Download GENE-SILENCING IN THE BRAIN IN VIVO USING siRNA

GLOBAL DOWN-REGULATION OF GENE EXPRESSION IN THE BRAIN
USING RNA INTERFERENCE, WITH EMPHASIS ON NEUROPEPTIDES,
GPCRS AND MONAMINE TRANSPORTERS.
D. Hoyer, PhD, DSc, Neurosciences Research, Novartis Institutes for BioMedical
Research, CH 4002, Basel, Switzerland.
The use of gene expression profiling to detect potential NS disorders targets
necessitates in vivo validation. RNA interference has emerged as a superior alternative
to traditional gene-silencing approaches. We developed and applied non-viral delivery
of RNAi in the brain. First, enhanced green fluorescent protein (eGFP)-targeting short
interfering RNA (siRNA), was administered, using 1- or 2-week osmotic minipumps,
into the dorsal third ventricle of eGFP-expressing mice. EGFP-siRNA produced a
significant, regioselective and temporal silencing of EGFP mRNA and protein in most
of the seventeen brain regions tested. We then targeted selectively and successfully the
dopamine transporter (DAT), serotonin transporter (SERT) and mGluR7 receptor. icv
siRNA resulted in knock down of a targeted protein and had marked behavioral
consequences, such as hyperlocomotor activity after DAT knockdown, antidepressant
like activity with 5-HTT SiRNA and anxiolytic activity following mGluR7 receptor
knock down. Remarkably and surprisingly, in vivo mRNA (and protein) down
regulation of as little as 25-30% resulted in significant functional effects. Similar data
have been presented recently for neuropeptides and neuropeptide receptor RNAi with
profound behavioural effects in animal models of pain and other neuropsychiatric
disorders. Undoubtedly, RNAi will assist in the genetic analysis and target validation
for neuropsychiatric disorders involving a complex interplay of genes from various
brain regions.
Questions:
What are the different modalities which can be used to when applying RNA
interference?
How does RNA interference compare with gene knock out as achieved in
transgenic animals?
Is RNA interference applicable in vivo? Are there therapeutic prospects?