Myosin 10 is Required for Spinal Motor Axon Growth and Guidance in Zebrafish Embryos

<p>Neurodevelopmental disorders are disabilities caused by malfunctioning mechanisms within the developing nervous tissue. These abnormalities often result in conditions such as autism spectrum disorders, Attention Deficient Hyperactivity Disorder (ADHD), motor dysfunctions, learning disabilities and mental retardation. Recent surveys indicate that there will be a 12% increase of children in the United States alone who are affected by neurodevelopmental disorders. Thus, it is important to understand both the normal and abnormal mechanisms of neural development. Neural development involves specification of new neurons and formation of neural circuits that connect the nervous system to every organ of the developing embryo. Neural circuits are formed by extensions of neuronal cell bodies called axons. Axons grow towards their specific target organs at growth cones, by sensing the environment for molecular cues which reorganizes their cytoskeleton to allow for their growth. Growth cones are actin rich suggesting that actin binding molecules play a vital role in axon guidance. Myosins are a class of actin binding proteins. <em>Myosin 10</em> (<em>myo10</em>) is a myosin that is highly localized in growth cones indicating their potential role in axon guidance and growth. While <em>myo10</em> has been shown to be involved in axon guidance in neural cell cultures, this has not been demonstrated <em>in vivo. </em>This aim of this project was to identify the roles of <em>myo10</em> in axon growth cone guidance <em>in vivo </em>utilizing a zebrafish (<em>Danio rerio</em>) model. I established that <em>myo10 </em>is required for spinal motor and hindbrain axon development in the zebrafish. In the absence of <em>myo10</em>, 100% of caudal primary motor neurons were defective and 88% of middle primary motor axons were defective. Additionally, I characterized the phenotype of <em>myo10 </em>deficient embryos further by examining the points of innervation of the motor axons. Spinal motor axons innervate the muscle. The post-synaptic muscle is lined with acetylcholine receptors. <em>Myo10</em> deficient embryos have a defective patterning of acetylcholine receptors and the muscles show indications of atrophy. Lastly, I provide some evidence for possible mechanisms in which <em>myo10 </em>may be functioning.</p>

Name thesis:degree_name

Master of Science in Biology (M.S.)

Level thesis:degree_level

Thesis (open access)

Discipline thesis:degree_discipline

Department of Biology

Year dc:date.available

2015

Author dc:creator

• Ivey, Crystal

Contributors dc:contributor

• John Harrison
• Oscar Pung

• ETD
• Myosin 10
• Zebrafish
• Axon Guidance
• Motor Neurons
• Developmental Biology

Repository record dc:identifier

https://digitalcommons.georgiasouthern.edu/etd/1310

OAI identifier oai:identifier

oai:digitalcommons.georgiasouthern.edu:etd-2386