Factors influencing the development of early- or late-onset Parkinson’s disease in a cohort of South African patients

Background. Neurodegenerative disorders such as Parkinson’s disease (PD) contribute significantly to global disease burden. PD can be categorised into early-onset PD (EOPD) with an age at onset (AAO) of ≤50 years and late-onset PD (LOPD) with an AAO of 50 years. Aims. To identify factors influencing EOPD and LOPD development in a group of patients in South Africa (SA). Methods. A total of 397 unrelated PD patients were recruited from the Movement Disorders Clinic at Tygerberg Hospital and via the Parkinson’s Association of SA. Patient demographic and environmental data were recorded and associations with PD onset (EOPD v. LOPD) were analysed with a Pearson’s Chi-squared test. The English- and Afrikaans-speaking (Afrikaner) white patients were analysed separately. Results. Logistic regression analysis showed that ethnicity (

ENIGMA and global neuroscience: A decade of large-scale studies of the brain in health and disease across more than 40 countries.

This review summarizes the last decade of work by the ENIGMA (Enhancing NeuroImaging Genetics through Meta Analysis) Consortium, a global alliance of over 1400 scientists across 43 countries, studying the human brain in health and disease. Building on large-scale genetic studies that discovered the first robustly replicated genetic loci associated with brain metrics, ENIGMA has diversified into over 50 working groups (WGs), pooling worldwide data and expertise to answer fundamental questions in neuroscience, psychiatry, neurology, and genetics. Most ENIGMA WGs focus on specific psychiatric and neurological conditions, other WGs study normal variation due to sex and gender differences, or development and aging; still other WGs develop methodological pipelines and tools to facilitate harmonized analyses of "big data" (i.e., genetic and epigenetic data, multimodal MRI, and electroencephalography data). These international efforts have yielded the largest neuroimaging studies to date in schizophrenia, bipolar disorder, major depressive disorder, post-traumatic stress disorder, substance use disorders, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism spectrum disorders, epilepsy, and 22q11.2 deletion syndrome. More recent ENIGMA WGs have formed to study anxiety disorders, suicidal thoughts and behavior, sleep and insomnia, eating disorders, irritability, brain injury, antisocial personality and conduct disorder, and dissociative identity disorder. Here, we summarize the first decade of ENIGMA's activities and ongoing projects, and describe the successes and challenges encountered along the way. We highlight the advantages of collaborative large-scale coordinated data analyses for testing reproducibility and robustness of findings, offering the opportunity to identify brain systems involved in clinical syndromes across diverse samples and associated genetic, environmental, demographic, cognitive, and psychosocial factors

ENIGMA and global neuroscience: A decade of large-scale studies of the brain in health and disease across more than 40 countries

This review summarizes the last decade of work by the ENIGMA (Enhancing NeuroImaging Genetics through Meta Analysis) Consortium, a global alliance of over 1400 scientists across 43 countries, studying the human brain in health and disease. Building on large-scale genetic studies that discovered the first robustly replicated genetic loci associated with brain metrics, ENIGMA has diversified into over 50 working groups (WGs), pooling worldwide data and expertise to answer fundamental questions in neuroscience, psychiatry, neurology, and genetics. Most ENIGMA WGs focus on specific psychiatric and neurological conditions, other WGs study normal variation due to sex and gender differences, or development and aging; still other WGs develop methodological pipelines and tools to facilitate harmonized analyses of "big data" (i.e., genetic and epigenetic data, multimodal MRI, and electroencephalography data). These international efforts have yielded the largest neuroimaging studies to date in schizophrenia, bipolar disorder, major depressive disorder, post-traumatic stress disorder, substance use disorders, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism spectrum disorders, epilepsy, and 22q11.2 deletion syndrome. More recent ENIGMA WGs have formed to study anxiety disorders, suicidal thoughts and behavior, sleep and insomnia, eating disorders, irritability, brain injury, antisocial personality and conduct disorder, and dissociative identity disorder. Here, we summarize the first decade of ENIGMA's activities and ongoing projects, and describe the successes and challenges encountered along the way. We highlight the advantages of collaborative large-scale coordinated data analyses for testing reproducibility and robustness of findings, offering the opportunity to identify brain systems involved in clinical syndromes across diverse samples and associated genetic, environmental, demographic, cognitive, and psychosocial factors

Analysis of copy number variation and disease mechanisms underlying Parkinson’s disease

Thesis (PhD)--Stellenbosch University, 2016ENGLISH ABSTRACT : Parkinson’s disease (PD) is a neurodegenerative movement disorder characterized by the loss of dopaminergic neurons in the substantia nigra of the midbrain. Although the aetiology of PD is still not fully understood, it is thought to involve a combination of environmental and genetic factors. To date, a number of PD-causing genes have been found. The PINK1 gene is of particular interest for this study, and mutations in this gene result in autosomal recessive inheritance of early onset PD. PINK1 plays a vital role in mitochondrial quality control and homeostasis, and in its absence it is thought to result in an accumulation of dysfunctional mitochondria in neurons, culminating in neuronal cell death. Whilst pharmacological and surgical interventions are available for PD, the current options exhibit adverse side effects with long term treatment. There is a great need to develop new treatments with i. less side effects and ii. that can simultaneously target the multiple pathways associated with this disorder. One molecule is curcumin, the core component of the curry spice turmeric, which is well known for its antioxidant and anti-inflammatory properties and has already been studied for its possible neuroprotective role in Alzheimer’s disease. The aim of the present study was to create a cellular model of PD by decreasing the expression of PINK1 in SH-SY5Y neuroblastoma cells. Thereafter, we aimed to test the protective effects of curcumin on this model in the presence and absence of a known stressor, paraquat. This study also aimed to detect possible copy number variation (CNV) in PINK1 (and other PD-causing genes) in a cohort of South African patients with PD, in order to obtain patient-derived fibroblasts to verify the results obtained from the original cellular model. PINK1 was knocked down using siRNA (Qiagen, USA) in SH-SY5Y neuroblastoma cells, and the knock down was verified by quantitative real time PCR (qRTPCR) and western blotting. Thereafter, PINK1 siRNA cells and control cells were separated into four treatment groups: i. untreated, ii. treated with 25μM paraquat for 24hours, iii. pre-treated with 2μM curcumin for 1hour then treated with 25μM paraquat for 24hours, or iv. treated with 2μM curcumin for 1hour, and various parameters of cellular and mitochondrial function were measured. Cell viability was measured by an MTT assay. Western blot analysis was performed using cleaved PARP and full-length caspase 3 markers to detect levels of apoptosis, and LC3-II and p62 markers to detect autophagic flux. Mitochondrial respiration experiments were completed on the Seahorse XF Analyser using the Mito Stress Test Kit and the Glycolysis Stress Test. Flow cytometry was utilised to measure mitochondrial membrane potential (MMP) using the JC- 1 fluorochrome, and mitochondrial network was analysed by fluorescent microscopy. For CNV detection, MLPA was performed on 210 South African PD patients and putative mutations were verified by qRTPCR on the Lightcycler 96. PINK1 was successfully knocked down at a gene and protein expression level. The PINK1 siRNA cells exhibited a significant decrease in cell viability (p=0.0036), and an increase in apoptosis (p=0.0144). A decrease in PINK1 expression also resulted in significantly decreased MMP (p=0.0008), mitochondrial respiration (p=0.0015), ATP production (p=0.002) and glycolytic capacity (p=0.0445). No significant changes were observed in the connectivity of the mitochondrial network, but autophagic flux was significantly increased in the PINK1 siRNA cells, as detected by increased LC3-II levels (p=0.0152). As expected, paraquat-treated cells exhibited decreased cell viability, increased apoptosis, decreased MMP, autophagic flux, and a more fragmented mitochondrial network. Paraquat treatment therefore successfully acted as a stressor on the cells. Curcumin pre-treatment followed by paraquat treatment rescued cell viability in control cells (p=0.003), and significantly decreased apoptosis in PINK1 siRNA cells (p=0.0018). Curcumin protected mitochondrial dysfunction in PINK1 siRNA cells by increasing MMP (p=0.0472) and maximal respiration (p=0.0014), as well as significantly increasing MMP (p=0.0307) and maximal respiration (p=0.032) in control cells. Additionally, curcumin treatment resulted in increased autophagic flux (p=0.0017) in stressed control cells. These results highlight a protective effect of curcumin against paraquat and against the damaging effects on the mitochondria in cells with decreased PINK1 expression. Lastly, MLPA analysis did not reveal any PINK1 CNV mutations in a total of 210 South African PD patients, and fibroblasts were therefore not obtained. A number of false positive mutations were identified that were not verified by qRTPCR. A common polymorphism M192L resulting in a false positive PARK2 exon 5 deletion was found in a number of patients, all of whom were of Black or Mixed Ancestry ethnic groups. One patient was shown to harbour a heterozygous deletion in PARK2 exon 4. In conclusion, PINK1 siRNA-mediated knock down in SH-SY5Y neuroblastoma cells can be used as a model of PD to study aspects of mitochondrial dysfunction. Furthermore, curcumin should be considered as a possible therapeutic target for PD, as it exhibits protective effects against paraquat at a mitochondrial level. Given the low toxicity of curcumin, and the fact that it is already part of a dietary regimen in most populations worldwide, further studies on elucidating its biochemical and cellular properties are therefore warranted. The use of natural compounds such as curcumin as therapeutic agents is currently a topical and fast-growing area of research, and holds much promise for clinical application in various diseases including neurodegenerative disorders such as Alzheimer’s disease and PD.AFRIKAANSE OPSOMMING : Parkinson se siekte (PD) is 'n neurodegeneratiewe beweging versteuring wat gekenmerk word deur die verlies van dopaminergiese neurone in die brein. Hoewel die etiologie van PD nog nie ten volle verstaan is nie, is daar denke dat dit 'n kombinasie van die omgewing en genetiese faktore behels. Tot dus ver is daar nog net ‘n aantal gene wat PD-veroorsaak gevind. Die PINK1 geen is van besondere belang vir hierdie studie, en mutasies in dié geen veroorsaak outosomale resessiewe oorerwing van vroeë aanvang PD. PINK1 speel 'n belangrike rol in die mitochondriale gehaltebeheer en homeostase, en in sy afwesigheid is dit gedink om te lei tot 'n opeenhoping van disfunksionele mitochondria in die neurone, wat kulmineer in neuronale sel dood. Terwyl farmakologiese en chirurgiese ingrepe beskikbaar is vir PD, die huidige opsies wys duidelike newe-effekte met lang termyn behandeling. Daar is 'n groot behoefte om nuwe behandelings te ontwikkel met i. minder newe-effekte en ii. wat gelyktydig die verskeie paaie wat verband hou met hierdie versteuring kan teiken. Een molekule is curcumin, die hoof komponent van die kerrie spesery borrie, wat wel bekend is vir, sy anti-oksidant en anti-inflammatoriese eienskappe, en is reeds bestudeer vir sy moontlike beskermende rol in Alzheimer’s se siekte. Die doel van hierdie projek is om 'n sellulêre model van PD te skep deur die vermindering van die uitdrukking van PINK1 in SH-SY5Y neuroblastoom selle. Ons daarop gemik om die beskermende effek van curcumin te toets in die teenwoordigheid en afwesigheid van 'n bekende stressor, parakwat in ons model. ‘n Additionele doelwit is om moontlike kopiegetal variasie (CNV) in die PINK1 gene (en ander PD veroorsaakende gene) op te tel in 'n groep van die Suid-Afrikaanse pasiënte met PD. Die doel van hierdie was om pasiënt-afgeleibare fibroblaste te kry om die resultate te verifieer vanuit die oorspronklike model. SH-SY5Y neuroblastoom selle was gekweek, en PINK1 is platgeslaan deur gebruik te maak van siRNA en HiPerfect Transfectie Reagens (Qiagen, VSA). Klop van PINK1 is bevestig deur kwantitatiewe real time PCR (qRTPCR) en westelike klad. Daarna, PINK1 siRNA selle en beheer selle was óf i. nie behandel nie, ii. behandel met 25 um paraquat vir 24 uur per dag, iii. vooraf behandel met 2μM curcumin vir 1 uur dan behandel met 25 um paraquat vir 24 uur per dag, of iv. behandel met 2μM curcumin vir 1 uur, en verskeie parameters van sellulêre en mitochondriale funksie is gemeet. Lewensvatbaarheid van die selle is gemeet deur 'n MTT toets. Westerne klad analise is uitgevoer met behulp van gekleefde PARP en vollengte caspase 3 merkers om die vlakke van apoptose te meet, en LC3-II en p62 merkers was gebruik om autophagic vloed op te spoor. Mitochondriale respirasie eksperimente is voltooi op die Seahorse XF Analyser met behulp van die Mito Stres Test Kit en die Glikolise Stres Toets. Vloeisitometrie is gebruik om mitochondriale membraan potensiaal (MMP) te meet met behulp van die JC-1 fluorochrome en die mitochondriale netwerk is geanaliseer deur fluorescent mikroskopie. Vir CNV opsporing, was MLPA uitgevoer op 210 Suid-Afrikaanse PD pasiënte en vermeende mutasies is bevestig deur qRTPCR op die Lightcycler 96. PINK1 is suksesvol platgeslaan op 'n geen en proteïen uitdrukking vlak. Die PINK1 siRNA selle betoon 'n beduidende afname in lewensvatbaarheid sel (p = 0.0036), en 'n toename in apoptose (p=0.0144). 'n Afname in PINK1 uitdrukking het ook daartoe gelei na ‘n beduidende vermindering in MMP (p=0.0008), mitochondriale respirasie (p=0.0015), ATP produksie (p=0.002) en glikolitiese kapasiteit (p=0.0445). Geen beduidende veranderinge is waargeneem in die verbinding van die mitochondriale netwerk nie, maar autophagic vloed het aansienlik toegeneem in die PINK1 siRNA selle, soos waargeneem deur verhoogde vlakke in LC3-II (p=0.0152). Soos verwag betoon, paraquat behandelde selle ‘n afname in sel lewensvatbaarheid, verhoogde apoptose, afname in MMP, autophagic vloed, en 'n meer gefragmenteerde mitochondriale netwerk. Parakwat behandeling het dus suksesvol opgetree as 'n stressor op die selle. Curcumin voorafbehandeling gevolg deur paraquat behandeling het sel lewensvatbaarheid gered in beheer selle (p=0.003), en aansienlik verminderde apoptose in PINK1 siRNA selle (p=0.0018) betoon. Curcumin beskerm mitochondriale disfunksie deur die verhoging van MMP (p=0.0472, p=0.0307) en maksimale respirasie (p=0.0014, p=0.032) in beide PINK1 siRNA en beheer selle. Additioneel, het curcumin behandeling gelei tot ‘n verhoogde autophagic vloed (p=0.0017) in onderdrukte beheer selle. Hierdie resultate beklemtoon die beskermende effek van curcumin teen parakwat en teen die skadelike resultaat op die mitochondria in die selle met verlaagde PINK1 uitdrukking. Laastens, MLPA ontleding het nie PINK1 CNV mutasies openbaar in 'n totaal van 210 Suid-Afrikaanse PD pasiënte, en fibroblaste is dus nie verkry nie. 'n Aantal vals positiewe mutasies is geïdentifiseer wat nie geverifieer is deur qRTPCR. 'n Algemene polimorfisme M192L is in 'n aantal pasiënte gevind wat in 'n vals positiewe PARK2 ekson 5 eliminasie ontaard, waarvan almal swart of gemengde afkoms etiese groepe is. Een pasiënt het getoon dat 'n heterosigotiese eliminasie in PARK2 ekson 4 bevind is. Ten slotte, PINK1 siRNA-gemedieerde wat platgeslaan is in SH-SY5Y neuroblastoom selle kan gebruik word as 'n model van PD om aspekte van mitochondriale disfunksie te bestudeer. Verder moet curcumin beskou word as 'n moontlike terapeutiese teiken vir PD, omdat dit beskermende effekte teen parakwat op 'n mitochondriale vlak vertoon. Gegewe die lae toksisiteit van curcumin en die feit dat dit reeds ‘n deel vorm van die dieët in meeste populasie groepe wêreldwyd, is verdere studies op die biochemiese en sellulêre eienskappe daarvan benodig. Die gebruik van natuurlike komposisies, soos curcumin as ‘n terapeutiese middel is tans ‘n relevante en vinnig groeiende area van navorsing en toon baie belofte vir kliniese toepassing in verskeie siektes soos Alzheimer’s siekte en PD

An investigation into the role of mitochondrial dysfunction in South African Parkinson’s disease patients

Thesis (MScMedSC)--Stellenbosch University, 2012.BibliographyENGLISH ABSTRACT: Parkinson’s disease (PD) is a neurodegenerative movement disorder characterized by the loss of dopaminergic neurons in the substantia nigra of the midbrain. Although the aetiology of PD is still not fully understood, it is thought to involve a combination of environmental (such as exposure to pesticides and neurotoxins) and genetic factors. A number of PD-causing genes have been found including SNCA, LRRK2, EIF4G1 and VPS35 (for autosomal dominant forms of PD) and parkin, PINK1, DJ-1 and ATP13A2 (for autosomal recessive forms of PD – arPD). Mutations in the parkin gene are the predominant cause of arPD. Parkin plays a role in the ubiquitin-proteasomal system which degrades damaged and unwanted proteins in the cell and it is also thought to be involved in maintaining healthy mitochondria. Numerous studies have implicated mitochondrial function in the pathogenesis of PD. Therefore the aim of the present study was to investigate the role of mitochondrial dysfunction in PD patients with parkin-null mutations. Four South African PD patients, each harbouring two parkin-null mutations, were recruited for this study. A muscle biopsy was performed for analysis of mitochondrial morphology using histology and transmission electron microscopy (TEM). Skin biopsies were taken, from which fibroblasts were cultured. These fibroblasts were used in i) mitochondrial morphological assessments using TEM, ii) mitochondrial network analysis, iii) functional studies via ROS measurement and iv) analysis of the proteome using a LTQ Orbitrap Velos mass spectrometer. In addition, RNA was isolated from peripheral blood samples for gene expression studies using the RT² Profiler PCR Array (SABiosciences, USA) and the RT² PCR Primer Assay (SABiosciences, USA). Heterozygous family members (carriers) and wild-type controls were also recruited for this study. Results from the histological and TEM analysis from the muscle biopsy observed subtle mitochondrial changes including the presence of type II fibres, atrophic fibres, the presence of lipids, and wrinkling of the sarcolemmal membrane. Enlarged mitochondria were also observed in one patient. TEM analysis on the patient’s fibroblasts observed an increase in the number of electron dense vacuoles, speculated to be autolysosomes. The mitochondrial network in two of the patients’ fibroblasts showed fragmented and dot-like networks which are indicative of damaged mitochondria. An increase in mitochondrial ROS levels was observed in three of the four patients. Expression studies found down-regulation of 14 genes from four of the five mitochondrial complexes and a total of 688 proteins were found only in the control and not in the patient fibroblasts. Some of these proteins are known to be part of the ‘mitochondrial dysfunction’ pathway. Taken together, these results indicate that the absence of parkin results in a number of mitochondrial alterations. Based on these findings, a model of PD was proposed: It is speculated that when parkin is absent, electron transport chain complex genes are down-regulated. This results in impaired oxidative phosphorylation, causing an increase in the production of mitochondrial ROS and subsequent oxidative stress. Mitochondria are then damaged; resulting in the fragmentation of the mitochondrial network. The impaired mitochondria are thus tagged for degradation, causing the recruitment of autolysosomes which engulf the mitochondria via mitophagy. Ultimately, as the compensatory mechanisms fail, this triggers the consequential cascade of cellular apoptotic events. This study has elucidated the effect of parkin on the mitochondria, and can act as a ‘stepping stone’ towards future development of therapeutic strategies and/or biochemical markers that will benefit not only patients with PD but also other neurodegenerative disorders.AFRIKAANSE OPSOMMING: Parkinson se siekte (PS) is ‘n neurodegeneratiewe bewegings-afwyking gedefineer deur die verlies van dopaminergiese neurone in die substantia nigra van die midde brein. Alhoewel die spesifieke oorsprong van die afwyking nog nie ten volle begryp is nie, word bydraes van beide omgewings faktore (bv. blootstelling aan plaagdoders en neurotoksienes) asook genetiese faktore gespekuleer. Vanuit ‘n genetiese aspek is ‘n aantal gene al geassosieer met PS. Hierdie gene sluit in SNCA, LRRK2, EIF4G1 en VPS35 (vir outosomale dominante vorms van PS) en parkin, PINK1, DJ-1, en ATP13A2 (vir outosomale resessiewe vorms van PS - orPS). Mutasies in die parkin geen is aangedui as die hoof oorsaak van orPS. Parkin speel ‘n rol in die ubiquitine-proteasomale sisteem wat beskadige en ongewensde proteïne binne in die sel verwyder en is verdink om by te dra tot die instandhouding van gesonde mitokondria. Mitokondriese wanfunksionering is ook deur talle studies gewys as ‘n bydraende faktor in die patologie van PS. Die doel van die studie is om ondersoek in te stel tot die spesifieke rol wat mitokondriese wanfunsionering speel in PS pasiënte met parkin-nul mutasies. Vier Suid-Afrikaanse PS-pasiënte, elk met twee parkin-nul mutasies, is gebruik vir die studie. Deur middel van spierbiopsies is monsters verkry vir mitokondriese morfologiese analises met behulp van histologiese en elektron-oordrag mikroskopie tegnieke (TEM). Vel biopsies is ook geneem en fibroblaste is gekweek vir die gebruik in: i) mitokondriese morfologiese assesering; ii) mitokondriese netwerk analiese; iii) funksionele studies waar vlakke van reaktiewe suurstof spesies (ROS) gemeet is; iv) proteoom analiese met behup van ‘n LTQ Orbitrap Velos massa spektrometer. RNA is ook geisoleer vanaf perifere bloedmonsters vir die gebruik in geen-uitdrukkings studies met behulp van ‘n RT² Profiler PCR Array en ‘n RT² Primer Assay. Selle vanaf famielie lede wat heterosigotiese draers is van die mutasie, asook normale (geen parkin mutasie) selle is gebruik as kontroles in die studie. TEM resultate vanaf die spier monsters het subtiele mitokondriese veranderinge getoon. Hierdie sluit in die teenwoordigheid van tipe II vesels, atrofiese vesels, teenwoordigheid van lipiedes, assook waarnemings van rimpeling van die sarcolemmal membraan. Vergrote mitokondrias is ook in een van die pasiënte opgelet. TEM resultate vanaf die fibroblaste het toename in die aantal elektron-digte vakuole vertoon, moontlik geidentifiseer as autolisosome. Gefragmenteerde en onderbreekte mitokondria netwerke is gelet tydens netwerk analiese van die fibroblaste, ‘n indikasie van beskadigde mitokondria. ‘n Toename in mitokondriese ROS vlakke is gevind in drie van die vier pasiënte. Af-regulering van 14 gene, geassosieerd met vier uit die vyf mitokondria komplekse, is verneem tydens die geen-uitdrukkings studie. Saam met dit is ‘n totaal van 688 proteïene geidentifiseer wat slegs teenwoordig is in die kontrole monsters en nie in die pasiënt monsters nie. Hierdie proteïene is almal uitgedruk en betrokke in die mitokondriese wanfunsionerings-weë. Hierdie resultate dui dat die afwesigheid van parkin mitokondriese afwykings tot gevolg het wat kan lei tot die afsterwing van selle. Dit dra ook by tot die vorming van ‘n beter-verstaande siekte-model vir PS: Mutasies in parkin (wat lei tot die afwesigheid van parkin) kan dus moontlik lei tot die af-regulasie van gene geassosieerd met die elektron-vervoer ketting komplekse in die mitokondria. Dit lei tot gebrekkige oksidatiewe fosforilering en veroorsaak ‘n toename in die vorming van ROS, wat dan ‘n toename in oksidatiewe stres binne in die sel tot gevolg het. Uiteindelik lei dit dus tot die beskadiging van die mitokondria wat gepaard gaan met fragmentering van die mitokondriese netwerk. Beskadigde mitokondrias word geetiketeer vir afbraking. Hierdie etiketering aktiveer omringende autophagosome wat die beskadigde mitokondrias dan verwyder deur middel van ‘n verswelgende proses genaamd mitophagy. Dit veroorsaak die aktivering van ‘n aantal gekorreleerde sellulêre prosesse wat lei tot apoptose (afsterwing van die sel). Hierdie studie dra by tot die verklaring van die spesifieke effek wat parkin mutasies het op die funksionering van die mitokondria. Resultate hier lê ook die grondslag vir toekomstige studies met die doel tot die ontwikkeling van terapeutiese strategeë en biochemiese merkers wat kan bydrae tot die genesing van beide pasiënte met PS, asook pasiënte met ander neurodegeneratiewe afwykings

Altered mitochondrial respiration and other features of mitochondrial function in parkin-mutant fibroblasts from parkinson’s disease patients

CITATION: Haylett, W., et al. 2016. Altered mitochondrial respiration and other features of mitochondrial function in parkin-mutant fibroblasts from parkinson’s disease patients. Parkinson’s Disease, 2016 (Article ID 1819209), doi:10.1155/2016/1819209.The original publication is available at https://www.hindawi.comMutations in the parkin gene are the most common cause of early-onset Parkinson’s disease (PD). Parkin, an E3 ubiquitin ligase, is involved in respiratory chain function, mitophagy, and mitochondrial dynamics. Human cellular models with parkin null mutations are particularly valuable for investigating the mitochondrial functions of parkin. However, published results reporting on patient-derived parkin-mutant fibroblasts have been inconsistent. This study aimed to functionally compare parkin-mutant fibroblasts from PD patients with wild-type control fibroblasts using a variety of assays to gain a better understanding of the role of mitochondrial dysfunction in PD. To this end, dermal fibroblasts were obtained from three PD patients with homozygous whole exon deletions in parkin and three unaffected controls. Assays of mitochondrial respiration, mitochondrial network integrity, mitochondrial membrane potential, and cell growth were performed as informative markers of mitochondrial function. Surprisingly, it was found that mitochondrial respiratory rates were markedly higher in the parkin-mutant fibroblasts compared to control fibroblasts (p = 0.0093), while exhibiting more fragmented mitochondrial networks (). Moreover, cell growth of the parkin-mutant fibroblasts was significantly higher than that of controls (). These unanticipated findings are suggestive of a compensatory mechanism to preserve mitochondrial function and quality control in the absence of parkin in fibroblasts, which warrants further investigation.https://www.hindawi.com/journals/pd/2016/1819209/Publisher's versio

Evidence for a common biological pathway linking three Parkinson's Disease causing genes

Parkinson’s disease (PD) is characterised by the loss of dopaminergic neurons in the midbrain. Autosomal recessive, early-onset cases of PD are predominantly caused by mutations in the parkin, PINK1 and DJ-1 genes. Animal and cellular models have verified a direct link between parkin and PINK1, whereby PINK1 phosphorylates and activates parkin at the outer mitochondrial membrane, resulting in removal of dysfunctional mitochondria via mitophagy. Despite the overwhelming evidence for this interaction, few studies have been able to identify a link for DJ-1 with parkin or PINK1. The aim of this review is to summarise the functions of these three proteins, and to analyse the existing evidence for direct and indirect interactions between them. DJ-1 is able to rescue the phenotype of PINK1 knock-out Drosophila models, but not of parkin knock-outs, suggesting that DJ-1 may act in a parallel pathway to that of the PINK1/parkin pathway. To further elucidate a commonality between these three proteins, bioinformatics analysis was performed which found that Miro (RHOT1) interacts with parkin and PINK1, and HSPA4 interacts with all three proteins. Furthermore, 30 transcription factors were found to be common amongst all three proteins, with many of them being involved in transcriptional regulation. Interestingly, expression of these proteins and their associated transcription factors are found to be significantly down-regulated in PD patients compared to healthy controls. In summary, this review provides insight into common pathways linking three PD-causing genes and highlights some key questions; the answers to which may provide critical insight into the disease process.Web of Scienc

Genetic contributions to autism spectrum disorder

Autism spectrum disorder (autism) is a heterogeneous group of neurodevelopmental conditions characterized by early childhood-onset impairments in communication and social interaction alongside restricted and repetitive behaviors and interests. This review summarizes recent developments in human genetics research in autism, complemented by epigenetic and transcriptomic findings. The clinical heterogeneity of autism is mirrored by a complex genetic architecture involving several types of common and rare variants, ranging from point mutations to large copy number variants, and either inherited or spontaneous (de novo). More than 100 risk genes have been implicated by rare, often de novo, potentially damaging mutations in highly constrained genes. These account for substantial individual risk but a small proportion of the population risk. In contrast, most of the genetic risk is attributable to common inherited variants acting en masse, each individually with small effects. Studies have identified a handful of robustly associated common variants. Different risk genes converge on the same mechanisms, such as gene regulation and synaptic connectivity. These mechanisms are also implicated by genes that are epigenetically and transcriptionally dysregulated in autism. Major challenges to understanding the biological mechanisms include substantial phenotypic heterogeneity, large locus heterogeneity, variable penetrance, and widespread pleiotropy. Considerable increases in sample sizes are needed to better understand the hundreds or thousands of common and rare genetic variants involved. Future research should integrate common and rare variant research, multi-omics data including genomics, epigenomics, and transcriptomics, and refined phenotype assessment with multidimensional and longitudinal measures

Factors influencing the development of early- or late-onset Parkinson's disease in a cohort of South African patients

CITATION: Van der Merwe, C. et al. 2012. Factors influencing the development of early- or late-onset Parkinson's disease in a cohort of South African patients. South African Medical Journal, 102(11):848-851, doi:10.7196/SAMJ.5879.The original publication is available at http://www.samj.org.zaBackground. Neurodegenerative disorders such as Parkinson’s disease (PD) contribute significantly to global disease burden. PD can be categorised into early-onset PD (EOPD) with an age at onset (AAO) of ≤50 years and late-onset PD (LOPD) with an AAO of 50 years. Aims. To identify factors influencing EOPD and LOPD development in a group of patients in South Africa (SA). Methods. A total of 397 unrelated PD patients were recruited from the Movement Disorders Clinic at Tygerberg Hospital and via the Parkinson’s Association of SA. Patient demographic and environmental data were recorded and associations with PD onset (EOPD v. LOPD) were analysed with a Pearson’s Chi-squared test. The English- and Afrikaans-speaking (Afrikaner) white patients were analysed separately. Results. Logistic regression analysis showed that ethnicity (p<0.001) and family history (p=0.004) were independently associated with AAO of PD. Average AAO was younger in black, coloured and Afrikaner patients than English-speaking white patients. A positive family history of PD, seen in 31.1% of LOPD patients, was associated with a younger AAO in the study population. Conclusions. These associations may be attributed to specific genetic and/or environmental risk factors that increase PD susceptibility and influence the clinical course of the disorder. More studies on PD in the unique SA populations are required to provide novel insights into mechanisms underlying this debilitating condition.http://www.samj.org.za/index.php/samj/article/view/5879Publisher's versio

P523: The NeuroDev Study: Genetic characterization of neurodevelopmental disorders in African populations

Introduction: Genetic association studies have made significant contributions to our understanding of the etiology of neurodevelopmental disorders (NDDs). However, the vast majority of these studies have focused on populations of European ancestry, and few include individuals from the African continent, creating substantial gaps in our understanding of the expression and variability of such disorders. Further, individuals of African ancestry are less likely to receive accurate genetic diagnoses and benefit from advances in genomic science and medicine. The NeuroDev study aims to address this diversity gap through detailed phenotypic and genetic characterization of children with NDDs from South Africa and Kenya. Here, we present the genetic findings from the NeuroDev pilot study, which consists of the study’s first 99 parent-child trios. Methods: Exome sequencing and data processing were performed by the Genomics Platform at the Broad Institute of MIT and Harvard, and the resulting data was uploaded to the seqr platform for analysis. A standard analysis protocol, which involves both de novo/dominant and recessive searches, was deployed across all trios to identify potential causal variants. When evaluating variants in established disease genes, NeuroDev phenotype data was assessed for possible consistencies with known clinical presentations for that gene, bearing in mind potential deviations from expectation due to ancestry. Genes not yet associated with a well-established human disease were evaluated using a variety of sources of evidence, and candidate variants were shared with the Matchmaker Ex- change (MME) network to identify additional cases with similar genotypic and phenotypic profiles. Potential causal variants were subjected to rigorous evaluation of the evidence for pathogenicity following the ACMG/AMP guidelines, and variants meeting pathogenic or likely pathogenic (P/LP) criteria in South African probands were nominated for clinical validation and return to interested families. Results: Exome sequencing analysis identified P/LP variants in 22 of the 99 cases. A total of 13 (17%) of the 75 cases from South Africa were found to have P/ LP variants eligible for return, including 6 single nucleotide variants (SNVs) or indels and 7 copy number variants (CNVs) impacting established NDD genes or cytogenetic regions. Of the 24 Kenyan cases, 9 (38%) were solved with P/LP variants, including 6 SNVs and 3 CNVs. In addition to the solved cases, 14 cases were found to have suspicious variants of uncertain significance (VUS) in candidate disease genes, which were submitted to MME. Matches were made for 7 of the 14 submitted candidates, each of which will be included in collaborative case series reports on the genes of interest. These variants may be reclassified in the future after re-evaluation of the evidence collected for these emerging gene-disease associations. Conclusion: The NeuroDev study is making progress towards addressing the diversity gap in studies of the genetic etiology of neurodevelopmental disorders. The results of the first 99 trios demonstrate the potential for genetic characterization and rare disease discovery in an African context. Additionally, the NeuroDev trio pilot data is now the largest African NDD collection for which genetic and phenotypic data are publicly available to the research community, through the National Human Genome Research Institute Analysis Visualization and Informatics Lab-space (AnVIL) controlled access data repository. Over the course of the next few years, the NeuroDev study will, in total, perform exome sequencing and share data for approximately 2,000 children with NDDs, which will be of significant benefit to the global genetics community