High-throughput siRNA Screens
Library screening using genome-wide siRNAs as well as microRNAs allows a researcher to analyze an entire signaling pathway of one or tens of thousands of genes. siRNA libraries composed of large numbers of siRNAs have been developed and are used to identify sets of genes functionally involved in a particular biological process or disease metabolism. siRNA library screening is now extensively used by pharma companies for validation of drug targets.
Phenotypic high throughput siRNA screens are a powerful approach to study structural and functional relationships of genes and to identify novels parts of signaling pathways. In fact, large-scale siRNA screening is now commonly used for functional genomics and drug target validation. High throughput applications that require reliable and reproducible transfections can be performed in a 96-, 384-, or 1536-well plate format. Several transfection reagents are compatible for high throughput small RNA transfection (see this list). A technique known as reverse transfection has been developed which allows for the plating of the cells and delivery of siRNA-reagent complexes on the same day, thereby eliminating a source of high degrees of variability in cell culture and improving transfection efficiency.
Library Screening Process
The process of producing a library of signal pathways involves brute testing of various siRNAs to determine their effect on gene expression. Such studies, if done by hand, require extensive amounts of time and dedication to precision. Currently, many companies offer to provide library screening services, while others provide robots that can accomplish screens more accurately and quicker than humans. In many cases, there are thousands of genes that need to be screened, and thousands of siRNAs being tested. In such research, human labor is inefficient and time consuming, and would merit the outsourcing of research to established contractors in the field.
Companies will usually use a client’s list of siRNAs desired for testing to develop a screening protocol that is identical for all cells being tested. The screening protocol utilizes many different reagents, and in advanced techniques is programmed into a robot for the process to be completed in an orderly manner. Results consist of data relating to the expression of certain, pre-determined genes. In the case that a segment of siRNA is effective at limiting expression, the resulting data will show a significant decrease in that gene’s expression. For many drug-development applications, this data can show any off-target effects and demonstrate the on-target specificity and effectiveness of a novel drug or therapeutic.
In Vivo Transfection Kits from Altogen Biosystems
RNAi has been used for in vivo target validation studies using animal models. The major challenge in performing RNAi studies in vivo is the effective, directed delivery of functional siRNA or microRNA molecules into specific tissues. Altogen® In Vivo Transfection Reagents could be conjugated with siRNA and systemically via intravenous (i.v) tail vein injection in order to provide directed gene silencing in specific tissues, including liver, pancreas, kidney, and tumors. Selective knockdown could be seen as early as 24 hours after injection.
siRNA Library Screening Services by Altogen Labs:
Altogen Labs provides siRNA and miRNA library screening services, as well as many other specialized biotech and pharma contract research services, including development of stable cell lines, A-to-Z RNA interference (RNAi) services, pharmacology and toxicology testing for IND applications (safety and efficacy), PK/PD, IC50, assay development, liposome encapsulation, and over 60 validated xenograft animal models.