Haque, Ziaul: Plexin-A2 and neuropilin-2 in the axonal guidance of cranial nerves in avian embryos. - Bonn, 2014. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5n-35401
@phdthesis{handle:20.500.11811/6059,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5n-35401,
author = {{Ziaul Haque}},
title = {Plexin-A2 and neuropilin-2 in the axonal guidance of cranial nerves in avian embryos},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2014,
month = mar,

note = {Secreted class-III semaphorins exert their effects in axon guidance and neuronal migration by binding with receptors, such as plexins and neuropilins. Neuropilins are insufficient to convey signals of their own; rather, they form complexes with plexins to propagate signals of semaphorins into the cells. Though the role of class-III semaphorins in governing fasciculation, axon growth and cell migration has been studied previously, it is far away from our understanding how their receptors (plexin-As and neuropilins) take part in the axonal guidance of cranial and spinal motor neurons. It has been demonstrated that plexin-A2 and neuropilin-2 (Npn-2) control the motor somal positioning in the chick spinal cord. However, it is still unknown whether they are involved in the regulation of cranial motor neurons. For this purpose, we first analyzed the expression of plexin-A1, plexin-A2, plexin-A4 and Npn-1 and Npn-2 in the motor neuronal groups within the chick hindbrain. Our results demonstrated that all analyzed plexins and neuropilins were selectively expressed by hindbrain motor neurons. For instance, plexin-A1, plexin-A2 and Npn-1 were expressed by both dorsal and ventral exiting cranial motor neurons, whereas plexin-A4 and Npn-2 only by dorsal exiting cranial motor neurons. Based on the expression data, we selected plexin-A2 and Npn-2 genes for knockdown experiments by in ovo-electroporation of short hairpin RNA (shRNA) constructs into the ventral neural tube at the post-otic hindbrain level, from which motor neurons of the vagus (nX), accessory (nXI) and hypoglossal (nXII) nerves originated. Unlike the spinal cord, where loss of function of either plexin-A2 or Npn-2 induced ectopic migration of motor neuron somata along the ventral root, only Npn-2 in the hindbrain induced ectopic migration of motor somata but along the dorsal root. In addition, inhibition of function of Npn-2 resulted in misrouting and severe defasciculation of dorsal exiting (vagus and accessory) motor axons. Furthermore, knockdown of plexin-A2 led to the significant (P<0.001) reduction of motor neuron population in the ventral neural tube and impaired fasciculation of ventral exiting (hypoglossal) motor axons. These results indicate that plexin-A2 and Npn-2 act independently in the axonal guidance of cranial nerves in chick embryos.},
url = {http://hdl.handle.net/20.500.11811/6059}
}

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