@article{WetzelJablonkaBlum2013,
  author    = {Wetzel, Andrea and Jablonka, Sibylle and Blum, Robert},
  title     = {Cell-autonomous axon growth of young motoneurons is triggered by a voltage-gated sodium channel},
  series = {Channels (Austin)},
  volume    = {7},
  journal   = {Channels (Austin)},
  number    = {1},
  doi       = {10.4161/chan.23153},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-132586},
  pages     = {51-56},
  year      = {2013},
  abstract  = {Spontaneous electrical activity preceding synapse formation contributes to the precise regulation of neuronal development. Examining the origins of spontaneous activity revealed roles for neurotransmitters that depolarize neurons and activate ion channels. Recently, we identified a new molecular mechanism underlying fluctuations in spontaneous neuronal excitability. We found that embryonic motoneurons with a genetic loss of the low-threshold sodium channel Na\(_V\)1.9 show fewer fluctuations in intracellular calcium in axonal compartments and growth cones than wild-type littermates. As a consequence, axon growth of Na\(_V\)1.9-deficient motoneurons in cell culture is drastically reduced while dendritic growth and cell survival are not affected. Interestingly, Na\(_V\)1.9 function is observed under conditions that would hardly allow a ligand- or neurotransmitter-dependent depolarization. Thus, Na\(_V\)1.9 may serve as a cell-autonomous trigger for neuronal excitation. In this addendum, we discuss a model for the interplay between cell-autonomous local neuronal activity and local cytoskeleton dynamics in growth cone function.},
  language  = {en}
}
@phdthesis{Subramanian2011,
  author    = {Subramanian, Narayan},
  title     = {Role of NaV1.9 in activity dependent axon growth in embryonic cultured motoneurons},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57536},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {Spontaneous neural activity has been shown to regulate crucial events in neurite growth including axonal branching and path finding. In animal models of spinal muscular atrophy (SMA) cultured embryonic mouse motoneurons show distinct defect in axon elongation and neural activity. This defect is governed by abnormal clustering of Ca2+ channels in the axonal regions and the protruding growth cone area. The mechanisms that regulate the opening of calcium channels in developing motoneurons are not yet clear. The question was addressed by blocking neural activity in embryonic cultured motoneurons by pharmacological inhibition of voltage-gated sodium channels (VGSC) by saxitoxin (STX) and tetrodotoxin (TTX). Low dosages of STX resulted in significant reduction of axon growth and neural activity in cultured motoneurons. This pharmacological treatment did not affect survival of motoneurons in comparison to control motoneurons that was grown in the presence of survival neurotrophic factors BDNF and CNTF. It was also found that STX was 10 times more potent than TTX a common inhibitor of VGSC with a reduced activity on the TTX-insensitive sodium channels NaV1.5, NaV1.8 and NaV1.9. Reverse Transcriptase-PCR experiments revealed the presence of NaV1.9 as the likely candidate that begins to express from embryonic stage sixteen in the mouse spinal cord. Immunolabelling experiments showed that the channel is expressed in the axonal compartments and axonal growth cones in cultured motoneurons. Suppression of NaV1.9 in cultured motoneurons by lentivirus mediated short hairpin-RNA (shRNA) resulted in shorter axon length in comparison with uninfected and scrambled constructs. Further, embryonic motoneurons cultured from NaV1.9 knockout mice also showed a significant reduction in neural activity and axon growth. The findings of this work highlight the role of NaV1.9 as an important contender in regulating activity dependent axon growth in embryonic cultured motoneurons. NaV1.9 could therefore be considered as a prospective molecule that could play an important role in regulating axon growth in motoneuron disease models like spinal muscular atrophy (SMA).},
  subject      = {Axon},
  language  = {en}
}
@phdthesis{Wetzel2013,
  author    = {Wetzel, Andrea},
  title     = {The role of TrkB and NaV1.9 in activity-dependent axon growth in motoneurons},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-92877},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {W{\"a}hrend der Entwicklung des Nervensystems lassen sich bei Motoneuronen aktivit{\"a}tsabh{\"a}ngige Kalziumstr{\"o}me eobachten, die das Axonwachstum regulieren. Diese Form der neuronalen Spontanaktivit{\"a}t sowie das Auswachsen von Axonen sind bei Motoneuronen, die aus Tiermodellen der Spinalen Muskelatrophie isoliert werden, gest{\"o}rt. Experimente aus unserer Arbeitsgruppe haben gezeigt, dass spontane Erregbarkeit und aktivit{\"a}tsabh{\"a}ngiges Axonwachstum von kultivierten Motoneuronen auch unter Verwendung von Toxinen beeintr{\"a}chtigt sind, welche die Aktivit{\"a}t von spannungsabh{\"a}ngigen Natriumkan{\"a}len blockieren. In diesen Versuchen war die Wirkung von Saxitoxin effizienter als die Wirkung von Tetrodotoxin. Wir identifizierten den Saxitoxin-sensitiven/Tetrodotoxin-insensitiven spannungsabh{\"a}ngigen Natriumkanal NaV1.9 als Trigger f{\"u}r das {\"O}ffnen spannungsabh{\"a}ngiger Kalziumkan{\"a}le. Die Expression von NaV1.9 in Motoneuronen konnte {\"u}ber quantitative RT-PCR nachgewiesen werden und antik{\"o}rperf{\"a}rbungen offenbarten eine Anreicherung des Kanals im axonalen Wachstumskegel sowie an Ranvier'schen Schn{\"u}rringen von isolierten Nervenfasern wildtypischer M{\"a}use. Motoneurone von NaV1.9 knock-out M{\"a}usen zeigen reduzierte Spontanaktivit{\"a}t und eine Reduktion des Axonwachstums, welche durch NaV1.9 {\"U}berexpression normalisiert werden kann. In Motoneuronen von Smn-defizienten M{\"a}usen konnte keine Abweichung der NaV1.9 Proteinverteilung nachgewiesen werden. K{\"u}rzlich wurden Patienten identifiziert, die eine missense-Mutation im NaV1.9 kodierenden SCN11A Gen tragen. Diese Patienten k{\"o}nnen keinerlei Schmerz empfinden und leiden zudem an Muskelschw{\"a}che in Kombination mit einer verz{\"o}gerten motorischen Entwicklung. Im Rahmen dieser Doktorarbeit konnten molekularbiologische Untersuchungen an M{\"a}usen, welche die Mutation im orthologen Scn11a Gen tragen, zur Aufkl{\"a}rung des Krankheitsmechanismus beitragen. Die Kooperationsstudie zeigte, dass eine gesteigerte Funktion von NaV1.9 diese spezifische Kanalerkrankung ausl{\"o}st, was die Wichtigkeit von NaV1.9 in menschlichen Motoneuronen unterstreicht. Eine fr{\"u}here Studie beschrieb an hippocampalen Neuronen, dass die Rezeptortyrosinkinase tropomyosin receptor kinase B (TrkB) den NaV1.9 Kanal {\"o}ffnen kann. Im Wachstumskegel von Motoneuronen ist TrkB nachweisbar und folglich in r{\"a}umlicher N{\"a}he zu NaV1.9 zu finden. Um zu pr{\"u}fen, ob TrkB in die spontane Erregbarkeit von Motoneuronen involviert ist, wurden TrkB knock-out M{\"a}use untersucht. Isolierte Motoneurone von TrkB knock-out M{\"a}usen weisen eine Reduktion der Spontanaktivit{\"a}t und eine Verringerung des Axonwachstums auf. Ob TrkB und NaV1.9 hierbei funktionell gekoppelt sind, ist Gegenstand k{\"u}nftiger Forschung.},
  subject      = {Motoneuron},
  language  = {en}
}
@phdthesis{Hugo2023,
  author    = {Hugo, Julian},
  title     = {'Signal-close-to-noise' calcium activity reflects neuronal excitability},
  doi       = {10.25972/OPUS-29260},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-292605},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Chronic pain conditions are a major reason for the utilization of the health care system. Inflammatory pain states can persist facilitated by peripheral sensitization of nociceptors. The voltage-gated sodium channel 1.9 (NaV1.9) is an important regulator of neuronal excitability and is involved in inflammation-induced pain hypersensitivity. Recently, oxidized 1-palmitoyl-2-arachidonoyl-sn-glycerol-3-phosphatidylcholine (OxPAPC) was identified as a mediator of acute inflammatory pain and persistent hyperalgesia, suggesting an involvement in proalgesic cascades and peripheral sensitization. Peripheral sensitization implies an increase in neuronal excitability. This thesis aims to characterize spontaneous calcium activity in neuronal compartments as a proxy to investigate neuronal excitability, making use of the computational tool Neural Activity Cubic (NA3). NA3 allows automated calcium activity event detection of signal-close-to-noise calcium activity and evaluation of neuronal activity states. Additionally, the influence of OxPAPC and NaV1.9 on the excitability of murine dorsal root ganglion (DRG) neurons and the effect of OxPAPC on the response of DRG neurons towards other inflammatory mediators (prostaglandin E2, histamine, and bradykinin) is investigated. Using calcium imaging, the presence of spontaneous calcium activity in murine DRG neurons was established. NA3 was used to quantify this spontaneous calcium activity, which revealed decreased activity counts in axons and somata of NaV1.9 knockout (KO) neurons compared to wildtype (WT). Incubation of WT DRG neurons with OxPAPC before calcium imaging did not show altered activity counts compared to controls. OxPAPC incubation also did not modify the response of DRG neurons treated with inflammatory mediators. However, the variance ratio computed by NA3 conclusively allowed to determine neuronal activity states. In conclusion, my findings indicate an important function of NaV1.9 in determining the neuronal excitability of DRG neurons in resting states. OxPAPC exposition does not influence neuronal excitability nor sensitizes neurons for other inflammatory mediators. This evidence reduces the primary mechanism of OxPAPC-induced hyperalgesia to acute effects. Importantly, it was possible to establish an approach for unbiased excitability quantification of DRG neurons by calcium activity event detection and calcium trace variance analysis by NA3. It was possible to show that signal-close-to-noise calcium activity reflects neuronal excitability states.},
  subject      = {Entz{\"u}ndung},
  language  = {en}
}