RNAi update

[Guest guest]

RNAi has been adopted as the research tool to discriminate gene

function.(includes areas of treatment for neurological and genetic

disorders)

DUBLIN, Ireland--(BUSINESS WIRE)--May 4, 2004

RNA interference (RNAi) or gene silencing involves the use of double

stranded RNA (dsRNA). Once inside the cell, this material is processed

into short 21-26 nucleotide RNAs termed siRNAs that are used in a

sequence-specific manner to recognize and destroy complementary RNA. The

report compares RNAi with other antisense approaches using

oligonucleotides, aptamers, ribozymes, peptide nucleic acid and locked

nucleic acid.

Various RNAi technologies are described, along with design and methods

of manufacture of siRNA reagents. These include chemical synthesis by in

vitro transcription and use of plasmid or viral vectors. Other

approaches to RNAi include DNA-directed RNAi (ddRNAi) that is used to

produce dsRNA inside the cell, which is cleaved into siRNA by the action

of Dicer, a specific type of RNAse III. MicroRNAs are derived by

processing of short hairpins that can inhibit the mRNAs. Expressed

interfering RNA (eiRNA) is used to express dsRNA intracellularly from

DNA plasmids.

Delivery of therapeutics to the target tissues is an important

consideration. siRNAs can be delivered to cells in culture by

electroporation or by transfection using plasmid or viral vectors. In

vivo delivery of siRNAs can be carried out by injection into tissues or

blood vessels or use of synthetic and viral vectors.

Because of its ability to silence any gene once the sequence is known,

RNAi has been adopted as the research tool to discriminate gene

function. After the genome of an organism is sequenced, RNAi can be

designed to target every gene in the genome and target for specific

phenotypes. Several methods of gene expression analysis are available

and there is still need for sensitive methods of detection of gene

expression as a baseline and measurement after gene silencing. RNAi

microarray has been devised and can be tailored to meet the needs for

high throughput screens for identifying appropriate RNAi probes. RNAi is

an important method for analyzing gene function and identifying new drug

targets that uses double-stranded RNA to knock down or silence specific

genes. With the advent of vector-mediated siRNA delivery methods it is

now possible to make transgenic animals that can silence gene expression

stably. These technologies point to the usefulness of RNAi for drug

discovery.

RNAi can be rationally designed to block the expression of any target

gene, including genes for which traditional small molecule inhibitors

cannot be found. Areas of therapeutic applications include virus

infections, cancer, genetic disorders and neurological diseases. Side

effects can result from unintended interaction between an siRNA compound

and an unrelated host gene. If RNAi compounds are designed poorly, there

is an increased chance for non-specific interaction with host genes that

may cause adverse effects in the host.