RESUMO
Temporal data on gene expression and context-specific open chromatin states can improve identification of key transcription factors (TFs) and the gene regulatory networks (GRNs) controlling cellular differentiation. However, their integration remains challenging. Here, we delineate a general approach for data-driven and unbiased identification of key TFs and dynamic GRNs, called EPIC-DREM. We generated time-series transcriptomic and epigenomic profiles during differentiation of mouse multipotent bone marrow stromal cell line (ST2) toward adipocytes and osteoblasts. Using our novel approach we constructed time-resolved GRNs for both lineages and identifed the shared TFs involved in both differentiation processes. To take an alternative approach to prioritize the identified shared regulators, we mapped dynamic super-enhancers in both lineages and associated them to target genes with correlated expression profiles. The combination of the two approaches identified aryl hydrocarbon receptor (AHR) and Glis family zinc finger 1 (GLIS1) as mesenchymal key TFs controlled by dynamic cell type-specific super-enhancers that become repressed in both lineages. AHR and GLIS1 control differentiation-induced genes and their overexpression can inhibit the lineage commitment of the multipotent bone marrow-derived ST2 cells.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Elementos Facilitadores Genéticos , Células-Tronco Mesenquimais/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Fatores de Transcrição/metabolismo , Adipócitos/metabolismo , Animais , Diferenciação Celular/genética , Linhagem Celular , Linhagem da Célula/genética , Redes Reguladoras de Genes , Células-Tronco Mesenquimais/citologia , Camundongos , Osteoblastos/metabolismoRESUMO
Despite the discovery of tyrosine kinase inhibitors (TKIs) for the treatment of breakpoint cluster region-Abelson (BCR-ABL)+ cancer types, patients with chronic myeloid leukemia (CML) treated with TKIs develop resistance and severe adverse effects. Combination treatment, especially with a histone deacetylase (HDAC) 6 inhibitor (HDAC6i), appears to be an attractive option to prevent TKI resistance, considering the potential capacity of an HDAC6i to diminish BCR-ABL expression. We first validated the in vivo anti-cancer potential of the compound 7b by significantly reducing the tumor burden of BALB/c mice xenografted with K-562 cells, without notable organ toxicity. Here, we hypothesize that the HDAC6i compound 7b can lead to BCR-ABL downregulation in CML cells and sensitize them to TKI treatment. The results showed that combination treatment with imatinib and 7b resulted in strong synergistic caspase-dependent apoptotic cell death and drastically reduced the proportion of leukemia stem cells, whereas this treatment only moderately affected healthy cells. Ultimately, the combination significantly decreased colony formation in a semisolid methylcellulose medium and tumor mass in xenografted zebrafish compared to each compound alone. Mechanistically, the combination induced BCR-ABL ubiquitination and downregulation followed by disturbance of key proteins in downstream pathways involved in CML proliferation and survival. Taken together, our results suggest that an HDAC6i potentiates the effect of imatinib and could overcome TKI resistance in CML cells.
Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Proteínas de Fusão bcr-abl/metabolismo , Desacetilase 6 de Histona/antagonistas & inibidores , Mesilato de Imatinib/farmacologia , Mesilato de Imatinib/uso terapêutico , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Inibidores de Proteínas Quinases/farmacologia , Inibidores de Proteínas Quinases/uso terapêutico , Ubiquitinação/efeitos dos fármacos , Animais , Caspases/efeitos dos fármacos , Regulação para Baixo , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Sinergismo Farmacológico , Humanos , Células K562 , Camundongos , Camundongos Endogâmicos BALB C , Ensaio Tumoral de Célula-Tronco , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Constraint-based network modelling is a powerful tool for analysing cellular metabolism at genomic scale. Here, we conducted an integrative analysis of metabolic networks reconstructed from RNA-seq data with paired epigenomic data from the EpiATLAS resource of the International Human Epigenome Consortium (IHEC). Applying a state-of-the-art contextualisation algorithm, we reconstructed metabolic networks across 1,555 samples corresponding to 58 tissues and cell types. Analysis of these networks revealed the distribution of metabolic functionalities across human cell types and provides a compendium of human metabolic activity. This integrative approach allowed us to define, across tissues and cell types, i) reactions that fulfil the basic metabolic processes (core metabolism), and ii) cell type-specific functions (unique metabolism), that shape the metabolic identity of a cell or a tissue. Integration with EpiATLAS-derived cell type-specific gene-level chromatin states and enhancer-gene interactions identified enhancers, transcription factors, and key nodes controlling core and unique metabolism. Transport and first reactions of pathways were enriched for high expression, active chromatin state, and Polycomb-mediated repression in cell types where pathways are inactive, suggesting that key nodes are targets of repression. This integrative analysis forms the basis for identifying regulation points that control metabolic identity in human cells.
RESUMO
Myelomonocytic and monocytic acute myeloid leukemia (AML) subtypes are intrinsically resistant to venetoclax-based regimens. Identifying targetable vulnerabilities would limit resistance and relapse. We previously documented the synergism of venetoclax and cardiac glycoside (CG) combination in AML. Despite preclinical evidence, the repurposing of cardiac glycosides (CGs) in cancer therapy remained unsuccessful due to a lack of predictive biomarkers. We report that the ex vivo response of AML patient blasts and the in vitro sensitivity of established cell lines to the hemi-synthetic CG UNBS1450 correlates with the ATPase Na+/K+ transporting subunit alpha 1 (ATP1A1)/BCL2 like 1 (BCL2L1) expression ratio. Publicly available AML datasets identify myelomonocytic/monocytic differentiation as the most robust prognostic feature, along with core-binding factor subunit beta (CBFB), lysine methyltransferase 2A (KMT2A) rearrangements, and missense Fms-related receptor tyrosine kinase 3 (FLT3) mutations. Mechanistically, BCL2L1 protects from cell death commitment induced by the CG-mediated stepwise triggering of ionic perturbation, protein synthesis inhibition, and MCL1 downregulation. In vivo, CGs showed an overall tolerable profile while impacting tumor growth with an effect ranging from tumor growth inhibition to regression. These findings suggest a predictive marker for CG repurposing in specific AML subtypes.
Assuntos
Glicosídeos Cardíacos , Leucemia Mieloide Aguda , Humanos , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patologia , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Sulfonamidas/farmacologia , Tirosina Quinase 3 Semelhante a fms/metabolismo , Linhagem Celular Tumoral , ATPase Trocadora de Sódio-Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/uso terapêutico , Proteína bcl-X/metabolismoRESUMO
Pyruvate dehydrogenase (PDH) is the central enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle. The importance of PDH function in T helper 17 (Th17) cells still remains to be studied. Here, we show that PDH is essential for the generation of a glucose-derived citrate pool needed for Th17 cell proliferation, survival, and effector function. In vivo, mice harboring a T cell-specific deletion of PDH are less susceptible to developing experimental autoimmune encephalomyelitis. Mechanistically, the absence of PDH in Th17 cells increases glutaminolysis, glycolysis, and lipid uptake in a mammalian target of rapamycin (mTOR)-dependent manner. However, cellular citrate remains critically low in mutant Th17 cells, which interferes with oxidative phosphorylation (OXPHOS), lipid synthesis, and histone acetylation, crucial for transcription of Th17 signature genes. Increasing cellular citrate in PDH-deficient Th17 cells restores their metabolism and function, identifying a metabolic feedback loop within the central carbon metabolism that may offer possibilities for therapeutically targeting Th17 cell-driven autoimmunity.
Assuntos
Ácido Cítrico , Células Th17 , Camundongos , Animais , Citratos , Oxirredutases , Lipídeos , Piruvatos , MamíferosRESUMO
Cellular energy metabolism is regulated by complex metabolic pathways. Although anaerobic glycolysis was reported as a primary source of energy in cancer leading to a high rate of lactate production, current evidence shows that the main energy source supporting cancer cell metabolism relies on mitochondrial metabolism. Mitochondria are the key organelle maintaining optimal cellular energy levels. MitoPlate™ S-1 provides a highly reproducible bioenergetics tool to analyze the electron flow rate in live cells. Measuring the rates of electron flow into and through the electron transport chain using different NADH and FADH2-producing metabolic substrates enables the assessment of mitochondrial functionality. MitoPlate™ S-1 are 96-well microplates pre-coated with different substrates used as probes to examine the activity of mitochondrial metabolic pathways based on a colorimetric assay. A comparative metabolic analysis between cell lines or primary cells allows to establish a specific metabolic profile and to detect possible alterations of the mitochondrial function of a tumor cell. Moreover, the direct measurements of electron flux triggered by metabolic pathway activation could highlight targets for potential drug candidates.
Assuntos
Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Neoplasias/metabolismo , Linhagem Celular Tumoral , Transporte de Elétrons , Ensaios de Triagem em Larga Escala/métodos , Humanos , Redes e Vias Metabólicas , Neoplasias/patologia , OxirreduçãoRESUMO
Autophagy is a highly conserved cellular process in which intracellular proteins and organelles are sequestered and degraded after the fusion of double-membrane vesicles known as autophagosomes with lysosomes. The process of autophagy is dependent on autophagy-related (ATG) proteins. The role of autophagy in cancer is very complex and still elusive. We investigated the expression of ATG proteins in benign nevi, primary and metastatic melanoma tissues using customized tissue microarrays (TMA). Results from immunohistochemistry show that the expression of ATG5 and ATG7 is significantly reduced in melanoma tissues compared to benign nevi. This reduction correlated with changes in the expression of autophagic activity markers, suggesting decreased basal levels of autophagy in primary and metastatic melanomas. Furthermore, the analysis of survival data of melanoma patients revealed an association between reduced ATG5 and ATG7 levels with an unfavourable clinical outcome. Currently, the mechanisms regulating ATG expression levels in human melanoma remains unknown. Using bioinformatic predictions of transcription factor (TF) binding motifs in accessible chromatin of primary melanocytes, we identified new TFs involved in the regulation of core ATGs. We then show that nuclear respiratory factor 1 (NRF1) stimulates the production of mRNA and protein as well as the promoter activity of ATG5 and ATG7. Moreover, NRF1 deficiency increased in vitro migration of melanoma cells. Our results support the concept that reduced autophagic activity contributes to melanoma development and progression, and identifies NRF1 as a novel TF involved in the regulation of both ATG5 and ATG7 genes.
RESUMO
Increasing evidence suggests that neurodevelopmental alterations might contribute to increase the susceptibility to develop neurodegenerative diseases. We investigate the occurrence of developmental abnormalities in dopaminergic neurons in a model of Parkinson's disease (PD). We monitor the differentiation of human patient-specific neuroepithelial stem cells (NESCs) into dopaminergic neurons. Using high-throughput image analyses and single-cell RNA sequencing, we observe that the PD-associated LRRK2-G2019S mutation alters the initial phase of neuronal differentiation by accelerating cell-cycle exit with a concomitant increase in cell death. We identify the NESC-specific core regulatory circuit and a molecular mechanism underlying the observed phenotypes. The expression of NR2F1, a key transcription factor involved in neurogenesis, decreases in LRRK2-G2019S NESCs, neurons, and midbrain organoids compared to controls. We also observe accelerated dopaminergic differentiation in vivo in NR2F1-deficient mouse embryos. This suggests a pathogenic mechanism involving the LRRK2-G2019S mutation, where the dynamics of dopaminergic differentiation are modified via NR2F1.
Assuntos
Encéfalo/enzimologia , Fator I de Transcrição COUP/metabolismo , Neurônios Dopaminérgicos/enzimologia , Células-Tronco Pluripotentes Induzidas/enzimologia , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/metabolismo , Células-Tronco Neurais/enzimologia , Neurogênese , Doença de Parkinson/enzimologia , Animais , Encéfalo/patologia , Fator I de Transcrição COUP/genética , Ciclo Celular , Linhagem Celular , Proliferação de Células , Sobrevivência Celular , Neurônios Dopaminérgicos/patologia , Feminino , Humanos , Células-Tronco Pluripotentes Induzidas/patologia , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/genética , Masculino , Camundongos da Linhagem 129 , Camundongos Knockout , Mutação , Células-Tronco Neurais/patologia , Doença de Parkinson/genética , Doença de Parkinson/patologia , Fenótipo , RNA-Seq , Transdução de Sinais , Análise de Célula Única , Fatores de TempoRESUMO
Although tyrosine kinase inhibitors (TKIs) revolutionized the management of chronic myeloid leukemia (CML), resistance against TKIs and leukemia stem cell (LSC) persistence remain a clinical concern. Therefore, new therapeutic strategies combining conventional and novel therapies are urgently needed. Since telomerase is involved in oncogenesis and tumor progression but is silent in most human normal somatic cells, it may be an interesting target for CML therapy by selectively targeting cancer cells while minimizing effects on normal cells. Here, we report that hTERT expression is associated with CML disease progression. We also provide evidence that hTERT-deficient K-562 cells do not display telomere shortening and that telomere length is maintained through the ALT pathway. Furthermore, we show that hTERT depletion exerts a growth-inhibitory effect in K-562 cells and potentiates imatinib through alteration of cell cycle progression leading to a senescence-like phenotype. Finally, we demonstrate that hTERT depletion potentiates the imatinib-induced reduction of the ALDH+-LSC population. Altogether, our results suggest that the combination of telomerase and TKI should be considered as an attractive strategy to treat CML patients to eradicate cancer cells and prevent relapse by targeting LSCs.
Assuntos
Mesilato de Imatinib/farmacologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Células-Tronco Neoplásicas/efeitos dos fármacos , Telomerase/genética , Família Aldeído Desidrogenase 1/genética , Apoptose/efeitos dos fármacos , Carcinogênese/efeitos dos fármacos , Linhagem da Célula/genética , Proliferação de Células/efeitos dos fármacos , Progressão da Doença , Resistencia a Medicamentos Antineoplásicos/genética , Feminino , Proteínas de Fusão bcr-abl/genética , Humanos , Células K562 , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Masculino , Células-Tronco Neoplásicas/patologia , Inibidores de Proteínas Quinases/farmacologiaRESUMO
BACKGROUND: Chronic myeloid leukemia (CML) pathogenesis is mainly driven by the oncogenic breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 (BCR-ABL) fusion protein. Since BCR-ABL displays abnormal constitutive tyrosine kinase activity, therapies using tyrosine kinase inhibitors (TKis) such as imatinib represent a major breakthrough for the outcome of CML patients. Nevertheless, the development of TKi resistance and the persistence of leukemia stem cells (LSCs) remain barriers to cure the disease, justifying the development of novel therapeutic approaches. Since the activity of histone deacetylase (HDAC) is deregulated in numerous cancers including CML, pan-HDAC inhibitors may represent promising therapeutic regimens for the treatment of CML cells in combination with TKi. RESULTS: We assessed the anti-leukemic activity of a novel hydroxamate-based pan-HDAC inhibitor MAKV-8, which complied with the Lipinski's "rule of five," in various CML cells alone or in combination with imatinib. We validated the in vitro HDAC-inhibitory potential of MAKV-8 and demonstrated efficient binding to the ligand-binding pocket of HDAC isoenzymes. In cellulo, MAKV-8 significantly induced target protein acetylation, displayed cytostatic and cytotoxic properties, and triggered concomitant ER stress/protective autophagy leading to canonical caspase-dependent apoptosis. Considering the specific upregulation of selected HDACs in LSCs from CML patients, we investigated the differential toxicity of a co-treatment with MAKV-8 and imatinib in CML versus healthy cells. We also showed that beclin-1 knockdown prevented MAKV-8-imatinib combination-induced apoptosis. Moreover, MAKV-8 and imatinib co-treatment synergistically reduced BCR-ABL-related signaling pathways involved in CML cell growth and survival. Since our results showed that LSCs from CML patients overexpressed c-MYC, importantly MAKV-8-imatinib co-treatment reduced c-MYC levels and the LSC population. In vivo, tumor growth of xenografted K-562 cells in zebrafish was completely abrogated upon combined treatment with MAKV-8 and imatinib. CONCLUSIONS: Collectively, the present findings show that combinations HDAC inhibitor-imatinib are likely to overcome drug resistance in CML pathology.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Inibidores de Histona Desacetilases/uso terapêutico , Mesilato de Imatinib/uso terapêutico , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Acetilação/efeitos dos fármacos , Adulto , Protocolos de Quimioterapia Combinada Antineoplásica/química , Apoptose/efeitos dos fármacos , Proteína Beclina-1/genética , Sítios de Ligação , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Simulação por Computador , Resistencia a Medicamentos Antineoplásicos , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Proteínas de Fusão bcr-abl/antagonistas & inibidores , Proteínas de Fusão bcr-abl/metabolismo , Inibidores de Histona Desacetilases/química , Inibidores de Histona Desacetilases/farmacologia , Histona Desacetilases/química , Humanos , Mesilato de Imatinib/farmacologia , Isoenzimas/química , Leucemia Mielogênica Crônica BCR-ABL Positiva/enzimologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Simulação de Acoplamento Molecular , Células-Tronco Neoplásicas/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Inibidores de Proteínas Quinases/uso terapêutico , Proteínas Proto-Oncogênicas c-myc/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-myc/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Sialic acid-binding Ig-like lectin (Siglec) receptors are linked to neurodegenerative processes, but the role of sialic acids in physiological aging is still not fully understood. We investigated the impact of reduced sialylation in the brain of mice heterozygous for the enzyme glucosamine-2-epimerase/N-acetylmannosamine kinase (GNE+/-) that is essential for sialic acid biosynthesis. We demonstrate that GNE+/- mice have hyposialylation in different brain regions, less synapses in the hippocampus and reduced microglial arborization already at 6 months followed by increased loss of neurons at 12 months. A transcriptomic analysis revealed no pro-inflammatory changes indicating an innate homeostatic immune process leading to the removal of synapses and neurons in GNE+/- mice during aging. Crossbreeding with complement C3-deficient mice rescued the earlier onset of neuronal and synaptic loss as well as the changes in microglial arborization. Thus, sialic acids of the glycocalyx contribute to brain homeostasis and act as a recognition system for the innate immune system in the brain.
Assuntos
Envelhecimento/imunologia , Envelhecimento/patologia , Neurônios/patologia , Ácidos Siálicos/fisiologia , Sinapses/patologia , Animais , Encéfalo/imunologia , Encéfalo/metabolismo , Homeostase , Imunidade Inata , Camundongos Transgênicos , Racemases e Epimerases/metabolismo , Lectinas Semelhantes a Imunoglobulina de Ligação ao Ácido Siálico/fisiologia , Ácidos Siálicos/biossínteseRESUMO
By comparing imatinib-sensitive and -resistant chronic myeloid leukemia (CML) cell models, we investigated the molecular mechanisms by which tetrahydrobenzimidazole derivative TMQ0153 triggered caspase-dependent apoptosis at low concentrations accompanied by loss of mitochondrial membrane potential (MMP) and increase of cytosolic free Ca2+ levels. Interestingly, at higher concentrations, TMQ0153 induced necroptotic cell death with accumulation of ROS, both preventable by N-acetyl-L-cysteine (NAC) pretreatment. At necroptosis-inducing concentrations, we observed increased ROS and decreased ATP and GSH levels, concomitant with protective autophagy induction. Inhibitors such as bafilomycin A1 (baf-A1) and siRNA against beclin 1 abrogated autophagy, sensitized CML cells against TMQ0153 and enhanced necroptotic cell death. Importantly, TMQ153-induced necrosis led to cell surface exposure of calreticulin (CRT) and ERp57 as well as the release of extracellular ATP and high mobility group box (HMGB1) demonstrating the capacity of this compound to release immunogenic cell death (ICD) markers. We validated the anti-cancer potential of TMQ0153 by in vivo inhibition of K562 microtumor formation in zebrafish. Taken together, our findings provide evidence that cellular stress and redox modulation by TMQ0153 concentration-dependently leads to different cell death modalities including controlled necrosis in CML cell models.
Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Benzimidazóis/farmacologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Necroptose/efeitos dos fármacos , Animais , Cálcio/metabolismo , Relação Dose-Resposta a Droga , Metabolismo Energético/efeitos dos fármacos , Regulação Leucêmica da Expressão Gênica , Humanos , Células K562 , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Peixe-ZebraRESUMO
Aim: Prediction of genes under dynamic post-transcriptional regulation from epigenomic data. Materials & methods: We used time-series profiles of chromatin immunoprecipitation-seq data of histone modifications from differentiation of mesenchymal progenitor cells toward adipocytes and osteoblasts to predict gene expression levels at five time points in both lineages and estimated the deviation of those predictions from the RNA-seq measured expression levels using linear regression. Results & conclusion: The genes with biggest changes in their estimated stability across the time series are enriched for noncoding RNAs and lineage-specific biological processes. Clustering mRNAs according to their stability dynamics allows identification of post-transcriptionally coregulated mRNAs and their shared regulators through sequence enrichment analysis. We identify miR-204 as an early induced adipogenic microRNA targeting Akr1c14 and Il1rl1.
Assuntos
Regulação da Expressão Gênica , Processamento Pós-Transcricional do RNA , Adipócitos/metabolismo , Aldeído Redutase/genética , Animais , Diferenciação Celular/genética , Linhagem Celular , Linhagem da Célula/genética , Imunoprecipitação da Cromatina , Análise por Conglomerados , Epigenômica , Proteína 1 Semelhante a Receptor de Interleucina-1/genética , Modelos Lineares , Camundongos , MicroRNAs/genética , MicroRNAs/metabolismo , MicroRNAs/fisiologia , Osteoblastos/metabolismoRESUMO
Parkinson's disease (PD) is a multifactorial disorder with complex etiology. The most prevalent PD associated mutation, LRRK2-G2019S is linked to familial and sporadic cases. Based on the multitude of genetic predispositions in PD and the incomplete penetrance of LRRK2-G2019S, we hypothesize that modifiers in the patients' genetic background act as susceptibility factors for developing PD. To assess LRRK2-G2019S modifiers, we used human induced pluripotent stem cell-derived neuroepithelial stem cells (NESCs). Isogenic controls distinguish between LRRK2-G2019S dependent and independent cellular phenotypes. LRRK2-G2019S patient and healthy mutagenized lines showed altered NESC self-renewal and viability, as well as impaired serine metabolism. In patient cells, phenotypes were only partly LRRK2-G2019S dependent, suggesting a significant contribution of the genetic background. In this context we identified the gene serine racemase (SRR) as a novel patient-specific, developmental, genetic modifier contributing to the aberrant phenotypes. Its enzymatic product, d-serine, rescued altered cellular phenotypes. Susceptibility factors in the genetic background, such as SRR, could be new targets for early PD diagnosis and treatment.