detection-axonally-localized-mrnas-brain-sections-using-high

Detection of Axonally Localized mRNAs in Brain Sections Using High-Resolution <em>In Situ</em> Hybridization

mRNAs are frequently localized to vertebrate axons and their local translation is required for axon pathfinding or branching during development and for ...

stereotaxic-infusion-oligomeric-amyloid-beta-into-mouse

Stereotaxic Infusion of Oligomeric Amyloid-beta into the Mouse Hippocampus

Alzheimer&#8217;s disease is a neurodegenerative disease affecting the aging population. A key neuropathological feature of the disease is the ...

Columbia University

Columbia University Medical Center

Columbia College

Serine proteases are considered to be involved in plasticity-related events in the nervous system, but their in vivo targets and the importance of their control by endogenous inhibitors are still not clarified. Here, we demonstrate the crucial role of a potent serine protease inhibitor, protease nexin-1 (PN-1), in the regulation of activity-dependent brain proteolytic activity and the functioning of sensory pathways. Neuronal activity regulates the expression of PN-1, which in turn controls brain proteolytic activity. In PN-1-/- mice, absence of PN-1 leads to increased brain proteolytic activity, which is correlated with an activity-dependent decrease in the NR1 subunit of the NMDA receptor. Correspondingly, reduced NMDA receptor signaling is detected in their barrel cortex. This is coupled to decreased sensory evoked potentials in the barrel cortex and impaired whisker-dependent sensory motor function. Thus, a tight control of serine protease activity is critical for the in vivo function of the NMDA receptors and the proper function of sensory pathways.

Regulation of brain proteolytic activity is necessary for the in vivo function of NMDA receptors.

Neuronal development requires highly coordinated regulation of the cytoskeleton within the developing axon. This dynamic regulation manifests itself in axonal branching, turning and pathfinding, presynaptic differentiation, and growth cone collapse and extension. Semaphorin 3A (Sema3A), a secreted guidance cue that primarily functions to repel axons from inappropriate targets, induces cytoskeletal rearrangements that result in growth cone collapse. These effects require intra-axonal messenger RNA translation. Here we show that transcripts for RhoA, a small guanosine triphosphatase (GTPase) that regulates the actin cytoskeleton, are localized to developing axons and growth cones, and this localization is mediated by an axonal targeting element located in the RhoA 3' untranslated region (UTR). Sema3A induces intra-axonal translation of RhoA mRNA, and this local translation of RhoA is necessary and sufficient for Sema3A-mediated growth cone collapse. These studies indicate that local RhoA translation regulates the neuronal cytoskeleton and identify a new mechanism for the regulation of RhoA signalling.

Local translation of RhoA regulates growth cone collapse.

Developing axons and growth cones contain "local" mRNAs that are translated in response to various extracellular signaling molecules and have roles in several processes during axonal development, including axonal pathfinding, orientation of axons in chemotactic gradients, and in the regulation of neurotransmitter release. The molecular mechanisms that regulate mRNA translation within axons and growth cones are unknown. Here we show that proteins involved in RNA interference (RNAi), including argonaute-3 and argonaute-4, Dicer, and the fragile X mental retardation protein, are found in developing axons and growth cones. These proteins assemble into functional RNA-induced silencing complexes as transfection of small interfering RNAs selectively into distal axons results in distal axon-specific mRNA knock-down, without reducing transcript levels in proximal axons or associated diffusion of small interfering RNA into proximal axons or cell bodies. RhoA mRNA is localized to axons and growth cones, and intra-axonal translation of RhoA is required for growth cone collapse elicited by Semaphorin 3A (Sema3A), an axonal guidance cue. Selective knock-down of axonal RhoA mRNA abolishes Sema3A-dependent growth cone collapse. Our results demonstrate functional and potent RNAi in axons and identify an approach to spatially regulate mRNA transcripts at a subcellular level in neurons.

Functional and selective RNA interference in developing axons and growth cones.

Growth cones at the tips of nascent and regenerating axons direct axon elongation. Netrin-1, a secreted molecule that promotes axon outgrowth and regulates axon pathfinding, elevates cyclic AMP (cAMP) levels in growth cones and regulates growth cone morphology and axonal outgrowth. These morphological effects depend on the intracellular levels of cAMP. However, the specific pathways that regulate cAMP levels in response to netrin-1 signaling are unclear. Here we show that 'soluble' adenylyl cyclase (sAC), an atypical calcium-regulated cAMP-generating enzyme previously implicated in sperm maturation, is expressed in developing rat axons and generates cAMP in response to netrin-1. Overexpression of sAC results in axonal outgrowth and growth cone elaboration, whereas inhibition of sAC blocks netrin-1-induced axon outgrowth and growth cone elaboration. Taken together, these results indicate that netrin-1 signals through sAC-generated cAMP, and identify a fundamental role for sAC in axonal development.

Soluble adenylyl cyclase is required for netrin-1 signaling in nerve growth cones.

The capacity to synthesize proteins in axons is limited to early stages of neuronal development, while axons are undergoing elongation and pathfinding. Although the roles of local protein synthesis are not fully understood, it has been implicated in regulating the morphological plasticity of growth cones. Recent studies have identified specific mRNAs that are translated in growth cones in response to specific extracellular signals. In this review, we discuss the functional relevance of axonal protein translation for developing axons, the differences in translational capacity between developing and mature vertebrate axons, and possible pathways governing the specific translational activation of axonal mRNAs.

Function and translational regulation of mRNA in developing axons.

During development of the nervous system, axons and growth cones contain mRNAs such as beta-actin, cofilin and RhoA, which are locally translated in response to guidance cues. Intra-axonal translation of these mRNAs results in local morphological responses; however, other functions of intra-axonal mRNA translation remain unknown. Here, we show that axons of developing mammalian neurons contain mRNA encoding the cAMP-responsive element (CRE)-binding protein (CREB). CREB is translated within axons in response to nerve growth factor (NGF) and is retrogradely trafficked to the cell body. In neurons that are selectively deficient in axonal CREB transcripts, increases in nuclear pCREB, CRE-mediated transcription and neuronal survival elicited by axonal application of NGF are abolished, indicating a signalling function for axonally synthesized CREB. These studies identify a signalling role for axonally derived CREB, and indicate that signal-dependent synthesis and retrograde trafficking of transcription factors enables specific transcriptional responses to signalling events at distal axons.

Intra-axonal translation and retrograde trafficking of CREB promotes neuronal survival.

&#x5728;&#x5F00;&#x53D1;&#x671F;&#x95F4;&#xFF0C;&#x8F74;&#x7A81;&#x751F;&#x957F;&#x901F;&#x5EA6;&#x7CBE;&#x786E;&#x8C03;&#x8282;&#x63D0;&#x4F9B;&#x5BFB;&#x8DEF;&#x7684;&#x65F6;&#x95F4;&#x63A7;&#x5236;&#x3002;&#x8F74;&#x7A81;&#x751F;&#x957F;&#x7684;&#x7CBE;&#x786E;&#x65F6;&#x7A7A;&#x89C4;&#x5F8B;&#x662F;&#x529F;&#x80FD;&#x6027;&#x7A81;&#x89E6;&#x7684;&#x5F62;&#x6210;&#x548C;&#x53D1;&#x751F;&#x5728;&#x4E2D;&#x67A2;&#x795E;&#x7ECF;&#x7CFB;&#x7EDF;&#x7684;&#x9002;&#x5F53;&#x683C;&#x5C40;&#x7684;&#x5173;&#x952E;&#x4E00;&#x6B65;&#x3002;&#x5F25;&#x6F2B;&#x6027;&#x8F74;&#x7D22;&#x4F38;&#x957F;&#x7387;&#x589E;&#x52A0;&#x523A;&#x6FC0;&#x8F74;&#x7A81;&#x4EA7;&#x7269;&#x4F7F;&#x7528;&#x672A;&#x5B8C;&#x5168;&#x5B9A;&#x4E49;&#x7684;&#x8DEF;&#x5F84; netrin-1 &#x548C;&#x795E;&#x7ECF;&#x751F;&#x957F;&#x56E0;&#x5B50; (NGF) &#x7B49;&#x56E0;&#x7D20;&#x3002;&#x4E3A;&#x4E86;&#x6F84;&#x6E05; netrin-1 &#x548C;&#x795E;&#x7ECF;&#x751F;&#x957F;&#x56E0;&#x5B50;&#x523A;&#x6FC0;&#x8F74;&#x7A81;&#x751F;&#x957F;&#x7684;&#x673A;&#x5236;&#xFF0C;&#x6211;&#x4EEC;&#x63A2;&#x8BA8;&#x672C;&#x5730;&#x86CB;&#x767D;&#x8D28;&#x7FFB;&#x8BD1;&#x7684;&#x4F5C;&#x7528;&#x3002;&#x6211;&#x4EEC;&#x53D1;&#x73B0;&#x5F25;&#x6F2B;&#x6027;&#x8F74;&#x7D22;&#x5185;&#x86CB;&#x767D;&#x8D28;&#x7FFB;&#x8BD1;&#x6240;&#x9700;&#x7684;&#x523A;&#x6FC0;&#xFF0C;&#x4F46;&#x4E0D;&#x662F;&#x5E95;&#xFF0C;&#x8F74;&#x7A81;&#x4EA7;&#x7269;&#x3002;&#x82E5;&#x8981;&#x6807;&#x8BC6;&#x7684;&#x673A;&#x5236;&#x4F9D;&#x8D56;&#x4E8E;&#x7FFB;&#x8BD1;&#x7684;&#x4EA7;&#x7269;&#xFF0C;&#x6211;&#x4EEC;&#x5BA1;&#x67E5;&#x4E86; PAR &#x590D;&#x6742;&#xFF0C;&#x7EC6;&#x80DE;&#x9AA8;&#x67B6;&#x8C03;&#x8282;&#x5668;&#x3002;&#x6211;&#x4EEC;&#x53D1;&#x73B0; PAR &#x590D;&#x6742;&#x3001; &#x5F53;&#x5730;&#x7FFB;&#x8BD1;&#xFF0C;&#x50CF;&#x662F;&#x6240;&#x5FC5;&#x9700;&#x7684;&#x523A;&#x6FC0;&#xFF0C;&#x4F46;&#x4E0D;&#x662F;&#x5E95;&#xFF0C;&#x4EA7;&#x7269;&#x3002;Par3 mRNA &#x88AB;&#x672C;&#x5730;&#x5316;&#x53D1;&#x5C55;&#x795E;&#x7ECF;&#x8F74;&#x7A81;&#xFF0C;&#x548C;&#x795E;&#x7ECF;&#x751F;&#x957F;&#x56E0;&#x5B50;&#x548C; netrin-1 &#x89E6;&#x53D1;&#x5176;&#x672C;&#x5730;&#x7FFB;&#x8BD1;&#x3002;&#x4ECE;&#x795E;&#x7ECF;&#x8F74;&#x7A81; Par3 mRNA &#x9009;&#x62E9;&#x6027;&#x6D88;&#x878D;&#x5E9F;&#x9664;&#x4EA7;&#x7269;&#x4FC3;&#x8FDB;&#x795E;&#x7ECF;&#x751F;&#x957F;&#x56E0;&#x5B50;&#x7684;&#x5F71;&#x54CD;&#x3002;&#x8FD9;&#x4E9B;&#x7ED3;&#x679C;&#x786E;&#x5B9A;&#x672C;&#x5730;&#x7FFB;&#x8BD1;&#x548C;&#x590D;&#x6742;&#x4E2D;&#x5F25;&#x6F2B;&#x7684;&#x4EA7;&#x7269;&#x4E3A;&#x9762;&#x503C;&#x7684;&#x65B0;&#x4F5C;&#x7528;&#x3002;

&#x5F25;&#x6F2B;&#x6027;&#x8F74;&#x7D22;&#x65AD;&#x88C2;&#x4F38;&#x957F;&#x7387;&#x7531;&#x523A;&#x6FC0;&#x5F15;&#x8D77;&#x672C;&#x5730;&#x7FFB;&#x8BD1;&#x7684;&#x6781;&#x6027;&#x7684;&#x590D;&#x6742;&#x86CB;&#x767D;&#x8D28;&#x89E6;&#x53D1;&#x3002;

During development, axon growth rates are precisely regulated to provide temporal control over pathfinding. The precise temporal regulation of axonal growth is a key step in the formation of functional synapses and the proper patterning of the nervous system. The rate of axonal elongation is increased by factors such as netrin-1 and nerve growth factor (NGF), which stimulate axon outgrowth using incompletely defined pathways. To clarify the mechanism of netrin-1- and NGF-stimulated axon growth, we explored the role of local protein translation. We found that intra-axonal protein translation is required for stimulated, but not basal, axon outgrowth. To identify the mechanism of translation-dependent outgrowth, we examined the PAR complex, a cytoskeleton regulator. We found that the PAR complex, like local translation, is required for stimulated, but not basal, outgrowth. Par3 mRNA is localized to developing axons, and NGF and netrin-1 trigger its local translation. Selective ablation of Par3 mRNA from axons abolishes the outgrowth-promoting effect of NGF. These results identify a new role for local translation and the PAR complex in axonal outgrowth.

Axonal elongation triggered by stimulus-induced local translation of a polarity complex protein.

Au cours du d&#xE9;veloppement, les taux de croissance des axones sont pr&#xE9;cis&#xE9;ment r&#xE9;gl&#xE9;es pour fournir un contr&#xF4;le temporel sur le pathfinding. Le r&#xE8;glement pr&#xE9;cise temporelle de la croissance axonale est une &#xE9;tape cl&#xE9; dans la formation de synapses fonctionnelles et la structuration ad&#xE9;quate du syst&#xE8;me nerveux. Le taux d&#x26;#39;allongement des axones est accrue par des facteurs tels que la n&#xE9;trine-1 et le facteur de croissance nerveuse (NGF), qui stimulent la croissance axonale en utilisant les voies incompl&#xE8;tement d&#xE9;finis. Afin de clarifier le m&#xE9;canisme de la n&#xE9;trine-1-et-NGF stimule la croissance des axones, nous avons explor&#xE9; le r&#xF4;le de la traduction locale de prot&#xE9;ines. Nous avons constat&#xE9; que la traduction des prot&#xE9;ines intra-axonal est n&#xE9;cessaire pour stimuler, mais pas de base la croissance axonale. Pour identifier le m&#xE9;canisme de la traduction d&#xE9;pendante de l&#x26;#39;excroissance, nous avons examin&#xE9; le complexe PAR, un r&#xE9;gulateur du cytosquelette. Nous avons trouv&#xE9; que le complexe PAR, comme la traduction locale, est n&#xE9;cessaire pour stimuler, mais pas de base, l&#x26;#39;excroissance. Par3 ARNm est localis&#xE9; au d&#xE9;veloppement des axones, et le NGF et la n&#xE9;trine-1 de d&#xE9;clencher sa traduction locale. L&#x26;#39;ablation s&#xE9;lective des Par3 ARNm &#xE0; partir des axones abolit l&#x26;#39;effet de promotion de l&#x26;#39;excroissance du NGF. Ces r&#xE9;sultats mettent en &#xE9;vidence un nouveau r&#xF4;le pour la traduction locale et le complexe PAR dans la croissance axonale.

&#xC9;longation axonale D&#xE9;clench&#xE9;e par stimulation induite par la traduction locale d&#x26;#39;une prot&#xE9;ine complexe de polarit&#xE9;

W&auml;hrend der Entwicklung werden Axon Wachstumsraten genau geregelt, um zeitliche Kontrolle der Pathfinding erm&ouml;glichen. Die genaue zeitliche Regulierung der Axonales Wachstum ist ein wichtiger Schritt bei der Bildung von funktionalen Synapsen und die richtige Musterung des Nervensystems. Die Rate der axonalen Dehnung wird durch Faktoren wie Netrin-1 und Nerv Wachstumfaktor (NGF), erh&ouml;ht die Axon Auswuchs mit unvollst&auml;ndig definierte Bahnen zu stimulieren. Den Mechanismus der Netrin-1 und NGF-stimuliert Axon Wachstum zu kl&auml;ren, erforschten wir die Rolle der Atomtypen &Uuml;bersetzung. Wir fanden, dass Intra-axonale Protein &Uuml;bersetzung f&uuml;r Axon angeregt, aber nicht basale, Auswuchs erforderlich ist. Um den Mechanismus der &Uuml;bersetzung-abh&auml;ngige Auswuchs zu identifizieren, haben wir die PAR-Komplex, ein Zytoskelett-Regulator gepr&uuml;ft. Wir fanden, dass der PAR-Komplex, wie lokale &Uuml;bersetzung f&uuml;r angeregt, aber nicht basale, Auswuchs erforderlich ist. Par3-mRNA wird lokalisiert, entwickeln Axone, und NGF und Netrin-1 Trigger seine lokale &Uuml;bersetzung. Selektive Ablation des Par3 mRNA von Axonen wird die F&ouml;rderung der Auswuchs Wirkung von NGF abgeschafft. Diese Ergebnisse geben eine neue Rolle f&uuml;r lokale &Uuml;bersetzung und die PAR-Komplex in axonale Auswuchs.

Axonale Dehnung durch Impulse induziert lokale &Uuml;bersetzung eines komplexen Polarit&auml;t-Proteins ausgel&ouml;st.

Durante lo sviluppo, i tassi di crescita axon sono regolati proprio per fornire un controllo temporale pathfinding. Il regolamento preciso temporale della crescita assonale &egrave; un passo fondamentale nella formazione delle sinapsi funzionali e la modellatura adeguata del sistema nervoso. Il tasso di allungamento assonale &egrave; aumentato da fattori quali la netrina-1 e nerve growth factor (NGF), che stimolano la escrescenza assone utilizzando percorsi definiti in modo incompleto. Per chiarire il meccanismo di crescita assone stimolato netrina-1 e NGF, abbiamo esplorato il ruolo della traduzione proteica locale. Abbiamo scoperto che la traduzione della proteina intra-assonale &egrave; richiesto per escrescenza assone stimolato, ma non basale. Per identificare il meccanismo di traduzione-dipendente escrescenza, abbiamo esaminato il complesso, PAR un regolatore del citoscheletro. Abbiamo trovato che il complesso PAR, come traduzione locale, &egrave; necessario per stimolata, ma non basale, escrescenza. Par3 mRNA &egrave; localizzato nello sviluppo di assoni e NGF e trigger netrina-1 traduzione del suo locale. Ablazione selettiva di mRNA Par3 da assoni abolisce l&#39;effetto escrescenza-promozione di NGF. Questi risultati identificano un nuovo ruolo per la traduzione locale e il complesso in escrescenza assonale PAR.

Allungamento assonale innescato dalla traduzione locale indotta da stimolo di una proteina complessa di polarit&agrave;.

&#x958B;&#x767A;&#x4E2D;&#x306B;&#x3001;&#x8EF8;&#x7D22;&#x306E;&#x6210;&#x9577;&#x7387;&#x3092;&#x6B63;&#x78BA;&#x306B;&#x8349;&#x5206;&#x3051;&#x4E0A;&#x306E;&#x4E00;&#x6642;&#x7684;&#x306A;&#x5236;&#x5FA1;&#x3092;&#x63D0;&#x4F9B;&#x3059;&#x308B;&#x305F;&#x3081;&#x306B;&#x898F;&#x5236;&#x3055;&#x308C;&#x3066;&#x3044;&#x308B;&#x3002;&#x8EF8;&#x7D22;&#x6210;&#x9577;&#x306E;&#x6B63;&#x78BA;&#x306A;&#x6642;&#x9593;&#x7684;&#x306A;&#x898F;&#x5236;&#x306F;&#x6A5F;&#x80FD;&#x7684;&#x306A;&#x30B7;&#x30CA;&#x30D7;&#x30B9;&#x3068;&#x795E;&#x7D4C;&#x7CFB;&#x306E;&#x9069;&#x5207;&#x306A;&#x30D1;&#x30BF;&#x30FC;&#x30CB;&#x30F3;&#x30B0;&#x306E;&#x5F62;&#x6210;&#x306B;&#x91CD;&#x8981;&#x306A;&#x30B9;&#x30C6;&#x30C3;&#x30D7;&#x3067;&#x3059;&#x3002;&#x8EF8;&#x7D22;&#x4F38;&#x9577;&#x306E;&#x901F;&#x5EA6;&#x306F;&#x3001;&#x305D;&#x306E;&#x3088;&#x3046;&#x306A;&#x30CD;&#x30C8;&#x30EA;&#x30F3;1&#x3068;&#x4E0D;&#x5B8C;&#x5168;&#x306B;&#x5B9A;&#x7FA9;&#x3055;&#x308C;&#x305F;&#x7D4C;&#x8DEF;&#x3092;&#x4F7F;&#x7528;&#x3057;&#x3066;&#x8EF8;&#x7D22;&#x4F38;&#x9577;&#x3092;&#x523A;&#x6FC0;&#x3059;&#x308B;&#x795E;&#x7D4C;&#x6210;&#x9577;&#x56E0;&#x5B50;&#xFF08;NGF&#xFF09;&#x306A;&#x3069;&#x306E;&#x8981;&#x56E0;&#x306B;&#x3088;&#x3063;&#x3066;&#x5897;&#x52A0;&#x3057;&#x307E;&#x3059;&#x3002;&#x306E;&#x30E1;&#x30AB;&#x30CB;&#x30BA;&#x30E0;&#x30CD;&#x30C8;&#x30EA;&#x30F3;1&#x3068;NGF&#x523A;&#x6FC0;&#x8EF8;&#x7D22;&#x306E;&#x6210;&#x9577;&#x3092;&#x660E;&#x3089;&#x304B;&#x306B;&#x3059;&#x308B;&#x305F;&#x3081;&#x306B;&#x3001;&#x6211;&#x3005;&#x306F;&#x3001;&#x5C40;&#x6240;&#x7684;&#x306A;&#x30BF;&#x30F3;&#x30D1;&#x30AF;&#x8CEA;&#x306E;&#x7FFB;&#x8A33;&#x306E;&#x5F79;&#x5272;&#x3092;&#x691C;&#x8A0E;&#x3057;&#x305F;&#x3002;&#x6211;&#x3005;&#x306F;&#x3001;&#x30A4;&#x30F3;&#x30C8;&#x30E9;&#x8EF8;&#x7D22;&#x30BF;&#x30F3;&#x30D1;&#x30AF;&#x8CEA;&#x306E;&#x7FFB;&#x8A33;&#x3092;&#x523A;&#x6FC0;&#x3059;&#x308B;&#x305F;&#x3081;&#x306B;&#x5FC5;&#x8981;&#x3055;&#x308C;&#x3066;&#x3044;&#x308B;&#x3053;&#x3068;&#x3092;&#x767A;&#x898B;&#x3057;&#x307E;&#x3057;&#x305F;&#x304C;&#x3001;&#x57FA;&#x790E;&#x3067;&#x306F;&#x306A;&#x304F;&#x3001;&#x8EF8;&#x7D22;&#x4F38;&#x9577;&#x3002;&#x7FFB;&#x8A33;&#x306B;&#x4F9D;&#x5B58;&#x3057;&#x305F;&#x4F38;&#x9577;&#x306E;&#x30E1;&#x30AB;&#x30CB;&#x30BA;&#x30E0;&#x3092;&#x8B58;&#x5225;&#x3059;&#x308B;&#x305F;&#x3081;&#x306B;&#x3001;&#x6211;&#x3005;&#x306F;PAR&#x8907;&#x5408;&#x4F53;&#x3001;&#x7D30;&#x80DE;&#x9AA8;&#x683C;&#x8ABF;&#x7BC0;&#x3092;&#x691C;&#x8A0E;&#x3057;&#x305F;&#x3002;&#x6211;&#x3005;&#x306F;PAR&#x8907;&#x5408;&#x4F53;&#x306F;&#x3001;&#x5C40;&#x6240;&#x7684;&#x7FFB;&#x8A33;&#x306E;&#x3088;&#x3046;&#x306B;&#x3001;&#x523A;&#x6FC0;&#x304C;&#x5FC5;&#x8981;&#x3067;&#x3042;&#x308B;&#x3053;&#x3068;&#x3092;&#x767A;&#x898B;&#x3057;&#x305F;&#x304C;&#x3001;&#x57FA;&#x790E;&#x3067;&#x306F;&#x306A;&#x304F;&#x3001;&#x4F38;&#x9577;&#x3002;&#x30D1;&#x30FC;3 mRNA&#x306F;&#x3001;&#x958B;&#x767A;&#x8EF8;&#x7D22;&#x306B;&#x5C40;&#x5728;&#x3057;&#x3001;NGF&#x304A;&#x3088;&#x3073;&#x30CD;&#x30C8;&#x30EA;&#x30F3;1&#x306F;&#x3001;&#x30ED;&#x30FC;&#x30AB;&#x30EB;&#x5909;&#x63DB;&#x3092;&#x30C8;&#x30EA;&#x30AC;&#x30FC;&#x3057;&#x3066;&#x3044;&#x307E;&#x3059;&#x3002;&#x8EF8;&#x7D22;&#x304B;&#x3089;&#x30D1;&#x30FC;3&#x306E;mRNA&#x306E;&#x9078;&#x629E;&#x7684;&#x306A;&#x30A2;&#x30D6;&#x30EC;&#x30FC;&#x30B7;&#x30E7;&#x30F3;&#x306F;&#x3001;NGF&#x306E;&#x4F38;&#x9577;&#x4FC3;&#x9032;&#x52B9;&#x679C;&#x3092;&#x5EC3;&#x6B62;&#x3002;&#x3053;&#x308C;&#x3089;&#x306E;&#x7D50;&#x679C;&#x306F;&#x3001;&#x8EF8;&#x7D22;&#x4F38;&#x9577;&#x306B;&#x304A;&#x3051;&#x308B;&#x5C40;&#x6240;&#x7684;&#x7FFB;&#x8A33;&#x3068;PAR&#x8907;&#x5408;&#x4F53;&#x306E;&#x65B0;&#x305F;&#x306A;&#x5F79;&#x5272;&#x3092;&#x8B58;&#x5225;&#x3057;&#x307E;&#x3059;&#x3002;

&#x6975;&#x6027;&#x8907;&#x96D1;&#x306A;&#x86CB;&#x767D;&#x8CEA;&#x306E;&#x523A;&#x6FC0;&#x306B;&#x3088;&#x3063;&#x3066;&#x8A98;&#x767A;&#x3055;&#x308C;&#x308B;&#x5C40;&#x6240;&#x7684;&#x7FFB;&#x8A33;&#x306B;&#x3088;&#x3063;&#x3066;&#x30C8;&#x30EA;&#x30AC;&#x3055;&#x308C;&#x308B;&#x8EF8;&#x7D22;&#x4F38;&#x9577;

&#xAC1C;&#xBC1C; &#xD558;&#xB294; &#xB3D9;&#xC548; &#xCD95; &#xC0AD; &#xC131;&#xC7A5;&#xB960; pathfinding &#xC2DC;&#xAC04;&#xC801; &#xC81C;&#xC5B4;&#xD560; &#xC218; &#xC788;&#xB3C4;&#xB85D; &#xC815;&#xD655; &#xD558; &#xAC8C; &#xD1B5;&#xC81C; &#xB41C;&#xB2E4;. Axonal &#xC131;&#xC7A5;&#xC758; &#xC815;&#xD655;&#xD55C; &#xC2DC;&#xAC04;&#xC801; &#xC870;&#xC808; &#xAE30;&#xB2A5; &#xC2DC; &#xB0C5; &#xC2A4; &#xD615;&#xC131; &#xBC0F; &#xC2E0;&#xACBD; &#xC2DC;&#xC2A4;&#xD15C;&#xC758; &#xC801;&#xC808; &#xD55C; &#xD328;&#xD134;&#xD654;&#xC5D0; &#xC911;&#xC694; &#xD55C; &#xB2E8;&#xACC4; &#xC774;&#xB2E4;. Axonal &#xC2E0;&#xC7A5; &#xB960; &#xCD95; &#xC0AD; &#xD30C;&#xC0DD;&#xBB3C; &#xBD88;&#xC644;&#xC804; &#xD558; &#xAC8C; &#xC815;&#xC758; &#xB41C; &#xACBD;&#xB85C; &#xC0AC;&#xC6A9; &#xD558; &#xC5EC; &#xC790;&#xADF9; netrin 1 &#xBC0F; &#xC2E0;&#xACBD; &#xC131;&#xC7A5; &#xC778;&#xC790; (NGF) &#xAC19;&#xC740; &#xC694;&#xC778;&#xC5D0; &#xC758;&#xD574; &#xC99D;&#xAC00; &#xB41C;&#xB2E4;. &#xCD95; &#xC0C9; &#xC131;&#xC7A5; netrin 1 NGF &#xC790;&#xADF9;&#xC758; &#xBA54;&#xCEE4;&#xB2C8;&#xC998;&#xC744; &#xBA85;&#xD655; &#xD558; &#xAC8C; &#xC6B0;&#xB9AC; &#xC9C0;&#xC5ED; &#xB2E8;&#xBC31;&#xC9C8; &#xBC88;&#xC5ED;&#xC758; &#xC5ED;&#xD560; &#xD0D0;&#xD5D8;. &#xC6B0;&#xB9AC; &#xB0B4;&#xBD80; axonal &#xB2E8;&#xBC31;&#xC9C8; &#xBC88;&#xC5ED; &#xD544;&#xC694;&#xD55C; &#xC790;&#xADF9;, &#xD558;&#xC9C0;&#xB9CC; &#xD558;&#xC9C0; &#xAE30;&#xC800; axon &#xD30C;&#xC0DD;&#xBB3C;&#xC5D0; &#xB300; &#xD55C; &#xBC1C;&#xACAC;. &#xBC88;&#xC5ED; &#xC885;&#xC18D; &#xD30C;&#xC0DD;&#xBB3C;&#xC758; &#xBA54;&#xCEE4;&#xB2C8;&#xC998;&#xC744; &#xC2DD;&#xBCC4; &#xD558;&#xAE30; &#xC704;&#xD574; &#xBCF5;&#xC7A1; &#xD55C;, &#xD30C; cytoskeleton &#xB808; &#xADE4; &#xB808;&#xC774; &#xD130; &#xAC80;&#xC0AC; &#xD558; &#xACE0;. &#xC6B0;&#xB9AC; &#xD604;&#xC9C0; &#xBC88;&#xC5ED; &#xCC98;&#xB7FC; &#xD30C; &#xBCF5;&#xC7A1; &#xD55C; &#xC790;&#xADF9;, &#xD558;&#xC9C0;&#xB9CC; &#xD558;&#xC9C0; &#xAE30;&#xC800; &#xD30C;&#xC0DD;&#xBB3C;&#xC5D0; &#xD544;&#xC694;&#xD55C; &#xBC1C;&#xACAC;. &#xCD95; &#xC0AD;, &#xD558; &#xACE0; NGF&#xC640; netrin 1 &#xD2B8;&#xB9AC;&#xAC70;&#xB294; &#xB85C;&#xCEEC; &#xBC88;&#xC5ED;&#xC744; &#xAC1C;&#xBC1C; &#xD558;&#xB294; Par3 mRNA &#xC9C0;&#xC5ED;&#xD654; &#xB429;&#xB2C8;&#xB2E4;. &#xCD95; &#xC0AD;&#xC5D0;&#xC11C; Par3 Mrna&#xC758; &#xC120;&#xD0DD;&#xC801; &#xC808;&#xC81C; &#xB9D0;&#xC0B4; NGF&#xC758; &#xD30C;&#xC0DD;&#xBB3C; &#xD64D;&#xBCF4; &#xD6A8;&#xACFC;. &#xC774; &#xACB0;&#xACFC; &#xB85C;&#xCEEC; &#xBC88;&#xC5ED; &#xBC0F; axonal &#xD30C;&#xC0DD;&#xBB3C;&#xC5D0; &#xBCF5;&#xC7A1; &#xD55C; &#xD30C;&#xC5D0; &#xB300; &#xD55C; &#xC0C8;&#xB85C;&#xC6B4; &#xC5ED;&#xD560;&#xC744; &#xC2DD;&#xBCC4;&#xD569;&#xB2C8;&#xB2E4;.

Axonal &#xC2E0;&#xC7A5; &#xADF9;&#xC131; &#xBCF5;&#xC7A1; &#xD55C; &#xB2E8;&#xBC31;&#xC9C8;&#xC758; &#xB85C;&#xCEEC; &#xBC88;&#xC5ED; &#xC790;&#xADF9; &#xC720;&#xB3C4; &#xC758;&#xD574; &#xD2B8;&#xB9AC;&#xAC70;&#xB429;&#xB2C8;&#xB2E4;.

Durante el desarrollo, las tasas de crecimiento de los axones est&#xE1;n estrictamente reglamentadas para proporcionar un control temporal sobre b&#xFA;squeda de caminos. La regulaci&#xF3;n precisa temporal de crecimiento axonal es una etapa clave en la formaci&#xF3;n de sinapsis funcionales y el patr&#xF3;n adecuado del sistema nervioso. La tasa de elongaci&#xF3;n axonal se incrementa por factores tales como netrina-1 y factor de crecimiento nervioso (NGF), que estimulan ax&#xF3;n utilizando v&#xED;as incompletamente definidos. Para aclarar el mecanismo de netrina-1-y NGF estimulada por el crecimiento del ax&#xF3;n, hemos explorado el papel de la traducci&#xF3;n local de prote&#xED;nas. Se encontr&#xF3; que dentro de la traducci&#xF3;n de prote&#xED;nas axonal se requiere para estimulada, pero no basales, ax&#xF3;n. Para identificar el mecanismo de la traducci&#xF3;n dependiente de la consecuencia, hemos examinado el complejo PAR, un regulador del citoesqueleto. Hemos encontrado que el complejo PAR, como la traducci&#xF3;n local, es necesaria para estimular, sino consecuencia, no basal. Par3 ARNm se localiza en el desarrollo de los axones, y NGF y netrina 1-activar su traducci&#xF3;n local. La ablaci&#xF3;n selectiva de los ARNm de los axones Par3 suprime el efecto consecuencia de promoci&#xF3;n de NGF. Estos resultados identifican un nuevo papel para la traducci&#xF3;n local y el complejo PAR en el crecimiento de los axones.

Elongaci&#xF3;n axonal desencadenado por est&#xED;mulos inducidos por la traducci&#xF3;n local de una prote&#xED;na compleja de polaridad

The surface of developing axons expands in a process mediated by the exocyst complex. The spatio-temporal regulation of the exocyst is only partially understood. Here we report that stimulated membrane enlargement in dorsal root ganglion (DRG) axons is triggered by intra-axonal synthesis of TC10, a small GTPase required for exocyst function. Induced membrane expansion and axon outgrowth are inhibited after axon-specific knockdown of TC10 mRNA. To determine the relationship of intra-axonal TC10 synthesis with the previously described stimulus-induced translation of the cytoskeletal regulator Par3, we investigate the signalling pathways controlling their local translation in response to NGF. Phosphoinositide 3-kinase (PI3K)-dependent activation of the Rheb-mTOR pathway triggers the simultaneous local synthesis of TC10 and Par3. These results reveal the importance of local translation in the control of membrane dynamics and demonstrate that localized, mTOR-dependent protein synthesis triggers the simultaneous activation of parallel pathways.

Local translation of TC10 is required for membrane expansion during axon outgrowth.

In Alzheimer's disease (AD) brain, exposure of axons to Aβ causes pathogenic changes that spread retrogradely by unknown mechanisms, affecting the entire neuron. We found that locally applied Aβ1-42 initiates axonal synthesis of a defined set of proteins including the transcription factor ATF4. Inhibition of local translation and retrograde transport or knockdown of axonal Atf4 mRNA abolished Aβ-induced ATF4 transcriptional activity and cell loss. Aβ1-42 injection into the dentate gyrus (DG) of mice caused loss of forebrain neurons whose axons project to the DG. Protein synthesis and Atf4 mRNA were upregulated in these axons, and coinjection of Atf4 siRNA into the DG reduced the effects of Aβ1-42 in the forebrain. ATF4 protein and transcripts were found with greater frequency in axons in the brain of AD patients. These results reveal an active role for intra-axonal translation in neurodegeneration and identify ATF4 as a mediator for the spread of AD pathology.

Axonally synthesized ATF4 transmits a neurodegenerative signal across brain regions.

Localized protein synthesis is a mechanism by which morphologically polarized cells react in a spatially confined and temporally acute manner to changes in their environment. During the development of the nervous system intra-axonal protein synthesis is crucial for the establishment of neuronal connections. In contrast, mature axons have long been considered as translationally inactive but upon nerve injury or under neurodegenerative conditions specific subsets of mRNAs are recruited into axons and locally translated. Intra-axonally synthesized proteins can have pathogenic or restorative and regenerative functions, and thus targeting the axonal translatome might have therapeutic value, for example in the treatment of spinal cord injury or Alzheimer's disease. In the case of Alzheimer's disease the local synthesis of the stress response transcription factor activating transcription factor 4 mediates the long-range retrograde spread of pathology across the brain, and inhibition of local Atf4 translation downstream of the integrated stress response might interfere with this spread. Several molecular tools and approaches have been developed to target specifically the axonal translatome by either overexposing proteins locally in axons or, conversely, knocking down selectively axonally localized mRNAs. Many questions about axonal translation remain to be answered, especially with regard to the mechanisms establishing specificity but, nevertheless, targeting the axonal translatome is a promising novel avenue to pursue in the development for future therapies for various neurological conditions.

Targeting axonal protein synthesis in neuroregeneration and degeneration.

Local translation mediates axonal responses to Semaphorin3A (Sema3A) and other guidance cues. However, only a subset of the axonal proteome is locally synthesized, whereas most proteins are trafficked from the soma. The reason why only specific proteins are locally synthesized is unknown. Here we show that local protein synthesis and degradation are linked events in growth cones. We find that growth cones exhibit high levels of ubiquitination and that local signalling pathways trigger the ubiquitination and degradation of RhoA, a mediator of Sema3A-induced growth cone collapse. Inhibition of RhoA degradation is sufficient to remove the protein-synthesis requirement for Sema3A-induced growth cone collapse. In addition to RhoA, we find that locally translated proteins are the main targets of the ubiquitin-proteasome system in growth cones. Thus, local protein degradation is a major feature of growth cones and creates a requirement for local translation to replenish proteins needed to maintain growth cone responses.

Ulrich Hengst

College of Physicians and Surgeons

Columbia University

Detection of Axonally Localized mRNAs in Brain Sections Using High-Resolution In Situ Hybridization

Stereotaxic Infusion of Oligomeric Amyloid-beta into the Mouse Hippocampus

Ulrich Hengst

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}College of Physicians and Surgeons

Columbia University

Detection of Axonally Localized mRNAs in Brain Sections Using High-Resolution In Situ Hybridization

Stereotaxic Infusion of Oligomeric Amyloid-beta into the Mouse Hippocampus

College of Physicians and Surgeons