Expression and functional characterization of the oligodendrocyte specific homeodomain protein, Gtx.

Format:

Book

Thesis/Dissertation

Author/Creator:

Awatramani, Rajeshwar Bhagwan.

Contributor:

Kamholz, John, advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Neurosciences.

Molecular biology.

0307.

0317.

Penn dissertations--Cell and molecular biology.

Cell and molecular biology--Penn dissertations.

Local Subjects:

Penn dissertations--Cell and molecular biology.

Cell and molecular biology--Penn dissertations.

0307.

0317.

Physical Description:

142 pages

Contained In:

Dissertation Abstracts International 59-11B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

The aim of these studies is to understand the mechanisms involved in oligodendrocyte differentiation and myelin gene expression. I have focused on the expression and function of the glial and testes specific homeodomain protein, Gtx. Expression studies demonstrate that Gtx is expressed coordinately with the mRNAs encoding the major structural proteins of myelin, MBP and PLP, during rodent brain development and in a variety of pathological situations. Furthermore Gtx is expressed specifically in mature oligodendrocytes, and not in immature oligodendrocytes or astrocytes. Bacterially expressed Gtx binds multiple sites on the MBP and PLP promoters. Comparison of these sites to sites selected by a SAAB assay reveal that many sites in the MBP and PLP promoters resemble SAAB selected sites. Transient cotransfection analyses, however, revealed that Gtx cannot alter transcription of the PLP, MBP, or Gtx promoters. Since transcription from any native promoter was not altered by Gtx, we created an artificial construct containing 5 high affinity Gtx binding sites upstream of a minimal thymidine kinase promoter. Gtx repressed this promoter although it also repressed a minimal TK promoter lacking Gtx binding sites. One possible explanation was that Gtx may not be binding its cognate sites in our transient cotransfection assays. When Gtx is tethered to DNA by way of a GAL4 DNA binding domain, it strongly represses transcription. Taken together, these data suggest that Gtx is a repressor at least in some circumstances, and that it probably requires cofactors to bind DNA in vivo. Since the best described homeodomain protein cofactors are the Pbx homeodomain proteins, I tested the possibility that the Pbx proteins cooperate with Gtx to bind DNA. Although the Pbx proteins are expressed in the oligodendrocyte lineage, site selection experiments indicate that these proteins do not cooperate with Gtx to bind DNA. Further experiments will be required to elucidate the partners and the bona fide targets of Gtx. The recent cloning of the Drosophila Gtx homologue may facilitate the functional analysis of Gtx in a simpler system.

Notes:

Thesis (Ph.D. in Cell and Molecular Biology) -- University of Pennsylvania, 1998.

Source: Dissertation Abstracts International, Volume: 59-11, Section: B, page: 5700.

Adviser: John Kamholz.

Local Notes:

School code: 0175.

ISBN:

9780599120358

Access Restriction:

Restricted for use by site license.