Motor neurons development

Raff The ventralizing signals such as Sonic hedgehog that are required for motor neuron development are also required for oligodendrocyte precursors to develop from CNS stem cells, at least in the spinal cord. 

Kanungo J, Zheng YL, Amin ND, Kaur S, Ramchandran R, Pant HC (2009) Specific inhibition of cyclin-dependent kinase 5 activity induces motor neuron development in vivo. Biochem Biophys Res Commun 386 263-267... 

Despite all these studies, gene targeting experiments suggest that BDNF is not essential for motor neuron development although its receptor, trkB, is... 

Jones, K.R., Farinas, I., Backus, C. and Reichardt, L.F. (1994) Targeted disruption of the BDNF gene perturbs brain and sensory neuron development but not motor neuron development. Cell 76 989-999. 

Participates in assembly, processing and trafficking of small nuclear RNPs (Zhang et al. 2006), supports motor neuron development (McAVhorter et al. 2003) Modulates transcription repression... 

Arlotta P, Molyneaux BJ, Chen J et al (2005) Neuronal subtype-specific genes that control corticospinal motor neuron development in vivo. Neuron 45 207-221... 

Desai, C., Garriga, G., Mclntire, S. L., andHorvitz, H. R. (1988). Agenetic pathway for the development of the Caenorhabditis elegans HSN motor neurons. Nature 336 638-646. 

Following the development of the motor program, neurons originating in the multimodal motor association areas transmit impulses by way of association tracts to neurons of the primary motor cortex. The primary motor cortex is located in the precentral gyrus, which is the most posterior region of the frontal lobe adjacent to the multimodal motor association areas (see Figure 6.3) this area initiates voluntary contractions of specific skeletal muscles. Neurons whose cell bodies reside here transmit impulses by way of descending projection tracts to the spinal cord, where they innervate the alpha motor neurons (which innervate skeletal muscles). 

Muscle fibers are incapable of mitosis. In fact, the number of muscle fibers per muscle is likely determined by the second trimester of fetal development. Therefore, enlargement of a whole muscle is not due to an increase in the number of fibers in the muscle, but rather to the hypertrophy of existing fibers. Because muscle fibers have no gap junctions between them, electrical activity cannot spread from one cell to the next. Therefore, each muscle fiber is innervated by a branch of an alpha motor neuron. A motor unit is defined as an alpha motor neuron and all of the muscle fibers that it innervates. 

Ensini, M., Tsuchida, T. M., Belting, H.-G. and Jessell, T. M. The control of rostrocaudal pattern in the developing spinal cord specification of motor neuron subtype identity is initiated by signals from paraxial mesoderm. Development 125 969-982,1998. 

Individual neurons and glial cells are responsive to a number of different growth factors. Growth factors play both unique and overlapping roles in the development and sustenance of these cells. Perhaps the most dramatic example of this is the elaborate array of trophic factors that have evolved to support spinal motor neurons. There are presently at least 15 different factors that are known to influence the survival of these cells [4]. 

IGF I has recently been the focus of considerable interest due to its actions on motor neurons. It can prevent normal motor neuron cell death during development, reduce the loss of these cells following nerve injury and enhance axonal regeneration. In the adult, injection of IGF I results in sprouting of motor neuron terminals and increases the size of the neuromuscular junction. These and other studies suggest potential therapeutic applications of IGF I in several neurological diseases including amyotrophic lateral sclerosis and peripheral neuropathies. 

HGF serves as an attractant for developing spinal motor neurons and thalamic axons in vitro. HGF was shown to protect cerebellar granule neurons against excitotoxicity. 

The development of motor neurons and oligodendrocytes is dependent on sonic hedgehog 508... 

The development of motor neurons and oligodendrocytes is dependent on sonic hedgehog. One of the most intensely studied cell types in the CNS is the spinal cord... 

Transgenic mice expressing wild type or mutant neurofilament genes develop motor neuron disease and neurofibrillary pathology 736... 

Reaume, A. G., Elliott, J. L., Hoffman, E. K. et al. Motor neurons in Cu/Zn superoxide dismutase-deficient mice develop normally but exhibit enhanced cell death after axonal injury. Nat. Genet. 13 43-47,1996. 

Oppenheim, R. W., Houenou, L. J., Johnson, J. E. et al. Developing motor neurons rescued from programmed and axotomy-induced cell death by GDNF. Nature 373 344-346,1995. 

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