A genetic approach to identify Hox regulatory microRNAs during Drosophila development

Liu, Wan (2016) A genetic approach to identify Hox regulatory microRNAs during Drosophila development. Doctoral thesis (PhD), University of Sussex.

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The Hox genes encode a family of transcriptional regulators that activate
distinct developmental programs along the anterior-posterior (AP) axis of
animals. Recent observations in Drosophila demonstrate that at least two
miRNAs can repress Hox gene expression during development suggesting that
miRNA-based regulation might be a general mechanism of Hox gene regulation.

Here explore this possibility by applying a comprehensive genetic approach to
identify miRNAs able to repress Hox gene expression during development.
Given that the reduction of Drosophila Hox gene Ultrabithorax (Ubx) expression
leads to easily tractable homeotic transformations in haltere, I use Ubx to test
the repressive effects of dozens of miRNAs in an overexpression screen.

Scoring over 10,000 halteres showed that out of 106 miRNAs tested, ~28%
produced Ubx mutant phenotypes suggesting that miRNA-dependent Hox
regulation might be a pervasive mechanism controlling Hox gene function
during development. I classify phenotypes into four major categories: Ubx
mutant effects (Class I and II) and others (Class III and IV).

Through the combination of RNA-Seq data and TaqMan RT-PCR approaches, I
confirm that there is no correlation between the phenotypic strength and miRNA
expression level indicating that haltere phenotypes emerge from miRNA
qualitative roles. Furthermore, using protein expression analysis and Ubx 3’
UTR fluorescent reporters, I confirmed that at least nine miRNAs affect Ubx
protein expression and that six of these directly target Ubx 3’ UTR in vivo.

Lastly, I explore the nature and effects of miRNA regulation of Ubx at the
cellular level in the Drosophila embryonic CNS and find that miR-252 is
sufficient and necessary to repress Ubx expression in specific neural lineages.

Our work thus contributes to the understanding of miRNA-mediated Hox gene
regulation and, more generally, to the study of miRNA-target interactions within
the physiological context of metazoan development.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QH Natural history > QH0301 Biology > QH0426 Genetics > QH0470.A-Z Experimental organisms, A-Z > QH0470.D7 Drosophila
Depositing User: Library Cataloguing
Date Deposited: 25 May 2016 14:27
Last Modified: 25 Jun 2018 05:32
URI: http://sro.sussex.ac.uk/id/eprint/60874

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