RESUMO
The study of individuals with autosomal dominant Alzheimer's disease affords one of the best opportunities to characterize the biological and cognitive changes of Alzheimer's disease that occur over the course of the preclinical and symptomatic stages. Unifying the knowledge gained from the past three decades of research in the world's largest single-mutation autosomal dominant Alzheimer's disease kindred - a family in Antioquia, Colombia with the E280A mutation in the Presenilin1 gene - will provide new directions for Alzheimer's research and a framework for generalizing the findings from this cohort to the more common sporadic form of Alzheimer's disease. As this specific mutation is virtually 100% penetrant for the development of the disease by midlife, we use a previously defined median age of onset for mild cognitive impairment for this cohort to examine the trajectory of the biological and cognitive markers of the disease as a function of the carriers' estimated years to clinical onset. Studies from this cohort suggest that structural and functional brain abnormalities - such as cortical thinning and hyperactivation in memory networks - as well as differences in biofluid and in vivo measurements of Alzheimer's-related pathological proteins distinguish Presenilin1 E280A mutation carriers from non-carriers as early as childhood, or approximately three decades before the median age of onset of clinical symptoms. We conclude our review with discussion on future directions for Alzheimer's disease research, with specific emphasis on ways to design studies that compare the generalizability of research in autosomal dominant Alzheimer's disease to the larger sporadic Alzheimer's disease population.
Assuntos
Doença de Alzheimer/fisiopatologia , Peptídeos beta-Amiloides/metabolismo , Encéfalo/diagnóstico por imagem , Fragmentos de Peptídeos/metabolismo , Presenilina-1/genética , Adolescente , Adulto , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/sangue , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Compostos de Anilina , Doenças Assintomáticas , Biomarcadores/sangue , Biomarcadores/líquido cefalorraquidiano , Biomarcadores/metabolismo , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Criança , Colômbia , Imagem de Tensor de Difusão , Progressão da Doença , Eletroencefalografia , Etilenoglicóis , Feminino , Neuroimagem Funcional , Humanos , Imageamento por Ressonância Magnética , Masculino , Testes de Estado Mental e Demência , Pessoa de Meia-Idade , Fragmentos de Peptídeos/sangue , Fragmentos de Peptídeos/líquido cefalorraquidiano , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos , Tomografia Computadorizada de Emissão de Fóton Único , Adulto JovemRESUMO
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in the notch3 epidermal growth factor-like repeats. A Colombian kindred carries a novel C455R mutation located in the predicted ligand-binding domain. Stroke occurred in the patients at an unusually early age (median age: 31 years) in comparison to the more frequent onset in the fourth decade of life in other CADASIL populations, including a second Colombian kindred with an R1031C mutation.
Assuntos
Demência por Múltiplos Infartos/genética , Mutação , Acidente Vascular Cerebral/genética , Adulto , Idade de Início , Idoso , Arginina/metabolismo , Colômbia , Cisteína/metabolismo , Análise Mutacional de DNA , Feminino , Heterozigoto , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
In cultured neurons, axon formation is preceded by the appearance in one of the multiple neurites of a large growth cone containing a labile actin network and abundant dynamic microtubules. The invasion-inducing T-lymphoma and metastasis 1 (Tiam1) protein that functions as a guanosine nucleotide exchange factor for Rac1 localizes to this neurite and its growth cone, where it associates with microtubules. Neurons overexpressing Tiam1 extend several axon-like neurites, whereas suppression of Tiam1 prevents axon formation, with most of the cells failing to undergo changes in growth cone size and in cytoskeletal organization typical of prospective axons. Cytochalasin D reverts this effect leading to multiple axon formation and penetration of microtubules within neuritic tips devoid of actin filaments. Taken together, these results suggest that by regulating growth cone actin organization and allowing microtubule invasion within selected growth cones, Tiam1 promotes axon formation and hence participates in neuronal polarization.
Assuntos
Axônios/fisiologia , Proteínas/fisiologia , Células Piramidais/fisiologia , Citoesqueleto de Actina/fisiologia , Animais , Polaridade Celular/fisiologia , Células Cultivadas , Imunofluorescência , Cones de Crescimento/fisiologia , Fatores de Troca do Nucleotídeo Guanina , Microtúbulos/fisiologia , Proteínas de Neoplasias , Ratos , Proteína 1 Indutora de Invasão e Metástase de Linfoma de Células TRESUMO
In this study we have examined the cellular functions of ERM proteins in developing neurons. The results obtained indicate that there is a high degree of spatial and temporal correlation between the expression and subcellular localization of radixin and moesin with the morphological development of neuritic growth cones. More importantly, we show that double suppression of radixin and moesin, but not of ezrin-radixin or ezrin-moesin, results in reduction of growth cone size, disappearance of radial striations, retraction of the growth cone lamellipodial veil, and disorganization of actin filaments that invade the central region of growth cones where they colocalize with microtubules. Neuritic tips from radixin-moesin suppressed neurons displayed high filopodial protrusive activity; however, its rate of advance is 8-10 times slower than the one of growth cones from control neurons. Radixin-moesin suppressed neurons have short neurites and failed to develop an axon-like neurite, a phenomenon that appears to be directly linked with the alterations in growth cone structure and motility. Taken collectively, our data suggest that by regulating key aspects of growth cone development and maintenance, radixin and moesin modulate neurite formation and the development of neuronal polarity.
Assuntos
Proteínas Sanguíneas/genética , Proteínas do Citoesqueleto , Cones de Crescimento/fisiologia , Proteínas de Membrana/genética , Proteínas dos Microfilamentos , Proteínas/genética , Células Piramidais/citologia , Actinas/metabolismo , Animais , Elementos Antissenso (Genética) , Proteínas Sanguíneas/metabolismo , Polaridade Celular/fisiologia , Células Cultivadas , Citoesqueleto/fisiologia , Expressão Gênica/fisiologia , Cones de Crescimento/química , Hipocampo/citologia , Proteínas de Membrana/metabolismo , Neuritos/química , Neuritos/fisiologia , Proteínas/metabolismo , Células Piramidais/química , Células Piramidais/ultraestrutura , Ratos , Frações Subcelulares/química , TionucleotídeosRESUMO
In the present study, we present evidence about the cellular functions of KIF2, a kinesin-like superfamily member having a unique structure in that its motor domain is localized at the center of the molecule (Noda Y., Y. Sato-Yoshitake, S. Kondo, M. Nangaku, and N. Hirokawa. 1995. J. Cell Biol. 129:157-167.). Using subcellular fractionation techniques, isopicnic sucrose density centrifugation of microsomal fractions from developing rat cerebral cortex, and immunoisolation with KIF2 antibodies, we have now identified a type of nonsynaptic vesicle that associates with KIF2. This type of organelle lacks synaptic vesicle markers (synapsin, synaptophysin), amyloid precursor protein, GAP-43, or N-cadherin. On the other hand, it contains betagc, which is a novel variant of the beta subunit of the IGF-1 receptor, which is highly enriched in growth cone membranes. Both betagc and KIF2 are upregulated by NGF in PC12 cells and highly concentrated in growth cones of developing neurons. We have also analyzed the consequences of KIF2 suppression by antisense oligonucleotide treatment on nerve cell morphogenesis and the distribution of synaptic and nonsynaptic vesicle markers. KIF2 suppression results in a dramatic accumulation of betagc within the cell body and in its complete disappearance from growth cones; no alterations in the distribution of synapsin, synaptophysin, GAP-43, or amyloid percursor protein are detected in KIF2-suppressed neurons. Instead, all of them remained highly enriched at nerve terminals. KIF2 suppression also produces a dramatic inhibition of neurite outgrowth; this phenomenon occurs after betagc has disappeared from growth cones. Taken collectively, our results suggest an important role for KIF2 in neurite extension, a phenomenon that may be related with the anterograde transport of a type of nonsynaptic vesicle that contains as one of its components a growth cone membrane receptor for IGF-1, a growth factor implicated in nerve cell development.
Assuntos
Cinesinas/fisiologia , Neuritos/fisiologia , Neurônios/fisiologia , Organelas/metabolismo , Precursor de Proteína beta-Amiloide/análise , Animais , Anticorpos Monoclonais , Córtex Cerebral/química , Proteína GAP-43 , Cinesinas/análise , Cinesinas/genética , Cinesinas/imunologia , Glicoproteínas de Membrana/análise , Fatores de Crescimento Neural/farmacologia , Proteínas do Tecido Nervoso/análise , Neurônios/citologia , Oligonucleotídeos Antissenso/farmacologia , Organelas/química , Células PC12 , Ratos , Receptor IGF Tipo 1/análise , Frações Subcelulares/química , Sinapsinas/análise , Vesículas Sinápticas/química , Vesículas Sinápticas/metabolismo , Sinaptofisina/análise , Tionucleotídeos/farmacologia , Regulação para CimaRESUMO
OBJECTIVES: To characterize clinical features of a very large pedigree with early-onset Alzheimer disease (AD) in which all affected individuals carry the identical glutamic acid-to-alanine mutation at codon 280 in the presenilin-1 gene. DESIGN: Clinical histories were obtained by patient and family interviews and through medical or civil records. Using standard diagnostic criteria, a case series of 128 individuals was identified, of which 6 have definitive (autopsy-proven) early-onset AD, 93 have probable early-onset AD, and 29 have possible early-onset AD. SETTING: Community based in Antioquia, Colombia. PATIENTS: A population-based sample in which all members of 5 extended families (nearly 3000 individuals) were surveyed. Criteria for inclusion required obtaining sufficient information to categorize the individual as affected. MAIN OUTCOME MEASURES: Age at onset, neuropsychological profile, neurologic history, and examination. RESULTS: The patients had a mean age at onset of 46.8 years (range, 34-62 years). The average interval until death was 8 years. Headache was noted in affected individuals significantly more frequently than in those not affected. The most frequent presentation was memory loss followed by behavior and personality changes and progressive loss of language ability. In the final stages, gait disturbances, seizures, and myoclonus were frequent. CONCLUSIONS: Other than the early onset, this clinical phenotype is indistinguishable from sporadic AD except that affected individuals frequently complained of headache preceding and during the disease. Despite the uniform genetic basis for the disease, there was significant variability in the age at onset, suggesting an important role for environmental factors or genetic modifiers in determining the age at onset.
Assuntos
Doença de Alzheimer/genética , Proteínas de Membrana/genética , Mutação Puntual , Adulto , Idade de Início , Alanina , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/fisiopatologia , Autopsia , Encéfalo/patologia , Códon , Feminino , Ácido Glutâmico , Cefaleia/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Linhagem , Fenótipo , Presenilina-1RESUMO
When cultured cerebellar macroneurons develop attached to a laminin-containing substrate or after the acute addition of laminin to the tissue culture medium, there is an acceleration in the rate and extent of axonal elongation. Furthermore, laminin is capable of inducing axonal formation and microtubule stabilization in neurons arrested at stage II of neuritic development by tau suppression (Caceres and Kosik, 1990; Caceres et al., 1991). Laminin-enhanced or induced axonal extension is paralleled by a selective and dramatic incorporation of phosphorylated MAP-1b into axonal microtubules. Axonal formation in neurons growing in the presence of laminin is prevented by treatment of the cultures with a mixture of MAP-1b and tau antisense oligonucleotides, but not by the single suppression of any one of these MAPs. However, suppression of MAP-1b, but not of tau, greatly reduces the increase in the rate and extent of axonal elongation induced by laminin. No such effects are elicited by MAP-1b antisense oligonucleotides in neurons growing in the absence of laminin, e.g. polylysine alone, where most of the MAP-1b present in the cells is dephosphorylated and not associated with the cytoskeleton. Taken collectively, these data suggest that, with regard to axonal elongation, MAP-1b and tau can be functionally substituted, and that extracellular matrix molecules, such as laminin, affect axonal extension by promoting the in vivo utilization of MAP-1b.
Assuntos
Axônios/efeitos dos fármacos , Cerebelo/efeitos dos fármacos , Laminina/farmacologia , Proteínas Associadas aos Microtúbulos/metabolismo , Neurônios/efeitos dos fármacos , Proteínas tau/metabolismo , Animais , Células Cultivadas , Cerebelo/citologia , Cerebelo/embriologia , Cerebelo/metabolismo , Neurônios/citologia , Neurônios/metabolismo , RatosRESUMO
The distribution of membrane-bound organelles was studied in cultured hippocampal neurons after antisense oligonucleotide suppression of the kinesin-heavy chain (KHC). We observed reduced 3,3'-dihexyloxacarbocyanine iodide (DiOC6(3)) fluorescent staining in neurites and growth cones. In astrocytes, KHC suppression results in the disappearance of the DiOC6(3)-positive reticular network from the cell periphery, and a parallel accumulation of label within the cell center. On the other hand, mitochondria microtubules and microfilaments display a distribution that closely resembles that observed in control cells. KHC suppression of neurons and astrocytes completely inhibited the Brefeldin A-induced spreading and tubulation of the Golgi-associated structure enriched in mannose-6-phosphate receptors. In addition, KHC suppression prevents the low pH-induced anterograde redistribution of late endocytic structures. Taken collectively, these observations suggest that in living neurons, kinesin mediates the anterograde transport of tubulovesicular structures originated in the central vacuolar system (e.g., the endoplasmic reticulum) and that the regulation of kinesin-membrane interactions may be of key importance for determining the intracellular distribution of selected organelles.
Assuntos
Hipocampo/fisiologia , Cinesinas/fisiologia , Oligonucleotídeos Antissenso/farmacologia , Organelas/fisiologia , Células Piramidais/fisiologia , Citoesqueleto de Actina/efeitos dos fármacos , Citoesqueleto de Actina/fisiologia , Citoesqueleto de Actina/ultraestrutura , Animais , Sequência de Bases , Brefeldina A , Carbocianinas , Células Cultivadas , Ciclopentanos/farmacologia , Endocitose/efeitos dos fármacos , Endocitose/fisiologia , Corantes Fluorescentes , Complexo de Golgi/fisiologia , Complexo de Golgi/ultraestrutura , Cinesinas/antagonistas & inibidores , Cinesinas/genética , Microtúbulos/efeitos dos fármacos , Microtúbulos/fisiologia , Microtúbulos/ultraestrutura , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/fisiologia , Mitocôndrias/ultraestrutura , Dados de Sequência Molecular , Neuritos/efeitos dos fármacos , Neuritos/fisiologia , Neuritos/ultraestrutura , Organelas/efeitos dos fármacos , Organelas/ultraestrutura , Inibidores da Síntese de Proteínas/farmacologia , Células Piramidais/efeitos dos fármacos , Células Piramidais/ultraestrutura , Rodamina 123 , RodaminasRESUMO
We show here that antisense MAP2 oligonucleotides inhibit neurite outgrowth in cultured cerebellar macroneurons. Unlike control neurons, which first extend a lamellipodial veil followed by a consolidation phase during which the cells extend minor neurites, MAP2-suppressed cells persist with lamellipodia and later become rounded. The induction of microtubules containing tyrosinated tubulin, which parallels neurite outgrowth in control neurons, was blocked under antisense conditions. The small but significant increase in acetylated microtubules was not affected. In contrast, the suppression of tau, which selectively blocks axonal elongation, completely prevented the increase of acetylated microtubules, but did not modify the induction of labile microtubules. These results suggest that MAP2 and tau have different functions: the initial establishment of neurites depends upon MAP2, whereas further neurite elongation depends upon tau and microtubule stabilization.