’s disease is a neurodegenerative disorder with a heterogeneous genetic etiology. The advent of next-generation sequencing (NGS) technologies has aided novel gene discovery in several complex diseases, including PD. This Perspective article aimed to explore the use of NGS approaches to identify novel loci in familial PD, and to consider their current relevance. A total of 17 studies, spanning various populations (including Asian, Middle Eastern and European ancestry), were identified. All the studies used whole-exome sequencing (WES), with only one study incorporating both WES and whole-genome sequencing. It is worth noting how additional genetic analyses (including linkage analysis, haplotyping and homozygosity mapping) were incorporated to enhance the efficacy of some studies. Also, the use of consanguineous families and the specific search for de novo mutations appeared to facilitate the finding of causal mutations. Across the studies, similarities and differences in downstream analysis methods and the types of bioinformatic tools used, were observed. Although these studies serve as a practical guide for novel gene discovery in familial PD, these approaches have not significantly resolved the “missing heritability” of PD. We speculate that what is needed is the use of third-generation sequencing technologies to identify complex genomic rearrangements and new sequence variation, missed with existing methods. Additionally, the study of ancestrally diverse populations (in particular those of Black African ancestry), with the concomitant optimization and tailoring of sequencing and analytic workflows to these populations, are critical. Only then, will this pave the way for exciting new discoveries in the field.

Revealing a novel contributing landscape of ferroptosis-related genes in Parkinson’s disease

Transcriptomics studies have yielded great insights into disease processes by detecting differentially expressed genes (DEGs). In this study, due to the high heritability of Parkinson’s disease (PD), we performed bioinformatics analyses on nine transcriptomic datasets regarding substantia nigra from Gene Expression Omnibus database, including seven microarray datasets and two next-generation sequencing datasets. As a result, between age-matched PD patients and normal control, we identified 630 DEGs, of which 22 hub DEGs involved in PD or ferroptosis were found to be associated with each other at the transcriptional level and protein-protein interaction network, suggesting their high correlations among these hub genes. Moreover, 16 DEGs were singled out due to their comparable AUC (>0.6) in random forest classifiers, including seven PD-related genes (MAP4K4, LRP10, UCHL1, PAM, RIT2, SNCA, GCH1) and nine ferroptosis-related genes (GCH1, DDIT4, RGS4, MAPK9, CAV1, RELA, DUSP1, ATP6V1G2, ATF4 and ISCU). Furthermore, to probe the potential of those hub genes in predicting the PD progression and survival, we constructed a Cox model featured by an eight-gene signature, including four PD-related genes (SNCA, UCHL1, LRP10, and GCH1) and four ferroptosis-related genes (DDIT4, RGS4, RELA, and CAV1), and validated it successful in an independent dataset, indicating that it would be an effective tool for clinical research to predict PD progression. In conclusion, ferroptosis-related DEGs identified in this study were closely correlated with the known PD-related genes, revealing the involvement of ferroptosis in the development of PD. This study presented the potential of several ferroptosis-related genes as novel clinical biomarkers for PD.

Detection of genomic structure variants associated with wrinkled skin in Xiang pig by next generation sequencing

Wrinkling is prominent manifestation of aging skin. A mutant phenotype characterized by systemic wrinkles and thickened skin was discovered in Xiang pig populations with incidence about 1-3%. The feature in histological structure was epidermal hyperplasia and thickening, collagen fibers disorder. To uncover genetic mechanisms for the mutant phenotype of Xiang pigs with systemic wrinkle (WXP), a genome-wide of structural variations (SVs) in WXP was described by next generation resequencing, taking Xiang pigs (XP) and European pigs (EUP) as compares. Total of 32,308 SVs were detected from three pig groups and 965 SVs were identified specifically from WXP, involving 481 protein-coding genes. These genes were mainly enriched in nuclear structure, ECM components and immunomodulatory pathways. According to gene function and enrichment analysis, we found that 65 candidate SVs in 59 protein genes were probably related with the systemic wrinkle of WXP. Of these, several genes are reported to be associate with aging, such as EIF4G2, NOLC1, XYLT1, FUT8, MDM2 and so on. The insertion/deletion and duplication variations of SVs in these genes resulted in the loss of stop-codon or frameshift mutation, and aberrant alternative splicing of transcripts. These genes are involved in cell lamin filament, intermediate filament cytoskeleton, supramolecular complex, cell differentiation and regulation of macromolecule metabolic process etc. Our study suggested that the loss of function or aberrant expression of these genes lead to structural disorder of nuclear and the extracellular matrix (ECM) in skin cells, which probably was the genetic mechanisms for the mutant phenotype of systemic skin wrinkle of Xiang pig.

Parkinson's disease-dementia in trans LRP10 and GBA variants: Response to deep brain stimulation

We report on a patient with Parkinson's disease and dementia who underwent DBS with excellent response in motor features; the genotype is heterozygous for a novel LRP10 variant in trans with a GBA variant. He had a more severe phenotype compared to the father who only carries the LRP10 variant.

Genotype-Phenotype Correlations in Monogenic Parkinson Disease: A Review on Clinical and Molecular Findings

Parkinson disease (PD) is a complex neurodegenerative disorder, usually with multifactorial etiology. It is characterized by prominent movement disorders and non-motor symptoms. Movement disorders commonly include bradykinesia, rigidity, and resting tremor. Non-motor symptoms can include behavior disorders, sleep disturbances, hyposmia, cognitive impairment, and depression. A fraction of PD cases instead is due to Parkinsonian conditions with Mendelian inheritance. The study of the genetic causes of these phenotypes has shed light onto common pathogenetic mechanisms underlying Parkinsonian conditions. Monogenic Parkinsonisms can present autosomal dominant, autosomal recessive, or even X-linked inheritance patterns. Clinical presentations vary from forms indistinguishable from idiopathic PD to severe childhood-onset conditions with other neurological signs. We provided a comprehensive description of each condition, discussing current knowledge on genotype-phenotype correlations. Despite the broad clinical spectrum and the many genes involved, the phenotype appears to be related to the disrupted cell function and inheritance pattern, and several assumptions about genotype-phenotype correlations can be made. The interest in these assumptions is not merely speculative, in the light of novel promising targeted therapies currently under development.

Low-frequency and rare coding variants of NUS1 contribute to susceptibility and phenotype of Parkinson's disease

NUS1 has been recently identified as a candidate gene for Parkinson's disease (PD). Few studies have examined the association of NUS1 variants with PD susceptibility and phenotypes. In the first cohort, whole-exome sequencing was performed to identify variants in NUS1 exon-coding and exon-intron regions in 1542 cases and 1625 controls. 13 variants were totally detected, of which 10 rare variants and 3 low-frequency variants. Burden analysis showed that rare NUS1 variants significantly enriched in PD (p=0.016). We also performed a meta-analysis based on previous and our studies to correlate NUS1 mutations with PD susceptibility. Integrating our previous cohort (3210 cases and 2807 controls) and the first cohort identified the significant association of rs539668656 with PD risk (odds ratio (OR) = 2.82, p = 0.016). The genotype-phenotype association analysis showed that patients carrying rare variants, or rs539668656 were significantly associated with earlier onset age, depression, emotional impairment and severe disease condition. Our results support the role of NUS1 rare variants and rs539668656 towards PD susceptibility and phenotype.

Influence of the rs6736 Polymorphism on Ischemic Stroke Susceptibility in Han Chinese Individuals via the Disruption of miR-7-1 Binding to the C14orf119 Gene

This study investigates the association between the C14orf119 gene rs6736 polymorphism and ischemic stroke (IS) susceptibility, and explores the influence of the rs6736 polymorphism on the binding between miR-7-1 and the C14orf119 gene. mRNA expression levels were determined in 45 IS patients and 45 matched controls via real-time quantitative PCR. A total of 774 IS patients and 793 matched controls were recruited from a Han Chinese population for genotyping, performed with the Sequenom MassARRAY iPLEX platform. A dual-luciferase reporter assay was used for the analysis of miRNA-mRNA binding. The results showed that the mRNA expression of C14orf119 differed significantly between IS patients and controls (t =  -2.235, P = 0.030). Significant associations were noted between the C14orf119 gene rs6736 polymorphism and IS susceptibility in Han Chinese individuals under the additive model [OR_adj (95% CI) = 0.87 (0.76-1.00) P_adj = 0.048] and dominant model [OR_adj (95% CI) = 0.76 (0.61-0.94), P_adj = 0.014], with adjustment for age and sex. Mutations in the rs6736 polymorphism disrupted the binding of miR-7-1 and the C14orf119 gene. The results of this study show that the rs6736 polymorphism in the 3'-untranslated region of the C14orf119 gene not only is associated with IS but also modifies the binding between miR-7-1 and the C14orf119 gene. The C14orf119 gene may participate in the relationship between IS and miR-7-1.

Role of LRP10 in Parkinson's disease in a Taiwanese cohort

INTRODUCTION

Variants in the low-density lipoprotein receptor-related protein 10 (LRP10), linked to inherited forms of α-synucleinopathies, have been reported. Nine variants of LRP10 were identified in the first such report, and subsequent studies have identified possible pathogenic variants in patients with sporadic Parkinson's disease (PD). Few studies have investigated the role of LRP10 in PD. We sought to validate the role of this gene in Taiwanese patients with PD.

METHODS

In total, 1277 individuals were included in this study (669 had PD and 608 were controls). The entire LRP10 coding exons and exon-intron boundaries were sequenced in 103 probands with early-onset PD or familial PD. We then genotyped the newly identified variants from the 103 patients and previously reported potential pathogenic variants in our cohort. The frequencies of variants were analyzed.

RESULTS

Five new and possibly pathogenic variants were identified initially. In total, 14 potentially pathogenic variants (including nine previously reported and five newly identified variants) were analyzed thereafter. We did not find any significant associations between any variant and the risk of PD. However, c.1424+5delG was identified in a patient with sporadic PD who was diagnosed as having PD and dementia and who had prominent psychiatric symptoms.

CONCLUSION

Although we identified a patient with sporadic PD and dementia carrying a c.1424+5delG variant, our data did not provide sufficient evidence to support the role of LRP10 in PD in Taiwanese adults.

Recalling the pathology of Parkinson's disease; lacking exact figure of prevalence and genetic evidence in Asia with an alarming outcome: A time to step-up

Parkinson's disease (PD) is the second most common and progressive neurodegenerative disease globally, with major symptoms like bradykinesia, impaired posture, and tremor. Several genetic and environmental factors have been identified but elucidating the main factors have been challenging due to the disease's complex nature. Diagnosis, prognosis, and management of such diseases are challenging and require effective targeted attention in developing countries. Recently, PD is growing rapidly in many crowded Asian countries as an alarming threat with inadequate knowledge of its prevalence, genetic architecture, and geographic distribution. This study gave an in-depth overview of the prevalence, incidence and genomic/genetics studies published so far in the Asian population. To the best of our knowledge, PD has increased significantly in several Asian countries, including China, South Korea, Japan, Thailand, and Israel over the past few years, requiring a greater level of care and attention. Genetic screening of families with PD at national levels and establishing an official database of PD cases are essential to get a comprehensive and conclusive view of the exact prevalence and genetic diversity of PD in the Asian population to properly manage and treat the disease.

LRP10 interacts with SORL1 in the intracellular vesicle trafficking pathway in non-neuronal brain cells and localises to Lewy bodies in Parkinson's disease and dementia with Lewy bodies

Loss-of-function variants in the low-density lipoprotein receptor-related protein 10 (LRP10) gene have been associated with autosomal-dominant Parkinson's disease (PD), PD dementia, and dementia with Lewy bodies (DLB). Moreover, LRP10 variants have been found in individuals diagnosed with progressive supranuclear palsy and amyotrophic lateral sclerosis. Despite this genetic evidence, little is known about the expression and function of LRP10 protein in the human brain under physiological or pathological conditions. To better understand how LRP10 variants lead to neurodegeneration, we first performed an in-depth characterisation of LRP10 expression in post-mortem brains and human-induced pluripotent stem cell (iPSC)-derived astrocytes and neurons from control subjects. In adult human brain, LRP10 is mainly expressed in astrocytes and neurovasculature but undetectable in neurons. Similarly, LRP10 is highly expressed in iPSC-derived astrocytes but cannot be observed in iPSC-derived neurons. In astrocytes, LRP10 is present at trans-Golgi network, plasma membrane, retromer, and early endosomes. Interestingly, LRP10 also partially co-localises and interacts with sortilin-related receptor 1 (SORL1). Furthermore, although LRP10 expression and localisation in the substantia nigra of most idiopathic PD and DLB patients and LRP10 variant carriers diagnosed with PD or DLB appeared unchanged compared to control subjects, significantly enlarged LRP10-positive vesicles were detected in a patient carrying the LRP10 p.Arg235Cys variant. Last, LRP10 was detected in Lewy bodies (LB) at late maturation stages in brains from idiopathic PD and DLB patients and in LRP10 variant carriers. In conclusion, high LRP10 expression in non-neuronal cells and undetectable levels in neurons of control subjects indicate that LRP10-mediated pathogenicity is initiated via cell non-autonomous mechanisms, potentially involving the interaction of LRP10 with SORL1 in vesicle trafficking pathways. Together with the specific pattern of LRP10 incorporation into mature LBs, these data support an important mechanistic role for disturbed vesicle trafficking and loss of LRP10 function in neurodegenerative diseases.

Screening of LRP10 mutations in Parkinson's disease patients from Italy

INTRODUCTION

Parkinson's disease (PD) belongs to a family of neurodegenerative diseases characterized by alpha-synuclein accumulation in neurons, whose etiopathogenesis remains largely uncovered. Recently, LRP10 has been associated with PD, Parkinson's disease Dementia (PDD) and Dementia with Lewy Bodies (DLB) by linkage analysis and positional cloning in an Italian family with late-onset PD. After the first characterization of a LRP10 pathogenic variant, other eight mutations have been detected in an international series of 660 probands with either a clinical or pathological diagnosis of PD, PDD or DLB. However, the results of following replication studies were inconclusive and the pathogenic role of LRP10 is still debated. The aim of this study is to sequence the LRP10 gene in an Italian cohort of clinically-diagnosed PD patients and to compare the frequency of the identified variants with the ones found in a large cohort of Italian exomes.

METHODS

A cohort of 664 PD patients was analyzed by targeted Next Generation Sequencing approach. Identified LRP10 variants were subsequently confirmed by Sanger sequencing and searched for in an in-house database including 3596 Italian exomes.

RESULTS

We identified three PD patients carrying a rare heterozygous, potentially pathogenic variant (p.R296C, p.R549Q, p.R661C). None of them was detected in 3596 Italian exomes. Two of them (p.R296C and p.R661C) have been previously reported in one sporadic PD and one definite Progressive supranuclear palsy patients respectively. All three carriers had late-onset PD responsive to levodopa, characterized by both motor and non-motor features, but no cognitive impairment.

CONCLUSION

We report three rare possibly-pathogenic LRP10 variants in PD patients from Italy. Further investigations are required to definitively establish their role in alpha-synucleinopathies.

An integrated genomic approach to dissect the genetic landscape regulating the cell-to-cell transfer of α-synuclein

Neuropathological and experimental evidence suggests that the cell-to-cell transfer of α-synuclein has an important role in the pathogenesis of Parkinson's disease (PD). However, the mechanism underlying this phenomenon is not fully understood. We undertook a small interfering RNA (siRNA), genome-wide screen to identify genes regulating the cell-to-cell transfer of α-synuclein. A genetically encoded reporter, GFP-2A-αSynuclein-RFP, suitable for separating donor and recipient cells, was transiently transfected into HEK cells stably overexpressing α-synuclein. We find that 38 genes regulate the transfer of α-synuclein-RFP, one of which is ITGA8, a candidate gene identified through a recent PD genome-wide association study (GWAS). Weighted gene co-expression network analysis (WGCNA) and weighted protein-protein network interaction analysis (WPPNIA) show that those hits cluster in networks that include known PD genes more frequently than expected by random chance. The findings expand our understanding of the mechanism of α-synuclein spread.

Clinical and Pathological Phenotypes of LRP10 Variant Carriers with Dementia

Background:

Rare variants in the low-density lipoprotein receptor related protein 10 gene (LRP10) have recently been implicated in the etiology of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB).

Objective:

We searched for LRP10 variants in a new series of brain donors with dementia and Lewy pathology (LP) at autopsy, or dementia and parkinsonism without LP but with various other neurodegenerative pathologies.

Methods:

Sanger sequencing of LRP10 was performed in 233 donors collected by the Netherlands Brain Bank.

Results:

Rare, possibly pathogenic heterozygous LRP10 variants were present in three patients: p.Gly453Ser in a patient with mixed Alzheimer’s disease (AD)/Lewy body disease (LBD), p.Arg151Cys in a DLB patient, and p.Gly326Asp in an AD patient without LP. All three patients had a positive family history for dementia or PD.

Conclusion:

Rare LRP10 variants are present in some patients with dementia and different brain pathologies including DLB, mixed AD/LBD, and AD. These findings suggest a role for LRP10 across a broad neurodegenerative spectrum.

Gene4PD: A Comprehensive Genetic Database of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder with a strong genetic component. A growing number of variants and genes have been reported to be associated with PD; however, there is no database that integrate different type of genetic data, and support analyzing of PD-associated genes (PAGs). By systematic review and curation of multiple lines of public studies, we integrate multiple layers of genetic data (rare variants and copy-number variants identified from patients with PD, associated variants identified from genome-wide association studies, differentially expressed genes, and differential DNA methylation genes) and age at onset in PD. We integrated five layers of genetic data (8302 terms) with different levels of evidences from more than 3,000 studies and prioritized 124 PAGs with strong or suggestive evidences. These PAGs were identified to be significantly interacted with each other and formed an interconnected functional network enriched in several functional pathways involved in PD, suggesting these genes may contribute to the pathogenesis of PD. Furthermore, we identified 10 genes were associated with a juvenile-onset (age ≤ 30 years), 11 genes were associated with an early-onset (age of 30–50 years), whereas another 10 genes were associated with a late-onset (age > 50 years). Notably, the AAOs of patients with loss of function variants in five genes were significantly lower than that of patients with deleterious missense variants, while patients with VPS13C (P = 0.01) was opposite. Finally, we developed an online database named Gene4PD (http://genemed.tech/gene4pd) which integrated published genetic data in PD, the PAGs, and 63 popular genomic data sources, as well as an online pipeline for prioritize risk variants in PD. In conclusion, Gene4PD provides researchers and clinicians comprehensive genetic knowledge and analytic platform for PD, and would also improve the understanding of pathogenesis in PD.

Genetic Architecture and Molecular, Imaging and Prodromic Markers in Dementia with Lewy Bodies: State of the Art, Opportunities and Challenges

Dementia with Lewy bodies (DLB) is one of the most common causes of dementia and belongs to the group of α-synucleinopathies. Due to its clinical overlap with other neurodegenerative disorders and its high clinical heterogeneity, the clinical differential diagnosis of DLB from other similar disorders is often difficult and it is frequently underdiagnosed. Moreover, its genetic etiology has been studied only recently due to the unavailability of large cohorts with a certain diagnosis and shows genetic heterogeneity with a rare contribution of pathogenic mutations and relatively common risk factors. The rapid increase in the reported cases of DLB highlights the need for an easy, efficient and accurate diagnosis of the disease in its initial stages in order to halt or delay the progression. The currently used diagnostic methods proposed by the International DLB consortium rely on a list of criteria that comprises both clinical observations and the use of biomarkers. Herein, we summarize the up-to-now reported knowledge on the genetic architecture of DLB and discuss the use of prodromal biomarkers as well as recent promising candidates from alternative body fluids and new imaging techniques.

Mosaic ring chromosome 18 in a Chinese child with epilepsy: a case report and review of the literature

BACKGROUND

Ring chromosome 18 (r[18]) is a rare syndrome in which one or both ends of chromosome 18 are lost and the remaining chromosome rejoins to form ring-shaped figures. It is characterized by developmental delay/cognitive disability, facial dysmorphisms, and immunological problems. The phenotype associated with epilepsy is rare and has not yet been reported in China.

METHODS

We report herein the case of a 12-year-old Chinese girl who presented with typical facial dysmorphisms, developmental delay, cognitive disability, hyperactivity, and epilepsy and discuss the clinical features of r(18) syndromes through comparison with previously described cases worldwide.

RESULTS

We describe the characteristics of all seizures that have been reported in these cases and propose that the appearance of epilepsy in r(18) patients may be associated with the abnormality of chromosome karyotypes. Further studies are warranted to confirm this.

Lipids, lysosomes and mitochondria: insights into Lewy body formation from rare monogenic disorders

Accumulation of the protein α-synuclein into insoluble intracellular deposits termed Lewy bodies (LBs) is the characteristic neuropathological feature of LB diseases, such as Parkinson's disease (PD), Parkinson's disease dementia (PDD) and dementia with LB (DLB). α-Synuclein aggregation is thought to be a critical pathogenic event in the aetiology of LB disease, based on genetic analyses, fundamental studies using model systems, and the observation of LB pathology in post-mortem tissue. However, some monogenic disorders not traditionally characterised as synucleinopathies, such as lysosomal storage disorders, iron storage disorders and mitochondrial diseases, appear disproportionately vulnerable to the deposition of LBs, perhaps suggesting the process of LB formation may be a result of processes perturbed as a result of these conditions. The present review discusses biological pathways common to monogenic disorders associated with LB formation, identifying catabolic processes, particularly related to lipid homeostasis, autophagy and mitochondrial function, as processes that could contribute to LB formation. These findings are discussed in the context of known mediators of α-synuclein aggregation, highlighting the potential influence of impairments to these processes in the aetiology of LB formation.

Prioritization of candidate genes for a South African family with Parkinson's disease using in-silico tools

Parkinson's disease (PD) is a neurodegenerative disorder exhibiting Mendelian inheritance in some families. Next-generation sequencing approaches, including whole exome sequencing (WES), have revolutionized the field of Mendelian disorders and have identified a number of PD genes. We recruited a South African family with autosomal dominant PD and used WES to identify a possible pathogenic mutation. After filtration and prioritization, we found five potential causative variants in CFAP65, RTF1, NRXN2, TEP1 and CCNF. The variant in NRXN2 was selected for further analysis based on consistent prediction of deleteriousness across computational tools, not being present in unaffected family members, ethnic-matched controls or public databases, and its expression in the substantia nigra. A protein model for NRNX2 was created which provided a three-dimensional (3D) structure that satisfied qualitative mean and global model quality assessment scores. Trajectory analysis showed destabilizing effects of the variant on protein structure, indicated by high flexibility of the LNS-6 domain adopting an extended conformation. We also found that the known substrate N-acetyl-D-glucosamine (NAG) contributed to restoration of the structural stability of mutant NRXN2. If NRXN2 is indeed found to be the causal gene, this could reveal a new mechanism for the pathobiology of PD.

TGM6 might not be a specific causative gene for spinocerebellar ataxia resulting from genetic analysis and functional study

OBJECTIVE

To investigate whether TGM6 is a specific causative gene for spinocerebellar ataxia type 35 (SCA35).

MATERIALS AND METHODS

The next-generation sequencing (NGS) data consisted of 47 SCA, 762 non-SCA patients and 2827 normal controls were analyzed. The allele frequencies of low frequent and deleterious TGM6 variants were compared. Functional studies were performed in five widely distributed variants (V314M, R342Q, P347L, V391M, L517W).

RESULTS

Two TGM6 detrimental variants were identified in one SCA patient, 14 in non-SCA patients and 43 in normal controls, the allele frequencies of TGM6 variants did not differ among the SCA and other controls. Seven reported pathogenic variants (c.7 + 1G > T, c.331C > T, c.1171G > A, c.1478C > T, c.1528G > C, c.1550 T > G and c.1722_1724delAGA) were identified in patients with various neurologic diseases or normal controls. All the 5 widely distributed variants led to destabilization and significantly reduction of enzymatic activity of TG6 as the reported pathogenic mutations.

CONCLUSIONS

TGM6 might not be a specific causative gene for SCA35, the relevant clinical consult or diagnostic should be pay more attention.

Defective Lysosomal Lipid Catabolism as a Common Pathogenic Mechanism for Dementia

Dementia poses an ever-growing burden to health care and social services as life expectancies have grown across the world and populations age. The most common forms of dementia are Alzheimer's disease (AD), vascular dementia, frontotemporal dementia (FTD), and Lewy body dementia, which includes Parkinson's disease (PD) dementia and dementia with Lewy bodies (DLB). Genomic studies over the past 3 decades have identified variants in genes regulating lipid transporters and endosomal processes as major risk determinants for AD, with the most significant being inheritance of the ε4 allele of the APOE gene, encoding apolipoprotein E. A recent surge in research on lipid handling and metabolism in glia and neurons has established defective lipid clearance from endolysosomes as a central driver of AD pathogenesis. The most prevalent genetic risk factors for DLB are the APOE ε4 allele, and heterozygous loss of function mutations in the GBA gene, encoding the lysosomal catabolic enzyme glucocerebrosidase; whilst heterozygous mutations in the GRN gene, required for lysosomal catabolism of sphingolipids, are responsible for a significant proportion of FTD cases. Homozygous mutations in the GBA or GRN genes produce the lysosomal storage diseases Gaucher disease and neuronal ceroid lipofuscinosis. Research from mouse and cell culture models, and neuropathological evidence from lysosomal storage diseases, has established that impaired cholesterol or sphingolipid catabolism is sufficient to produce the pathological hallmarks of dementia, indicating that defective lipid catabolism is a common mechanism in the etiology of dementia.

The role of genetics in Parkinson's disease: a large cohort study in Chinese mainland population

This study aimed to determine the mutational spectrum of familial Parkinson's disease and sporadic early-onset Parkinson's disease (sEOPD) in a mainland Chinese population and the clinical features of mutation carriers. We performed multiplex ligation-dependent probe amplification assays and whole-exome sequencing for 1676 unrelated patients with Parkinson's disease in a mainland Chinese population, including 192 probands from families with autosomal-recessive Parkinson's disease, 242 probands from families with autosomal-dominant Parkinson's disease, and 1242 sEOPD patients (age at onset ≤ 50). According to standards and guidelines from the American College of Medical Genetics and Genomics, pathogenic/likely pathogenic variants in 23 known Parkinson's disease-associated genes occurred more frequently in the autosomal-recessive Parkinson's disease cohort (65 of 192, 33.85%) than in the autosomal-dominant Parkinson's disease cohort (10 of 242, 4.13%) and the sEOPD cohort (57 of 1242, 4.59%), which leads to an overall molecular diagnostic yield of 7.88% (132 of 1676). We found that PRKN was the most frequently mutated gene (n = 83, 4.95%) and present the first evidence of an SNCA duplication and LRRK2 p.N1437D variant in mainland China. In addition, several novel pathogenic/likely pathogenic variants including LRRK2 (p.V1447M and p.Y1645S), ATP13A2 (p.R735X and p.A819D), FBXO7 (p.G67E), LRP10 (c.322dupC/p.G109Rfs*51) and TMEM230 (c.429delT/p.P144Qfs*2) were identified in our cohort. Furthermore, the age at onset of the 132 probands with genetic diagnoses (median, 31.5 years) was about 14.5 years earlier than that of patients without molecular diagnoses (i.e. non-carriers, median 46.0 years). Specifically, the age at onset of Parkinson's disease patients with pathogenic/likely pathogenic variants in ATP13A2, PLA2G6, PRKN, or PINK1 was significantly lower than that of non-carriers, while the age at onset of carriers with other gene pathogenic/likely pathogenic variants was similar to that of non-carriers. The clinical spectrum of Parkinson's disease-associated gene carriers in this mainland Chinese population was similar to that of other populations. We also detected 61 probands with GBA possibly pathogenic variants (3.64%) and 59 probands with GBA p.L444P (3.52%). These results shed insight into the genetic spectrum and clinical manifestations of Parkinson's disease in mainland China and expand the existing repertoire of pathogenic or likely pathogenic variants involved in known Parkinson's disease-associated genes. Our data highlight the importance of genetic testing in Parkinson's disease patients with age at onset < 40 years, especially in those from families with a recessive inheritance pattern, who may benefit from early diagnosis and treatment.

Meta-Analysis of Differentially Expressed Genes in the Substantia Nigra in Parkinson's Disease Supports Phenotype-Specific Transcriptome Changes

Background

Studies regarding differentially expressed genes (DEGs) in Parkinson’s disease (PD) have focused on common upstream regulators or dysregulated pathways or ontologies; however, the relationships between DEGs and disease-related or cell type-enriched genes have not been systematically studied. Meta-analysis of DEGs (meta-DEGs) are expected to overcome the limitations, such as replication failure and small sample size of previous studies.

Purpose

Meta-DEGs were performed to investigate dysregulated genes enriched with neurodegenerative disorder causative or risk genes in a phenotype-specific manner.

Methods

Six microarray datasets from PD patients and controls, for which substantia nigra sample transcriptome data were available, were downloaded from the NINDS data repository. Meta-DEGs were performed using two methods, combining p-values and combing effect size, and common DEGs were used for secondary analyses. Gene sets of cell type-enriched or disease-related genes for PD, Alzheimer’s disease (AD), and hereditary progressive ataxia were constructed by curation of public databases and/or published literatures.

Results

Our meta-analyses revealed 449 downregulated and 137 upregulated genes. Overrepresentation analyses with cell type-enriched genes were significant in neuron-enriched genes but not in astrocyte- or microglia-enriched genes. Meta-DEGs were significantly enriched in causative genes for hereditary disorders accompanying parkinsonism but not in genes associated with AD or hereditary progressive ataxia. Enrichment of PD-related genes was highly significant in downregulated DEGs but insignificant in upregulated genes.

Conclusion

Downregulated meta-DEGs were associated with PD-related genes, but not with other neurodegenerative disorder genes. These results highlight disease phenotype-specific changes in dysregulated genes in PD.

EIF2AK2 Missense Variants Associated with Early Onset Generalized Dystonia

Objective

The study was undertaken to identify a monogenic cause of early onset, generalized dystonia.

Methods

Methods consisted of genome‐wide linkage analysis, exome and Sanger sequencing, clinical neurological examination, brain magnetic resonance imaging, and protein expression studies in skin fibroblasts from patients.

Results

We identified a heterozygous variant, c.388G>A, p.Gly130Arg, in the eukaryotic translation initiation factor 2 alpha kinase 2 (EIF2AK2) gene, segregating with early onset isolated generalized dystonia in 5 patients of a Taiwanese family. EIF2AK2 sequencing in 191 unrelated patients with unexplained dystonia yielded 2 unrelated Caucasian patients with an identical heterozygous c.388G>A, p.Gly130Arg variant, occurring de novo in one case, another patient carrying a different heterozygous variant, c.413G>C, p.Gly138Ala, and one last patient, born from consanguineous parents, carrying a third, homozygous variant c.95A>C, p.Asn32Thr. These 3 missense variants are absent from gnomAD, and are located in functional domains of the encoded protein. In 3 patients, additional neurological manifestations were present, including intellectual disability and spasticity. EIF2AK2 encodes a kinase (protein kinase R [PKR]) that phosphorylates eukaryotic translation initiation factor 2 alpha (eIF2α), which orchestrates the cellular stress response. Our expression studies showed abnormally enhanced activation of the cellular stress response, monitored by PKR‐mediated phosphorylation of eIF2α, in fibroblasts from patients with EIF2AK2 variants. Intriguingly, PKR can also be regulated by PRKRA (protein interferon‐inducible double‐stranded RNA‐dependent protein kinase activator A), the product of another gene causing monogenic dystonia.

Interpretation

We identified EIF2AK2 variants implicated in early onset generalized dystonia, which can be dominantly or recessively inherited, or occur de novo. Our findings provide direct evidence for a key role of a dysfunctional eIF2α pathway in the pathogenesis of dystonia. ANN NEUROL 2021;89:485–497

Genetics of Parkinson's disease

Less than a quarter century after the discovery of SNCA as the first attributable gene in Parkinson's disease (PD), our knowledge of the genetic architecture underlying this disease has improved by leaps and bounds. About 5-10% of all patients suffer from a monogenic form of PD where mutations in autosomal-dominant (AD) genes-SNCA, LRRK2, and VPS35 and autosomal recessive (AR) genes-PINK1, DJ-1, and Parkin cause the disease. Whole-exome sequencing has described AR DNAJC6 mutations not only in predominantly atypical, but also in patients with typical PD. Majority of PD is genetically complex, caused by the combination of common genetic variants in concert with environmental factors. Genome-wide association studies have identified twenty six PD risk loci till date; however, these show only moderate effects on the risk for PD. The validation of novel genes and its association with PD remains extremely challenging as families harboring rare genetic variants are sparse and globally widespread. This review article aims to provide a comprehensive overview on PD genetics.