Abstract
X-linked dystonia-parkinsonism is a neurodegenerative disorder caused by a founder retrotransposon insertion, in which a polymorphic hexanucleotide repeat accounts for ~50% of age at onset ...variability. Employing a genome-wide association study to identify additional factors modifying age at onset, we establish that three independent loci are significantly associated with age at onset (
p
< 5 × 10
−8
). The lead single nucleotide polymorphisms collectively account for 25.6% of the remaining variance not explained by the hexanucleotide repeat and 13.0% of the overall variance in age at onset in X-linked dystonia-parkinsonism with the protective alleles delaying disease onset by seven years. These regions harbor or lie adjacent to
MSH3
and
PMS2
, the genes that were recently implicated in modifying age at onset in Huntington’s disease, likely through a common pathway influencing repeat instability. Our work indicates the existence of three modifiers of age at onset in X-linked dystonia-parkinsonism that likely affect the DNA mismatch repair pathway.
Mutations in WDR45 cause neurodegeneration with brain iron accumulation. Seibler et al. report that loss of WDR45 function in cells from patients results in increased cellular iron levels and ...oxidative stress, accompanied by mitochondrial and lysosomal dysfunction. Activation of autophagy may serve as a potential therapeutic approach.
Abstract
Beta-propeller protein-associated neurodegeneration is a subtype of monogenic neurodegeneration with brain iron accumulation caused by de novo mutations in WDR45. The WDR45 protein functions as a beta-propeller scaffold and plays a putative role in autophagy through its interaction with phospholipids and autophagy-related proteins. Loss of WDR45 function due to disease-causing mutations has been linked to defects in autophagic flux in patient and animal cells. However, the role of WDR45 in iron homeostasis remains elusive. Here we studied patient-specific WDR45 mutant fibroblasts and induced pluripotent stem cell-derived midbrain neurons. Our data demonstrated that loss of WDR45 increased cellular iron levels and oxidative stress, accompanied by mitochondrial abnormalities, autophagic defects, and diminished lysosomal function. Restoring WDR45 levels partially rescued oxidative stress and the susceptibility to iron treatment, and activation of autophagy reduced the observed iron overload in WDR45 mutant cells. Our data suggest that iron-containing macromolecules and organelles cannot effectively be degraded through the lysosomal pathway due to loss of WDR45 function.
Objective
Even though genetic predisposition has proven to be an important element in Parkinson's disease (PD) etiology, monozygotic (MZ) twins with PD displayed a concordance rate of only about 20% ...despite their shared identical genetic background.
Methods
We recruited 5 pairs of MZ twins discordant for idiopathic PD and established skin fibroblast cultures to investigate mitochondrial phenotypes in these cellular models against the background of a presumably identical genome. To test for genetic differences, we performed whole genome sequencing, deep mitochondrial DNA (mtDNA) sequencing, and tested for mitochondrial deletions by multiplex real‐time polymerase chain reaction (PCR) in the fibroblast cultures. Further, the fibroblast cultures were tested for mitochondrial integrity by immunocytochemistry, immunoblotting, flow cytometry, and real‐time PCR to quantify gene expression.
Results
Genome sequencing did not identify any genetic difference. We found decreased mitochondrial functionality with reduced cellular adenosine triphosphate (ATP) levels, altered mitochondrial morphology, elevated protein levels of superoxide dismutase 2 (SOD2), and increased levels of peroxisome proliferator‐activated receptor‐gamma coactivator‐α (PPARGC1A) messenger RNA (mRNA) in skin fibroblast cultures from the affected compared to the unaffected twins. Further, there was a tendency for a higher number of somatic mtDNA variants among the affected twins.
Interpretation
We demonstrate disease‐related differences in mitochondrial integrity in the genetically identical twins. Of note, the clinical expression matches functional alterations of the mitochondria. ANN NEUROL 2021;89:158–164
Abstract In the present study, we investigated the role of the main intracellular energy sensor, AMP-activated protein kinase (AMPK), in the in vitro neurotoxicity of α-synuclein (ASYN), one of the ...key culprits in the pathogenesis of Parkinson's disease. The loss of viability in retinoic acid-differentiated SH-SY5Y human neuroblastoma cells inducibly overexpressing wild-type ASYN was associated with the reduced activation of AMPK and its activator LKB1, as well as AMPK target Raptor. ASYN-overexpressing rat primary neurons also displayed lower activity of LKB1/AMPK/Raptor pathway. Restoration of AMPK activity by metformin or AICAR reduced the in vitro neurotoxicity of ASYN overexpression, acting independently of the prosurvival kinase Akt or the induction of autophagic response. The conditioned medium from ASYN-overexpressing cells, containing secreted ASYN, as well as dopamine-modified or nitrated recombinant ASYN oligomers, all inhibited AMPK activation in differentiated SH-SY5Y cells and reduced their viability, but not in the presence of metformin or AICAR. The RNA interference-mediated knockdown of AMPK increased the sensitivity of SH-SY5Y cells to the harmful effects of secreted ASYN. AMPK-dependent protection from extracellular ASYN was also observed in rat neuron-like pheochromocytoma cell line PC12. These data demonstrate the protective role of AMPK against the toxicity of both intracellular and extracellular ASYN, suggesting that modulation of AMPK activity may be a promising therapeutic strategy in Parkinson's disease.
VPS13D promotes peroxisome biogenesis Baldwin, Heather A; Wang, Chunxin; Kanfer, Gil ...
The Journal of cell biology,
05/2021, Volume:
220, Issue:
5
Journal Article
Peer reviewed
Open access
The VPS13 gene family consists of VPS13A-D in mammals. Although all four genes have been linked to human diseases, their cellular functions are poorly understood, particularly those of VPS13D. We ...generated and characterized knockouts of each VPS13 gene in HeLa cells. Among the individual knockouts, only VPS13D-KO cells exhibit abnormal mitochondrial morphology. Additionally, VPS13D loss leads to either partial or complete peroxisome loss in several transformed cell lines and in fibroblasts derived from a VPS13D mutation-carrying patient with recessive spinocerebellar ataxia. Our data show that VPS13D regulates peroxisome biogenesis.
Beta-propeller protein-associated neurodegeneration (BPAN) is a subtype of neurodegeneration with brain iron accumulation (NBIA) caused by loss-of-function variants in WDR45. The underlying mechanism ...of iron accumulation in WDR45 deficiency remains elusive. We established a primary skin fibroblast culture of a new BPAN patient with a missense variant p.(Asn61Lys) in WDR45 (NM_007075.3: c.183C>A). The female patient has generalized dystonia, anarthria, parkinsonism, spasticity, stereotypies, and a distinctive cranial MRI with generalized brain atrophy, predominantly of the cerebellum. For the functional characterization of this variant and to provide a molecular link of WDR45 and iron accumulation, we looked for disease- and variant-related changes in the patient’s fibroblasts by qPCR, immunoblotting and immunofluorescence comparing to three controls and a previously reported WDR45 patient. We demonstrated molecular changes in mutant cells comprising an impaired mitochondrial network, decreased levels of lysosomal proteins and enzymes, and altered autophagy, confirming the pathogenicity of the variant. Compared to increased levels of the ferritinophagy marker Nuclear Coactivator 4 (NCOA4) in control cells upon iron treatment, patients’ cells revealed unchanged NCOA4 protein levels, indicating disturbed ferritinophagy. Additionally, we observed abnormal protein levels of markers of the iron-dependent cell death ferroptosis in patients’ cells. Altogether, our data suggests that WDR45 deficiency affects ferritinophagy and ferroptosis, consequentially disturbing iron recycling.
Novel Pd(II) complex with N‐heteroaromatic Schiff base ligand, derived from 8‐quinolinecarboxaldehyde (q8a) and ethyl hydrazinoacetate (haOEt), was synthesized and characterized by analytical and ...spectroscopy methods. The structure of novel complex, as well as structures of its quinoline and pyridine analogues, was optimized by density functional theory calculations, and theoretical data show good agreement with experimental results. A cytotoxic action of the complexes was evaluated on cultures of human promyelocytic leukemia (HL‐60), human glioma (U251), rat glioma (C6), and mouse fibrosarcoma (L929) cell lines. Among investigated compounds, only complexes with quinoline‐based ligands reduce the cell numbers in a dose‐dependent manner in investigated cell lines. The observed cytotoxic effect of two isomeric quinoline‐based complexes is predominantly mediated through the induction of apoptotic cell death in HL‐60 cell line. The cytotoxicity of most efficient novel Pd(II) complex is comparable to the activity of cisplatin, in all cell lines investigated.
The effect of the chelate ring size and complex lipophilicity on in vitro cytotoxic activity of Pd(II) complexes with NN bidentate N‐heteroaromatic hydrazones was investigated. It was shown that more lipophilic complexes with quinoline backbone were more potent in the cytotoxic action than pyridine analogues. The cytotoxicity of most efficient novel Pd(II) complex 1 is comparable to the activity of cisplatin in all cell lines investigated and is predominantly mediated through the induction of apoptotic cell death.
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