Name: Cell Transfection and 5-Bromo-2'-Deoxyuridine (BrdU) Incorporation in HeLa Cells
Uploaded: 2023-05-05T14:55:00
Description: Watch this Scientific Journal Video about Cell Transfection and 5-Bromo-2'-Deoxyuridine BrdU Incorporation in HeLa Cells at JoVE.com

The video demonstrates a protocol for transfecting HeLa cells using siRNA, followed by BrdU incorporation to study mitochondrial DNA. It outlines the steps of cell seeding, incubation times, and conditions, emphasizing the experimental setup to analyze BrdU specificity in mitochondrial DNA by using rho0 cells.

cell transfection and 5-bromo-2&#39;-deoxyuridine (brdu) incorporation in hela cells

mtDNAの合成と分布のハイスループット定量

For most eukaryotic cells mitochondria are essential organelles, as they play a crucial role in numerous cellular processes. First and foremost, mitochondria are the key energy suppliers of cells1. Mitochondria are also involved in regulating cellular homeostasis (for instance, intracellular redox2 and the calcium balance3), cell signaling4,5, apoptosis6, the synthesis of different biochemical compounds7,8, and the innate immune response9. Mitochondrial dysfunction is associated with various pathological states and human diseases10. 
The functioning of mitochondria depends on the genetic information located in two separate genomes: the nuclear and mitochondrial genomes. The mitochondrial genome encodes a small number of genes compared to the nuclear genome, but all the mtDNA-encoded genes are essential for human life. The mitochondrial protein machinery necessary to maintain the mtDNA is encoded by nDNA. The basic components of the mitochondrial replisome, as well as some mitochondrial biogenesis factors, have already been identified (reviewed in previous research11,12). However, mitochondrial DNA replication and maintenance mechanisms are still far from being understood. In contrast to nDNA, the mitochondrial genome exists in multiple copies, which provides an additional layer for regulating mitochondrial gene expression. Much less is currently known about the distribution and segregation of mtDNA within organelles, to what extent these processes are regulated, and if they are, which proteins are involved13. The segregation pattern is crucial when cells contain a mixed population of wild-type and mutated mtDNA. Their unequal distribution may lead to the generation of cells with a detrimental amount of mutated mtDNA.
So far, the protein factors necessary for mtDNA maintenance have been identified mainly by biochemical methods, bioinformatic analyses, or through disease-associated studies. In this work, in order to ensure a high chance of identifying factors that have previously escaped identification, a different strategy is described. The method is based on the labeling of mtDNA during replication or repair with 5-bromo-2'-deoxyuridine (BrdU), a nucleoside analog of thymidine. BrdU is readily incorporated into nascent DNA strands during DNA synthesis and, in general, is used for monitoring the replication of nuclear DNA14. However, the procedure developed here has been optimized for detecting BrdU incorporated into mtDNA using the immunofluorescence of anti-BrdU antibodies.
The approach allows for the high-throughput quantification of mtDNA synthesis and distribution in human cells cultured in vitro. A high-throughput strategy is necessary to conduct tests under different experimental conditions in a relatively short time; therefore, it is proposed in the protocol to utilize a multi-well format for cell culturing and automated fluorescence microscopy for imaging. The protocol includes the transfection of human HeLa cells with an siRNA library and the subsequent monitoring of mtDNA replication or repair using the metabolic labeling of newly synthesized DNA with BrdU. This approach is combined with immunostaining of the DNA with the help of anti-DNA antibodies. Both parameters are analyzed using quantitative fluorescence microscopy. Additionally, mitochondria are visualized with a specific dye. To demonstrate the specificity of the protocol, BrdU staining was tested on cells devoid of mtDNA (rho0 cells), on HeLa cells upon the silencing of well-known mtDNA maintenance factors, and on HeLa cells after treatment with an mtDNA replication inhibitor. The mtDNA levels were also measured by an independent method, namely qPCR.

著者スポットライト:ミトコンドリアDNA合成と分布のハイスループット画像ベースの定量化  

ミトコンドリアDNA合成と分布のハイスループット画像ベースの定量

The protocol aims to identify proteins with dysfunction leads to changes in the number of mitochondrial DNA molecules. This research may also reveal the factors involving the distribution of mitochondrial DNA within the mitochondria. Mitochondrial replication and maintenance mechanisms are still not fully understood.Much less is known about regulating the distribution of mitochondrial genomes within organoids and the proteins involved in it. As a result, identifying and characterizing some new players will be of great importance. The main advantage of the technique is its high-throughput and high content protocol.We can simultaneously test many experimental conditions and measure various parameters during a single experiment. In genome-wide studies, the proposed protocol provides an opportunity to outline a global picture of how nuclear encoded genetic information regulates its mitochondrial counterpart. Additionally, it has the potential to identify proteins whose dysfunction causes mitochondrial DNA stress and activates the interferon response pathway.

Watch this Scientific Journal Video about Cell Transfection and 5-Bromo-2'-Deoxyuridine BrdU Incorporation in HeLa Cells at JoVE.com

Cell Transfection and 5-Bromo-2'-Deoxyuridine (BrdU) Incorporation in HeLa Cells  

細胞トランスフェクションおよびHeLa細胞への5-ブロモ-2&#39;-デオキシウリジン(BrdU)の取り込み

細胞トランスフェクションを開始するには、希釈siRNAを含む384ウェルプレートウェルに20マイクロリットルのHeLa細胞懸濁液を添加し、ウェルあたり700個のHeLa細胞を播種します。室温で1時間インキュベートした後、ウェルプレートをインキュベーターに37°C、5%二酸化炭素で72時間置きます。トランスフェクションした細胞にBrdUを取り込むには、siRNAトランスフェクションの56時間後に、10マイクロリットルの90マイクロモルBrdU溶液を各ウェルに加えます。細胞を摂氏37度、二酸化炭素5%で16時間インキュベートします。HeLa細胞のミトコンドリアDNAへのBrdUの取り込みの特異性を、ミトコンドリアDNAを欠失したrho0細胞を用いて研究した。

Research

JoVE Journal

Biochemistry

Cell Transfection and 5-Bromo-2&#39;-Deoxyuridine (BrdU) Incorporation in HeLa Cells

High-Throughput Image-Based Quantification of Mitochondrial DNA Synthesis and Distribution

The vast majority of cellular processes require a continuous supply of energy, the most common carrier of which is the ATP molecule. Eukaryotic cells ...

生化学

Preparation of siRNA Mixture for Mitochondrial DNA Synthesis

ミトコンドリアDNA合成のためのsiRNA混合物の調製

5-Bromo-2&#39;-Deoxyuridine (BrdU) Labeling of Mitochondrial DNA in HeLa Cells

5-Bromo-2'-Deoxyuridine (BrdU) Labeling of Mitochondrial DNA in HeLa Cells  

HeLa細胞におけるミトコンドリアDNAの5-ブロモ-2&#39;-デオキシウリジン(BrdU)標識

HeLa Cell Fixation with Hoechst 33342 and Blocking

ヘキスト33342によるHeLa細胞固定とブロッキング

Addition of Primary and Secondary Antibodies to the Transfected HeLa Cells to Monitor the mtDNA Distribution

mtDNA分布をモニタリングするためのトランスフェクトされたHeLa細胞への一次抗体および二次抗体の添加

Quantitative Image Analysis to Measure the mtDNA and Gene Expression Levels in the Transfected HeLa Cells

トランスフェクトされたHeLa細胞におけるmtDNAおよび遺伝子発現レベルを測定するための定量的画像解析