MECHANISM OF ACTION OF HISTONE DEACETYLASE INHIBITORS ON SURVIVAL MOTOR NEURON 2 PROMOTER
Date
2018-05
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
Spinal muscular atrophy (SMA) is an early-onset recessive neurodegenerative
disease that primarily affects the α-motor neurons in the anterior horn of the spinal
cord. The degeneration of these motor neurons leads to gradual muscular atrophy,
eventual respiratory complications, and early death in severe types of SMA. Due to
deletion or mutation events, patients with SMA lack a functional copy of the Survival
Motor Neuron 1 (SMN1) gene. Humans however have a nearly identical copy of
SMN1 known as Survival Motor Neuron 2 (SMN2), which is retained in SMA patients.
The major difference between SMN1 and SMN2 is that SMN2 contains a nucleotide
substitution in exon 7 that results in the exclusion of this exon in the majority of
mRNA transcripts produced from SMN2. This exclusion of exon 7 results in low
levels of functional SMN protein. In animal models and within patient populations, it
has been shown that increasing SMN2 copy number results in a less severe SMA
phenotype, making SMN2 an ideal target for SMA therapeutics. Histone deacetylase
(HDAC) inhibitors have been extensively studied for treatment of SMA through
increasing transcription of the SMN2 gene; however, several of these HDAC inhibitors
demonstrated a highly variable patient response and possible toxicity. In this project, I
examine the HDAC inhibitors RGFP106, RGFP109, CAY10433, and HDACi-IV to
determine their potential for increasing SMN2 transcription and develop a SMN2
promoter dual luciferase assay for studying the potential mechanism of action of these
drug compounds. These compounds were selected to study as they have shown
positive effects on SMN2 expression in human SMA fibroblast cell lines. RGFP106
and RGFP109 increased transcription of Smn in NSC-34 motor neuron-like cells. The
preliminary test of the SMN2 dual luciferase assay showed that all test compounds
activated the SMN2 promoter, but this data was possibly skewed due to concurrent upregulation
of the TK promoter control. My drug compounds of interest failed to
significantly increase promoter activation in a SMN2 β-lactamase promoter assay. My
findings indicate that these HDAC inhibitors may not act on the SMN2 promoter
through direct transcription factor based activity, thus an alternative mechanism must
be explored.
Description
Keywords
Biological Sciences, Histone deacetlyalse inhibitors, survival motor neuron 2 promoter