The leech Hox gene Lox6 plays a role in nervous system differentiation and patterning.
Item
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Title
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The leech Hox gene Lox6 plays a role in nervous system differentiation and patterning.
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Identifier
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AAI3063860
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identifier
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3063860
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Creator
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Mercado-Pimentel, Melania Ester.
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Contributor
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Adviser: Gabriel O. Aisemberg
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Date
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2002
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Neuroscience | Biology, Animal Physiology
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Abstract
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The main site of Hox gene expression in metazoans is the nervous system. These transcription factors have an important role in nervous system development and function. I describe here the expression pattern and function of the Hox gene Lox6 in the embryonic nervous system of the leech Hirudo medicinalis. Using a new, improved approach, I purified two different glutathione S-transferase fusion proteins containing large fragments of the coding regions of the leech Hox genes Lox2 and Lox6. These fusion proteins were used for raising and purifying antibodies against Lox2 and Lox6. The Lox6 antibody allowed me to identify neurons and muscle cells of the central nervous system, the peripheral nervous system and the body wall that express this gene in the embryonic leech. Lox6 expression was detected in the bipolar neurons, the mechanosensory P D neurons, the netrin expressing NE-C neurons, the serotonergic Retzius, AMS, and PMS neurons, a FMRFamide excitatory motor neuron, and putative glial cells. Some of these cells have been shown or suggested to play a role in axon guidance. I also identified Lox6 expression in putative photoreceptors of the eye primordia and in other sensory neurons of the body wall. The developmental expression of Lox6 had a widespread early phase and a restricted late phase. The long anterior-posterior domain of early Lox6 expression suggested that Lox6 is involved in general processes of early nervous system development, probably regulating cell-autonomous and non-cell autonomous molecules necessary for axon growth and guidance, and target selection. The late, restricted expression of Lox6 may be involved in specifying segment-specific connections to peripheral sensory organs that express Lox6 in one rostral neuromere. I also describe here the effects of knocking down Lox6 expression by RNAi. Lox6 RNAi disrupted axon patterning in all major nerves, indicating that Lox6 plays a significant role in the early patterning of the nervous system. My results also suggested that Lox6 controlled pioneer axon generation or growth in the bipolar neurons and partially regulated their expression of the axon guidance molecule netrin.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
