DNA methylation profiling Gene specific profiling MRC-5

DNA damage assay is a standard method for determining in-vivo/in-vitro genotoxicity by measuring the breaks in the DNA chain of animal and plant cells. Initial DNA damage leads to cell cycle arrest and, at the final stages, leads to induction of senescence or cell death (apoptosis, necrosis, autophagy, or mitotic catastrophe). Detection of DNA damage from mild to moderate to severe is challenging when studying genotoxicity in the pool of cells. It is favorable to use DNA damage assay kits available for prominent identification of the extent of damage in the analysis.

DNA damage assay is a standard method for determining in-vivo/in-vitro genotoxicity by measuring the breaks in the DNA chain of animal and plant cells. Initial DNA damage leads to cell cycle arrest and, at the final stages, leads to induction of senescence or cell death (apoptosis, necrosis, autophagy, or mitotic catastrophe). Detection of DNA damage from mild to moderate to severe is challenging when studying genotoxicity in the pool of cells. It is favorable to use DNA damage assay kits available for prominent identification of the extent of damage in the analysis.

A PCR reaction consists of the template DNA, two primers covering the amplification site, an enzyme, and buffers. A quantitative, real-time PCR reaction typically includes all of that plus a probe that can be detected fluorescently as the reaction runs, with no gel required. for detection. However, non-specific product amplification and primer-dimer formation during set-up are major causes of PCR failure. Nevertheless, high-quality DNA polymerase and optimize reaction buffers will certainly lead to a successful PCR reaction.

A PCR reaction consists of the template DNA, two primers covering the amplification site, an enzyme, and buffers. A quantitative, real-time PCR reaction typically includes all of that plus a probe that can be detected fluorescently as the reaction runs, with no gel required. for detection. However, non-specific product amplification and primer-dimer formation during set-up are major causes of PCR failure. Nevertheless, high-quality DNA polymerase and optimize reaction buffers will certainly lead to a successful PCR reaction.

Reporter gene assays are designed to test the regulation of the expression of a gene of interest. This is usually done by linking the promoter of the gene of interest with a gene such as a firefly luciferase, which can be easily detected by addition of luciferin that leads to an enzymatic reaction to produce luminescence. The enzymatic reaction can be correlated to the expression of the gene of interest. Another luciferase gene that can be used is Renilla luciferase. For an appropriate luciferase assay: 1. the reporter should express uniformly in all cells, 2. specifically respond to effectors that the assay intends to monitor, 3. have low intrinsic stability to quickly reflect transcriptional dynamics. It is important to have an equal number of cells plated in each testing condition to avoid any incorrect readouts. Reporter assays could be single or dual reporter assays. The reporter could be both luciferases. Most dual-luciferase assays involve adding two reagents to each sample and measuring luminescence following each addition. Adding the first reagent activates the first luciferase reporter reaction; adding the second reagent extinguishes first luciferase reporter activity and initiates the second luciferase reaction. Dual-luciferase assays have some advantages, including 1. reduces variability, 2. reduces background, 3. normalizes differences in transfection efficiencies between samples.

miRNA is the inherent gene silencing machinery which can have more than one mRNA target, whereas siRNA can be designed to target a particular mRNA target. By design, both siRNA and miRNA are 20-25 nucleotides in length. The target sequence for siRNAs is usually located within the open reading frame, between 50 and 100 nucleotides downstream of the start codon. There are two ways in which cells can be transfected with desired RNAi: 1. Direct transfection (with calcium phosphate co-precipitation or cationic lipid mediated transfection using lipofectamine or oligofectamine), and 2. Making RNAi lentiviral constructs (followed by transformation and transduction). Lentiviral constructs are time consuming, but provide a more permanent expression of RNAi in the cells, and consistent gene silencing. Direct transfection of oligonucleotides provides temporary genetic suppression. Traditional methods like calcium phosphate co-precipitation have challenges like low efficiency, poor reproducibility and cell toxicity. Whereas, cationic lipid-based transfection reagents are able to overcome these challenges, along with applicability to a large variety of eukaryotic cell lines. When using oligos, the ideal concentration lies between 10-50nM for effective transfection.

miRNA is the inherent gene silencing machinery which can have more than one mRNA target, whereas siRNA can be designed to target a particular mRNA target. By design, both siRNA and miRNA are 20-25 nucleotides in length. The target sequence for siRNAs is usually located within the open reading frame, between 50 and 100 nucleotides downstream of the start codon. There are two ways in which cells can be transfected with desired RNAi: 1. Direct transfection (with calcium phosphate co-precipitation or cationic lipid mediated transfection using lipofectamine or oligofectamine), and 2. Making RNAi lentiviral constructs (followed by transformation and transduction). Lentiviral constructs are time consuming, but provide a more permanent expression of RNAi in the cells, and consistent gene silencing. Direct transfection of oligonucleotides provides temporary genetic suppression. Traditional methods like calcium phosphate co-precipitation have challenges like low efficiency, poor reproducibility and cell toxicity. Whereas, cationic lipid-based transfection reagents are able to overcome these challenges, along with applicability to a large variety of eukaryotic cell lines. When using oligos, the ideal concentration lies between 10-50nM for effective transfection.

Short hairpin or small hairpin RNA (shRNA) is artificial RNA, which has a hairpin loop structure, and uses inherent microRNA (miRNA) machinery to silence target gene expression. This is called RNA interference (RNAi). These can be delivered via plasmids or viral/bacterial vectors. Challenges in shRNA-mediated gene silencing include 1. Off-target silencing, 2. Packaging shRNA encoding lentivirus, and 3. Stable transduction in cells. RNAi has been designed to have anywhere from 19-27 bs, but the most effective design has 19 bp. In case commercial shRNAs are not available, potential target sites can be chosen within exon, 5’- or 3’ UTR, depending on which splice variants of the gene are desired. One should use the latest algorithms and choose at least two different sequences, targeting different regions, in order to have confidence in overcoming off-target effects. A BLAST search after selecting potential design will eliminate potential off-target sequences. For the second challenge, sequencing the vector using primers for either strand (50-100 bp upstream) is suggested, along with using enzymatic digestion on agarose gel for the vector. Next, once the shRNA-containing vector is packaged in a virus, it is important to check the viral titer before transduction. Finally, using a marker in the lentiviral vector (fluorescent protein or antibiotic resistance), along with qPCR for target gene expression can help in determining the efficacy of transduction and shRNA on its target site.

Short hairpin or small hairpin RNA (shRNA) is artificial RNA, which has a hairpin loop structure, and uses inherent microRNA (miRNA) machinery to silence target gene expression. This is called RNA interference (RNAi). These can be delivered via plasmids or viral/bacterial vectors. Challenges in shRNA-mediated gene silencing include 1. Off-target silencing, 2. Packaging shRNA encoding lentivirus, and 3. Stable transduction in cells. RNAi has been designed to have anywhere from 19-27 bs, but the most effective design has 19 bp. In case commercial shRNAs are not available, potential target sites can be chosen within exon, 5’- or 3’ UTR, depending on which splice variants of the gene are desired. One should use the latest algorithms and choose at least two different sequences, targeting different regions, in order to have confidence in overcoming off-target effects. A BLAST search after selecting potential design will eliminate potential off-target sequences. For the second challenge, sequencing the vector using primers for either strand (50-100 bp upstream) is suggested, along with using enzymatic digestion on agarose gel for the vector. Next, once the shRNA-containing vector is packaged in a virus, it is important to check the viral titer before transduction. Finally, using a marker in the lentiviral vector (fluorescent protein or antibiotic resistance), along with qPCR for target gene expression can help in determining the efficacy of transduction and shRNA on its target site.

Short hairpin or small hairpin RNA (shRNA) is artificial RNA, which has a hairpin loop structure, and uses inherent microRNA (miRNA) machinery to silence target gene expression. This is called RNA interference (RNAi). These can be delivered via plasmids or viral/bacterial vectors. Challenges in shRNA-mediated gene silencing include 1. Off-target silencing, 2. Packaging shRNA encoding lentivirus, and 3. Stable transduction in cells. RNAi has been designed to have anywhere from 19-27 bs, but the most effective design has 19 bp. In case commercial shRNAs are not available, potential target sites can be chosen within exon, 5’- or 3’ UTR, depending on which splice variants of the gene are desired. One should use the latest algorithms and choose at least two different sequences, targeting different regions, in order to have confidence in overcoming off-target effects. A BLAST search after selecting potential design will eliminate potential off-target sequences. For the second challenge, sequencing the vector using primers for either strand (50-100 bp upstream) is suggested, along with using enzymatic digestion on agarose gel for the vector. Next, once the shRNA-containing vector is packaged in a virus, it is important to check the viral titer before transduction. Finally, using a marker in the lentiviral vector (fluorescent protein or antibiotic resistance), along with qPCR for target gene expression can help in determining the efficacy of transduction and shRNA on its target site.