Background:
Protein misfolding is a critical factor in the progression of a large number
of neurodegenerative diseases. The incorrectly folded protein is prone to aggregation, leading to
aberrant interaction with other cellular proteins, elevated oxidative stress, impaired cellular machinery,
finally resulting in cell death. Due to its monogenic origin, Huntington’s disease (HD) is
a poster child of protein misfolding neurodegenerative disorders. The presence of neuronal inclusions
of mutant huntingtin N-terminal fragments, mainly in the cortex and striatum, is a neuropathological
hallmark of HD. Inhibition of protein misfolding and aggregation has been attempted
using a variety of conventional protein stabilizers.
Methods:
This review describes how, in recent times, nucleic acid therapeutics has emerged as a
selective tool to downregulate the aberrant transcript and reduce expression of mutant huntingtin,
thereby alleviating protein aggregation. Different strategies of use of nucleic acids, including antisense
oligonucleotides, short inhibitory RNA sequences and aptamers have been discussed. The
following patent databases were consulted: European Patent Office (EPO), the United States Patent
and Trademark Office (USPTO), Patent scope Search International and National Patent Collections
(WIPO) and Google Patents.
Results:
Tools such as RNA interference (RNAi) and antisense oligonucleotides (ASOs) are potential
therapeutic agents which target the post-transcriptional step, accelerating mRNA degradation
and inhibiting the production of the mutant protein. These nucleic acid sequences not only
target the elongated CAG triplet repeat translating to an expanded polyglutamine tract in the mutant
protein, but have also been used to target single nucleotide polymorphisms associated with the
mutant allele. The therapeutic sequences have been investigated in a number of cells and animal
models of HD. One antisense sequence, with desirable safety properties, has recently shown
downregulation of huntingtin protein in a limited clinical trial. RNA aptamers have also shown
promising results in inhibiting protein aggregation in a yeast model of HD. Novel drug delivery
techniques have been employed to overcome the blood brain barrier for the use of these therapeutic
sequences.
Conclusion:
The selectivity and specificity imparted by nucleic acids, along with novel delivery
techniques, make them hopeful candidates for the development of a curative strategy for HD.
Silencing Antibiotic Resistance with Antisense Oligonucleotides