Pax6 and Six1/2 orthologs in leech ectodermal patterning

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Pax6 and Six1/2 orthologs in leech ectodermal patterning

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dc.contributor.advisor Shankland, Marty
dc.creator Quigley, Ian Kirk
dc.date.accessioned 2012-10-09T17:40:22Z
dc.date.available 2012-10-09T17:40:22Z
dc.date.created 2008-12
dc.date.issued 2012-10-09
dc.identifier.uri http://hdl.handle.net/2152/18246
dc.description.abstract Clitellate annelids display conserved mechanisms of segmental ectodermal and mesodermal patterning. These tissues are generated by asymmetric divisions of large stem cells called teloblasts, elongating the ectoderm and mesoderm of the embryo. Each teloblast-derived lineage makes highly stereotyped contributions to the leech: the N, O, P, and Q contribute specific neurons, epidermis, and other ectodermal tissues along the ventral-to-dorsal axis of the embryo, respectively. The N and Q ectodermal lineages appear to be specified autonomously, but specification of the O and P lineages depends upon interactions with other, neighboring teloblast lineages. Until quite recently, there have been precious few teloblast lineage-specific markers, and virtually no molecular candidates for genes influencing the proper differentiation of any of these lineages. Here, I explore the possibility that members of the Pax-Six-Eyes absent-Dachshund network are involved in leech ectodermal patterning. I show that the leech Helobdella sp. Austin has two Pax6 paralogs, and demonstrate that Hau-Pax6A is expressed early in a subset of N-derived cells and O-derived cells. Next, I demonstrate that an ortholog of the six gene family, Hau-six1/2a, is expressed in the P lineage. I show through a series of cell ablations that Hau-six1/2a expression is regulated by neighboring teloblasts in a manner consistent with P fate induction, hinting that this transcription factor may be involved in P specification. The identification of these genes is a first step towards dissecting the molecular mechanisms of ectodermal teloblast differentiation in the leech embryo. The evolutionary context of the deployment of these genes is also discussed. In the appendices, I present two projects on the evolution of pigment patterns in Danio rerio and its relatives. In the first, I show that the larval melanin-containing pigment cells of Danio nigrofasciatus are uniquely redeployed into the adult pigment pattern, in contrast to seven related fishes. In the second, I show that variation in yellow pigment cell populations in different danio species may be dependent on variable signaling through the receptor tyrosine kinase fms pathway.
dc.format.medium electronic
dc.language.iso eng
dc.rights Copyright © is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.
dc.subject.lcsh Leeches--Genetics
dc.subject.lcsh Leeches--Embryology
dc.subject.lcsh Zebra danio--Color
dc.subject.lcsh Danio--Color
dc.subject.lcsh Chromatophores
dc.subject.lcsh Zebra danio--Genetics
dc.subject.lcsh Danio--Genetics
dc.subject.lcsh Genetic regulation
dc.title Pax6 and Six1/2 orthologs in leech ectodermal patterning
dc.description.department Biological Sciences, School of
dc.type.genre Thesis
dc.type.material text
thesis.degree.department Ecology, Evolution, and Behavior
thesis.degree.discipline Ecology, Evolution, and Behavior
thesis.degree.grantor The University of Texas at Austin
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy

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