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The expression and regulation of the Po gene during development of the rat: Regulation of basal level and early expression

Lee, Meng-Jen; (1998) The expression and regulation of the Po gene during development of the rat: Regulation of basal level and early expression. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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This thesis represents a study of the Po gene, the major myelin protein gene in Schwann cells, during development of the rat. The major function of Po is in compaction of the myelin membrane during myelination, but I have found, using sensitive in situ hybridisation methods, that the gene is expressed much earlier than the onset of myelination. My experiments show that the Po gene is constitutively expressed early in development of the Schwann cell lineage, and that in adult nerves the Po gene is up-regulated and down-regulated differently in the two mature Schwann cell phenotypes. I found that Po mRNA is expressed at similar levels in Schwann cells at embryonic day 18, both in the sciatic nerve, where many Schwann cells will begin to myelinate shortly after birth, and also in the sympathetic trunk, where most Schwann cells are non-myelinating. Exploration of Po expression at earlier developmental stages, revealed that Po mRNA is expressed in Schwann cell precursors, the immediate precursors of Schwann cells in peripheral nerves, and also in a subpopulation of neural crest cells 1 used the neural crest/ peripheral nervous system lineage, a relative simple model, to understand how cells of the neural lineage differentiated after they were generated from ectodermal cells in the process of neurulation. In the second part of my study, by correlating Po mRNA expression patterns in whole mount preparations and sections at embryonic ages from day 10 to day 14 with known neural crest migration patterns and with expression of neuronal and other neural crest lineage markers, I conclude that Po expression is restricted to a subpopulation of migrating crest cells which are likely to represent a cell population showing early commitment to the glial lineage. Special attention is paid to expression patterns in the forelimb and hind limb regions at embryo day 12, to expression patterns in the head at embryonic days 10 and 1 1, and to expression patterns in the developing gut at embryonic days 12-14, The onset of Po mRNA expression is compared with that of other molecules known to be specific to the Schwann cell lineage, and it is concluded that Po is the earliest well characterised marker of a glial phenotype. In the third part of the study 1 describe the unexpected expression of Po mRNA in the inner ear, where it has not previously been described. The expression of Po in the otic placode/pit stage at embryonic day 10, in the otic vesicle at embryonic day 12 and in the embryonic inner ear at later stages of development is described, and compared to several known molecular markers of the development of inner ear. The pattern of Po expression is broad but specific, with boundaries that clearly delineate segments of inner ear. Olfactory glial cells, which are placode derived, are Po positive during development. Po expression in olfactory glial cells persist through adulthood, although the olfactory nerves are not myelinated.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The expression and regulation of the Po gene during development of the rat: Regulation of basal level and early expression
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10101193
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