Methods

Introduction

Our experiments can be divided into two parts, one is the design and construction of genes and vectors, the other is test of parts and circuits with cells, including hepatoma cells, liver cells and iPSCs. So our protocol can be clearly be divided into these two parts, one for molecular operation, the other for cellular tests. Besides, quantitive measurement, like qPCR and western-blotting, is added in the molecular operation parts because it does not need cell operation.

Molecular Operation

< In the process of constructing circuit on vectors, PCR, PCR clean up, digestion of restriction endonuclease, gel extraction, ligation, transformation, colony PCR and plasmid extraction is implemented. Besides, for quantitive measurement, qPCR and western-blotting is used..

PCR

1. Prepare the reaction mix:

2. Set the program of thermal cycler

3. Run the PCR program.

4. After PCR, load ~2ul to a 1% agarose gel to have a quick run checking the production of desired fragment.

PCR clean up

Use Anxygen PCR clean up kit for PCR clean up. In addition, restriction endonuclease digestion mix can be cleaned if the fragment to be deserted is less than 50bp.

1. Add 150ul of buffer PCR-A, vortex.

2. Pipette the liquid to a column, wait for 1min, then centrifuge 1000xg for 1min and 12000xg 30s.

3. Use Buffer W2(700ul for the first step and 400ul again) to wash, 12000xg for 1min.

4. Dry the column on 65°C, warm the elutent in the meantime.

5. Use 25-30ul preheated elutent to wash DNA, wait for 1min and centrifuge 12000xg for 1min.

5. Use 25-30ul preheated elutent to wash DNA, wait for 1min and centrifuge 12000xg for 1min.

5. Use 25-30ul preheated elutent to wash DNA, wait for 1min and centrifuge 12000xg for 1min.

5. Use 25-30ul preheated elutent to wash DNA, wait for 1min and centrifuge 12000xg for 1min.

6. Use Nanodrop to measure the concentration and quality of the DNA product.

Digestion of restriction endonuclease

NEB, Fermentas and Takara restriction enzymes are used. Before use, check the proper buffer for the enzyme, if the activity is low, add twice the amount but prevent the enzyme volume more than 10%, or star activity may rise.

1. Set up the reaction mix:

2. Carefully mix the reaction mix and put it into 37°C water bath. Control the reaction time 2. Carefully mix the reaction mix and put it into 37°C water bath. Control the reaction time .

3. Load 1.5ul mix on 1% agarose gel to have a quick run to check if the reaction is clear.

4. 75°C water bath for 5min to stop the reaction.

Gel Extraction

Use Omega Gel Extraction Kit to do gel extraction.

1. Cut the gel slice and weigh, 1ug for 1ul equal volume.

2. Add 1x sample volume of Binding Buffer(XP2), add 1x sample volume of isopropanol if DNA is less than 500bp. Add 5ul of 5M pH5.2 NaAc when necessary.(When the color of liquid is orange or red, add it until it turns light yellow)

3. Incubate the mixture in 65°C for 7min or until totally dissolved. Vortex every 2-3min helps.

4. Put it in room temperature to let it cool down to some extent(control the temperature before the liquid become solid). Load it into a column(for more than 700ul, load it in several times). Centrifuge 1000xg for 1min then 10000xg for 30s.

5. Add 300ul Binding Buffer to wash the column, 10000xg 1min.

6. Wash with buffer SPW, add 700ul, wait 2-3min and centrifuge 10000xg. Repeat 1 time.

7. Discard the liquid and centrifuge 10000xg 2-3min to dry.

8. 65°C dry heat for elutent and column for totally dry. Wash it by 30-50ul elutent, centrifuge for 1min.

9. Use Nanodrop to measure the concentration and quality of the DNA product.

Use Fermentas T4 ligase for ligation.

For overnight ligation, use 0.3ul ligase, and for ligation that only proceeds in 2 hour, use 0.8ul ligase. The reaction temperature is room temperature, or a little bit lower than room temperature.(16°C)

Transformation

1. Add 200ul TCM to whole reaction mix(for ligation mix or digestion mix), put on ice for 3-5min. This step is optional when plasmid is transformed.

2. Add 50ul chemical competent cells（Top10）and mix gently. Incubate on ice for 30 min

3. Heat-shock in a 42℃ bath for 60 sec. Put it on ice for 3min.

4. Add 0.5 ml LB/SOC(antibiotic free) medium and incubate at 37.0C for 30-60 min

5. Spin at 8,000*g for 3min. Decant most of LB medium but leave –100ul behind to resuspend the bug.

6. Plate all of the bug suspensions onto one LB(Amp+) plate. Mark the name of the plate and put it into 37°C incubator for 14-18h.

Colony PCR

Just like PCR protocol, but use takara rTaq enzyme.

Plasmid Extraction

Use Omega Endo-free kit for the plasmids for cell.

Use Anxygen Plasmid miniprep kit for plasmids for molecular cloning.

Follow the protocals provided in the kit. But a 65°C elutent can cause higher efficiency.

Cellular tests

In the process of cellular tests, transient transfection, virus package, selecting stable cell line are included.

Transient transfection

1. Seed cells a night before.

2. Refresh medium right before transduction. Cell density should be around 60% at the time of transduction.

3. For a single well in a 12-well plate, dilute 1.5ug plasmid DNA in 100ul opti-MEM and then add 4ul PEI.

4. Gently mix and then incubate for 20min.

5. Add the mixture to cells and refresh after 6-8h.

6. 1:1000 doxycycline is used to induce the Tet system.

Transient transfection

1. seed cells a night before.

2. refresh medium right before transduction. Cell density should be 40% at the time of transduction.

3. For a single well in a 6-well plate, dilute totally 3ug plasmids in 100 ul CaCl2,gently mix.We use PCGP/VSVG to package retrovirus and PSPAX2/MD2G to package lentivirus.

4. Add the mixture to 100ul BBS carefully and incubate for 20min.

5. Add the mixture to the cells and refresh after 6-8h.

6. collect virus after 48h and store in -80°C.

7. For condensed virus, use 10cm culture medium and proportionally increase the reagents as described above. Medium containing virus is sealed by mineral oil and ultracentrifugate at 70000g for 1.5h. Collect the last 1ml medium and resuspend for further experiment.

Selecting stable cell line

1. Seed cells a night before.

2. Refresh medium first.Add polybrene 8ul/ml final concentration. Gently add 100ul virus to every well in a 24-well plate. .

3. Add 1:1000 blastisidin or 1:2000 2mg/ml puromycin to culture medium.

4. Three later, refresh culture medium and passage cells into new plates.

Basic cell culturing

Medium: 10% FBS+ 88% DMEM (high-glucose)+1% P/S (5000 mg/ml penicillin and 5000 mg/ml streptomycin)+1% L-glutamine (200 mM). Cells were passaged with 0.25%Trypsin.

hiPSC Culturing

hiPSCs are cultured in Gibco Essential 8 Medium coated with matrigel(BD low growth factor). Essential 8 supplement(50*) should be thawed at 2-8 degree and mix with DMEM/F-12(1:1). Complete medium can be used for 2 weeks. The preparation of matrigel should be always on ice to prevent too early condensing. For each 6 well plate, 1ml/well DMEM/F12 diluted matrigel sis added. hiPSCs were passaged by 0.5mM EDTA pH8.0 in DPBS without Calcium and Magnesium. When the edge cells starts to round up, remove the EDTA and add new Essential 8 complete medium.