RESUMO
Alzheimer's disease (AD) is a neurodegenerative disease characterized by severe cognitive deterioration. While causes of AD pathology are debated, a large body of evidence suggests that increased cleavage of Amyloid Precursor Protein (APP) producing the neurotoxic Amyloid-ß (Aß) peptide plays a fundamental role in AD pathogenesis. One of the detrimental behavioral symptoms commonly associated with AD is the fragmentation of sleep-activity cycles with increased nighttime activity and daytime naps in humans. Sleep-activity cycles, as well as physiological and cellular rhythms, which may be important for neuronal homeostasis, are generated by a molecular system known as the circadian clock. Links between AD and the circadian system are increasingly evident but not well understood. Here we examined whether genetic manipulations of APP-like (APPL) protein cleavage in Drosophila melanogaster affect rest-activity rhythms and core circadian clock function in this model organism. We show that the increased ß-cleavage of endogenous APPL by the ß-secretase (dBACE) severely disrupts circadian behavior and leads to reduced expression of clock protein PER in central clock neurons of aging flies. Our data suggest that behavioral rhythm disruption is not a product of APPL-derived Aß production but rather may be caused by a mechanism common to both α and ß-cleavage pathways. Specifically, we show that increased production of the endogenous Drosophila Amyloid Intracellular Domain (dAICD) caused disruption of circadian rest-activity rhythms, while flies overexpressing endogenous APPL maintained stronger circadian rhythms during aging. In summary, our study offers a novel entry point toward understanding the mechanism of circadian rhythm disruption in Alzheimer's disease.
Assuntos
Envelhecimento , Precursor de Proteína beta-Amiloide/metabolismo , Relógios Circadianos/genética , Regulação da Expressão Gênica/genética , Fatores Etários , Secretases da Proteína Precursora do Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Animais Geneticamente Modificados , Sistema Nervoso Central/citologia , Desintegrinas/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Análise de Fourier , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Longevidade , Metaloendopeptidases/metabolismo , Atividade Motora/genética , Neurônios/metabolismo , Proteínas Circadianas Period/metabolismoRESUMO
The purpose of these guidelines is to assist physicians in recommending, performing, interpreting and reporting the results of FDG PET/CT for oncological imaging of adult patients. PET is a quantitative imaging technique and therefore requires a common quality control (QC)/quality assurance (QA) procedure to maintain the accuracy and precision of quantitation. Repeatability and reproducibility are two essential requirements for any quantitative measurement and/or imaging biomarker. Repeatability relates to the uncertainty in obtaining the same result in the same patient when he or she is examined more than once on the same system. However, imaging biomarkers should also have adequate reproducibility, i.e. the ability to yield the same result in the same patient when that patient is examined on different systems and at different imaging sites. Adequate repeatability and reproducibility are essential for the clinical management of patients and the use of FDG PET/CT within multicentre trials. A common standardised imaging procedure will help promote the appropriate use of FDG PET/CT imaging and increase the value of publications and, therefore, their contribution to evidence-based medicine. Moreover, consistency in numerical values between platforms and institutes that acquire the data will potentially enhance the role of semiquantitative and quantitative image interpretation. Precision and accuracy are additionally important as FDG PET/CT is used to evaluate tumour response as well as for diagnosis, prognosis and staging. Therefore both the previous and these new guidelines specifically aim to achieve standardised uptake value harmonisation in multicentre settings.
Assuntos
Fluordesoxiglucose F18 , Imagem Multimodal/métodos , Neoplasias/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/métodos , Compostos Radiofarmacêuticos , Tomografia Computadorizada por Raios X/métodos , HumanosRESUMO
Circadian clocks coordinate physiological, neurological, and behavioral functions into circa 24 hour rhythms, and the molecular mechanisms underlying circadian clock oscillations are conserved from Drosophila to humans. Clock oscillations and clock-controlled rhythms are known to dampen during aging; additionally, genetic or environmental clock disruption leads to accelerated aging and increased susceptibility to age-related pathologies. Neurodegenerative diseases, such as Alzheimer's disease (AD), are associated with a decay of circadian rhythms, but it is not clear whether circadian disruption accelerates neuronal and motor decline associated with these diseases. To address this question, we utilized transgenic Drosophila expressing various Amyloid-ß (Aß) peptides, which are prone to form aggregates characteristic of AD pathology in humans. We compared development of AD-like symptoms in adult flies expressing Aß peptides in the wild type background and in flies with clocks disrupted via a null mutation in the clock gene period (per01). No significant differences were observed in longevity, climbing ability and brain neurodegeneration levels between control and clock-deficient flies, suggesting that loss of clock function does not exacerbate pathogenicity caused by human-derived Aß peptides in flies. However, AD-like pathologies affected the circadian system in aging flies. We report that rest/activity rhythms were impaired in an age-dependent manner. Flies expressing the highly pathogenic arctic Aß peptide showed a dramatic degradation of these rhythms in tune with their reduced longevity and impaired climbing ability. At the same time, the central pacemaker remained intact in these flies providing evidence that expression of Aß peptides causes rhythm degradation downstream from the central clock mechanism.
Assuntos
Envelhecimento/fisiologia , Doença de Alzheimer/fisiopatologia , Ritmo Circadiano/fisiologia , Drosophila melanogaster/fisiologia , Envelhecimento/genética , Doença de Alzheimer/genética , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Animais , Animais Geneticamente Modificados , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/fisiopatologia , Modelos Animais de Doenças , Proteínas de Drosophila/deficiência , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Feminino , Humanos , Imuno-Histoquímica , Longevidade/genética , Longevidade/fisiologia , Masculino , Atividade Motora/genética , Atividade Motora/fisiologia , Mutação , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Proteínas Circadianas Period/deficiência , Proteínas Circadianas Period/genéticaAssuntos
Comitês Consultivos , Pesquisa Biomédica/métodos , Pessoal de Laboratório Médico/educação , Pessoal de Laboratório Médico/tendências , Imagem Molecular/métodos , Medicina Nuclear/educação , Animais , Pesquisa Biomédica/tendências , Educação de Pós-Graduação em Medicina/métodos , Educação de Pós-Graduação em Medicina/tendências , Marcadores Fiduciais/tendências , Humanos , Imageamento por Ressonância Magnética/métodos , Imagem Molecular/tendências , Imagem Multimodal/métodos , Medicina Nuclear/métodos , Medicina Nuclear/tendências , Tomografia por Emissão de Pósitrons/métodos , Tomografia por Emissão de Pósitrons/tendências , Compostos Radiofarmacêuticos , Sociedades MédicasAssuntos
Comitês Consultivos , Educação de Pós-Graduação em Medicina/métodos , Pessoal de Laboratório Médico/educação , Medicina Nuclear/educação , Medicina Nuclear/métodos , Educação de Pós-Graduação em Medicina/tendências , Humanos , Pessoal de Laboratório Médico/tendências , Imagem Molecular/métodos , Imagem Molecular/tendências , Medicina Nuclear/tendências , Sociedades MédicasRESUMO
Work on axon growth has classically focused on understanding how extrinsic cues control growth cone dynamics independent of the cell body. However, more recently, neuron-intrinsic transcription factors have been shown to influence both normal and regenerative axon growth, suggesting that understanding their mechanism of action is of clinical importance. We are studying axon targeting in the Drosophila visual system and here show that the BTB/POZ zinc-finger transcription factor Tramtrack69 (Ttk69) plays an instructive role in inhibiting the growth of R7 photoreceptor axon terminals. Although ttk69 mutant R7 axons project to the correct medullar target layer, M6, their terminals fail to remain retinotopically restricted and instead grow laterally within M6. This overgrowth is not caused by an inability to be repelled by neighboring R7 axons or by an inability to recognize and initiate synapse formation with postsynaptic targets. The overgrowth is progressive and occurs even if contact between ttk69 mutant R7 axons and their normal target layer is disrupted. Ttk69 is first expressed in wild-type R7s after their axons have reached the medulla; ttk69 mutant R7 axon terminal overgrowth begins shortly after this time point. We find that expressing Ttk69 prematurely in R7s collapses their growth cones and disrupts axon extension, indicating that Ttk69 plays an instructive role in this process. A TGF-ß/Activin pathway was shown previously to inhibit R7 axon terminal growth. We find that Ttk69 is required for normal activation of this pathway but that Ttk69 likely also inhibits R7 axon growth by a TGF-ß/Activin-independent mechanism.
Assuntos
Ativinas/metabolismo , Axônios/metabolismo , Proteínas de Drosophila/metabolismo , Células Fotorreceptoras de Invertebrados/metabolismo , Proteínas Repressoras/metabolismo , Transdução de Sinais/fisiologia , Fator de Crescimento Transformador beta/metabolismo , Animais , Animais Geneticamente Modificados , DrosophilaRESUMO
Genetic analyses in both worm and fly have identified the RhoGAP-like protein Syd-1 as a key positive regulator of presynaptic assembly. In worm, loss of syd-1 can be fully rescued by overexpressing wild-type Liprin-α, suggesting that the primary function of Syd-1 in this process is to recruit Liprin-α. We show that loss of syd-1 from Drosophila R7 photoreceptors causes two morphological defects that occur at distinct developmental time points. First, syd-1 mutant R7 axons often fail to form terminal boutons in their normal M6 target layer. Later, those mutant axons that do contact M6 often project thin extensions beyond it. We find that the earlier defect coincides with a failure to localize synaptic vesicles, suggesting that it reflects a failure in presynaptic assembly. We then analyze the relationship between syd-1 and Liprin-α in R7s. We find that loss of Liprin-α causes a stronger early R7 defect and provide a possible explanation for this disparity: we show that Liprin-α promotes Kinesin-3/Unc-104/Imac-mediated axon transport independently of Syd-1 and that Kinesin-3/Unc-104/Imac is required for normal R7 bouton formation. Unlike loss of syd-1, loss of Liprin-α does not cause late R7 extensions. We show that overexpressing Liprin-α partly rescues the early but not the late syd-1 mutant R7 defect. We therefore conclude that the two defects are caused by distinct molecular mechanisms. We find that Trio overexpression rescues both syd-1 defects and that trio and syd-1 have similar loss- and gain-of-function phenotypes, suggesting that the primary function of Syd-1 in R7s may be to promote Trio activity.
Assuntos
Proteínas de Drosophila/deficiência , Proteínas de Drosophila/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Proteínas de Membrana/deficiência , Neurogênese/genética , Fosfoproteínas/metabolismo , Células Fotorreceptoras de Invertebrados/metabolismo , Terminações Pré-Sinápticas/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Animais , Animais Geneticamente Modificados , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Drosophila/genética , Drosophila melanogaster/citologia , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Células Fotorreceptoras de Invertebrados/ultraestrutura , Terminações Pré-Sinápticas/ultraestrutura , Vesículas Sinápticas/genética , Vesículas Sinápticas/metabolismo , Vesículas Sinápticas/ultraestruturaRESUMO
Motoneurons are an essential component of all metazoan nervous systems, but it is unknown whether there is an evolutionarily conserved mechanism for generating motoneurons during neurogenesis. In the vertebrate CNS, HB9/MNR2 transcription factors are specifically expressed in all somatic motoneurons and are necessary to distinguish motoneurons from interneurons, in part by repressing interneuron-specific gene expression. Here, we identify and characterize the single Drosophila ortholog of the HB9/MNR2 gene family. Drosophila HB9 is detected in a subset of motoneurons with ventral muscle targets and in a small group of interneurons, including the well characterized serotonergic interneurons. RNA interference knockdown of HB9 levels leads to defects in motoneuron ventral muscle target recognition, ectopic expression of a marker for dorsally projecting motoneurons (Even-skipped), and defects in serotonergic interneuronal projections. Conversely, ectopic HB9 expression causes an expansion of ventral motoneuron projections and repression of Even-skipped. Thus, Drosophila HB9 is required in a subset of motoneurons and interneurons for establishing proper axon projections but does not have a general role in distinguishing motoneuron and interneuron cell types.