Mutation of the Conserved Polyadenosine RNA binding protein, ZC3H14/dNab2, Impairs Neural Function in Drosophila and Humans Öffentlichkeit
Pak, ChangHui (2011)
Abstract
Every cell contains the same DNA sequence. Yet tight
regulation of gene expression occurs such that different tissues of
a multicellular
organism achieve gene expression profiles in cell-type
specific,
spatial and temporal manners. While this regulation of gene
expression can occur at the
level of transcription and epigenetic modification,
post-transcriptional regulatory
mechanisms are also critical. Between transcription and
translation, many processes are
dedicated to ensure proper processing and maturation of transcripts
and thus allow for
proper regulation of translation. RNA-binding proteins play
critical roles in achieving this regulation as highlighted by
many human diseases. Interestingly, mutations in genes encoding
RNA-binding proteins
that are ubiquitously expressed and play important roles for
overall RNA metabolism in
all cell types result in tissue-specific phenotypes. Why certain
tissues are more sensitive
to defects in general RNA-binding protein functions is unclear.
Studies addressing both
developmental and tissue-specific functional characterization of
critical RNA-binding
proteins will allow for better understanding of human disease
biology.
We show for the first time that mutations in the human
ZC3H14 gene lead to non-
syndromic autosomal recessive intellectual disability (NS-ARID) and
use Drosophila
melanogaster to model key aspects of the disease. Here we
describe the first
identification and characterization of dNab2, a Drosophila
orthologue of ZC3H14/Nab2
class of Cys3 His (CCCH) tandem zinc finger (ZnF) polyadenosine
RNA-binding protein.
dNab2 is essential for development and required in neurons for
normal locomotion and
flight. Biochemical and genetic data indicate that dNab2 restricts
bulk poly(A) tail length
in vivo, suggesting that this function may underlie its role
in development and disease.
Furthermore, we define the role of dNab2 in controlling locomotor
activity and memory
formation in the Drosophila mushroom bodies (MBs), a highly
specialized structure
involved in higher cognitive functions and locomotion. Finally,
using a genetic modifier
screen, we identify putative dNab2 targets and/or interacting
proteins that modulate
dNab2-mediated neuronal function. These studies reveal a conserved
requirement for
ZC3H14/dNab2 in the metazoan nervous system and allow for
future studies on the
molecular mechanisms underlying ZC3H14-associated human
intellectual disability.
Table of Contents
Table of Contents
Chapter 1 Introduction
1
Introduction
2
I. Post-transcriptional regulation of gene expression in
eukaryotes
3
II. Control of poly(A) tail length as a key step in
post-transcriptional regulation of gene
expression
6
III. RNA-binding proteins implicated in human disease
14
IV. Drosophila melanogaster as a model system
19
V. Scope and significance of the dissertation
24
Figures
28
References
36
Chapter 2 Mutation of the Conserved Polyadenosine RNA binding
protein,
ZC3H14/dNab2 , Impairs Neural Function in
Drosophila and Humans
51
Introduction
54
Results
56
Discussion
63
Figures
65
Experimental procedures
82
References
87
Chapter 3 Defining the role of dNab2 in the
Drosophila mushroom bodies
93
Introduction
94
Results
97
Discussion
104
Figures
107
Experimental procedures
117
References
119
Chapter 4 A genetic-modifier screen identifies factors that
functionally interact with
the Drosophila dNab2 gene
123
Introduction
124
Results
126
Discussion
133
Figures
136
Experimental procedures
148
References
150
Chapter 5 Conclusion and Discussion
153
Conclusion
154
A model
154
Remaining questions
157
Future directions
159
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