Overlapping and distinct functions for Gli proteins: Key mediators of hedgehog signaling in cell specification during embryonic development

2003 2003

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Abstract (summary)

Hedgehog (Hh) signaling is important for patterning and cell differentiation within many embryonic tissues. Hh is expressed in the notochord and the floor plate and acts as a morphogen in patterning of the ventral central nervous system (CNS), pituitary gland, somites, pancreas, and many other tissues. Gli transcription factors act as main mediators of Hh signaling in vertebrates. Their unique and overlapping functions lead to differential outcome of Hh signaling in different cells and tissues. The goal of my dissertation is to determine how zebrafish Gli proteins work together to transduce Hh signals and to activate or repress the transcription of Hh target genes. I have shown that Gli1 acts only as an activator of Hh signaling similar to what is known from other species, while Gli2 and Gli3 act as both activators and repressors. Gli2 functions as a co-activator of Gli1 in subset of ventral cells in the posterior diencephalon and in the adaxial cells in the embryonic trunk. In contrast, activator role of Gli3 overlaps with Gli1 throughout the ventral CNS during early development of the embryo. Later, GO represses Hh targets in the dorsal spinal cord, but not in the forebrain. In contrast, Gli2 represses genes in both, the dorsal telencephalon and the spinal cord. I also demonstrate that Gli3 repressor function is temporally regulated by active Hh signaling, unlike Hh independent Gli2 repressor function. Thus, my detailed analysis of zebrafish Gli functions reveals complex interactions between Gli proteins in embryonic patterning.

I also studied a novel zebrafish mutation umleitung (uml) that was identified because of defects in axon guidance and neural patterning in the ventral forebrain. My detailed phenotypic analysis showed that the uml mutation disrupts Hh signaling and forebrain patterning. I have genetically mapped uml on zebrafish chromosome 24 near the Zmarker z10372. My linkage analysis indicates there are no known components of the Hh signaling cascade in the uml genetic region. This leads to the exciting possibility that uml may encode a previously undefined regulator of Hh signaling. I have initiated a genomic walk toward finding a gene that encodes uml.

Indexing (details)

Molecular biology;
0307: Molecular biology
0317: Neurology
0369: Genetics
Identifier / keyword
Biological sciences; Cell specification; Embryonic development; Hedgehog; umleitung
Overlapping and distinct functions for Gli proteins: Key mediators of hedgehog signaling in cell specification during embryonic development
Tyurina, Oksana V.
Number of pages
Publication year
Degree date
School code
DAI-B 64/10, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Karlstrom, Rolf O.
University of Massachusetts Amherst
University location
United States -- Massachusetts
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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