Mitochondrial genome study in blood of maternally inherited ALS cases.

BACKGROUND: ALS is a heterogeneous disease in which different factors such as mitochondrial phenotypes act in combination with a genetic predisposition. This study addresses the question of whether homoplasmic (total mitochondrial genome of a sample is affected) and/or heteroplasmic mutations (wildtype and mutant mitochondrial DNA molecules coexist) might play a role in familial ALS. Blood was drawn from familial ALS patients with a possible maternal pattern of inheritance according to their pedigrees, which was compared to blood of ALS patients without maternal association as well as age-matched controls. In two cohorts, we analyzed the mitochondrial genome from whole blood or isolated white blood cells and platelets using a resequencing microarray (Affymetrix MitoChip v2.0) that is able to detect homoplasmic and heteroplasmic mitochondrial DNA mutations and allows the assessment of low-level heteroplasmy. RESULTS: We identified an increase in homoplasmic ND5 mutations, a subunit of respiratory chain complex I, in whole blood of ALS patients that allowed maternal inheritance. This effect was more pronounced in patients with bulbar onset. Heteroplasmic mutations were significantly increased in different mitochondrial genes in platelets of patients with possible maternal inheritance. No increase of low-level heteroplasmy was found in maternal ALS patients. CONCLUSION: Our results indicate a contribution of homoplasmic ND5 mutations to maternally associated ALS with bulbar onset. Therefore, it might be conceivable that specific maternally transmitted rather than randomly acquired mitochondrial DNA mutations might contribute to the disease process. This stands in contrast with observations from Alzheimer's and Parkinson's diseases showing an age-dependent accumulation of unspecific mutations in mitochondrial DNA.

ALS is imprinted in the chromatin accessibility of blood cells.

Amyotrophic Lateral Sclerosis (ALS) is a complex and incurable neurodegenerative disorder in which genetic and epigenetic factors contribute to the pathogenesis of all forms of ALS. The interplay of genetic predisposition and environmental footprints generates epigenetic signatures in the cells of affected tissues, which then alter transcriptional programs. Epigenetic modifications that arise from genetic predisposition and systemic environmental footprints should in theory be detectable not only in affected CNS tissue but also in the periphery. Here, we identify an ALS-associated epigenetic signature ('epiChromALS') by chromatin accessibility analysis of blood cells of ALS patients. In contrast to the blood transcriptome signature, epiChromALS includes also genes that are not expressed in blood cells; it is enriched in CNS neuronal pathways and it is present in the ALS motor cortex. By combining simultaneous ATAC-seq and RNA-seq with single-cell sequencing in PBMCs and motor cortex from ALS patients, we demonstrate that epigenetic changes associated with the neurodegenerative disease can be found in the periphery, thus strongly suggesting a mechanistic link between the epigenetic regulation and disease pathogenesis.

Thoracic trauma promotes alpha-Synuclein oligomerization in murine Parkinson's disease.

BACKGROUND: Systemic and neuroinflammatory processes play key roles in neurodegenerative diseases such as Parkinson's disease (PD). Physical trauma which induces considerable systemic inflammatory responses, represents an evident environmental factor in aging. However, little is known about the impact of physical trauma, on the immuno-pathophysiology of PD. Especially blunt chest trauma which is associated with a high morbidity and mortality rate in the elderly population, can induce a strong pulmonary and systemic inflammatory reaction. Hence, we sought out to combine a well-established thoracic trauma mouse model with a well-established PD mouse model to characterize the influence of physical trauma to neurodegenerative processes in PD. METHODS: To study the influence of peripheral trauma in a PD mouse model we performed a highly standardized blunt thorax trauma in a well-established PD mouse model and determined the subsequent local and systemic response. RESULTS: We could show that blunt chest trauma leads to a systemic inflammatory response which is quantifiable with increased inflammatory markers in bronchoalveolar fluids (BALF) and plasma regardless of the presence of a PD phenotype. A difference of the local inflammatory response in the brain between the PD group and non-PD group could be detected, as well as an increase in the formation of oligomeric pathological alpha-Synuclein (asyn) suggesting an interplay between peripheral thoracic trauma and asyn pathology in PD. CONCLUSION: Taken together this study provides evidence that physical trauma is associated with increased asyn oligomerization in a PD mouse model underlining the relevance of PD pathogenesis under traumatic settings.

A serum microRNA sequence reveals fragile X protein pathology in amyotrophic lateral sclerosis.

Knowledge about converging disease mechanisms in the heterogeneous syndrome amyotrophic lateral sclerosis (ALS) is rare, but may lead to therapies effective in most ALS cases. Previously, we identified serum microRNAs downregulated in familial ALS, the majority of sporadic ALS patients, but also in presymptomatic mutation carriers. A 5-nucleotide sequence motif (GDCGG; D = G, A or U) was strongly enriched in these ALS-related microRNAs. We hypothesized that deregulation of protein(s) binding predominantly to this consensus motif was responsible for the ALS-linked microRNA fingerprint. Using microRNA pull-down assays combined with mass spectrometry followed by extensive biochemical validation, all members of the fragile X protein family, FMR1, FXR1 and FXR2, were identified to directly and predominantly interact with GDCGG microRNAs through their structurally disordered RGG/RG domains. Preferential association of this protein family with ALS-related microRNAs was confirmed by in vitro binding studies on a transcriptome-wide scale. Immunohistochemistry of lumbar spinal cord revealed aberrant expression level and aggregation of FXR1 and FXR2 in C9orf72- and FUS-linked familial ALS, but also patients with sporadic ALS. Further analysis of ALS autopsies and induced pluripotent stem cell-derived motor neurons with FUS mutations showed co-aggregation of FXR1 with FUS. Hence, our translational approach was able to take advantage of blood microRNAs to reveal CNS pathology, and suggests an involvement of the fragile X-related proteins in familial and sporadic ALS already at a presymptomatic stage. The findings may uncover disease mechanisms relevant to many patients with ALS. They furthermore underscore the systemic, extra-CNS aspect of ALS.

T-cell dysregulation is associated with disease severity in Parkinson's Disease.

The dysregulation of peripheral immunity in Parkinson's Disease (PD) includes changes in both the relative numbers and gene expression of T cells. The presence of peripheral T-cell abnormalities in PD is well-documented, but less is known about their association to clinical parameters, such as age, age of onset, progression rate or severity of the disease. We took a detailed look at T-cell numbers, gene expression and activation in cross-sectional cohorts of PD patients and age-matched healthy controls by means of flow cytometry and NanoString gene expression assay. We show that the well-pronounced decrease in relative T-cell numbers in PD blood is mostly driven by a decrease of CD8+ cytotoxic T cells and is primarily associated with the severity of the disease. In addition, we demonstrate that the expression of inflammatory genes in T cells from PD patients is also associated with disease severity. PD T cells presented with increased activation upon stimulation with phytohemagglutinin that also correlated with disease severity. In summary, our data suggest that the consequences of disease severity account for the changes in PD T cells, rather than age, age of onset, duration or the disease progression rate.

CHCHD10 mutations p.R15L and p.G66V cause motoneuron disease by haploinsufficiency.

Mutations in the mitochondrially located protein CHCHD10 cause motoneuron disease by an unknown mechanism. In this study, we investigate the mutations p.R15L and p.G66V in comparison to wild-type CHCHD10 and the non-pathogenic variant p.P34S in vitro, in patient cells as well as in the vertebrate in vivo model zebrafish. We demonstrate a reduction of CHCHD10 protein levels in p.R15L and p.G66V mutant patient cells to approximately 50%. Quantitative real-time PCR revealed that expression of CHCHD10 p.R15L, but not of CHCHD10 p.G66V, is already abrogated at the mRNA level. Altered secondary structure and rapid protein degradation are observed with regard to the CHCHD10 p.G66V mutant. In contrast, no significant differences in expression, degradation rate or secondary structure of non-pathogenic CHCHD10 p.P34S are detected when compared with wild-type protein. Knockdown of CHCHD10 expression in zebrafish to about 50% causes motoneuron pathology, abnormal myofibrillar structure and motility deficits in vivo. Thus, our data show that the CHCHD10 mutations p.R15L and p.G66V cause motoneuron disease primarily based on haploinsufficiency of CHCHD10.

Increased Immune Activation by Pathologic α-Synuclein in Parkinson's Disease.

OBJECTIVE: Excessive inflammation in the central nervous system (CNS) and the periphery can result in neurodegeneration and parkinsonism. Recent evidence suggests that immune responses in Parkinson disease patients are dysregulated, leading to an increased inflammatory reaction to unspecific triggers. Although α-synuclein pathology is the hallmark of Parkinson disease, it has not been investigated whether pathologic α-synuclein is a specific trigger for excessive inflammatory responses in Parkinson disease. METHODS: We investigated the immune response of primary human monocytes and a microglial cell line to pathologic forms of α-synuclein by assessing cytokine release upon exposure. RESULTS: We show that pathologic α-synuclein (mutations, aggregation) results in a robust inflammatory activation of human monocytes and microglial BV2 cells. The activation is conformation- dependent, with increasing fibrillation and early onset mutations having the strongest effect on immune activation. We also found that activation of immune cells by extracellular α-synuclein is potentiated by extracellular vesicles, possibly by facilitating the uptake of α-synuclein. Blood extracellular vesicles from Parkinson disease patients induce a stronger activation of monocytes than blood extracellular vesicles from healthy controls. Most importantly, monocytes from Parkinson disease patients are dysregulated and hyperactive in response to stimulation with pathologic α-synuclein. Furthermore, we demonstrate that α-synuclein pathology in the CNS is sufficient to induce the monocyte dysregulation in the periphery of a mouse model. INTERPRETATION: Taken together, our data suggest that α-synuclein pathology and dysregulation of monocytes in Parkinson disease can act together to induce excessive inflammatory responses to α-synuclein. ANN NEUROL 2019;86:593-606.

Hot-spot KIF5A mutations cause familial ALS.

Heterozygous missense mutations in the N-terminal motor or coiled-coil domains of the kinesin family member 5A (KIF5A) gene cause monogenic spastic paraplegia (HSP10) and Charcot-Marie-Tooth disease type 2 (CMT2). Moreover, heterozygous de novo frame-shift mutations in the C-terminal domain of KIF5A are associated with neonatal intractable myoclonus, a neurodevelopmental syndrome. These findings, together with the observation that many of the disease genes associated with amyotrophic lateral sclerosis disrupt cytoskeletal function and intracellular transport, led us to hypothesize that mutations in KIF5A are also a cause of amyotrophic lateral sclerosis. Using whole exome sequencing followed by rare variant analysis of 426 patients with familial amyotrophic lateral sclerosis and 6137 control subjects, we detected an enrichment of KIF5A splice-site mutations in amyotrophic lateral sclerosis (2/426 compared to 0/6137 in controls; P = 4.2 × 10-3), both located in a hot-spot in the C-terminus of the protein and predicted to affect splicing exon 27. We additionally show co-segregation with amyotrophic lateral sclerosis of two canonical splice-site mutations in two families. Investigation of lymphoblast cell lines from patients with KIF5A splice-site mutations revealed the loss of mutant RNA expression and suggested haploinsufficiency as the most probable underlying molecular mechanism. Furthermore, mRNA sequencing of a rare non-synonymous missense mutation (predicting p.Arg1007Gly) located in the C-terminus of the protein shortly upstream of the splice donor of exon 27 revealed defective KIF5A pre-mRNA splicing in respective patient-derived cell lines owing to abrogation of the donor site. Finally, the non-synonymous single nucleotide variant rs113247976 (minor allele frequency = 1.00% in controls, n = 6137), also located in the C-terminal region [p.(Pro986Leu) in exon 26], was significantly enriched in familial amyotrophic lateral sclerosis patients (minor allele frequency = 3.40%; P = 1.28 × 10-7). Our study demonstrates that mutations located specifically in a C-terminal hotspot of KIF5A can cause a classical amyotrophic lateral sclerosis phenotype, and underline the involvement of intracellular transport processes in amyotrophic lateral sclerosis pathogenesis.

Dysregulation of a novel miR-1825/TBCB/TUBA4A pathway in sporadic and familial ALS.

Genetic and functional studies suggest diverse pathways being affected in the neurodegenerative disease amyotrophic lateral sclerosis (ALS), while knowledge about converging disease mechanisms is rare. We detected a downregulation of microRNA-1825 in CNS and extra-CNS system organs of both sporadic (sALS) and familial ALS (fALS) patients. Combined transcriptomic and proteomic analysis revealed that reduced levels of microRNA-1825 caused a translational upregulation of tubulin-folding cofactor b (TBCB). Moreover, we found that excess TBCB led to depolymerization and degradation of tubulin alpha-4A (TUBA4A), which is encoded by a known ALS gene. Importantly, the increase in TBCB and reduction of TUBA4A protein was confirmed in brain cortex tissue of fALS and sALS patients, and led to motor axon defects in an in vivo model. Our discovery of a microRNA-1825/TBCB/TUBA4A pathway reveals a putative pathogenic cascade in both fALS and sALS extending the relevance of TUBA4A to a large proportion of ALS cases.

Release and uptake of pathologic alpha-synuclein.

Parkinson's disease (PD) is a chronic progressive neurodegenerative disease, which is characterized by severe loss of dopaminergic neurons and formation of Lewy bodies, which are rich in aggregated alpha-synuclein (α-syn). Two decades of intensive research have compiled a massive body of evidence that aggregation of α-syn is a critical process in PD and other synucleinopathies. The dissemination of Lewy body pathology throughout the central nervous system strongly suggests a cell-to-cell transmission of α-syn. Although in vitro and in vivo evidence has convincingly demonstrated that aggregation-prone α-syn can spread from cell to cell, the exact mechanisms and the role for the disease pathology remain elusive. Except for cases of direct contact, the transmission of α-syn from cell to cell requires that α-syn is released to the extracellular space and taken up by recipient cells. Furthermore, internalized α-syn needs to gain access to the cytoplasm and/or target organelles of the recipient cell. Here, we review the current state of knowledge about release and uptake of α-syn and discuss the key questions that remain unanswered.

ALS-causing mutations differentially affect PGC-1α expression and function in the brain vs. peripheral tissues.

BACKGROUND: Monogenetic forms of amyotrophic lateral sclerosis (ALS) offer an opportunity for unraveling the molecular mechanisms underlying this devastating neurodegenerative disorder. In order to identify a link between ALS-related metabolic changes and neurodegeneration, we investigated whether ALS-causing mutations interfere with the peripheral and brain-specific expression and signaling of the metabolic master regulator PGC (PPAR gamma coactivator)-1α (PGC-1α). METHODS: We analyzed the expression of PGC-1α isoforms and target genes in two mouse models of familial ALS and validated the stimulated PGC-1α signaling in primary adipocytes and neurons of these animal models and in iPS derived motoneurons of two ALS patients harboring two different frame-shift FUS/TLS mutations. RESULTS: Mutations in SOD1 and FUS/TLS decrease Ppargc1a levels in the CNS whereas in muscle and brown adipose tissue Ppargc1a mRNA levels were increased. Probing the underlying mechanism in neurons, we identified the monocarboxylate lactate as a previously unrecognized potent and selective inducer of the CNS-specific PGC-1α isoforms. Lactate also induced genes like brain-derived neurotrophic factor, transcription factor EB and superoxide dismutase 3 that are down-regulated in PGC-1α deficient neurons. The lactate-induced CNS-specific PGC-1α signaling system is completely silenced in motoneurons derived from induced pluripotent stem cells obtained from two ALS patients harboring two different frame-shift FUS/TLS mutations. CONCLUSION: ALS mutations increase the canonical PGC-1α system in the periphery while inhibiting the CNS-specific isoforms. We identify lactate as an inducer of the neuronal PGC-1α system directly linking brain metabolism and neuroprotection. Changes in the PGC-1α system might be involved in the ALS accompanied metabolic changes and in neurodegeneration.

Impaired activation of ALS monocytes by exosomes.

Amyotrophic lateral sclerosis (ALS) is a fatal and progressive neurodegenerative disease affecting predominantly motor neurons in the spinal cord and motor cortex. Neurodegeneration in ALS is accompanied by a well-characterized neuroinflammatory reaction within the central nervous system and, as described more recently, cells of the peripheral immune system. Particularly monocytes have been implicated in ALS pathogenesis. Exosomes are membrane-enclosed vesicles secreted by various cell types with a diameter of 50-150 nm. Circulating blood exosomes have been shown to be important mediators and regulators of immunity. Therefore, we hypothesize that circulating blood exosomes are putative mediators of monocytic deregulation in ALS. Here we characterize exosomal uptake and the respective immunological reaction of peripheral monocytes from ALS patients and healthy donors using both serum-derived exosomes and TDP-43-loaded exosomes produced in cell culture. We found the pro-inflammatory cytokine secretion by ALS monocytes upon exosomal stimulation to be impaired compared with control monocytes. Moreover, we demonstrate that exosomal TDP-43 induces increased monocytic activation compared with non-aggregation-prone cargo. Therefore, this study underlines the functional deregulation of ALS monocytes and the impact of circulating blood exosomes on monocyte activation.

Aggregated α-Synuclein Increases SOD1 Oligomerization in a Mouse Model of Amyotrophic Lateral Sclerosis.

Aggregation of misfolded disease-related proteins is a hallmark of neurodegenerative diseases. Aggregate propagation accompanying disease progression has been demonstrated for different proteins (eg, for α-synuclein). Additional evidence supports aggregate cross-seeding activity for α-synuclein. For mutated superoxide dismutase 1 (SOD1), which causes familial amyotrophic lateral sclerosis (ALS), self-propagation of aggregation and cell-to-cell transmission have been demonstrated in vitro. However, there is a prominent lack of in vivo data concerning aggregation and cross-aggregation processes of SOD1. We analyzed the effect of α-synuclein and SOD1 seeds in cell culture using protein fragment complementation assay and intracerebral injection of α-synuclein and SOD1 seeds into SOD1(G93A) transgenic ALS mice. Survival of injected mice was determined, and SOD1 aggregates in the facial nuclei were quantified during disease course. We found that α-synuclein preformed fibrils increased the oligomerization rate of SOD1 in vivo and in vitro, whereas aggregated SOD1 did not exert any effect in both experimental setups. Notably, survival of ALS mice was not changed after inoculation of preformed fibrils. We conclude that misfolded α-synuclein can increase SOD1 aggregation and suppose that α-synuclein seeds are transported from the temporal cortex to the facial nuclei. However, unlike other proteins, the further enhancement of a self-aggregation process by additional SOD1 could not be confirmed in our models.

Induction of α-synuclein aggregate formation by CSF exosomes from patients with Parkinson's disease and dementia with Lewy bodies.

Extracellular α-synuclein has been proposed as a crucial mechanism for induction of pathological aggregate formation in previously healthy cells. In vitro, extracellular α-synuclein is partially associated with exosomal vesicles. Recently, we have provided evidence that exosomal α-synuclein is present in the central nervous system in vivo. We hypothesized that exosomal α-synuclein species from patients with α-synuclein related neurodegeneration serve as carriers for interneuronal disease transmission. We isolated exosomes from cerebrospinal fluid from patients with Parkinson's disease, dementia with Lewy bodies, progressive supranuclear palsy as a non-α-synuclein related disorder that clinically overlaps with Parkinson's disease, and neurological controls. Cerebrospinal fluid exosome numbers, α-synuclein protein content of cerebrospinal fluid exosomes and their potential to induce oligomerization of α-synuclein were analysed. The quantification of cerebrospinal fluid exosomal α-synuclein showed distinct differences between patients with Parkinson's disease and dementia with Lewy bodies. In addition, exosomal α-synuclein levels correlated with the severity of cognitive impairment in cross-sectional samples from patients with dementia with Lewy bodies. Importantly, cerebrospinal fluid exosomes derived from Parkinson's disease and dementia with Lewy bodies induce oligomerization of α-synuclein in a reporter cell line in a dose-dependent manner. Our data suggest that cerebrospinal fluid exosomes from patients with Parkinson's disease and dementia with Lewy bodies contain a pathogenic species of α-synuclein, which could initiate oligomerization of soluble α-synuclein in target cells and confer disease pathology.

Systematic comparison of the effects of alpha-synuclein mutations on its oligomerization and aggregation.

Aggregation of alpha-synuclein (ASYN) in Lewy bodies and Lewy neurites is the typical pathological hallmark of Parkinson's disease (PD) and other synucleinopathies. Furthermore, mutations in the gene encoding for ASYN are associated with familial and sporadic forms of PD, suggesting this protein plays a central role in the disease. However, the precise contribution of ASYN to neuronal dysfunction and death is unclear. There is intense debate about the nature of the toxic species of ASYN and little is known about the molecular determinants of oligomerization and aggregation of ASYN in the cell. In order to clarify the effects of different mutations on the propensity of ASYN to oligomerize and aggregate, we assembled a panel of 19 ASYN variants and compared their behaviour. We found that familial mutants linked to PD (A30P, E46K, H50Q, G51D and A53T) exhibited identical propensities to oligomerize in living cells, but had distinct abilities to form inclusions. While the A30P mutant reduced the percentage of cells with inclusions, the E46K mutant had the opposite effect. Interestingly, artificial proline mutants designed to interfere with the helical structure of the N-terminal domain, showed increased propensity to form oligomeric species rather than inclusions. Moreover, lysine substitution mutants increased oligomerization and altered the pattern of aggregation. Altogether, our data shed light into the molecular effects of ASYN mutations in a cellular context, and established a common ground for the study of genetic and pharmacological modulators of the aggregation process, opening new perspectives for therapeutic intervention in PD and other synucleinopathies.

Mutual exacerbation of peroxisome proliferator-activated receptor γ coactivator 1α deregulation and α-synuclein oligomerization.

OBJECTIVE: Aggregation of α-synuclein (α-syn) and α-syn cytotoxicity are hallmarks of sporadic and familial Parkinson disease (PD), with accumulating evidence that prefibrillar oligomers and protofibrils are the pathogenic species in PD and related synucleinopathies. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a key regulator of mitochondrial biogenesis and cellular energy metabolism, has recently been associated with the pathophysiology of PD. Despite extensive effort on studying the function of PGC-1α in mitochondria, no studies have addressed whether PGC-1α directly influences oligomerization of α-syn or whether α-syn oligomers impact PGC-1α expression. MATERIALS AND METHODS: We tested whether pharmacological or genetic activation of PGC-1α or PGC-11α knockdown could modulate the oligomerization of α-syn in vitro by using an α-syn -fragment complementation assay. RESULTS: In this study, we found that both PGC-1α reference gene (RG-PGC-1α) and the central nervous system (CNS)-specific PGC-1α (CNS-PGC-1α) are downregulated in human PD brain, in A30P α-syn transgenic animals, and in a cell culture model for α-syn oligomerization. Importantly, downregulation of both RG-PGC-1α and CNS-PGC-1α in cell culture or neurons from RG-PGC-1α-deficient mice leads to a strong induction of α-syn oligomerization and toxicity. In contrast, pharmacological activation or genetic overexpression of RG-PGC-1α reduced α-syn oligomerization and rescued α-syn-mediated toxicity. INTERPRETATION: Based on our results, we propose that PGC-1α downregulation and α-syn oligomerization form a vicious circle, thereby influencing and/or potentiating each other. Our data indicate that restoration of PGC-1α is a promising approach for development of effective drugs for the treatment of PD and related synucleinopathies.

Age-dependent defects of alpha-synuclein oligomer uptake in microglia and monocytes.

Extracellular alpha-synuclein (αsyn) oligomers, associated to exosomes or free, play an important role in the pathogenesis of Parkinson's disease (PD). Increasing evidence suggests that these extracellular moieties activate microglia leading to enhanced neuronal damage. Despite extensive efforts on studying neuroinflammation in PD, little is known about the impact of age on microglial activation and phagocytosis, especially of extracellular αsyn oligomers. Here, we show that microglia isolated from adult mice, in contrast to microglia from young mice, display phagocytosis deficits of free and exosome-associated αsyn oligomers combined with enhanced TNFα secretion. In addition, we describe a dysregulation of monocyte subpopulations with age in mice and humans. Accordingly, human monocytes from elderly donors also show reduced phagocytic activity of extracellular αsyn. These findings suggest that these age-related alterations may contribute to an increased susceptibility to pathogens or abnormally folded proteins with age in neurodegenerative diseases.

Peripheral monocytes are functionally altered and invade the CNS in ALS patients.

Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disease affecting primarily the upper and lower motor neurons. A common feature of all ALS cases is a well-characterized neuroinflammatory reaction within the central nervous system (CNS). However, much less is known about the role of the peripheral immune system and its interplay with CNS resident immune cells in motor neuron degeneration. Here, we characterized peripheral monocytes in both temporal and spatial dimensions of ALS pathogenesis. We found the circulating monocytes to be deregulated in ALS regarding subtype constitution, function and gene expression. Moreover, we show that CNS infiltration of peripheral monocytes correlates with improved motor neuron survival in a genetic ALS mouse model. Furthermore, application of human immunoglobulins or fusion proteins containing only the human Fc, but not the Fab antibody fragment, increased CNS invasion of peripheral monocytes and delayed the disease onset. Our results underline the importance of peripheral monocytes in ALS pathogenesis and are in agreement with a protective role of monocytes in the early phase of the disease. The possibility to boost this beneficial function of peripheral monocytes by application of human immunoglobulins should be evaluated in clinical trials.

PGC-1α is a male-specific disease modifier of human and experimental amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a devastating, adult-onset neurodegenerative disorder of the upper and lower motor systems. It leads to paresis, muscle wasting and inevitably to death, typically within 3-5 years. However, disease onset and survival vary considerably ranging in extreme cases from a few months to several decades. The genetic and environmental factors underlying this variability are of great interest as potential therapeutic targets. In ALS, men are affected more often and have an earlier age of onset than women. This gender difference is recapitulated in transgenic rodent models, but no underlying mechanism has been elucidated. Here we report that SNPs in the brain-specific promoter region of the transcriptional co-activator PGC-1α, a master regulator of metabolism, modulate age of onset and survival in two large and independent ALS populations and this occurs in a strictly male-specific manner. In complementary animal studies, we show that deficiency of full-length (FL) Pgc-1α leads to a significantly earlier age of onset and a borderline shortened survival in male, but not in female ALS-transgenic mice. In the animal model, FL Pgc-1α-loss is associated with reduced mRNA levels of the trophic factor Vegf-A in males, but not in females. In summary, we indentify PGC-1α as a novel and clinically relevant disease modifier of human and experimental ALS and report a sex-dependent effect of PGC-1α in this neurodegenerative disorder.