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Title: Regulation of Ubx expression in the central nervous system of Drosophila : a cell-specific study
Author: Barrett, R. M.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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Homeotic genes control morphology along the anterior-posterior axis at both the parasegmental and single cell level, specifying what program of development a cell should follow. It is therefore essential that the cell-specific pattern of Hox gene expression is tightly controlled. To investigate how this is achieved, I have studied the role that the cis-regulatory sequences of the Hox gene Ultrabithorax (Ubx) play in directing the pattern of expression in the neural stem cells (neuroblasts) of the Drosophila embryo. Neuroblasts can be uniquely identified up to 7h 30 of development, allowing me to look at Ubx expression at the single-cell level. Cis-regulatory DNA is arranged in modules of clustered binding sites for transcription factors; a module can lie anywhere within the non-coding DNA of a gene. Each module directs a subfunction of the endogenous expression pattern when placed in a reporter construct. Many reporter constructs containing fragments of Ubx regulatory DNA already exist. I have utilized some of these along with a number of Ubx regulatory mutants to try to locate modules involved in creating the wildtype pattern of neural Ubx expression and characterize the regulatory inputs that they provide. In order to do this, I first described the wildtype Ubx expression pattern in the neuroblasts during the period of their formation (3h 10 to 7h 20) in parasegments 5-7. I employed neuroblast markers to uniquely identify specific cells. Ubx expression is both complex and dynamic in these cells at this time. Through reporter construct and regulatory mutant analysis involving both the abx region and the majority of the upstream regulatory DNA, I find that the parasegment 5 pattern is controlled by sequences lying between -8 and -12 upstream from the start site and is boosted to functional levels by abx sequences at +48 from the start site. The pattern seen in parasegments 6 and 7 is composed of two physically separable subfunctions: 1) complexity, specified by sequences at -15; 2) expression in all neuroblasts, generated by pan-neural enhancers that may be widely distributed in the upstream DNA.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available