Tip60 Mediated Regulation of Cognition
Linked Gene Targets in Drosophila
Anisha Sunkerneni, Priyalakshmi Panniker and Felice Elefant
Elefant Lab, Department of Biology, Drexel University, Philadelphia, PA 19104
Introduction
Neurodegenerative diseases, such as Alzheimer’s Disease (AD), are commonly
associated with gene misregulation related to cognitive function. Epigenetic
machinery is essential for proper cognitive function. Various epigenetic modifiers,
such as histone acetyltransferases (HATs), can cause genetic alterations in the
human genome. Histone acetyltransferases are capable of acetylating lysine
amino acids located on histone proteins and subsequently transferring an acetyl
group from acetyl CoA to create ε-N-acetyllysine. This leads to transcriptional
activation of genes. Tip60 (Tat interactive protein 60kDa) is one such HAT that
has been linked to various neurodegenerative conditions, including Alzheimer’s
Disease (AD). Previously our lab has shown a critical role of Tip60 in mediating
various neuronal functions
(Genetics, 2007; PLoS ONE, 2010;
PLoS ONE, 2011, PloS ONE,
2012). Additionally, our lab has
discovered that increasing Tip60
HAT levels in an AD
neurodegenerative fly model
rescues impaired cognition-linked
processes. However, the
mechanism underlying this still
remains unclear.
Here we hypothesize that excess Tip60 rescues the defects seen in various
neuronal processes by positively impacting gene expression of various Tip60
genes involved in these processes.
Investigating potential alterations in
the expression of various Tip60
gene targets, specifically associated
with learning and memory, under
neurodegenerative conditions would
provide an insight into Tip60 based
epigenetic gene control mechanism.
Tip60 and Alzheimer’s Disease
Results
Tip60 has been implicated
in AD via its interaction
with AD-linked amyloid
precursor protein
intracellular domain
(AICD). The AICD-Tip60
complex is recruited by the
promoters of certain target
genes where it acts to
acetylate select histone
proteins to epigenetically
regulate gene
transcription.
Methods
To identify changes in gene expression of various Tip60 gene targets, we used the
various AD fly lines generated in our lab by former graduate students.
+
In the APPoverexpressing flies,
there was a significant
decrease in the
expression of all the
Tip60 target genes.
GAL4 inducible
hAPP
APP;dTip60WT
Expressing human APP
Overexpress WT Tip60
with hAPP
When Tip60 was
overexpressed in these
lines, there was a
significant increase in the
expression of most of the
genes.
Our lab specifically uses the targeted GAL4/UAS inducible expression system to
express mutations in the drosophila flies. Here we use our GAL4 responsive
transgenic fly lines carrying APP with Tip60WT transgene to look at the changes
caused by excess HAT Tip60.
Therefore, these results
indicate positive
regulation of certain
cognition-linked genes by
Tip60 under APP-induced
neurodegeneration.
Role of Tip60 in Epigenetics
Future Directions
• Identify the transcription factors that bind to Tip60 at specific target gene
promoter and how they mediate changes in gene expression.
Real-time PCR was used to assess all the changes in gene expression of the
selected twelve Tip60 target genes using primer pairs designed from target gene
sequences obtained at Flybase.
gene
gene
• Identify various other factors which act along with Tip60 in regulting gene
expression
References
Borrelli, E., Nestler, E. J., Allis, C. D., Coris, P, S., 2010. Decoding the epigenetic language of neuronal plasticity. Neuron, 6,
961-974.
Fischer, A., Sananbenesi, F., Wang, X., Dobbin, M., Tsai, L., 2007. Recovery of learning and memory is associated with
chromatin remodelling. Nature Articles, 447. Lorbeck, M., Pirooznia, K., Sarthi, J., Zhu, X., Elefant, F., 2011. Microarray
Analysis Uncovers a Role for Tip60 in Nervous System Function and General Metabolism. PloS One 6, 14.􀀁
Mir-X MicroRNA Quantification. MicroRNA Quantification- Accurately Quantify MiRNAs and MRNA Targets. N.p., n.d. Web.
Pirooznia, S., Sarthi, J., Johnson, A., Toth, M., Chiu, K., Koduri, S., Elefant, F, 2012b. Tip60 HAT Activity Mediates APP
Induced Lethality and Apoptotic Cell Death in the CNS of a Drosophila Alzheimer’s Disease Model. Plos 7, e41776.
Zhu, X., Singh, N., Donnelly, C., Boimel, P., Elefant, F., 2007. The cloning and characterization of the histone
acetyltransferase human homolog Dmel\TIP60 in Drosophila melanogaster: Dmel\TIP60 is essential for multicellular
development. Genetics 175, 1229-1240.
Ackowledgements
This work was supported by NIH grant R01HD057939 to F.E.